diff --git a/doc/Pacemaker_Explained/en-US/Ch-Advanced-Options.txt b/doc/Pacemaker_Explained/en-US/Ch-Advanced-Options.txt index d1cf176d70..1aaf53b6ae 100644 --- a/doc/Pacemaker_Explained/en-US/Ch-Advanced-Options.txt +++ b/doc/Pacemaker_Explained/en-US/Ch-Advanced-Options.txt @@ -1,710 +1,715 @@ = Advanced Configuration = [[s-remote-connection]] == Connecting from a Remote Machine == indexterm:[Cluster,Remote connection] indexterm:[Cluster,Remote administration] Provided Pacemaker is installed on a machine, it is possible to connect to the cluster even if the machine itself is not in the same cluster. To do this, one simply sets up a number of environment variables and runs the same commands as when working on a cluster node. .Environment Variables Used to Connect to Remote Instances of the CIB [width="95%",cols="1m,1,3<",options="header",align="center"] |========================================================= |Environment Variable |Default |Description |CIB_user |$USER |The user to connect as. Needs to be part of the +hacluster+ group on the target host. indexterm:[Environment Variable,CIB_user] |CIB_passwd | |The user's password. Read from the command line if unset. indexterm:[Environment Variable,CIB_passwd] |CIB_server |localhost |The host to contact indexterm:[Environment Variable,CIB_server] |CIB_port | |The port on which to contact the server; required. indexterm:[Environment Variable,CIB_port] |CIB_encrypted |TRUE |Whether to encrypt network traffic indexterm:[Environment Variable,CIB_encrypted] |========================================================= So, if *c001n01* is an active cluster node and is listening on port 1234 for connections, and *someuser* is a member of the *hacluster* group, then the following would prompt for *someuser*'s password and return the cluster's current configuration: ---- # export CIB_port=1234; export CIB_server=c001n01; export CIB_user=someuser; # cibadmin -Q ---- For security reasons, the cluster does not listen for remote connections by default. If you wish to allow remote access, you need to set the +remote-tls-port+ (encrypted) or +remote-clear-port+ (unencrypted) CIB properties (i.e., those kept in the +cib+ tag, like +num_updates+ and +epoch+). .Extra top-level CIB properties for remote access [width="95%",cols="1m,1,3<",options="header",align="center"] |========================================================= |Field |Default |Description |remote-tls-port |_none_ |Listen for encrypted remote connections on this port. indexterm:[remote-tls-port,Remote Connection Option] indexterm:[Remote Connection,Option,remote-tls-port] |remote-clear-port |_none_ |Listen for plaintext remote connections on this port. indexterm:[remote-clear-port,Remote Connection Option] indexterm:[Remote Connection,Option,remote-clear-port] |========================================================= [[s-recurring-start]] == Specifying When Recurring Actions are Performed == By default, recurring actions are scheduled relative to when the resource started. So if your resource was last started at 14:32 and you have a backup set to be performed every 24 hours, then the backup will always run at in the middle of the business day -- hardly desirable. To specify a date and time that the operation should be relative to, set the operation's +interval-origin+. The cluster uses this point to calculate the correct +start-delay+ such that the operation will occur at _origin + (interval * N)_. So, if the operation's interval is 24h, its interval-origin is set to 02:00 and it is currently 14:32, then the cluster would initiate the operation with a start delay of 11 hours and 28 minutes. If the resource is moved to another node before 2am, then the operation is cancelled. The value specified for +interval+ and +interval-origin+ can be any date/time conforming to the http://en.wikipedia.org/wiki/ISO_8601[ISO8601 standard]. By way of example, to specify an operation that would run on the first Monday of 2009 and every Monday after that, you would add: .Specifying a Base for Recurring Action Intervals ===== [source,XML] ===== == Moving Resources == indexterm:[Moving,Resources] indexterm:[Resource,Moving] === Moving Resources Manually === There are primarily two occasions when you would want to move a resource from its current location: when the whole node is under maintenance, and when a single resource needs to be moved. ==== Standby Mode ==== Since everything eventually comes down to a score, you could create constraints for every resource to prevent them from running on one node. While pacemaker configuration can seem convoluted at times, not even we would require this of administrators. Instead, one can set a special node attribute which tells the cluster "don't let anything run here". There is even a helpful tool to help query and set it, called `crm_standby`. To check the standby status of the current machine, run: ---- # crm_standby -G ---- A value of +on+ indicates that the node is _not_ able to host any resources, while a value of +off+ says that it _can_. You can also check the status of other nodes in the cluster by specifying the `--node` option: ---- # crm_standby -G --node sles-2 ---- To change the current node's standby status, use `-v` instead of `-G`: ---- # crm_standby -v on ---- Again, you can change another host's value by supplying a hostname with `--node`. ==== Moving One Resource ==== When only one resource is required to move, we could do this by creating location constraints. However, once again we provide a user-friendly shortcut as part of the `crm_resource` command, which creates and modifies the extra constraints for you. If +Email+ were running on +sles-1+ and you wanted it moved to a specific location, the command would look something like: ---- # crm_resource -M -r Email -H sles-2 ---- Behind the scenes, the tool will create the following location constraint: [source,XML] It is important to note that subsequent invocations of `crm_resource -M` are not cumulative. So, if you ran these commands ---- # crm_resource -M -r Email -H sles-2 # crm_resource -M -r Email -H sles-3 ---- then it is as if you had never performed the first command. To allow the resource to move back again, use: ---- # crm_resource -U -r Email ---- Note the use of the word _allow_. The resource can move back to its original location but, depending on +resource-stickiness+, it might stay where it is. To be absolutely certain that it moves back to +sles-1+, move it there before issuing the call to `crm_resource -U`: ---- # crm_resource -M -r Email -H sles-1 # crm_resource -U -r Email ---- Alternatively, if you only care that the resource should be moved from its current location, try: ---- # crm_resource -B -r Email ---- Which will instead create a negative constraint, like [source,XML] This will achieve the desired effect, but will also have long-term consequences. As the tool will warn you, the creation of a +-INFINITY+ constraint will prevent the resource from running on that node until `crm_resource -U` is used. This includes the situation where every other cluster node is no longer available! In some cases, such as when +resource-stickiness+ is set to +INFINITY+, it is possible that you will end up with the problem described in <>. The tool can detect some of these cases and deals with them by creating both positive and negative constraints. E.g. +Email+ prefers +sles-1+ with a score of +-INFINITY+ +Email+ prefers +sles-2+ with a score of +INFINITY+ which has the same long-term consequences as discussed earlier. [[s-failure-migration]] === Moving Resources Due to Failure === Normally, if a running resource fails, pacemaker will try to start it again on the same node. However if a resource fails repeatedly, it is possible that there is an underlying problem on that node, and you might desire trying a different node in such a case. +indexterm:[migration-threshold] +indexterm:[failure-timeout] +indexterm:[start-failure-is-fatal] + Pacemaker allows you to set your preference via the +migration-threshold+ resource option. footnote:[ The naming of this option was perhaps unfortunate as it is easily confused with live migration, the process of moving a resource from one node to another without stopping it. Xen virtual guests are the most common example of resources that can be migrated in this manner. ] Simply define +migration-threshold=pass:[N]+ for a resource and it will migrate to a new node after 'N' failures. There is no threshold defined by default. To determine the resource's current failure status and limits, run `crm_mon --failcounts`. By default, once the threshold has been reached, the troublesome node will no longer be allowed to run the failed resource until the administrator manually resets the resource's failcount using `crm_failcount` (after hopefully first fixing the failure's cause). Alternatively, it is possible to expire them by setting the +failure-timeout+ option for the resource. For example, a setting of +migration-threshold=2+ and +failure-timeout=60s+ would cause the resource to move to a new node after 2 failures, and allow it to move back (depending on stickiness and constraint scores) after one minute. There are two exceptions to the migration threshold concept: when a resource either fails to start or fails to stop. -Start failures cause the failcount to be set to +INFINITY+ and thus always -cause the resource to move immediately. +If the cluster property +start-failure-is-fatal+ is set to +true+ (which is the +default), start failures cause the failcount to be set to +INFINITY+ and thus +always cause the resource to move immediately. Stop failures are slightly different and crucial. If a resource fails to stop and STONITH is enabled, then the cluster will fence the node in order to be able to start the resource elsewhere. If STONITH is not enabled, then the cluster has no way to continue and will not try to start the resource elsewhere, but will try to stop it again after the failure timeout. [IMPORTANT] Please read <> to understand how timeouts work before configuring a +failure-timeout+. === Moving Resources Due to Connectivity Changes === You can configure the cluster to move resources when external connectivity is lost in two steps. ==== Tell Pacemaker to Monitor Connectivity ==== First, add an *ocf:pacemaker:ping* resource to the cluster. The *ping* resource uses the system utility of the same name to a test whether list of machines (specified by DNS hostname or IPv4/IPv6 address) are reachable and uses the results to maintain a node attribute called +pingd+ by default. footnote:[ The attribute name is customizable, in order to allow multiple ping groups to be defined. ] [NOTE] =========== Older versions of Heartbeat required users to add ping nodes to +ha.cf+, but this is no longer required. Older versions of Pacemaker used a different agent *ocf:pacemaker:pingd* which is now deprecated in favor of *ping*. If your version of Pacemaker does not contain the *ping* resource agent, download the latest version from https://github.com/ClusterLabs/pacemaker/tree/master/extra/resources/ping =========== Normally, the ping resource should run on all cluster nodes, which means that you'll need to create a clone. A template for this can be found below along with a description of the most interesting parameters. .Common Options for a 'ping' Resource [width="95%",cols="1m,4<",options="header",align="center"] |========================================================= |Field |Description |dampen |The time to wait (dampening) for further changes to occur. Use this to prevent a resource from bouncing around the cluster when cluster nodes notice the loss of connectivity at slightly different times. indexterm:[dampen,Ping Resource Option] indexterm:[Ping Resource,Option,dampen] |multiplier |The number of connected ping nodes gets multiplied by this value to get a score. Useful when there are multiple ping nodes configured. indexterm:[multiplier,Ping Resource Option] indexterm:[Ping Resource,Option,multiplier] |host_list |The machines to contact in order to determine the current connectivity status. Allowed values include resolvable DNS host names, IPv4 and IPv6 addresses. indexterm:[host_list,Ping Resource Option] indexterm:[Ping Resource,Option,host_list] |========================================================= .An example ping cluster resource that checks node connectivity once every minute ===== [source,XML] ------------ ------------ ===== [IMPORTANT] =========== You're only half done. The next section deals with telling Pacemaker how to deal with the connectivity status that +ocf:pacemaker:ping+ is recording. =========== ==== Tell Pacemaker How to Interpret the Connectivity Data ==== [IMPORTANT] ====== Before attempting the following, make sure you understand <>. ====== There are a number of ways to use the connectivity data. The most common setup is for people to have a single ping target (e.g. the service network's default gateway), to prevent the cluster from running a resource on any unconnected node. .Don't run a resource on unconnected nodes ===== [source,XML] ------- ------- ===== A more complex setup is to have a number of ping targets configured. You can require the cluster to only run resources on nodes that can connect to all (or a minimum subset) of them. .Run only on nodes connected to three or more ping targets. ===== [source,XML] ------- ... ... ... ------- ===== Alternatively, you can tell the cluster only to _prefer_ nodes with the best connectivity. Just be sure to set +multiplier+ to a value higher than that of +resource-stickiness+ (and don't set either of them to +INFINITY+). .Prefer the node with the most connected ping nodes ===== [source,XML] ------- ------- ===== It is perhaps easier to think of this in terms of the simple constraints that the cluster translates it into. For example, if *sles-1* is connected to all five ping nodes but *sles-2* is only connected to two, then it would be as if you instead had the following constraints in your configuration: .How the cluster translates the above location constraint ===== [source,XML] ------- ------- ===== The advantage is that you don't have to manually update any constraints whenever your network connectivity changes. You can also combine the concepts above into something even more complex. The example below shows how you can prefer the node with the most connected ping nodes provided they have connectivity to at least three (again assuming that +multiplier+ is set to 1000). .A more complex example of choosing a location based on connectivity ===== [source,XML] ------- ------- ===== === Migrating Resources === Normally, when the cluster needs to move a resource, it fully restarts the resource (i.e. stops the resource on the current node and starts it on the new node). However, some types of resources, such as Xen virtual guests, are able to move to another location without loss of state (often referred to as live migration or hot migration). In pacemaker, this is called resource migration. Pacemaker can be configured to migrate a resource when moving it, rather than restarting it. Not all resources are able to migrate; see the Migration Checklist below, and those that can, won't do so in all situations. Conceptually, there are two requirements from which the other prerequisites follow: * The resource must be active and healthy at the old location; and * everything required for the resource to run must be available on both the old and new locations. The cluster is able to accommodate both 'push' and 'pull' migration models by requiring the resource agent to support two special actions: +migrate_to+ (performed on the current location) and +migrate_from+ (performed on the destination). In push migration, the process on the current location transfers the resource to the new location where is it later activated. In this scenario, most of the work would be done in the +migrate_to+ action and, if anything, the activation would occur during +migrate_from+. Conversely for pull, the +migrate_to+ action is practically empty and +migrate_from+ does most of the work, extracting the relevant resource state from the old location and activating it. There is no wrong or right way for a resource agent to implement migration, as long as it works. .Migration Checklist * The resource may not be a clone. * The resource must use an OCF style agent. * The resource must not be in a failed or degraded state. * The resource agent must support +migrate_to+ and +migrate_from+ actions, and advertise them in its metadata. * The resource must have the +allow-migrate+ meta-attribute set to +true+ (which is not the default). If an otherwise migratable resource depends on another resource via an ordering constraint, there are special situations in which it will be restarted rather than migrated. For example, if the resource depends on a clone, and at the time the resource needs to be moved, the clone has instances that are stopping and instances that are starting, then the resource will be restarted. The Policy Engine is not yet able to model this situation correctly and so takes the safer (if less optimal) path. In pacemaker 1.1.11 and earlier, a migratable resource will be restarted when moving if it directly or indirectly depends on 'any' primitive or group resources. Even in newer versions, if a migratable resource depends on a non-migratable resource, and both need to be moved, the migratable resource will be restarted. [[s-reusing-config-elements]] == Reusing Rules, Options and Sets of Operations == Sometimes a number of constraints need to use the same set of rules, and resources need to set the same options and parameters. To simplify this situation, you can refer to an existing object using an +id-ref+ instead of an id. So if for one resource you have [source,XML] ------ ------ Then instead of duplicating the rule for all your other resources, you can instead specify: .Referencing rules from other constraints ===== [source,XML] ------- ------- ===== [IMPORTANT] =========== The cluster will insist that the +rule+ exists somewhere. Attempting to add a reference to a non-existing rule will cause a validation failure, as will attempting to remove a +rule+ that is referenced elsewhere. =========== The same principle applies for +meta_attributes+ and +instance_attributes+ as illustrated in the example below: .Referencing attributes, options, and operations from other resources ===== [source,XML] ------- ------- ===== == Reloading Services After a Definition Change == The cluster automatically detects changes to the definition of services it manages. The normal response is to stop the service (using the old definition) and start it again (with the new definition). This works well, but some services are smarter and can be told to use a new set of options without restarting. To take advantage of this capability, the resource agent must: . Accept the +reload+ operation and perform any required actions. _The actions here depend completely on your application!_ + .The DRBD agent's logic for supporting +reload+ ===== [source,Bash] ------- case $1 in start) drbd_start ;; stop) drbd_stop ;; reload) drbd_reload ;; monitor) drbd_monitor ;; *) drbd_usage exit $OCF_ERR_UNIMPLEMENTED ;; esac exit $? ------- ===== . Advertise the +reload+ operation in the +actions+ section of its metadata + .The DRBD Agent Advertising Support for the +reload+ Operation ===== [source,XML] ------- 1.1 Master/Slave OCF Resource Agent for DRBD ... ------- ===== . Advertise one or more parameters that can take effect using +reload+. + Any parameter with the +unique+ set to 0 is eligible to be used in this way. + .Parameter that can be changed using reload ===== [source,XML] ------- Full path to the drbd.conf file. Path to drbd.conf ------- ===== Once these requirements are satisfied, the cluster will automatically know to reload the resource (instead of restarting) when a non-unique field changes. [NOTE] ====== Metadata will not be re-read unless the resource needs to be started. This may mean that the resource will be restarted the first time, even though you changed a parameter with +unique=0+. ====== [NOTE] ====== If both a unique and non-unique field are changed simultaneously, the resource will still be restarted. ====== diff --git a/doc/Pacemaker_Explained/en-US/Ch-Advanced-Resources.txt b/doc/Pacemaker_Explained/en-US/Ch-Advanced-Resources.txt index 9d0bb7a43c..298c244ca1 100644 --- a/doc/Pacemaker_Explained/en-US/Ch-Advanced-Resources.txt +++ b/doc/Pacemaker_Explained/en-US/Ch-Advanced-Resources.txt @@ -1,1052 +1,1035 @@ = Advanced Resource Types = [[group-resources]] == Groups - A Syntactic Shortcut == indexterm:[Group Resources] indexterm:[Resources,Groups] One of the most common elements of a cluster is a set of resources that need to be located together, start sequentially, and stop in the reverse order. To simplify this configuration, we support the concept of groups. .A group of two primitive resources ====== [source,XML] ------- ------- ====== Although the example above contains only two resources, there is no limit to the number of resources a group can contain. The example is also sufficient to explain the fundamental properties of a group: * Resources are started in the order they appear in (+Public-IP+ first, then +Email+) * Resources are stopped in the reverse order to which they appear in (+Email+ first, then +Public-IP+) If a resource in the group can't run anywhere, then nothing after that is allowed to run, too. * If +Public-IP+ can't run anywhere, neither can +Email+; * but if +Email+ can't run anywhere, this does not affect +Public-IP+ in any way The group above is logically equivalent to writing: .How the cluster sees a group resource ====== [source,XML] ------- ------- ====== Obviously as the group grows bigger, the reduced configuration effort can become significant. Another (typical) example of a group is a DRBD volume, the filesystem mount, an IP address, and an application that uses them. === Group Properties === .Properties of a Group Resource [width="95%",cols="3m,5<",options="header",align="center"] |========================================================= |Field |Description |id |A unique name for the group indexterm:[id,Group Resource Property] indexterm:[Resource,Group Property,id] |========================================================= === Group Options === Groups inherit the +priority+, +target-role+, and +is-managed+ properties from primitive resources. See <> for information about those properties. === Group Instance Attributes === Groups have no instance attributes. However, any that are set for the group object will be inherited by the group's children. === Group Contents === Groups may only contain a collection of cluster resources (see <>). To refer to a child of a group resource, just use the child's +id+ instead of the group's. === Group Constraints === Although it is possible to reference a group's children in constraints, it is usually preferable to reference the group itself. .Some constraints involving groups ====== [source,XML] ------- ------- ====== === Group Stickiness === indexterm:[resource-stickiness,Groups] Stickiness, the measure of how much a resource wants to stay where it is, is additive in groups. Every active resource of the group will contribute its stickiness value to the group's total. So if the default +resource-stickiness+ is 100, and a group has seven members, five of which are active, then the group as a whole will prefer its current location with a score of 500. [[s-resource-clone]] == Clones - Resources That Get Active on Multiple Hosts == indexterm:[Clone Resources] indexterm:[Resources,Clones] Clones were initially conceived as a convenient way to start multiple instances of an IP address resource and have them distributed throughout the cluster for load balancing. They have turned out to quite useful for a number of purposes including integrating with the Distributed Lock Manager (used by many cluster filesystems), the fencing subsystem, and OCFS2. You can clone any resource, provided the resource agent supports it. Three types of cloned resources exist: * Anonymous * Globally unique * Stateful 'Anonymous' clones are the simplest. These behave completely identically everywhere they are running. Because of this, there can be only one copy of an anonymous clone active per machine. 'Globally unique' clones are distinct entities. A copy of the clone running on one machine is not equivalent to another instance on another node, nor would any two copies on the same node be equivalent. 'Stateful' clones are covered later in <>. .A clone of an LSB resource ====== [source,XML] ------- ------- ====== === Clone Properties === .Properties of a Clone Resource [width="95%",cols="3m,5<",options="header",align="center"] |========================================================= |Field |Description |id |A unique name for the clone indexterm:[id,Clone Property] indexterm:[Clone,Property,id] |========================================================= === Clone Options === Options inherited from <> resources: +priority, target-role, is-managed+ .Clone-specific configuration options [width="95%",cols="1m,1,3<",options="header",align="center"] |========================================================= |Field |Default |Description |clone-max |number of nodes in cluster |How many copies of the resource to start indexterm:[clone-max,Clone Option] indexterm:[Clone,Option,clone-max] |clone-node-max |1 |How many copies of the resource can be started on a single node indexterm:[clone-node-max,Clone Option] indexterm:[Clone,Option,clone-node-max] |clone-min |1 |Require at least this number of clone instances to be runnable before allowing resources depending on the clone to be runnable '(since 1.1.14)' indexterm:[clone-min,Clone Option] indexterm:[Clone,Option,clone-min] |notify |true |When stopping or starting a copy of the clone, tell all the other copies beforehand and again when the action was successful. Allowed values: +false+, +true+ indexterm:[notify,Clone Option] indexterm:[Clone,Option,notify] |globally-unique |false |Does each copy of the clone perform a different function? Allowed values: +false+, +true+ indexterm:[globally-unique,Clone Option] indexterm:[Clone,Option,globally-unique] |ordered |false |Should the copies be started in series (instead of in parallel)? Allowed values: +false+, +true+ indexterm:[ordered,Clone Option] indexterm:[Clone,Option,ordered] |interleave |false |If this clone depends on another clone via an ordering constraint, is it allowed to start after the local instance of the other clone starts, rather than wait for all instances of the other clone to start? Allowed values: +false+, +true+ indexterm:[interleave,Clone Option] indexterm:[Clone,Option,interleave] |========================================================= === Clone Instance Attributes === Clones have no instance attributes; however, any that are set here will be inherited by the clone's children. === Clone Contents === Clones must contain exactly one primitive or group resource. [WARNING] You should never reference the name of a clone's child. If you think you need to do this, you probably need to re-evaluate your design. === Clone Constraints === In most cases, a clone will have a single copy on each active cluster node. If this is not the case, you can indicate which nodes the cluster should preferentially assign copies to with resource location constraints. These constraints are written no differently from those for primitive resources except that the clone's +id+ is used. .Some constraints involving clones ====== [source,XML] ------- ------- ====== Ordering constraints behave slightly differently for clones. In the example above, +apache-stats+ will wait until all copies of +apache-clone+ that need to be started have done so before being started itself. Only if _no_ copies can be started will +apache-stats+ be prevented from being active. Additionally, the clone will wait for +apache-stats+ to be stopped before stopping itself. Colocation of a primitive or group resource with a clone means that the resource can run on any machine with an active copy of the clone. The cluster will choose a copy based on where the clone is running and the resource's own location preferences. Colocation between clones is also possible. If one clone +A+ is colocated with another clone +B+, the set of allowed locations for +A+ is limited to nodes on which +B+ is (or will be) active. Placement is then performed normally. [[s-clone-stickiness]] === Clone Stickiness === indexterm:[resource-stickiness,Clones] To achieve a stable allocation pattern, clones are slightly sticky by default. If no value for +resource-stickiness+ is provided, the clone will use a value of 1. Being a small value, it causes minimal disturbance to the score calculations of other resources but is enough to prevent Pacemaker from needlessly moving copies around the cluster. [NOTE] ==== For globally unique clones, this may result in multiple instances of the clone staying on a single node, even after another eligible node becomes active (for example, after being put into standby mode then made active again). If you do not want this behavior, specify a +resource-stickiness+ of 0 for the clone temporarily and let the cluster adjust, then set it back to 1 if you want the default behavior to apply again. ==== === Clone Resource Agent Requirements === Any resource can be used as an anonymous clone, as it requires no additional support from the resource agent. Whether it makes sense to do so depends on your resource and its resource agent. Globally unique clones do require some additional support in the resource agent. In particular, it must only respond with +$\{OCF_SUCCESS}+ if the node has that exact instance active. All other probes for instances of the clone should result in +$\{OCF_NOT_RUNNING}+ (or one of the other OCF error codes if they are failed). Individual instances of a clone are identified by appending a colon and a numerical offset, e.g. +apache:2+. Resource agents can find out how many copies there are by examining the +OCF_RESKEY_CRM_meta_clone_max+ environment variable and which copy it is by examining +OCF_RESKEY_CRM_meta_clone+. The resource agent must not make any assumptions (based on +OCF_RESKEY_CRM_meta_clone+) about which numerical instances are active. In particular, the list of active copies will not always be an unbroken sequence, nor always start at 0. ==== Clone Notifications ==== Supporting notifications requires the +notify+ action to be implemented. If supported, the notify action will be passed a number of extra variables which, when combined with additional context, can be used to calculate the current state of the cluster and what is about to happen to it. .Environment variables supplied with Clone notify actions [width="95%",cols="5,3<",options="header",align="center"] |========================================================= |Variable |Description |OCF_RESKEY_CRM_meta_notify_type |Allowed values: +pre+, +post+ indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,type] indexterm:[type,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_operation |Allowed values: +start+, +stop+ indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,operation] indexterm:[operation,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_start_resource |Resources to be started indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,start_resource] indexterm:[start_resource,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_stop_resource |Resources to be stopped indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,stop_resource] indexterm:[stop_resource,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_active_resource |Resources that are running indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,active_resource] indexterm:[active_resource,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_inactive_resource |Resources that are not running indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,inactive_resource] indexterm:[inactive_resource,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_start_uname |Nodes on which resources will be started indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,start_uname] indexterm:[start_uname,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_stop_uname |Nodes on which resources will be stopped indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,stop_uname] indexterm:[stop_uname,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_active_uname |Nodes on which resources are running indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,active_uname] indexterm:[active_uname,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_inactive_uname |Nodes on which resources are not running indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,inactive_uname] indexterm:[inactive_uname,Notification Environment Variable] |========================================================= The variables come in pairs, such as +OCF_RESKEY_CRM_meta_notify_start_resource+ and +OCF_RESKEY_CRM_meta_notify_start_uname+ and should be treated as an array of whitespace-separated elements. Thus in order to indicate that +clone:0+ will be started on +sles-1+, +clone:2+ will be started on +sles-3+, and +clone:3+ will be started on +sles-2+, the cluster would set .Notification variables ====== [source,Bash] ------- OCF_RESKEY_CRM_meta_notify_start_resource="clone:0 clone:2 clone:3" OCF_RESKEY_CRM_meta_notify_start_uname="sles-1 sles-3 sles-2" ------- ====== ==== Proper Interpretation of Notification Environment Variables ==== .Pre-notification (stop): * Active resources: +$OCF_RESKEY_CRM_meta_notify_active_resource+ * Inactive resources: +$OCF_RESKEY_CRM_meta_notify_inactive_resource+ * Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ .Post-notification (stop) / Pre-notification (start): * Active resources ** +$OCF_RESKEY_CRM_meta_notify_active_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ * Inactive resources ** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ * Resources that were started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ .Post-notification (start): * Active resources: ** +$OCF_RESKEY_CRM_meta_notify_active_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Inactive resources: ** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources that were started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ [[s-resource-multistate]] == Multi-state - Resources That Have Multiple Modes == indexterm:[Multi-state Resources] indexterm:[Resources,Multi-state] Multi-state resources are a specialization of clone resources; please ensure you understand <> before continuing! Multi-state resources allow the instances to be in one of two operating modes (called 'roles'). The roles are called 'master' and 'slave', but can mean whatever you wish them to mean. The only limitation is that when an instance is started, it must come up in the slave role. === Multi-state Properties === .Properties of a Multi-State Resource [width="95%",cols="3m,5<",options="header",align="center"] |========================================================= |Field |Description |id |Your name for the multi-state resource indexterm:[id,Multi-State Property] indexterm:[Multi-State,Property,id] |========================================================= === Multi-state Options === Options inherited from <> resources: +priority+, +target-role+, +is-managed+ Options inherited from <> resources: +clone-max+, +clone-node-max+, +notify+, +globally-unique+, +ordered+, +interleave+ .Multi-state-specific resource configuration options [width="95%",cols="1m,1,3<",options="header",align="center"] |========================================================= |Field |Default |Description |master-max |1 |How many copies of the resource can be promoted to the +master+ role indexterm:[master-max,Multi-State Option] indexterm:[Multi-State,Option,master-max] |master-node-max |1 |How many copies of the resource can be promoted to the +master+ role on a single node indexterm:[master-node-max,Multi-State Option] indexterm:[Multi-State,Option,master-node-max] |========================================================= === Multi-state Instance Attributes === Multi-state resources have no instance attributes; however, any that are set here will be inherited by a master's children. === Multi-state Contents === Masters must contain exactly one primitive or group resource. [WARNING] You should never reference the name of a master's child. If you think you need to do this, you probably need to re-evaluate your design. === Monitoring Multi-State Resources === The usual monitor actions are insufficient to monitor a multi-state resource, because pacemaker needs to verify not only that the resource is active, but also that its actual role matches its intended one. Define two monitoring actions: the usual one will cover the slave role, and an additional one with +role="master"+ will cover the master role. .Monitoring both states of a multi-state resource ====== [source,XML] ------- ------- ====== [IMPORTANT] =========== It is crucial that _every_ monitor operation has a different interval! Pacemaker currently differentiates between operations only by resource and interval; so if (for example) a master/slave resource had the same monitor interval for both roles, Pacemaker would ignore the role when checking the status -- which would cause unexpected return codes, and therefore unnecessary complications. =========== === Multi-state Constraints === In most cases, multi-state resources will have a single copy on each active cluster node. If this is not the case, you can indicate which nodes the cluster should preferentially assign copies to with resource location constraints. These constraints are written no differently from those for primitive resources except that the master's +id+ is used. When considering multi-state resources in constraints, for most -purposes it is sufficient to treat them as clones. The exception is -when the +rsc-role+ and/or +with-rsc-role+ fields (for colocation -constraints) and +first-action+ and/or +then-action+ fields (for -ordering constraints) are used. +purposes it is sufficient to treat them as clones. The exception is +that the +first-action+ and/or +then-action+ fields for ordering constraints +may be set to +promote+ or +demote+ to constrain the master role, +and colocation constraints may contain +rsc-role+ and/or +with-rsc-role+ +fields. -.Additional constraint options relevant to multi-state resources +.Additional colocation constraint options for multi-state resources [width="95%",cols="1m,1,3<",options="header",align="center"] |========================================================= |Field |Default |Description |rsc-role |started |An additional attribute of colocation constraints that specifies the role that +rsc+ must be in. Allowed values: +started+, +master+, +slave+. indexterm:[rsc-role,Ordering Constraints] indexterm:[Constraints,Ordering,rsc-role] |with-rsc-role |started |An additional attribute of colocation constraints that specifies the role that +with-rsc+ must be in. Allowed values: +started+, +master+, +slave+. indexterm:[with-rsc-role,Ordering Constraints] indexterm:[Constraints,Ordering,with-rsc-role] -|first-action -|start -|An additional attribute of ordering constraints that specifies the - action that the +first+ resource must complete before executing the - specified action for the +then+ resource. Allowed values: +start+, - +stop+, +promote+, +demote+. - indexterm:[first-action,Ordering Constraints] - indexterm:[Constraints,Ordering,first-action] - -|then-action -|value of +first-action+ -|An additional attribute of ordering constraints that specifies the - action that the +then+ resource can only execute after the - +first-action+ on the +first+ resource has completed. Allowed - values: +start+, +stop+, +promote+, +demote+. - indexterm:[then-action,Ordering Constraints] - indexterm:[Constraints,Ordering,then-action] - |========================================================= .Constraints involving multi-state resources ====== [source,XML] ------- ------- ====== In the example above, +myApp+ will wait until one of the database copies has been started and promoted to master before being started itself on the same node. Only if no copies can be promoted will +myApp+ be prevented from being active. Additionally, the cluster will wait for +myApp+ to be stopped before demoting the database. Colocation of a primitive or group resource with a multi-state resource means that it can run on any machine with an active copy of the multi-state resource that has the specified role (+master+ or +slave+). In the example above, the cluster will choose a location based on where database is running as a +master+, and if there are multiple +master+ instances it will also factor in +myApp+'s own location preferences when deciding which location to choose. Colocation with regular clones and other multi-state resources is also possible. In such cases, the set of allowed locations for the +rsc+ clone is (after role filtering) limited to nodes on which the +with-rsc+ multi-state resource is (or will be) in the specified role. Placement is then performed as normal. ==== Using Multi-state Resources in Colocation Sets ==== .Additional colocation set options relevant to multi-state resources [width="95%",cols="1m,1,6<",options="header",align="center"] |========================================================= |Field |Default |Description |role |started |The role that 'all members' of the set must be in. Allowed values: +started+, +master+, +slave+. indexterm:[role,Ordering Constraints] indexterm:[Constraints,Ordering,role] |========================================================= In the following example +B+'s master must be located on the same node as +A+'s master. Additionally resources +C+ and +D+ must be located on the same node as +A+'s and +B+'s masters. .Colocate C and D with A's and B's master instances ====== [source,XML] ------- ------- ====== ==== Using Multi-state Resources in Ordering Sets ==== .Additional ordered set options relevant to multi-state resources [width="95%",cols="1m,1,3<",options="header",align="center"] |========================================================= |Field |Default |Description |action |value of +first-action+ |An additional attribute of ordering constraint sets that specifies the action that applies to 'all members' of the set. Allowed values: +start+, +stop+, +promote+, +demote+. indexterm:[action,Ordering Constraints] indexterm:[Constraints,Ordering,action] |========================================================= .Start C and D after first promoting A and B ====== [source,XML] ------- ------- ====== In the above example, +B+ cannot be promoted to a master role until +A+ has been promoted. Additionally, resources +C+ and +D+ must wait until +A+ and +B+ have been promoted before they can start. === Multi-state Stickiness === indexterm:[resource-stickiness,Multi-State] As with regular clones, multi-state resources are slightly sticky by default. See <> for details. === Which Resource Instance is Promoted === During the start operation, most resource agents should call the `crm_master` utility. This tool automatically detects both the resource and host and should be used to set a preference for being promoted. Based on this, +master-max+, and +master-node-max+, the instance(s) with the highest preference will be promoted. An alternative is to create a location constraint that indicates which nodes are most preferred as masters. .Explicitly preferring node1 to be promoted to master ====== [source,XML] ------- ------- ====== === Requirements for Multi-state Resource Agents === Since multi-state resources are an extension of cloned resources, all the requirements for resource agents that support clones are also requirements for resource agents that support multi-state resources. Additionally, multi-state resources require two extra actions, +demote+ and +promote+, which are responsible for changing the state of the resource. Like +start+ and +stop+, they should return +$\{OCF_SUCCESS}+ if they completed successfully or a relevant error code if they did not. The states can mean whatever you wish, but when the resource is started, it must come up in the mode called +slave+. From there the cluster will decide which instances to promote to +master+. In addition to the clone requirements for monitor actions, agents must also _accurately_ report which state they are in. The cluster relies on the agent to report its status (including role) accurately and does not indicate to the agent what role it currently believes it to be in. .Role implications of OCF return codes [width="95%",cols="1,1<",options="header",align="center"] |========================================================= |Monitor Return Code |Description |OCF_NOT_RUNNING |Stopped indexterm:[Return Code,OCF_NOT_RUNNING] |OCF_SUCCESS |Running (Slave) indexterm:[Return Code,OCF_SUCCESS] |OCF_RUNNING_MASTER |Running (Master) indexterm:[Return Code,OCF_RUNNING_MASTER] |OCF_FAILED_MASTER |Failed (Master) indexterm:[Return Code,OCF_FAILED_MASTER] |Other |Failed (Slave) |========================================================= ==== Multi-state Notifications ==== Like clones, supporting notifications requires the +notify+ action to be implemented. If supported, the notify action will be passed a number of extra variables which, when combined with additional context, can be used to calculate the current state of the cluster and what is about to happen to it. .Environment variables supplied with multi-state notify actions footnote:[Emphasized variables are specific to +Master+ resources, and all behave in the same manner as described for Clone resources.] [width="95%",cols="5,3<",options="header",align="center"] |========================================================= |Variable |Description |OCF_RESKEY_CRM_meta_notify_type |Allowed values: +pre+, +post+ indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,type] indexterm:[type,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_operation |Allowed values: +start+, +stop+ indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,operation] indexterm:[operation,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_active_resource |Resources the that are running indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,active_resource] indexterm:[active_resource,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_inactive_resource |Resources the that are not running indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,inactive_resource] indexterm:[inactive_resource,Notification Environment Variable] |_OCF_RESKEY_CRM_meta_notify_master_resource_ |Resources that are running in +Master+ mode indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,master_resource] indexterm:[master_resource,Notification Environment Variable] |_OCF_RESKEY_CRM_meta_notify_slave_resource_ |Resources that are running in +Slave+ mode indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,slave_resource] indexterm:[slave_resource,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_start_resource |Resources to be started indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,start_resource] indexterm:[start_resource,Notification Environment Variable] |indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,stop_resource] indexterm:[stop_resource,Notification Environment Variable] OCF_RESKEY_CRM_meta_notify_stop_resource |Resources to be stopped |_OCF_RESKEY_CRM_meta_notify_promote_resource_ |Resources to be promoted indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,promote_resource] indexterm:[promote_resource,Notification Environment Variable] |_OCF_RESKEY_CRM_meta_notify_demote_resource_ |Resources to be demoted indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,demote_resource] indexterm:[demote_resource,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_start_uname |Nodes on which resources will be started indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,start_uname] indexterm:[start_uname,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_stop_uname |Nodes on which resources will be stopped indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,stop_uname] indexterm:[stop_uname,Notification Environment Variable] |_OCF_RESKEY_CRM_meta_notify_promote_uname_ |Nodes on which resources will be promote indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,promote_uname] indexterm:[promote_uname,Notification Environment Variable] |_OCF_RESKEY_CRM_meta_notify_demote_uname_ |Nodes on which resources will be demoted indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,demote_uname] indexterm:[demote_uname,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_active_uname |Nodes on which resources are running indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,active_uname] indexterm:[active_uname,Notification Environment Variable] |OCF_RESKEY_CRM_meta_notify_inactive_uname |Nodes on which resources are not running indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,inactive_uname] indexterm:[inactive_uname,Notification Environment Variable] |_OCF_RESKEY_CRM_meta_notify_master_uname_ |Nodes on which resources are running in +Master+ mode indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,master_uname] indexterm:[master_uname,Notification Environment Variable] |_OCF_RESKEY_CRM_meta_notify_slave_uname_ |Nodes on which resources are running in +Slave+ mode indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,slave_uname] indexterm:[slave_uname,Notification Environment Variable] |========================================================= ==== Proper Interpretation of Multi-state Notification Environment Variables ==== .Pre-notification (demote): * +Active+ resources: +$OCF_RESKEY_CRM_meta_notify_active_resource+ * +Master+ resources: +$OCF_RESKEY_CRM_meta_notify_master_resource+ * +Slave+ resources: +$OCF_RESKEY_CRM_meta_notify_slave_resource+ * Inactive resources: +$OCF_RESKEY_CRM_meta_notify_inactive_resource+ * Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+ * Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ .Post-notification (demote) / Pre-notification (stop): * +Active+ resources: +$OCF_RESKEY_CRM_meta_notify_active_resource+ * +Master+ resources: ** +$OCF_RESKEY_CRM_meta_notify_master_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * +Slave+ resources: +$OCF_RESKEY_CRM_meta_notify_slave_resource+ * Inactive resources: +$OCF_RESKEY_CRM_meta_notify_inactive_resource+ * Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+ * Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ * Resources that were demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+ .Post-notification (stop) / Pre-notification (start) * +Active+ resources: ** +$OCF_RESKEY_CRM_meta_notify_active_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ * +Master+ resources: ** +$OCF_RESKEY_CRM_meta_notify_master_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * +Slave+ resources: ** +$OCF_RESKEY_CRM_meta_notify_slave_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ * Inactive resources: ** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ * Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+ * Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ * Resources that were demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ .Post-notification (start) / Pre-notification (promote) * +Active+ resources: ** +$OCF_RESKEY_CRM_meta_notify_active_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+ * +Master+ resources: ** +$OCF_RESKEY_CRM_meta_notify_master_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * +Slave+ resources: ** +$OCF_RESKEY_CRM_meta_notify_slave_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Inactive resources: ** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+ * Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ * Resources that were started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources that were demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ .Post-notification (promote) * +Active+ resources: ** +$OCF_RESKEY_CRM_meta_notify_active_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+ * +Master+ resources: ** +$OCF_RESKEY_CRM_meta_notify_master_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_demote_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_promote_resource+ * +Slave+ resources: ** +$OCF_RESKEY_CRM_meta_notify_slave_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_promote_resource+ * Inactive resources: ** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+ ** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+ ** minus +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+ * Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ * Resources that were started: +$OCF_RESKEY_CRM_meta_notify_start_resource+ * Resources that were promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+ * Resources that were demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+ * Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+ diff --git a/doc/Pacemaker_Explained/en-US/Ch-Constraints.txt b/doc/Pacemaker_Explained/en-US/Ch-Constraints.txt index 6826074b4a..43c28f01b4 100644 --- a/doc/Pacemaker_Explained/en-US/Ch-Constraints.txt +++ b/doc/Pacemaker_Explained/en-US/Ch-Constraints.txt @@ -1,686 +1,705 @@ = Resource Constraints = indexterm:[Resource,Constraints] == Scores == Scores of all kinds are integral to how the cluster works. Practically everything from moving a resource to deciding which resource to stop in a degraded cluster is achieved by manipulating scores in some way. Scores are calculated on a per-resource basis, and any node with a negative score for a resource can't run that resource. After calculating the scores for a resource, the cluster then chooses the node with the highest one. === Infinity Math === Pacemaker implements +INFINITY+ (or equivalently, ++INFINITY+) internally as a score of 1,000,000. Addition and subtraction with it follow these three basic rules: * Any value + +INFINITY+ = +INFINITY+ * Any value - +INFINITY+ = +-INFINITY+ * +INFINITY+ - +INFINITY+ = +-INFINITY+ [NOTE] ====== What if you want to use a score higher than 1,000,000? Typically this possibility arises when someone wants to base the score on some external metric that might go above 1,000,000. The short answer is you can't. The long answer is it is sometimes possible work around this limitation creatively. You may be able to set the score to some computed value based on the external metric rather than use the metric directly. For nodes, you can store the metric as a node attribute, and query the attribute when computing the score (possibly as part of a custom resource agent). ====== == Deciding Which Nodes a Resource Can Run On == indexterm:[Location Constraints] indexterm:[Resource,Constraints,Location] There are two alternative strategies for specifying which nodes a resources can run on. One way is to say that by default they can run anywhere and then create location constraints for nodes that are not allowed. The other option is to have nodes "opt-in" -- to start with nothing able to run anywhere and selectively enable allowed nodes. Whether you should choose opt-in or opt-out depends on your personal preference and the make-up of your cluster. If most of your resources can run on most of the nodes, then an opt-out arrangement is likely to result in a simpler configuration. On the other-hand, if most resources can only run on a small subset of nodes, an opt-in configuration might be simpler. === Location Properties === .Properties for Simple Location Constraints [width="95%",cols="2m,1,5 ------- ====== === Symmetrical "Opt-Out" Clusters === indexterm:[Symmetrical Opt-Out Clusters] indexterm:[Cluster Type,Symmetrical Opt-Out] To create an opt-out cluster, start by allowing resources to run anywhere by default: ---- # crm_attribute --name symmetric-cluster --update true ---- Then start disabling nodes. The following fragment is the equivalent of the above opt-in configuration. .Opt-out location constraints for two resources ====== [source,XML] ------- ------- ====== [[node-score-equal]] === What if Two Nodes Have the Same Score === If two nodes have the same score, then the cluster will choose one. This choice may seem random and may not be what was intended, however the cluster was not given enough information to know any better. .Constraints where a resource prefers two nodes equally ====== [source,XML] ------- ------- ====== In the example above, assuming no other constraints and an inactive cluster, +Webserver+ would probably be placed on +sles-1+ and +Database+ on +sles-2+. It would likely have placed +Webserver+ based on the node's uname and +Database+ based on the desire to spread the resource load evenly across the cluster. However other factors can also be involved in more complex configurations. [[s-resource-ordering]] == Specifying the Order in which Resources Should Start/Stop == indexterm:[Resource,Constraints,Ordering] indexterm:[Resource,Start Order] indexterm:[Ordering Constraints] The way to specify the order in which resources should start is by creating +rsc_order+ constraints. [IMPORTANT] ==== Ordering constraints affect 'only' the ordering of resources; they do not require that the resources be placed on the same node. If you want resources to be started on the same node 'and' in a specific order, you need an ordering constraint 'and' a location constraint (see <>). ==== === Ordering Properties === .Properties of an Ordering Constraint [width="95%",cols="1m,1,4> resources. + === Optional and mandatory ordering === Here is an example of ordering constraints where +Database+ 'must' start before +Webserver+, and +IP+ 'should' start before +Webserver+ if they both need to be started: .Optional and mandatory ordering constraints ====== [source,XML] ------- ------- ====== Because the above example lets +symmetrical+ default to TRUE, +Webserver+ must be stopped before +Database+ can be stopped, and +Webserver+ should be stopped before +IP+ if they both need to be stopped. [[s-resource-colocation]] == Placing Resources Relative to other Resources == indexterm:[Resource,Constraints,Colocation] indexterm:[Resource,Location Relative to other Resources] When the location of one resource depends on the location of another one, we call this colocation. Colocation has an important side-effect: it affects the order in which resources are assigned to a node. footnote:['Not' the order in which they are started. For that, see <>.] Think about it: You can't place A relative to B unless you know where B is. footnote:[ While the human brain is sophisticated enough to read the constraint in any order and choose the correct one depending on the situation, the cluster is not quite so smart. Yet. ] So when you are creating colocation constraints, it is important to consider whether you should colocate A with B, or B with A. Another thing to keep in mind is that, assuming A is colocated with B, the cluster will take into account A's preferences when deciding which node to choose for B. For a detailed look at exactly how this occurs, see http://clusterlabs.org/doc/Colocation_Explained.pdf[Colocation Explained]. === Colocation Properties === .Properties of a Colocation Constraint [width="95%",cols="2m,5<",options="header",align="center"] |========================================================= |Field |Description |id |A unique name for the constraint. indexterm:[id,Colocation Constraints] indexterm:[Constraints,Colocation,id] |rsc |The name of a resource that should be located relative to +with-rsc+. indexterm:[rsc,Colocation Constraints] indexterm:[Constraints,Colocation,rsc] |with-rsc |The name of the resource used as the colocation target. The cluster will decide where to put this resource first and then decide where to put +rsc+. indexterm:[with-rsc,Colocation Constraints] indexterm:[Constraints,Colocation,with-rsc] |score |Positive values indicate the resources should run on the same node. Negative values indicate the resources should run on different nodes. Values of \+/- +INFINITY+ change "should" to "must". indexterm:[score,Colocation Constraints] indexterm:[Constraints,Colocation,score] |========================================================= === Mandatory Placement === Mandatory placement occurs when the constraint's score is ++INFINITY+ or +-INFINITY+. In such cases, if the constraint can't be satisfied, then the +rsc+ resource is not permitted to run. For +score=INFINITY+, this includes cases where the +with-rsc+ resource is not active. If you need resource +A+ to always run on the same machine as resource +B+, you would add the following constraint: .Mandatory colocation constraint for two resources ==== [source,XML] ==== Remember, because +INFINITY+ was used, if +B+ can't run on any of the cluster nodes (for whatever reason) then +A+ will not be allowed to run. Whether +A+ is running or not has no effect on +B+. Alternatively, you may want the opposite -- that +A+ 'cannot' run on the same machine as +B+. In this case, use +score="-INFINITY"+. .Mandatory anti-colocation constraint for two resources ==== [source,XML] ==== Again, by specifying +-INFINITY+, the constraint is binding. So if the only place left to run is where +B+ already is, then +A+ may not run anywhere. As with +INFINITY+, +B+ can run even if +A+ is stopped. However, in this case +A+ also can run if +B+ is stopped, because it still meets the constraint of +A+ and +B+ not running on the same node. === Advisory Placement === If mandatory placement is about "must" and "must not", then advisory placement is the "I'd prefer if" alternative. For constraints with scores greater than +-INFINITY+ and less than +INFINITY+, the cluster will try to accommodate your wishes but may ignore them if the alternative is to stop some of the cluster resources. As in life, where if enough people prefer something it effectively becomes mandatory, advisory colocation constraints can combine with other elements of the configuration to behave as if they were mandatory. .Advisory colocation constraint for two resources ==== [source,XML] ==== [[s-resource-sets-ordering]] == Ordering Sets of Resources == A common situation is for an administrator to create a chain of ordered resources, such as: .A chain of ordered resources ====== [source,XML] ------- ------- ====== .Visual representation of the four resources' start order for the above constraints image::images/resource-set.png["Ordered set",width="16cm",height="2.5cm",align="center"] === Ordered Set === To simplify this situation, there is an alternate format for ordering constraints: .A chain of ordered resources expressed as a set ====== [source,XML] ------- ------- ====== [WARNING] ========= Always pay attention to how your tools expose this functionality. In some tools +create set A B+ is *NOT* equivalent to +create A then B+. ========= While the set-based format is not less verbose, it is significantly easier to get right and maintain. It can also be expanded to allow ordered sets of (un)ordered resources. In the example below, +A+ and +B+ can both start in parallel, as can +C+ and +D+, however +C+ and +D+ can only start once _both_ +A+ _and_ +B+ are active. .Ordered sets of unordered resources ====== [source,XML] ------- ------- ====== .Visual representation of the start order for two ordered sets of unordered resources image::images/two-sets.png["Two ordered sets",width="13cm",height="7.5cm",align="center"] Of course either set -- or both sets -- of resources can also be internally ordered (by setting +sequential="true"+) and there is no limit to the number of sets that can be specified. .Advanced use of set ordering - Three ordered sets, two of which are internally unordered ====== [source,XML] ------- ------- ====== .Visual representation of the start order for the three sets defined above image::images/three-sets.png["Three ordered sets",width="16cm",height="7.5cm",align="center"] === Resource Set OR Logic === The unordered set logic discussed so far has all been "AND" logic. To illustrate this take the 3 resource set figure in the previous section. Those sets can be expressed, +(A and B) then \(C) then (D) then (E and F)+. Say for example we want to change the first set, +(A and B)+, to use "OR" logic so the sets look like this: +(A or B) then \(C) then (D) then (E and F)+. This functionality can be achieved through the use of the +require-all+ option. This option defaults to TRUE which is why the "AND" logic is used by default. Setting +require-all=false+ means only one resource in the set needs to be started before continuing on to the next set. Note that the +require-all=false+ option only makes sense to use in conjunction with unordered sets, +sequential=false+. Think of it like this, +sequential=false+ modifies the set to be an unordered set that uses "AND" logic by default, by adding +require-all=false+ the unordered set's "AND" logic is flipped to "OR" logic. .Resource Set "OR" logic: Three ordered sets, where the first set is internally unordered with "OR" logic ====== [source,XML] ------- ------- ====== [[s-resource-sets-colocation]] == Colocating Sets of Resources == Another common situation is for an administrator to create a set of colocated resources. One way to do this would be to define a resource group (see <>), but that cannot always accurately express the desired state. Another way would be to define each relationship as an individual constraint, but that causes a constraint explosion as the number of resources and combinations grow. An example of this approach: .Chain of colocated resources ====== [source,XML] ------- ------- ====== To make things easier, we allow an alternate form of colocation constraints using +resource_set+. As with the chained version, a resource that can't be active prevents any resource that must be colocated with it from being active. For example, if +C+ is not able to run, then both +B+ and by inference +A+ must also remain stopped. Here is an example +resource_set+: .Equivalent colocation chain expressed using +resource_set+ ====== [source,XML] ------- ------- ====== [WARNING] ========= Always pay attention to how your tools expose this functionality. In some tools +create set A B+ is 'not' equivalent to +create A with B+. ========= This notation can also be used to tell the cluster that a set of resources must all be located with a common peer, but have no dependencies on each other. In this scenario, unlike the previous, +B+ 'would' be allowed to remain active even if +A+ or +C+ (or both) were inactive. .Using colocation sets to specify a common peer ====== [source,XML] ------- ------- ====== There is no inherent limit to the number and size of the sets used. The only thing that matters is that in order for any member of one set in the constraint to be active, all members of sets listed after it must also be active (and naturally on the same node); and if a set has +sequential="true"+, then in order for one member of that set to be active, all members listed after it must also be active. You can even specify the role in which the members of a set must be in using the set's +role+ attribute. .A colocation chain where the members of the middle set have no interdependencies and the last has master status. ====== [source,XML] ------- ------- ====== .Visual representation of a colocation chain where the members of the middle set have no inter-dependencies image::images/three-sets-complex.png["Colocation chain",width="16cm",height="9cm",align="center"] diff --git a/doc/Pacemaker_Explained/en-US/Ch-Options.txt b/doc/Pacemaker_Explained/en-US/Ch-Options.txt index f8bca12d0a..d7afb61e47 100644 --- a/doc/Pacemaker_Explained/en-US/Ch-Options.txt +++ b/doc/Pacemaker_Explained/en-US/Ch-Options.txt @@ -1,398 +1,399 @@ = Cluster-Wide Configuration = == CIB Properties == Certain settings are defined by CIB properties (that is, attributes of the +cib+ tag) rather than with the rest of the cluster configuration in the +configuration+ section. The reason is simply a matter of parsing. These options are used by the configuration database which is, by design, mostly ignorant of the content it holds. So the decision was made to place them in an easy-to-find location. .CIB Properties [width="95%",cols="2m,5<",options="header",align="center"] |========================================================= |Field |Description | admin_epoch | indexterm:[Configuration Version,Cluster] indexterm:[Cluster,Option,Configuration Version] indexterm:[admin_epoch,Cluster Option] indexterm:[Cluster,Option,admin_epoch] When a node joins the cluster, the cluster performs a check to see which node has the best configuration. It asks the node with the highest (+admin_epoch+, +epoch+, +num_updates+) tuple to replace the configuration on all the nodes -- which makes setting them, and setting them correctly, very important. +admin_epoch+ is never modified by the cluster; you can use this to make the configurations on any inactive nodes obsolete. _Never set this value to zero_. In such cases, the cluster cannot tell the difference between your configuration and the "empty" one used when nothing is found on disk. | epoch | indexterm:[epoch,Cluster Option] indexterm:[Cluster,Option,epoch] The cluster increments this every time the configuration is updated (usually by the administrator). | num_updates | indexterm:[num_updates,Cluster Option] indexterm:[Cluster,Option,num_updates] The cluster increments this every time the configuration or status is updated (usually by the cluster) and resets it to 0 when epoch changes. | validate-with | indexterm:[validate-with,Cluster Option] indexterm:[Cluster,Option,validate-with] Determines the type of XML validation that will be done on the configuration. If set to +none+, the cluster will not verify that updates conform to the DTD (nor reject ones that don't). This option can be useful when operating a mixed-version cluster during an upgrade. |cib-last-written | indexterm:[cib-last-written,Cluster Property] indexterm:[Cluster,Property,cib-last-written] Indicates when the configuration was last written to disk. Maintained by the cluster; for informational purposes only. |have-quorum | indexterm:[have-quorum,Cluster Property] indexterm:[Cluster,Property,have-quorum] Indicates if the cluster has quorum. If false, this may mean that the cluster cannot start resources or fence other nodes (see +no-quorum-policy+ below). Maintained by the cluster. |dc-uuid | indexterm:[dc-uuid,Cluster Property] indexterm:[Cluster,Property,dc-uuid] Indicates which cluster node is the current leader. Used by the cluster when placing resources and determining the order of some events. Maintained by the cluster. |========================================================= === Working with CIB Properties === Although these fields can be written to by the user, in most cases the cluster will overwrite any values specified by the user with the "correct" ones. To change the ones that can be specified by the user, for example +admin_epoch+, one should use: ---- # cibadmin --modify --crm_xml '' ---- A complete set of CIB properties will look something like this: .Attributes set for a cib object ====== [source,XML] ------- ------- ====== == Cluster Options == Cluster options, as you might expect, control how the cluster behaves when confronted with certain situations. They are grouped into sets within the +crm_config+ section, and, in advanced configurations, there may be more than one set. (This will be described later in the section on <> where we will show how to have the cluster use different sets of options during working hours than during weekends.) For now, we will describe the simple case where each option is present at most once. You can obtain an up-to-date list of cluster options, including their default values, by running the `man pengine` and `man crmd` commands. .Cluster Options [width="95%",cols="5m,2,11>). +Should a failure to start a resource on a particular node prevent further start +attempts on that node? If FALSE, the cluster will decide whether to try +starting on the same node again based on the resource's current failure count +and +migration-threshold+ (see <>). | enable-startup-probes | TRUE | indexterm:[enable-startup-probes,Cluster Option] indexterm:[Cluster,Option,enable-startup-probes] Should the cluster check for active resources during startup? | maintenance-mode | FALSE | indexterm:[maintenance-mode,Cluster Option] indexterm:[Cluster,Option,maintenance-mode] Should the cluster refrain from monitoring, starting and stopping resources? | stonith-enabled | TRUE | indexterm:[stonith-enabled,Cluster Option] indexterm:[Cluster,Option,stonith-enabled] Should failed nodes and nodes with resources that can't be stopped be shot? If you value your data, set up a STONITH device and enable this. If true, or unset, the cluster will refuse to start resources unless one or more STONITH resources have been configured. | stonith-action | reboot | indexterm:[stonith-action,Cluster Option] indexterm:[Cluster,Option,stonith-action] Action to send to STONITH device. Allowed values are +reboot+ and +off+. The value +poweroff+ is also allowed, but is only used for legacy devices. | stonith-timeout | 60s | indexterm:[stonith-timeout,Cluster Option] indexterm:[Cluster,Option,stonith-timeout] How long to wait for STONITH actions (reboot, on, off) to complete | cluster-delay | 60s | indexterm:[cluster-delay,Cluster Option] indexterm:[Cluster,Option,cluster-delay] Estimated maximum round-trip delay over the network (excluding action execution). If the TE requires an action to be executed on another node, it will consider the action failed if it does not get a response from the other node in this time (after considering the action's own timeout). The "correct" value will depend on the speed and load of your network and cluster nodes. | dc-deadtime | 20s | indexterm:[dc-deadtime,Cluster Option] indexterm:[Cluster,Option,dc-deadtime] How long to wait for a response from other nodes during startup. The "correct" value will depend on the speed/load of your network and the type of switches used. | cluster-recheck-interval | 15min | indexterm:[cluster-recheck-interval,Cluster Option] indexterm:[Cluster,Option,cluster-recheck-interval] Polling interval for time-based changes to options, resource parameters and constraints. The Cluster is primarily event-driven, but your configuration can have elements that take effect based on the time of day. To ensure these changes take effect, we can optionally poll the cluster's status for changes. A value of 0 disables polling. Positive values are an interval (in seconds unless other SI units are specified, e.g. 5min). | pe-error-series-max | -1 | indexterm:[pe-error-series-max,Cluster Option] indexterm:[Cluster,Option,pe-error-series-max] The number of PE inputs resulting in ERRORs to save. Used when reporting problems. A value of -1 means unlimited (report all). | pe-warn-series-max | -1 | indexterm:[pe-warn-series-max,Cluster Option] indexterm:[Cluster,Option,pe-warn-series-max] The number of PE inputs resulting in WARNINGs to save. Used when reporting problems. A value of -1 means unlimited (report all). | pe-input-series-max | -1 | indexterm:[pe-input-series-max,Cluster Option] indexterm:[Cluster,Option,pe-input-series-max] The number of "normal" PE inputs to save. Used when reporting problems. A value of -1 means unlimited (report all). | remove-after-stop | FALSE | indexterm:[remove-after-stop,Cluster Option] indexterm:[Cluster,Option,remove-after-stop] _Advanced Use Only:_ Should the cluster remove resources from the LRM after they are stopped? Values other than the default are, at best, poorly tested and potentially dangerous. | startup-fencing | TRUE | indexterm:[startup-fencing,Cluster Option] indexterm:[Cluster,Option,startup-fencing] _Advanced Use Only:_ Should the cluster shoot unseen nodes? Not using the default is very unsafe! | election-timeout | 2min | indexterm:[election-timeout,Cluster Option] indexterm:[Cluster,Option,election-timeout] _Advanced Use Only:_ If you need to adjust this value, it probably indicates the presence of a bug. | shutdown-escalation | 20min | indexterm:[shutdown-escalation,Cluster Option] indexterm:[Cluster,Option,shutdown-escalation] _Advanced Use Only:_ If you need to adjust this value, it probably indicates the presence of a bug. | crmd-integration-timeout | 3min | indexterm:[crmd-integration-timeout,Cluster Option] indexterm:[Cluster,Option,crmd-integration-timeout] _Advanced Use Only:_ If you need to adjust this value, it probably indicates the presence of a bug. | crmd-finalization-timeout | 30min | indexterm:[crmd-finalization-timeout,Cluster Option] indexterm:[Cluster,Option,crmd-finalization-timeout] _Advanced Use Only:_ If you need to adjust this value, it probably indicates the presence of a bug. | crmd-transition-delay | 0s | indexterm:[crmd-transition-delay,Cluster Option] indexterm:[Cluster,Option,crmd-transition-delay] _Advanced Use Only:_ Delay cluster recovery for the configured interval to allow for additional/related events to occur. Useful if your configuration is sensitive to the order in which ping updates arrive. Enabling this option will slow down cluster recovery under all conditions. |default-resource-stickiness | 0 | indexterm:[default-resource-stickiness,Cluster Option] indexterm:[Cluster,Option,default-resource-stickiness] _Deprecated:_ See <> instead | is-managed-default | TRUE | indexterm:[is-managed-default,Cluster Option] indexterm:[Cluster,Option,is-managed-default] _Deprecated:_ See <> instead | default-action-timeout | 20s | indexterm:[default-action-timeout,Cluster Option] indexterm:[Cluster,Option,default-action-timeout] _Deprecated:_ See <> instead |========================================================= === Querying and Setting Cluster Options === indexterm:[Querying,Cluster Option] indexterm:[Setting,Cluster Option] indexterm:[Cluster,Querying Options] indexterm:[Cluster,Setting Options] Cluster options can be queried and modified using the `crm_attribute` tool. To get the current value of +cluster-delay+, you can run: ---- # crm_attribute --query --name cluster-delay ---- which is more simply written as ---- # crm_attribute -G -n cluster-delay ---- If a value is found, you'll see a result like this: ---- # crm_attribute -G -n cluster-delay scope=crm_config name=cluster-delay value=60s ---- If no value is found, the tool will display an error: ---- # crm_attribute -G -n clusta-deway scope=crm_config name=clusta-deway value=(null) Error performing operation: No such device or address ---- To use a different value (for example, 30 seconds), simply run: ---- # crm_attribute --name cluster-delay --update 30s ---- To go back to the cluster's default value, you can delete the value, for example: ---- # crm_attribute --name cluster-delay --delete Deleted crm_config option: id=cib-bootstrap-options-cluster-delay name=cluster-delay ---- === When Options are Listed More Than Once === If you ever see something like the following, it means that the option you're modifying is present more than once. .Deleting an option that is listed twice ======= ------ # crm_attribute --name batch-limit --delete Multiple attributes match name=batch-limit in crm_config: Value: 50 (set=cib-bootstrap-options, id=cib-bootstrap-options-batch-limit) Value: 100 (set=custom, id=custom-batch-limit) Please choose from one of the matches above and supply the 'id' with --id ------- ======= In such cases, follow the on-screen instructions to perform the requested action. To determine which value is currently being used by the cluster, refer to <>.