Clusters from Scratch

diff --git a/doc/Clusters_from_Scratch/en-US/Book_Info.xml b/doc/Clusters_from_Scratch/en-US/Book_Info.xml index 4eb6943f70..d0d556712d 100644 --- a/doc/Clusters_from_Scratch/en-US/Book_Info.xml +++ b/doc/Clusters_from_Scratch/en-US/Book_Info.xml @@ -1,67 +1,67 @@ %BOOK_ENTITIES; ]> Clusters from Scratch - Creating Active/Passive and Active/Active Clusters on Fedora + Step-by-Step Instructions for Building Your First High-Availability Cluster Pacemaker 1.1 8 1 The purpose of this document is to provide a start-to-finish guide to building an example active/passive cluster with Pacemaker and show how it can be converted to an active/active one. The example cluster will use: &DISTRO; &DISTRO_VERSION; as the host operating system Corosync to provide messaging and membership services, Pacemaker to perform resource management, DRBD as a cost-effective alternative to shared storage, GFS2 as the cluster filesystem (in active/active mode) - Given the graphical nature of the Fedora install process, a number of screenshots are included. However the guide is primarily composed of commands, the reasons for executing them and their expected outputs. + Given the graphical nature of the install process, a number of screenshots are included. However the guide is primarily composed of commands, the reasons for executing them and their expected outputs. diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Active-Passive.txt b/doc/Clusters_from_Scratch/en-US/Ch-Active-Passive.txt index eae49ea616..9e82bd8184 100644 --- a/doc/Clusters_from_Scratch/en-US/Ch-Active-Passive.txt +++ b/doc/Clusters_from_Scratch/en-US/Ch-Active-Passive.txt @@ -1,425 +1,425 @@ = Create an Active/Passive Cluster = == Explore the Existing Configuration == When Pacemaker starts up, it automatically records the number and details of the nodes in the cluster, as well as which stack is being used and the version of Pacemaker being used. The first few lines of output should look like this: ---- [root@pcmk-1 ~]# pcs status Cluster name: mycluster WARNING: no stonith devices and stonith-enabled is not false Last updated: Tue Dec 16 16:15:29 2014 Last change: Tue Dec 16 15:49:47 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 0 Resources configured Online: [ pcmk-1 pcmk-2 ] ---- For those who are not of afraid of XML, you can see the raw cluster configuration and status by using the `pcs cluster cib` command. .The last XML you'll see in this document ====== ---- [root@pcmk-1 ~]# pcs cluster cib ---- [source,XML] ---- ---- ====== Before we make any changes, it's a good idea to check the validity of the configuration. ---- [root@pcmk-1 ~]# crm_verify -L -V error: unpack_resources: Resource start-up disabled since no STONITH resources have been defined error: unpack_resources: Either configure some or disable STONITH with the stonith-enabled option error: unpack_resources: NOTE: Clusters with shared data need STONITH to ensure data integrity Errors found during check: config not valid ---- As you can see, the tool has found some errors. In order to guarantee the safety of your data, footnote:[If the data is corrupt, there is little point in continuing to make it available] the default for STONITH footnote:[A common node fencing mechanism. Used to ensure data integrity by powering off "bad" nodes] in Pacemaker is *enabled*. However, it also knows when no STONITH configuration has been supplied and reports this as a problem (since the cluster would not be able to make progress if a situation requiring node fencing arose). We will disable this feature for now and configure it later. To disable STONITH, set the *stonith-enabled* cluster option to false: ---- [root@pcmk-1 ~]# pcs property set stonith-enabled=false [root@pcmk-1 ~]# crm_verify -L ---- With the new cluster option set, the configuration is now valid. [WARNING] ========= The use of `stonith-enabled=false` is completely inappropriate for a production cluster. It tells the cluster to simply pretend that failed nodes are safely powered off. Some vendors will refuse to support clusters that have STONITH disabled. We disable STONITH here only to defer the discussion of its configuration, which can differ widely from one installation to the next. See <<_what_is_stonith>> for information on why STONITH is important and details on how to configure it. ========= == Add a Resource == Our first resource will be a unique IP address that the cluster can bring up on either node. Regardless of where any cluster service(s) are running, end users need a consistent address to contact them on. Here, I will choose 192.168.122.120 as the floating address, give it the imaginative name ClusterIP and tell the cluster to check whether it is running every 30 seconds. [WARNING] =========== The chosen address must not already be in use on the network. Do not reuse an IP address one of the nodes already has configured. =========== ---- [root@pcmk-1 ~]# pcs resource create ClusterIP ocf:heartbeat:IPaddr2 \ ip=192.168.122.120 cidr_netmask=32 op monitor interval=30s ---- Another important piece of information here is *ocf:heartbeat:IPaddr2*. This tells Pacemaker three things about the resource you want to add: * The first field (*ocf* in this case) is the standard to which the resource script conforms and where to find it. * The second field (*heartbeat* in this case) is standard-specific; for OCF resources, it tells the cluster which OCF namespace the resource script is in. * The third field (*IPaddr2* in this case) is the name of the resource script. To obtain a list of the available resource standards (the *ocf* part of *ocf:heartbeat:IPaddr2*), run: ---- [root@pcmk-1 ~]# pcs resource standards ocf lsb service systemd stonith ---- To obtain a list of the available OCF resource providers (the *heartbeat* part of *ocf:heartbeat:IPaddr2*), run: ---- [root@pcmk-1 ~]# pcs resource providers heartbeat pacemaker ---- Finally, if you want to see all the resource agents available for a specific OCF provider (the *IPaddr2* part of *ocf:heartbeat:IPaddr2*), run: ---- [root@pcmk-1 ~]# pcs resource agents ocf:heartbeat AoEtarget AudibleAlarm CTDB ClusterMon Delay Dummy . . (skipping lots of resources to save space) . IPaddr2 . . . tomcat varnish vmware zabbixserver ---- Now, verify that the IP resource has been added, and display the cluster's status to see that it is now active: ---- [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Tue Dec 16 17:44:40 2014 Last change: Tue Dec 16 17:44:26 2014 Stack: corosync Current DC: pcmk-1 (1) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 1 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- == Perform a Failover == Since our ultimate goal is high availability, we should test failover of our new resource before moving on. First, find the node on which the IP address is running. ---- [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Tue Dec 16 17:44:40 2014 Last change: Tue Dec 16 17:44:26 2014 Stack: corosync Current DC: pcmk-1 (1) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 1 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 ---- You can see that the status of the *ClusterIP* resource is *Started* on a particular node (in this example, *pcmk-1*). Shut down Pacemaker and Corosync on that machine to trigger a failover. ---- [root@pcmk-1 ~]# pcs cluster stop pcmk-1 Stopping Cluster... ---- [NOTE] ====== A cluster command such as +pcs cluster stop pass:[nodename]+ can be run from any node in the cluster, not just the affected node. ====== Verify that pacemaker and corosync are no longer running: ---- [root@pcmk-1 ~]# pcs status Error: cluster is not currently running on this node ---- Go to the other node, and check the cluster status. ---- [root@pcmk-2 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 10:30:56 2014 Last change: Tue Dec 16 17:44:26 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 1 Resources configured Online: [ pcmk-2 ] OFFLINE: [ pcmk-1 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- Notice that *pcmk-1* is *OFFLINE* for cluster purposes (its *PCSD* is still *Online*, allowing it to receive `pcs` commands, but it is not participating in the cluster). Also notice that *ClusterIP* is now running on pcmk-2 -- failover happened automatically, and no errors are reported. [IMPORTANT] .Quorum ==== If a cluster splits into two (or more) groups of nodes that can no longer communicate with each other (aka. _partitions_), _quorum_ is used to prevent resources from starting on more nodes than desired, which would risk data corruption. A cluster has quorum when more than half of all known nodes are online in the same partition, or for the mathematically inclined, whenever the following equation is true: .... total_nodes < 2 * active_nodes .... For example, if a 5-node cluster split into 3- and 2-node paritions, the 3-node partition would have quorum and could continue serving resources. If a 6-node cluster split into two 3-node partitions, neither partition would have quorum; pacemaker's default behavior in such cases is to stop all resources, in order to prevent data corruption. Two-node clusters are a special case. By the above definition, a two-node cluster would only have quorum when both nodes are running. This would make the creation of a two-node cluster pointless, footnote:[Some would argue that two-node clusters are always pointless, but that is an argument for another time] but corosync has the ability to treat two-node clusters as if only one node is required for quorum. The `pcs cluster setup` command will automatically configure *two_node: 1* in +corosync.conf+, so a two-node cluster will "just work". If you are using a different cluster shell, you will have to configure +corosync.conf+ appropriately yourself. If you are using older versions of corosync, you will have to ignore quorum at the pacemaker level, using `pcs property set no-quorum-policy=ignore` (or the equivalent command if you are using a different cluster shell). ==== Now, simulate node recovery by restarting the cluster stack on *pcmk-1*, and check the cluster's status. ---- [root@pcmk-1 ~]# pcs cluster start pcmk-1 pcmk-1: Starting Cluster... [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 10:50:11 2014 Last change: Tue Dec 16 17:44:26 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 1 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- [NOTE] ====== With older versions of pacemaker, the cluster might move the IP back to its original location (*pcmk-1*). Usually, this is no longer the case. ====== == Prevent Resources from Moving after Recovery == In most circumstances, it is highly desirable to prevent healthy resources from being moved around the cluster. Moving resources almost always requires a period of downtime. For complex services such as databases, this period can be quite long. To address this, Pacemaker has the concept of resource _stickiness_, which controls how strongly a service prefers to stay running where it is. You may like to think of it as the "cost" of any downtime. By default, Pacemaker assumes there is zero cost associated with moving resources and will do so to achieve "optimal" footnote:[Pacemaker's definition of optimal may not always agree with that of a human's. The order in which Pacemaker processes lists of resources and nodes creates implicit preferences in situations where the administrator has not explicitly specified them.] resource placement. We can specify a different stickiness for every resource, but it is often sufficient to change the default. ---- [root@pcmk-1 ~]# pcs resource defaults resource-stickiness=100 [root@pcmk-1 ~]# pcs resource defaults resource-stickiness: 100 ---- [NOTE] ====== -Earlier versions of pcs, such as the one shipped with Fedora 20, -require that `rsc` be added after `resource` in the above commands. +Older versions of `pcs` required that `rsc` be added after `resource` in the +above commands. ====== diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Apache.txt b/doc/Clusters_from_Scratch/en-US/Ch-Apache.txt index cbb1669bdc..567b7f4ff5 100644 --- a/doc/Clusters_from_Scratch/en-US/Ch-Apache.txt +++ b/doc/Clusters_from_Scratch/en-US/Ch-Apache.txt @@ -1,429 +1,428 @@ = Add Apache as a Cluster Service = Now that we have a basic but functional active/passive two-node cluster, we're ready to add some real services. We're going to start with Apache because it is a feature of many clusters and relatively simple to configure. == Install Apache == Before continuing, we need to make sure Apache is installed on both hosts. We also need the wget tool in order for the cluster to be able to check the status of the Apache server. ---- # yum install -y httpd wget ---- [IMPORTANT] ==== Do *not* enable the httpd service. Services that are intended to be managed via the cluster software should never be managed by the OS. It is often useful, however, to manually start the service, verify that it works, then stop it again, before adding it to the cluster. This allows you to resolve any non-cluster-related problems before continuing. Since this is a simple example, we'll skip that step here. ==== == Create Website Documents == -We need to create a page for Apache to serve. On Fedora, the +We need to create a page for Apache to serve. On &DISTRO; &DISTRO_VERSION;, the default Apache document root is /var/www/html, so we'll create an index file there. For the moment, we will simplify things by serving a static site and manually synchronizing the data between the two nodes, so run this command on both nodes: ----- # cat <<-END >/var/www/html/index.html My Test Site - $(hostname) END ----- == Enable the Apache status URL == In order to monitor the health of your Apache instance, and recover it if it fails, the resource agent used by Pacemaker assumes the server-status URL is available. On both nodes, enable the URL with: ---- # cat <<-END >/etc/httpd/conf.d/status.conf SetHandler server-status Order deny,allow Deny from all Allow from 127.0.0.1 END ---- [NOTE] ====== -If you are using a different operating system or an earlier version of Fedora, -server-status may already be enabled or may be configurable in a different -location. +If you are using a different operating system, server-status may already be +enabled or may be configurable in a different location. ====== == Configure the Cluster == At this point, Apache is ready to go, and all that needs to be done is to add it to the cluster. Let's call the resource WebSite. We need to use an OCF resource script called apache in the heartbeat namespace. footnote:[Compare the key used here, *ocf:heartbeat:apache*, with the one we used earlier for the IP address, *ocf:heartbeat:IPaddr2*] The script's only required parameter is the path to the main Apache configuration file, and we'll tell the cluster to check once a minute that Apache is still running. ---- [root@pcmk-1 ~]# pcs resource create WebSite ocf:heartbeat:apache \ configfile=/etc/httpd/conf/httpd.conf \ statusurl="http://localhost/server-status" \ op monitor interval=1min ---- By default, the operation timeout for all resources' start, stop, and monitor operations is 20 seconds. In many cases, this timeout period is less than a particular resource's advised timeout period. For the purposes of this tutorial, we will adjust the global operation timeout default to 240 seconds. ---- [root@pcmk-1 ~]# pcs resource op defaults timeout=240s [root@pcmk-1 ~]# pcs resource op defaults timeout: 240s ---- [NOTE] ====== In a production cluster, it is usually better to adjust each resource's start, stop, and monitor timeouts to values that are appropriate to the behavior observed in your environment, rather than adjust the global default. ====== After a short delay, we should see the cluster start Apache. ----- [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 12:40:41 2014 Last change: Wed Dec 17 12:40:05 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 2 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 WebSite (ocf::heartbeat:apache): Started pcmk-1 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ----- Wait a moment, the WebSite resource isn't running on the same host as our IP address! [NOTE] ====== If, in the `pcs status` output, you see the WebSite resource has failed to start, then you've likely not enabled the status URL correctly. You can check whether this is the problem by running: .... wget -O - http://127.0.0.1/server-status .... If you see *Connection refused* in the output, then this is likely the problem. Ensure that *Allow from 127.0.0.1* is present for the ** block. ====== == Ensure Resources Run on the Same Host == To reduce the load on any one machine, Pacemaker will generally try to spread the configured resources across the cluster nodes. However, we can tell the cluster that two resources are related and need to run on the same host (or not at all). Here, we instruct the cluster that WebSite can only run on the host that ClusterIP is active on. To achieve this, we use a _colocation constraint_ that indicates it is mandatory for WebSite to run on the same node as ClusterIP. The "mandatory" part of the colocation constraint is indicated by using a score of INFINITY. The INFINITY score also means that if ClusterIP is not active anywhere, WebSite will not be permitted to run. [NOTE] ======= If ClusterIP is not active anywhere, WebSite will not be permitted to run anywhere. ======= [IMPORTANT] =========== Colocation constraints are "directional", in that they imply certain things about the order in which the two resources will have a location chosen. In this case, we're saying that *WebSite* needs to be placed on the same machine as *ClusterIP*, which implies that the cluster must know the location of *ClusterIP* before choosing a location for *WebSite*. =========== ----- [root@pcmk-1 ~]# pcs constraint colocation add WebSite with ClusterIP INFINITY [root@pcmk-1 ~]# pcs constraint Location Constraints: Ordering Constraints: Colocation Constraints: WebSite with ClusterIP (score:INFINITY) [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 13:57:58 2014 Last change: Wed Dec 17 13:57:22 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 2 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 WebSite (ocf::heartbeat:apache): Started pcmk-2 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ----- == Ensure Resources Start and Stop in Order == Like many services, Apache can be configured to bind to specific IP addresses on a host or to the wildcard IP address. If Apache binds to the wildcard, it doesn't matter whether an IP address is added before or after Apache starts; Apache will respond on that IP just the same. However, if Apache binds only to certain IP address(es), the order matters: If the address is added after Apache starts, Apache won't respond on that address. To be sure our WebSite responds regardless of Apache's address configuration, we need to make sure ClusterIP not only runs on the same node, but starts before WebSite. A colocation constraint only ensures the resources run together, not the order in which they are started and stopped. We do this by adding an ordering constraint. By default, all order constraints are mandatory, which means that the recovery of ClusterIP will also trigger the recovery of WebSite. ----- [root@pcmk-1 ~]# pcs constraint order ClusterIP then WebSite Adding ClusterIP WebSite (kind: Mandatory) (Options: first-action=start then-action=start) [root@pcmk-1 ~]# pcs constraint Location Constraints: Ordering Constraints: start ClusterIP then start WebSite (kind:Mandatory) Colocation Constraints: WebSite with ClusterIP (score:INFINITY) ----- == Prefer One Node Over Another == Pacemaker does not rely on any sort of hardware symmetry between nodes, so it may well be that one machine is more powerful than the other. In such cases, it makes sense to host the resources on the more powerful node if it is available. To do this, we create a location constraint. In the location constraint below, we are saying the WebSite resource prefers the node pcmk-1 with a score of 50. Here, the score indicates how badly we'd like the resource to run at this location. ----- [root@pcmk-1 ~]# pcs constraint location WebSite prefers pcmk-1=50 [root@pcmk-1 ~]# pcs constraint Location Constraints: Resource: WebSite Enabled on: pcmk-1 (score:50) Ordering Constraints: start ClusterIP then start WebSite (kind:Mandatory) Colocation Constraints: WebSite with ClusterIP (score:INFINITY) [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 14:11:49 2014 Last change: Wed Dec 17 14:11:20 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 2 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 WebSite (ocf::heartbeat:apache): Started pcmk-2 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ----- Wait a minute, the resources are still on pcmk-2! Even though WebSite now prefers to run on pcmk-1, that preference is (intentionally) less than the resource stickiness (how much we preferred not to have unnecessary downtime). To see the current placement scores, you can use a tool called crm_simulate. ---- [root@pcmk-1 ~]# crm_simulate -sL Current cluster status: Online: [ pcmk-1 pcmk-2 ] ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 WebSite (ocf::heartbeat:apache): Started pcmk-2 Allocation scores: native_color: ClusterIP allocation score on pcmk-1: 50 native_color: ClusterIP allocation score on pcmk-2: 200 native_color: WebSite allocation score on pcmk-1: -INFINITY native_color: WebSite allocation score on pcmk-2: 100 Transition Summary: ---- == Move Resources Manually == There are always times when an administrator needs to override the cluster and force resources to move to a specific location. In this example, we will force the WebSite to move to pcmk-1 by updating our previous location constraint with a score of INFINITY. ----- [root@pcmk-1 ~]# pcs constraint location WebSite prefers pcmk-1=INFINITY [root@pcmk-1 ~]# pcs constraint Location Constraints: Resource: WebSite Enabled on: pcmk-1 (score:INFINITY) Ordering Constraints: start ClusterIP then start WebSite (kind:Mandatory) Colocation Constraints: WebSite with ClusterIP (score:INFINITY) [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 14:19:34 2014 Last change: Wed Dec 17 14:18:37 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 2 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 WebSite (ocf::heartbeat:apache): Started pcmk-1 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ----- Once we've finished whatever activity required us to move the resources to pcmk-1 (in our case nothing), we can then allow the cluster to resume normal operation by removing the new constraint. Since we previously configured a default stickiness, the resources will remain on pcmk-1. First, use the `--full` option to get the constraint's ID: ----- [root@pcmk-1 ~]# pcs constraint --full Location Constraints: Resource: WebSite Enabled on: pcmk-1 (score:INFINITY) (id:location-WebSite-pcmk-1-INFINITY) Ordering Constraints: start ClusterIP then start WebSite (kind:Mandatory) (id:order-ClusterIP-WebSite-mandatory) Colocation Constraints: WebSite with ClusterIP (score:INFINITY) (id:colocation-WebSite-ClusterIP-INFINITY) ----- Then remove the desired contraint using its ID: ----- [root@pcmk-1 ~]# pcs constraint remove location-WebSite-pcmk-1-INFINITY [root@pcmk-1 ~]# pcs constraint Location Constraints: Ordering Constraints: start ClusterIP then start WebSite (kind:Mandatory) Colocation Constraints: WebSite with ClusterIP (score:INFINITY) ----- Note that the location constraint is now gone. If we check the cluster status, we can also see that (as expected) the resources are still active on pcmk-1. ----- # pcs status Cluster name: mycluster Last updated: Wed Dec 17 14:25:21 2014 Last change: Wed Dec 17 14:24:29 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 2 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 WebSite (ocf::heartbeat:apache): Started pcmk-1 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ----- diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt b/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt index 1c2303b999..3491f7d543 100644 --- a/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt +++ b/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt @@ -1,527 +1,524 @@ = Installation = -== Install the OS == +== Install &DISTRO; &DISTRO_VERSION; == Detailed instructions for installing Fedora are available at http://docs.fedoraproject.org/en-US/Fedora/21/html/Installation_Guide/ in a number of languages. The abbreviated version is as follows: Point your browser to https://getfedora.org/, choose a flavor (Server is an appropriate choice), and download the installation image appropriate to your hardware. Burn the installation image to a DVD or USB drive footnote:[http://docs.fedoraproject.org/en-US/Fedora/21/html/Installation_Guide/sect-preparing-boot-media.html] and boot from it, or use the image to boot a virtual machine. After starting the installation, select your language and keyboard layout at the welcome screen. footnote:[http://docs.fedoraproject.org/en-US/Fedora/21/html/Installation_Guide/sect-installation-graphical-mode.html] At this point, you get a chance to tweak the default installation options. In the *NETWORK & HOSTNAME* section you'll want to: - Assign your machine a host name. I happen to control the clusterlabs.org domain name, so I will use pcmk-1.clusterlabs.org here. - Assign a fixed IPv4 address. In this example, I'll use 192.168.122.101. [IMPORTANT] =========== Do not accept the default network settings. Cluster machines should never obtain an IP address via DHCP, because DHCP's periodic address renewal will interfere with corosync. If you miss this step during installation, it can easily be fixed later. You will have to navigate to *system settings* and select *network*. From there, you can select what device to configure. =========== In the *Software Selection* section (try saying that 10 times quickly), leave all *Add-Ons* unchecked so that we see everything that gets installed. We'll install any extra software we need later. [IMPORTANT] =========== By default Fedora uses LVM for partitioning which allows us to dynamically change the amount of space allocated to a given partition. However, by default it also allocates all free space to the +/+ (aka. *root*) partition, which cannot be dynamically _reduced_ in size (dynamic increases are fine, by the way). So if you plan on following the DRBD or GFS2 portions of this guide, you should reserve at least 1GiB of space on each machine from which to create a shared volume. To do so, enter the *Installation Destination* section where you are be given an opportunity to reduce the size of the *root* partition (after choosing which hard drive you wish to install to). If you want the reserved space to be available within an LVM volume group, be sure to select *Modify...* next to the volume group name and change the *Size policy:* to *Fixed* or *As large as possible*. =========== It is highly recommended to enable NTP on your cluster nodes. Doing so ensures all nodes agree on the current time and makes reading log files significantly easier. You can do this in the *DATE & TIME* section. footnote:[http://docs.fedoraproject.org/en-US/Fedora/21/html/Installation_Guide/sect-installation-gui-date-and-time.html] Once you've completed the installation, set a root password as instructed. For the purposes of this document, it is not necessary to create any additional users. After the node reboots, you'll see a (possibly mangled) login prompt on the console. Login using *root* and the password you created earlier. image::images/Console.png["Initial Console",align="center",scaledwidth="65%"] [NOTE] ====== From here on, we're going to be working exclusively from the terminal. ====== == Configure the OS == === Verify Networking === Ensure that the machine has the static IP address you configured earlier. ----- [root@pcmk-1 ~]# ip addr 1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 52:54:00:d7:d6:08 brd ff:ff:ff:ff:ff:ff inet 192.168.122.101/24 brd 192.168.122.255 scope global eth0 valid_lft forever preferred_lft forever inet6 fe80::5054:ff:fed7:d608/64 scope link valid_lft forever preferred_lft forever ----- [NOTE] ===== If you ever need to change the node's IP address from the command line, follow these instructions: .... [root@pcmk-1 ~]# vim /etc/sysconfig/network-scripts/ifcfg-${device} # manually edit as desired [root@pcmk-1 ~]# nmcli dev disconnect ${device} [root@pcmk-1 ~]# nmcli con reload ${device} [root@pcmk-1 ~]# nmcli con up ${device} .... This makes *NetworkManager* aware that a change was made on the config file. ===== Next, ensure that the routes are as expected: ----- [root@pcmk-1 ~]# ip route default via 192.168.122.1 dev eth0 proto static metric 1024 192.168.122.0/24 dev eth0 proto kernel scope link src 192.168.122.101 ----- If there is no line beginning with *default via*, then you may need to add a line such as [source,Bash] GATEWAY=192.168.122.1 to +/etc/sysconfig/network+ and restart the network. Now, check for connectivity to the outside world. Start small by testing whether we can reach the gateway we configured. ----- [root@pcmk-1 ~]# ping -c 1 192.168.122.1 PING 192.168.122.1 (192.168.122.1) 56(84) bytes of data. 64 bytes from 192.168.122.1: icmp_req=1 ttl=64 time=0.249 ms --- 192.168.122.1 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.249/0.249/0.249/0.000 ms ----- Now try something external; choose a location you know should be available. ----- [root@pcmk-1 ~]# ping -c 1 www.google.com PING www.l.google.com (173.194.72.106) 56(84) bytes of data. 64 bytes from tf-in-f106.1e100.net (173.194.72.106): icmp_req=1 ttl=41 time=167 ms --- www.l.google.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 167.618/167.618/167.618/0.000 ms ----- === Login Remotely === The console isn't a very friendly place to work from, so we will now switch to accessing the machine remotely via SSH where we can use copy and paste, etc. From another host, check whether we can see the new host at all: ----- beekhof@f16 ~ # ping -c 1 192.168.122.101 PING 192.168.122.101 (192.168.122.101) 56(84) bytes of data. 64 bytes from 192.168.122.101: icmp_req=1 ttl=64 time=1.01 ms --- 192.168.122.101 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 1.012/1.012/1.012/0.000 ms ----- Next, login as root via SSH. ----- beekhof@f16 ~ # ssh -l root 192.168.122.11 root@192.168.122.11's password: Last login: Fri Mar 30 19:41:19 2012 from 192.168.122.1 [root@pcmk-1 ~]# ----- === Apply Updates === Apply any package updates released since your installation image was created: ---- [root@pcmk-1 ~]# yum update ---- === Disable Security During Testing === To simplify this guide and focus on the aspects directly connected to clustering, we will now disable the machine's firewall and SELinux installation. [WARNING] =========== These actions create significant security issues and should not be performed on machines that will be exposed to the outside world. =========== //// TODO: Create an Appendix that deals with (at least) re-enabling the firewall. //// ---- [root@pcmk-1 ~]# setenforce 0 [root@pcmk-1 ~]# sed -i.bak "s/SELINUX=enforcing/SELINUX=permissive/g" /etc/selinux/config [root@pcmk-1 ~]# systemctl disable firewalld.service [root@pcmk-1 ~]# systemctl stop firewalld.service [root@pcmk-1 ~]# iptables --flush ---- [NOTE] =========== If you are using Fedora 17 or earlier or are using the iptables service for your firewall, the commands would be: ---- [root@pcmk-1 ~]# setenforce 0 [root@pcmk-1 ~]# sed -i.bak "s/SELINUX=enforcing/SELINUX=permissive/g" /etc/selinux/config [root@pcmk-1 ~]# systemctl disable iptables.service [root@pcmk-1 ~]# rm -f /etc/systemd/system/basic.target.wants/iptables.service [root@pcmk-1 ~]# systemctl stop iptables.service [root@pcmk-1 ~]# iptables --flush ---- =========== === Use Short Node Names === During installation, we filled in the machine's fully qualified domain name (FQDN), which can be rather long when it appears in cluster logs and status output. See for yourself how the machine identifies itself: (((Nodes, short name))) ---- [root@pcmk-1 ~]# uname -n pcmk-1.clusterlabs.org [root@pcmk-1 ~]# dnsdomainname clusterlabs.org ---- (((Nodes, Domain name (Query)))) The output from the second command is fine, but we really don't need the domain name included in the basic host details. To address this, we need to use the `hostnamectl` tool to strip off the domain name. ---- [root@pcmk-1 ~]# hostnamectl set-hostname $(uname -n | sed s/\\..*//) ---- (((Nodes, Domain name (Remove from host name)))) Now check the machine is using the correct names ---- [root@pcmk-1 ~]# uname -n pcmk-1 [root@pcmk-1 ~]# dnsdomainname clusterlabs.org ---- If it concerns you that the shell prompt has not been updated, simply log out and back in again. == Repeat for Second Node == -Repeat the Installation steps so far, so that you have two Fedora +Repeat the Installation steps so far, so that you have two nodes ready to have the cluster software installed. For the purposes of this document, the additional node is called pcmk-2 with address 192.168.122.102. == Configure Communication Between Nodes == === Configure Host Name Resolution === Confirm that you can communicate between the two new nodes: ---- [root@pcmk-1 ~]# ping -c 3 192.168.122.102 PING 192.168.122.102 (192.168.122.102) 56(84) bytes of data. 64 bytes from 192.168.122.102: icmp_seq=1 ttl=64 time=0.343 ms 64 bytes from 192.168.122.102: icmp_seq=2 ttl=64 time=0.402 ms 64 bytes from 192.168.122.102: icmp_seq=3 ttl=64 time=0.558 ms --- 192.168.122.102 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2000ms rtt min/avg/max/mdev = 0.343/0.434/0.558/0.092 ms ---- Now we need to make sure we can communicate with the machines by their name. If you have a DNS server, add additional entries for the two machines. Otherwise, you'll need to add the machines to +/etc/hosts+ on both nodes. Below are the entries for my cluster nodes: ---- [root@pcmk-1 ~]# grep pcmk /etc/hosts 192.168.122.101 pcmk-1.clusterlabs.org pcmk-1 192.168.122.102 pcmk-2.clusterlabs.org pcmk-2 ---- We can now verify the setup by again using ping: ---- [root@pcmk-1 ~]# ping -c 3 pcmk-2 PING pcmk-2.clusterlabs.org (192.168.122.101) 56(84) bytes of data. 64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=1 ttl=64 time=0.164 ms 64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=2 ttl=64 time=0.475 ms 64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=3 ttl=64 time=0.186 ms --- pcmk-2.clusterlabs.org ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2001ms rtt min/avg/max/mdev = 0.164/0.275/0.475/0.141 ms ---- === Configure SSH === SSH is a convenient and secure way to copy files and perform commands remotely. For the purposes of this guide, we will create a key without a password (using the -N option) so that we can perform remote actions without being prompted. (((SSH))) [WARNING] ========= Unprotected SSH keys (those without a password) are not recommended for servers exposed to the outside world. We use them here only to simplify the demo. ========= Create a new key and allow anyone with that key to log in: .Creating and Activating a new SSH Key ---- [root@pcmk-1 ~]# ssh-keygen -t dsa -f ~/.ssh/id_dsa -N "" Generating public/private dsa key pair. Your identification has been saved in /root/.ssh/id_dsa. Your public key has been saved in /root/.ssh/id_dsa.pub. The key fingerprint is: 91:09:5c:82:5a:6a:50:08:4e:b2:0c:62:de:cc:74:44 root@pcmk-1.clusterlabs.org The key's randomart image is: +--[ DSA 1024]----+ |==.ooEo.. | |X O + .o o | | * A + | | + . | | . S | | | | | | | | | +-----------------+ [root@pcmk-1 ~]# cp ~/.ssh/id_dsa.pub ~/.ssh/authorized_keys ---- (((Creating and Activating a new SSH Key))) Install the key on the other node and test that you can now run commands remotely, without being prompted. .Installing the SSH Key on Another Host ---- [root@pcmk-1 ~]# scp -r ~/.ssh pcmk-2: The authenticity of host 'pcmk-2 (192.168.122.102)' can't be established. RSA key fingerprint is b1:2b:55:93:f1:d9:52:2b:0f:f2:8a:4e:ae:c6:7c:9a. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'pcmk-2,192.168.122.102' (RSA) to the list of known hosts.root@pcmk-2's password: id_dsa.pub 100% 616 0.6KB/s 00:00 id_dsa 100% 672 0.7KB/s 00:00 known_hosts 100% 400 0.4KB/s 00:00 authorized_keys 100% 616 0.6KB/s 00:00 [root@pcmk-1 ~]# ssh pcmk-2 -- uname -n pcmk-2 ---- == Install the Cluster Software == -Fedora 17 and later comes with everything you need, so simply fire up a shell -on both nodes and run the following to install pacemaker and command-line -cluster management software: - +Fire up a shell on both nodes and run the following to install pacemaker, and while +we're at it, some command-line tools to make our lives easier: ---- # yum install -y pacemaker pcs psmisc ---- [IMPORTANT] =========== This document will show commands that need to be executed on both nodes with a simple `#` prompt. Be sure to run them on each node individually. =========== [NOTE] =========== This document uses pcs for cluster management. Other alternatives, such as crmsh, are available, but their syntax will differ from the examples used here. =========== == Configure the Cluster Software == === Enable pcs Daemon === Before the cluster can be configured, the pcs daemon must be started and enabled to start at boot time on each node. This daemon works with the pcs command-line interface to manage synchronizing the corosync configuration across all nodes in the cluster. Start and enable the daemon by issuing the following commands on each node: ---- # systemctl start pcsd.service # systemctl enable pcsd.service ---- The installed packages will create a *hacluster* user with a disabled password. While this is fine for running `pcs` commands locally, the account needs a login password in order to perform such tasks as syncing the corosync configuration, or starting and stopping the cluster on other nodes. This tutorial will make use of such commands, so now we will set a password for the *hacluster* user, using the same password on both nodes: ---- # passwd hacluster password: ---- [NOTE] =========== Alternatively, to script this process or set the password on a different machine from the one you're logged into, you can use the `--stdin` option for `passwd`: ---- [root@pcmk-1 ~]# ssh pcmk-2 -- 'echo redhat1 | passwd --stdin hacluster' ---- =========== === Configure Corosync === On either node, use `pcs cluster auth` to authenticate as the *hacluster* user: ---- [root@pcmk-1 ~]# pcs cluster auth pcmk-1 pcmk-2 Username: hacluster Password: pcmk-1: Authorized pcmk-2: Authorized ---- [IMPORTANT] =========== The version of pcs shipped with Fedora 21 will bind only to the host's IPv6 address in some circumstances. If you get errors with `pcs cluster auth`, add this line before the first *server.run* line in +/usr/lib/pcsd/ssl.rb+ to bind to IPv4 only: ---- webrick_options[:BindAddress] = '0.0.0.0' ---- And restart pcsd: ---- [root@pcmk-1 ~]# systemctl restart pcsd ---- This is a temporary workaround that will get removed if the pcsd package is later updated. =========== Next, use `pcs cluster setup` to generate and synchronize the corosync configuration: ---- [root@pcmk-1 ~]# pcs cluster setup --name mycluster pcmk-1 pcmk-2 Shutting down pacemaker/corosync services... Redirecting to /bin/systemctl stop pacemaker.service Redirecting to /bin/systemctl stop corosync.service Killing any remaining services... Removing all cluster configuration files... pcmk-1: Succeeded pcmk-2: Succeeded ---- If you received an authorization error for either of those commands, make sure you configured the *hacluster* user account on each node with the same password. [NOTE] ====== -Early versions of pcs, such as the one shipped with Fedora 20 and earlier, -require that `--name` be omitted from the above command. +Early versions of pcs required that `--name` be omitted from the above command. If using a different cluster shell such as crmsh rather than pcs, you must manually create a corosync.conf and copy it to all nodes. The pcs command will configure corosync to use UDP unicast transport; if you choose to use multicast instead, choose a multicast address carefully. footnote:[For some subtle issues, see the now-defunct http://web.archive.org/web/20101211210054/http://29west.com/docs/THPM/multicast-address-assignment.html or the more detailed treatment in http://www.cisco.com/c/dam/en/us/support/docs/ip/ip-multicast/ipmlt_wp.pdf[Cisco's Guidelines for Enterprise IP Multicast Address Allocation] paper.] ====== The final /etc/corosync.conf configuration on each node should look something like the sample in Appendix B, Sample Corosync Configuration. [NOTE] ====== With versions of Corosync before 2.0, Pacemaker could obtain membership and quorum from a custom Corosync plugin. This plugin also had the capability to start Pacemaker automatically when Corosync was started. Neither behavior is possible with Corosync 2.0 and later, as support for plugins was removed. Because Pacemaker made use of the plugin for message routing, a cluster node using an older Corosync cannot talk to one using Corosync 2.0 or later. Rolling upgrades between these versions are therefore not possible, and an alternate strategy footnote:[http://www.clusterlabs.org/doc/en-US/Pacemaker/1.1/html/Pacemaker_Explained/ap-upgrade.html] must be used. ====== diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt b/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt index b5c87f5ec9..fe47caae42 100644 --- a/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt +++ b/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt @@ -1,509 +1,510 @@ = Replicate Storage Using DRBD = Even if you're serving up static websites, having to manually synchronize the contents of that website to all the machines in the cluster is not ideal. For dynamic websites, such as a wiki, it's not even an option. Not everyone care afford network-attached storage, but somehow the data needs to be kept in sync. Enter DRBD, which can be thought of as network-based RAID-1. footnote:[See http://www.drbd.org/ for details.] == Install the DRBD Packages == DRBD itself is included in the upstream kernel, footnote:[Since version 2.6.33] but we do need some utilities to use it effectively. On both nodes, run: ---- # yum install -y drbd-pacemaker drbd-udev ---- == Allocate a Disk Volume for DRBD == DRBD will need its own block device on each node. This can be a physical disk partition or logical volume, of whatever size you need for your data. For this document, we will use a 1GiB logical volume, which is more than sufficient for a single HTML file and (later) GFS2 metadata. ---- [root@pcmk-1 ~]# vgdisplay | grep -e Name -e Free VG Name fedora-server_pcmk-1 Free PE / Size 511 / 2.00 GiB [root@pcmk-1 ~]# lvcreate --name drbd-demo --size 1G fedora-server_pcmk-1 Logical volume "drbd-demo" created [root@pcmk-1 ~]# lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert drbd-demo fedora-server_pcmk-1 -wi-a----- 1.00g root fedora-server_pcmk-1 -wi-ao---- 5.00g swap fedora-server_pcmk-1 -wi-ao---- 1.00g ---- Repeat this on the second node, making sure to use the same size. ---- [root@pcmk-1 ~]# ssh pcmk-2 -- lvcreate --name drbd-demo --size 1G fedora-server_pcmk-2 Logical volume "drbd-demo" created ---- == Configure DRBD == There is no series of commands for building a DRBD configuration, so simply run this on both nodes to use this sample configuration: ---- # cat </etc/drbd.d/wwwdata.res resource wwwdata { protocol C; meta-disk internal; device /dev/drbd1; syncer { verify-alg sha1; } net { allow-two-primaries; } on pcmk-1 { disk /dev/fedora-server_pcmk-1/drbd-demo; address 192.168.122.101:7789; } on pcmk-2 { disk /dev/fedora-server_pcmk-2/drbd-demo; address 192.168.122.102:7789; } } END ---- [IMPORTANT] ========= Edit the file to use the hostnames, IP addresses and logical volume paths of your nodes if they differ from the ones used in this guide. ========= [NOTE] ======= Detailed information on the directives used in this configuration (and other alternatives) is available at http://www.drbd.org/users-guide/ch-configure.html The *allow-two-primaries* option would not normally be used in an active/passive cluster. We are adding it here for the convenience of changing to an active/active cluster later. ======= == Initialize DRBD == With the configuration in place, we can now get DRBD running. These commands create the local metadata for the DRBD resource, ensure the DRBD kernel module is loaded, and bring up the DRBD resource. Run them on one node: ---- # drbdadm create-md wwwdata initializing activity log NOT initializing bitmap Writing meta data... New drbd meta data block successfully created. # modprobe drbd # drbdadm up wwwdata ---- We can confirm DRBD's status on this node: ---- # cat /proc/drbd version: 8.4.5 (api:1/proto:86-101) srcversion: 153833F4A69E341D3F3E707 1: cs:WFConnection ro:Secondary/Unknown ds:Inconsistent/DUnknown C r----s ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1048508 ---- Because we have not yet initialized the data, this node's data is marked as *Inconsistent*. Because we have not yet initialized the second node, the local state is *WFConnection* (waiting for connection), and the partner node's status is marked as *Unknown*. Now, repeat the above commands on the second node. This time, when we check the status, it shows: ---- # cat /proc/drbd version: 8.4.5 (api:1/proto:86-101) srcversion: 153833F4A69E341D3F3E707 1: cs:Connected ro:Secondary/Secondary ds:Inconsistent/Inconsistent C r----- ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1048508 ---- You can see the state has changed to *Connected*, meaning the two DRBD nodes are communicating properly, and both nodes are in *Secondary* role with *Inconsistent* data. To make the data consistent, we need to tell DRBD which node should be considered to have the correct data. In this case, since we are creating a new resource, both have garbage, so we'll just pick pcmk-1 and run this command on it: ---- [root@pcmk-1 ~]# drbdadm primary --force wwwdata ---- [NOTE] ====== In DRBD 8.3 and earlier, the equivalent command is: ---- [root@pcmk-1 ~]# drbdadm -- --overwrite-data-of-peer primary wwwdata ---- ====== If we check the status immediately, we'll see something like this: ---- [root@pcmk-1 ~]# cat /proc/drbd version: 8.4.5 (api:1/proto:86-101) srcversion: 153833F4A69E341D3F3E707 1: cs:SyncSource ro:Primary/Secondary ds:UpToDate/Inconsistent C r----- ns:2872 nr:0 dw:0 dr:3784 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1045636 [>....................] sync'ed: 0.4% (1045636/1048508)K finish: 0:10:53 speed: 1,436 (1,436) K/sec ---- We can see that this node has the *Primary* role, the partner node has the *Secondary* role, this node's data is now considered *UpToDate*, the partner node's data is still *Inconsistent*, and a progress bar shows how far along the partner node is in synchronizing the data. After a while, the sync should finish, and you'll see something like: ---- [root@pcmk-1 ~]# cat /proc/drbd version: 8.4.5 (api:1/proto:86-101) srcversion: 153833F4A69E341D3F3E707 1: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r----- ns:1048508 nr:0 dw:0 dr:1049420 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0 ---- Both sets of data are now *UpToDate*, and we can proceed to creating and populating a filesystem for our WebSite resource's documents. == Populate the DRBD Disk == On the node with the primary role (pcmk-1 in this example), create a filesystem on the DRBD device: ---- [root@pcmk-1 ~]# mkfs.ext4 /dev/drbd1 mke2fs 1.42.11 (09-Jul-2014) Creating filesystem with 262127 4k blocks and 65536 inodes Filesystem UUID: 26879260-9077-4d6d-ad69-7d31d3d8d8d4 Superblock backups stored on blocks: 32768, 98304, 163840, 229376 Allocating group tables: done Writing inode tables: done Creating journal (4096 blocks): done Writing superblocks and filesystem accounting information: done ---- [NOTE] ==== In this example, we create an ext4 filesystem with no special options. In a production environment, you should choose a filesystem type and options that are suitable for your application. ==== Mount the newly created filesystem, populate it with our web document, then unmount it (the cluster will handle mounting and unmounting it later): ---- [root@pcmk-1 ~]# mount /dev/drbd1 /mnt [root@pcmk-1 ~]# cat <<-END >/mnt/index.html My Test Site - DRBD END [root@pcmk-1 ~]# umount /dev/drbd1 ---- == Configure the Cluster for the DRBD device == One handy feature `pcs` has is the ability to queue up several changes into a file and commit those changes atomically. To do this, start by populating the file with the current raw XML config from the CIB. ---- # pcs cluster cib drbd_cfg ---- Using the `pcs -f` option, make changes to the configuration saved in the +drbd_cfg+ file. These changes will not be seen by the cluster until the +drbd_cfg+ file is pushed into the live cluster's CIB later. Here, we create a cluster resource for the DRBD device, and an additional _clone_ resource to allow the resource to run on both nodes at the same time. ---- [root@pcmk-1 ~]# pcs -f drbd_cfg resource create WebData ocf:linbit:drbd \ drbd_resource=wwwdata op monitor interval=60s [root@pcmk-1 ~]# pcs -f drbd_cfg resource master WebDataClone WebData \ master-max=1 master-node-max=1 clone-max=2 clone-node-max=1 \ notify=true [root@pcmk-1 ~]# pcs -f drbd_cfg resource show ClusterIP (ocf::heartbeat:IPaddr2): Started WebSite (ocf::heartbeat:apache): Started Master/Slave Set: WebDataClone [WebData] Stopped: [ pcmk-1 pcmk-2 ] ---- After you are satisfied with all the changes, you can commit them all at once by pushing the drbd_cfg file into the live CIB. ---- [root@pcmk-1 ~]# pcs cluster cib-push drbd_cfg CIB updated ---- [NOTE] ==== Early versions of `pcs` required `push cib` in place of `cib-push` above. ==== Let's see what the cluster did with the new configuration: ---- [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 16:39:43 2014 Last change: Wed Dec 17 16:39:30 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 4 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 WebSite (ocf::heartbeat:apache): Started pcmk-1 Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-1 ] Slaves: [ pcmk-2 ] PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- We can see that *WebDataClone* (our DRBD device) is running as master (DRBD's primary role) on *pcmk-1* and slave (DRBD's secondary role) on *pcmk-2*. [IMPORTANT] ==== The resource agent should load the DRBD module when needed if it's not already loaded. If that does not happen, configure your operating system to load the -module at boot time. For Fedora 21, you would run this on both nodes: +module at boot time. For &DISTRO; &DISTRO_VERSION;, you would run this on both +nodes: ---- # echo drbd >/etc/modules-load.d/drbd.conf ---- ==== == Configure the Cluster for the Filesystem == Now that we have a working DRBD device, we need to mount its filesystem. In addition to defining the filesystem, we also need to tell the cluster where it can be located (only on the DRBD Primary) and when it is allowed to start (after the Primary was promoted). We are going to take a shortcut when creating the resource this time. Instead of explicitly saying we want the *ocf:heartbeat:Filesystem* script, we are only going to ask for *Filesystem*. We can do this because we know there is only one resource script named *Filesystem* available to pacemaker, and that pcs is smart enough to fill in the *ocf:heartbeat:* portion for us correctly in the configuration. If there were multiple *Filesystem* scripts from different OCF providers, we would need to specify the exact one we wanted. Once again, we will queue our changes to a file and then push the new configuration to the cluster as the final step. ---- [root@pcmk-1 ~]# pcs cluster cib fs_cfg [root@pcmk-1 ~]# pcs -f fs_cfg resource create WebFS Filesystem \ device="/dev/drbd1" directory="/var/www/html" \ fstype="ext4" [root@pcmk-1 ~]# pcs -f fs_cfg constraint colocation add WebFS with WebDataClone INFINITY with-rsc-role=Master [root@pcmk-1 ~]# pcs -f fs_cfg constraint order promote WebDataClone then start WebFS Adding WebDataClone WebFS (kind: Mandatory) (Options: first-action=promote then-action=start) ---- We also need to tell the cluster that Apache needs to run on the same machine as the filesystem and that it must be active before Apache can start. ---- [root@pcmk-1 ~]# pcs -f fs_cfg constraint colocation add WebSite with WebFS INFINITY [root@pcmk-1 ~]# pcs -f fs_cfg constraint order WebFS then WebSite Adding WebFS WebSite (kind: Mandatory) (Options: first-action=start then-action=start) ---- Review the updated configuration. ---- [root@pcmk-1 ~]# pcs -f fs_cfg constraint Location Constraints: Ordering Constraints: start ClusterIP then start WebSite (kind:Mandatory) promote WebDataClone then start WebFS (kind:Mandatory) start WebFS then start WebSite (kind:Mandatory) Colocation Constraints: WebSite with ClusterIP (score:INFINITY) WebFS with WebDataClone (score:INFINITY) (with-rsc-role:Master) WebSite with WebFS (score:INFINITY) [root@pcmk-1 ~]# pcs -f fs_cfg resource show ClusterIP (ocf::heartbeat:IPaddr2): Started WebSite (ocf::heartbeat:apache): Started Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-1 ] Slaves: [ pcmk-2 ] WebFS (ocf::heartbeat:Filesystem): Stopped ---- After reviewing the new configuration, upload it and watch the cluster put it into effect. ---- [root@pcmk-1 ~]# pcs cluster cib-push fs_cfg [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 17:02:45 2014 Last change: Wed Dec 17 17:02:42 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 5 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 WebSite (ocf::heartbeat:apache): Started pcmk-1 Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-1 ] Slaves: [ pcmk-2 ] WebFS (ocf::heartbeat:Filesystem): Started pcmk-1 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- == Test Cluster Failover == Previously, we used `pcs cluster stop pcmk-1` to stop all cluster services on *pcmk-1*, failing over the cluster resources, but there is another way to safely simulate node failure. We can put the node into _standby mode_. Nodes in this state continue to run corosync and pacemaker but are not allowed to run resources. Any resources found active there will be moved elsewhere. This feature can be particularly useful when performing system administration tasks such as updating packages used by cluster resources. Put the active node into standby mode, and observe the cluster move all the resources to the other node. The node's status will change to indicate that it can no longer host resources. ---- [root@pcmk-1 ~]# pcs cluster standby pcmk-1 [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 17:14:05 2014 Last change: Wed Dec 17 17:14:02 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 5 Resources configured Node pcmk-1 (1): standby Online: [ pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 WebSite (ocf::heartbeat:apache): Started pcmk-2 Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-2 ] Stopped: [ pcmk-1 ] WebFS (ocf::heartbeat:Filesystem): Started pcmk-2 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- Once we've done everything we needed to on pcmk-1 (in this case nothing, we just wanted to see the resources move), we can allow the node to be a full cluster member again. ---- [root@pcmk-1 ~]# pcs cluster unstandby pcmk-1 [root@pcmk-1 ~]# pcs status Cluster name: mycluster Last updated: Wed Dec 17 17:15:36 2014 Last change: Wed Dec 17 17:15:33 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 5 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 WebSite (ocf::heartbeat:apache): Started pcmk-2 Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-2 ] Slaves: [ pcmk-1 ] WebFS (ocf::heartbeat:Filesystem): Started pcmk-2 PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- Notice that *pcmk-1* is back to the *Online* state, and that the cluster resources stay where they are due to our resource stickiness settings configured earlier. diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Verification.txt b/doc/Clusters_from_Scratch/en-US/Ch-Verification.txt index 496176388a..7a1505926b 100644 --- a/doc/Clusters_from_Scratch/en-US/Ch-Verification.txt +++ b/doc/Clusters_from_Scratch/en-US/Ch-Verification.txt @@ -1,154 +1,151 @@ = Start and Verify Cluster = == Start the Cluster == Now that corosync is configured, it is time to start the cluster. The command below will start corosync and pacemaker on both nodes in the cluster. If you are issuing the start command from a different node than the one you ran the `pcs cluster auth` command on earlier, you must authenticate on the current node you are logged into before you will be allowed to start the cluster. ---- [root@pcmk-1 ~]# pcs cluster start --all pcmk-1: Starting Cluster... pcmk-2: Starting Cluster... ---- [NOTE] ====== An alternative to using the `pcs cluster start --all` command is to issue either of the below command sequences on each node in the cluster separately: ---- # pcs cluster start Starting Cluster... ---- or ---- # systemctl start corosync.service # systemctl start pacemaker.service ---- ====== [IMPORTANT] ==== In this example, we are not enabling the corosync and pacemaker services to start at boot. If a cluster node fails or is rebooted, you will need to run +pcs cluster start pass:[nodename]+ (or `--all`) to start the cluster on it. While you could enable the services to start at boot, requiring a manual start of cluster services gives you the opportunity to do a post-mortem investigation of a node failure before returning it to the cluster. ==== == Verify Corosync Installation == First, use `corosync-cfgtool` to check whether cluster communication is happy: ---- [root@pcmk-1 ~]# corosync-cfgtool -s Printing ring status. Local node ID 1 RING ID 0 id = 192.168.122.101 status = ring 0 active with no faults ---- We can see here that everything appears normal with our fixed IP address (not a 127.0.0.x loopback address) listed as the *id*, and *no faults* for the status. If you see something different, you might want to start by checking the node's network, firewall and selinux configurations. Next, check the membership and quorum APIs: ---- [root@pcmk-1 ~]# corosync-cmapctl | grep members runtime.totem.pg.mrp.srp.members.1.ip (str) = r(0) ip(192.168.122.101) runtime.totem.pg.mrp.srp.members.1.join_count (u32) = 1 runtime.totem.pg.mrp.srp.members.1.status (str) = joined runtime.totem.pg.mrp.srp.members.2.ip (str) = r(0) ip(192.168.122.102) runtime.totem.pg.mrp.srp.members.2.join_count (u32) = 1 runtime.totem.pg.mrp.srp.members.2.status (str) = joined [root@pcmk-1 ~]# pcs status corosync Membership information -------------------------- Nodeid Votes Name 1 1 pcmk-1 (local) 2 1 pcmk-2 ---- You should see both nodes have joined the cluster. == Verify Pacemaker Installation == Now that we have confirmed that Corosync is functional, we can check the rest of the stack. Pacemaker has already been started, so verify the necessary processes are running: ---- [root@pcmk-1 ~]# ps axf PID TTY STAT TIME COMMAND 2 ? S 0:00 [kthreadd] ...lots of processes... 28019 ? Ssl 0:03 /usr/sbin/corosync 28047 ? Ss 0:00 /usr/sbin/pacemakerd -f 28048 ? Ss 0:00 \_ /usr/libexec/pacemaker/cib 28049 ? Ss 0:00 \_ /usr/libexec/pacemaker/stonithd 28050 ? Ss 0:00 \_ /usr/lib64/heartbeat/lrmd 28051 ? Ss 0:00 \_ /usr/libexec/pacemaker/attrd 28052 ? Ss 0:00 \_ /usr/libexec/pacemaker/pengine 28053 ? Ss 0:00 \_ /usr/libexec/pacemaker/crmd ---- If that looks OK, check the `pcs status` output: ---- [root@pcmk-1 ~]# pcs status Cluster name: mycluster WARNING: no stonith devices and stonith-enabled is not false Last updated: Tue Dec 16 16:15:29 2014 Last change: Tue Dec 16 15:49:47 2014 Stack: corosync Current DC: pcmk-2 (2) - partition with quorum Version: 1.1.12-a9c8177 2 Nodes configured 0 Resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: PCSD Status: pcmk-1: Online pcmk-2: Online Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- Finally, ensure there are no startup errors (aside from messages relating to not having STONITH configured, which are OK at this point): ---- [root@pcmk-1 ~]# journalctl | grep -i error ---- [NOTE] ====== -Other operating systems will report startup errors in other locations. -For example, on Fedora 19 and earlier, the command would be: ----- -[root@pcmk-1 ~]# grep -i error /var/log/messages ----- +Other operating systems may report startup errors in other locations, +for example +/var/log/messages+. ====== Repeat these checks on the other node. The results should be the same.