diff --git a/doc/sphinx/Pacemaker_Explained/rules.rst b/doc/sphinx/Pacemaker_Explained/rules.rst index 296438c11e..d03165ac66 100644 --- a/doc/sphinx/Pacemaker_Explained/rules.rst +++ b/doc/sphinx/Pacemaker_Explained/rules.rst @@ -1,963 +1,979 @@ .. index:: single: rule .. _rules: Rules ----- Rules can be used to make your configuration more dynamic, allowing values to change depending on the time or the value of a node attribute. Examples of things rules are useful for: * Set a higher value for :ref:`resource-stickiness ` during working hours, to minimize downtime, and a lower value on weekends, to allow resources to move to their most preferred locations when people aren't around to notice. * Automatically place the cluster into maintenance mode during a scheduled maintenance window. * Assign certain nodes and resources to a particular department via custom node attributes and meta-attributes, and add a single location constraint that restricts the department's resources to run only on those nodes. Each constraint type or property set that supports rules may contain one or more ``rule`` elements specifying conditions under which the constraint or properties take effect. Examples later in this chapter will make this clearer. .. index:: pair: XML element; rule Rule Properties ############### .. table:: **Attributes of a rule Element** :widths: 1 1 3 +-----------------+-------------+-------------------------------------------+ | Attribute | Default | Description | +=================+=============+===========================================+ | id | | .. index:: | | | | pair: rule; id | | | | | | | | A unique name for this element (required) | +-----------------+-------------+-------------------------------------------+ | role | ``Started`` | .. index:: | | | | pair: rule; role | | | | | | | | The rule is in effect only when the | | | | resource is in the specified role. | | | | Allowed values are ``Started``, | | | | ``Unpromoted``, and ``Promoted``. A rule | | | | with a ``role`` of ``Promoted`` cannot | | | | determine the initial location of a clone | | | | instance and will only affect which of | | | | the active instances will be promoted. | +-----------------+-------------+-------------------------------------------+ | score | | .. index:: | | | | pair: rule; score | | | | | | | | If this rule is used in a location | | | | constraint and evaluates to true, apply | | | | this score to the constraint. Only one of | | | | ``score`` and ``score-attribute`` may be | | | | used. | +-----------------+-------------+-------------------------------------------+ | score-attribute | | .. index:: | | | | pair: rule; score-attribute | | | | | | | | If this rule is used in a location | | | | constraint and evaluates to true, use the | | | | value of this node attribute as the score | | | | to apply to the constraint. Only one of | | | | ``score`` and ``score-attribute`` may be | | | | used. | +-----------------+-------------+-------------------------------------------+ | boolean-op | ``and`` | .. index:: | | | | pair: rule; boolean-op | | | | | | | | If this rule contains more than one | | | | condition, a value of ``and`` specifies | | | | that the rule evaluates to true only if | | | | all conditions are true, and a value of | | | | ``or`` specifies that the rule evaluates | | | | to true if any condition is true. | +-----------------+-------------+-------------------------------------------+ A ``rule`` element must contain one or more conditions. A condition may be an ``expression`` element, a ``date_expression`` element, or another ``rule`` element. .. index:: single: rule; node attribute expression single: node attribute; rule expression pair: XML element; expression .. _node_attribute_expressions: Node Attribute Expressions ########################## Expressions are rule conditions based on the values of node attributes. .. table:: **Attributes of an expression Element** :class: longtable :widths: 1 2 3 +--------------+---------------------------------+-------------------------------------------+ | Attribute | Default | Description | +==============+=================================+===========================================+ | id | | .. index:: | | | | pair: expression; id | | | | | | | | A unique name for this element (required) | +--------------+---------------------------------+-------------------------------------------+ | attribute | | .. index:: | | | | pair: expression; attribute | | | | | | | | The node attribute to test (required) | +--------------+---------------------------------+-------------------------------------------+ | type | The default type for | .. index:: | | | ``lt``, ``gt``, ``lte``, and | pair: expression; type | | | ``gte`` operations is ``number``| | | | if either value contains a | How the node attributes should be | | | decimal point character, or | compared. Allowed values are ``string``, | | | ``integer`` otherwise. The | ``integer`` *(since 2.0.5)*, ``number``, | | | default type for all other | and ``version``. ``integer`` truncates | | | operations is ``string``. If a | floating-point values if necessary before | | | numeric parse fails for either | performing a 64-bit integer comparison. | | | value, then the values are | ``number`` performs a double-precision | | | compared as type ``string``. | floating-point comparison | | | | *(32-bit integer before 2.0.5)*. | +--------------+---------------------------------+-------------------------------------------+ | operation | | .. index:: | | | | pair: expression; operation | | | | | | | | The comparison to perform (required). | | | | Allowed values: | | | | | | | | * ``lt:`` True if the node attribute value| | | | is less than the comparison value | | | | * ``gt:`` True if the node attribute value| | | | is greater than the comparison value | | | | * ``lte:`` True if the node attribute | | | | value is less than or equal to the | | | | comparison value | | | | * ``gte:`` True if the node attribute | | | | value is greater than or equal to the | | | | comparison value | | | | * ``eq:`` True if the node attribute value| | | | is equal to the comparison value | | | | * ``ne:`` True if the node attribute value| | | | is not equal to the comparison value | | | | * ``defined:`` True if the node has the | | | | named attribute | | | | * ``not_defined:`` True if the node does | | | | not have the named attribute | +--------------+---------------------------------+-------------------------------------------+ | value | | .. index:: | | | | pair: expression; value | | | | | | | | User-supplied value for comparison | | | | (required for operations other than | | | | ``defined`` and ``not_defined``) | +--------------+---------------------------------+-------------------------------------------+ | value-source | ``literal`` | .. index:: | | | | pair: expression; value-source | | | | | | | | How the ``value`` is derived. Allowed | | | | values: | | | | | | | | * ``literal``: ``value`` is a literal | | | | string to compare against | | | | * ``param``: ``value`` is the name of a | | | | resource parameter to compare against | | | | (only valid in location constraints) | | | | * ``meta``: ``value`` is the name of a | | | | resource meta-attribute to compare | | | | against (only valid in location | | | | constraints) | +--------------+---------------------------------+-------------------------------------------+ .. _node-attribute-expressions-special: In addition to custom node attributes defined by the administrator, the cluster defines special, built-in node attributes for each node that can also be used in rule expressions. .. table:: **Built-in Node Attributes** :widths: 1 4 +---------------+-----------------------------------------------------------+ | Name | Value | +===============+===========================================================+ | #uname | :ref:`Node name ` | +---------------+-----------------------------------------------------------+ | #id | Node ID | +---------------+-----------------------------------------------------------+ | #kind | Node type. Possible values are ``cluster``, ``remote``, | | | and ``container``. Kind is ``remote`` for Pacemaker Remote| | | nodes created with the ``ocf:pacemaker:remote`` resource, | | | and ``container`` for Pacemaker Remote guest nodes and | | | bundle nodes | +---------------+-----------------------------------------------------------+ | #is_dc | ``true`` if this node is the cluster's Designated | | | Controller (DC), ``false`` otherwise | +---------------+-----------------------------------------------------------+ | #cluster-name | The value of the ``cluster-name`` cluster property, if set| +---------------+-----------------------------------------------------------+ | #site-name | The value of the ``site-name`` node attribute, if set, | | | otherwise identical to ``#cluster-name`` | +---------------+-----------------------------------------------------------+ | #role | The role the relevant promotable clone resource has on | | | this node. Valid only within a rule for a location | | | constraint for a promotable clone resource. | +---------------+-----------------------------------------------------------+ .. Add_to_above_table_if_released: +---------------+-----------------------------------------------------------+ | #ra-version | The installed version of the resource agent on the node, | | | as defined by the ``version`` attribute of the | | | ``resource-agent`` tag in the agent's metadata. Valid only| | | within rules controlling resource options. This can be | | | useful during rolling upgrades of a backward-incompatible | | | resource agent. *(since x.x.x)* | .. index:: single: rule; date/time expression pair: XML element; date_expression Date/Time Expressions ##################### Date/time expressions are rule conditions based (as the name suggests) on the current date and time. A ``date_expression`` element may optionally contain a ``date_spec`` or ``duration`` element depending on the context. .. table:: **Attributes of a date_expression Element** :widths: 1 4 +---------------+-----------------------------------------------------------+ | Attribute | Description | +===============+===========================================================+ | id | .. index:: | | | pair: id; date_expression | | | | | | A unique name for this element (required) | +---------------+-----------------------------------------------------------+ | start | .. index:: | | | pair: start; date_expression | | | | | | A date/time conforming to the | | | `ISO8601 `_ | | | specification. May be used when ``operation`` is | | | ``in_range`` (in which case at least one of ``start`` or | | | ``end`` must be specified) or ``gt`` (in which case | | | ``start`` is required). | +---------------+-----------------------------------------------------------+ | end | .. index:: | | | pair: end; date_expression | | | | | | A date/time conforming to the | | | `ISO8601 `_ | | | specification. May be used when ``operation`` is | | | ``in_range`` (in which case at least one of ``start`` or | | | ``end`` must be specified) or ``lt`` (in which case | | | ``end`` is required). | +---------------+-----------------------------------------------------------+ | operation | .. index:: | | | pair: operation; date_expression | | | | | | Compares the current date/time with the start and/or end | | | date, depending on the context. Allowed values: | | | | | | * ``gt:`` True if the current date/time is after ``start``| | | * ``lt:`` True if the current date/time is before ``end`` | | | * ``in_range:`` True if the current date/time is after | | | ``start`` (if specified) and before either ``end`` (if | | | specified) or ``start`` plus the value of the | | | ``duration`` element (if one is contained in the | - | | ``date_expression``) | + | | ``date_expression``). If both ``end`` and ``duration`` | + | | are specified, ``duration`` is ignored. | | | * ``date_spec:`` True if the current date/time matches | | | the specification given in the contained ``date_spec`` | | | element (described below) | +---------------+-----------------------------------------------------------+ .. note:: There is no ``eq``, ``neq``, ``gte``, or ``lte`` operation, since they would be valid only for a single second. .. index:: single: date specification pair: XML element; date_spec Date Specifications ___________________ A ``date_spec`` element is used to create a cron-like expression relating to time. Each field can contain a single number or range. Any field not supplied is ignored. .. table:: **Attributes of a date_spec Element** :widths: 1 3 +---------------+-----------------------------------------------------------+ | Attribute | Description | +===============+===========================================================+ | id | .. index:: | | | pair: id; date_spec | | | | | | A unique name for this element (required) | +---------------+-----------------------------------------------------------+ + | seconds | .. index:: | + | | pair: seconds; date_spec | + | | | + | | Allowed values: 0-59 | + +---------------+-----------------------------------------------------------+ + | minutes | .. index:: | + | | pair: minutes; date_spec | + | | | + | | Allowed values: 0-59 | + +---------------+-----------------------------------------------------------+ | hours | .. index:: | | | pair: hours; date_spec | | | | | | Allowed values: 0-23 (where 0 is midnight and 23 is | | | 11 p.m.) | +---------------+-----------------------------------------------------------+ | monthdays | .. index:: | | | pair: monthdays; date_spec | | | | | | Allowed values: 1-31 (depending on month and year) | +---------------+-----------------------------------------------------------+ | weekdays | .. index:: | | | pair: weekdays; date_spec | | | | | | Allowed values: 1-7 (where 1 is Monday and 7 is Sunday) | +---------------+-----------------------------------------------------------+ | yeardays | .. index:: | | | pair: yeardays; date_spec | | | | | | Allowed values: 1-366 (depending on the year) | +---------------+-----------------------------------------------------------+ | months | .. index:: | | | pair: months; date_spec | | | | | | Allowed values: 1-12 | +---------------+-----------------------------------------------------------+ | weeks | .. index:: | | | pair: weeks; date_spec | | | | | | Allowed values: 1-53 (depending on weekyear) | +---------------+-----------------------------------------------------------+ | years | .. index:: | | | pair: years; date_spec | | | | | | Year according to the Gregorian calendar | +---------------+-----------------------------------------------------------+ | weekyears | .. index:: | | | pair: weekyears; date_spec | | | | | | Year in which the week started; for example, 1 January | | | 2005 can be specified in ISO 8601 as "2005-001 Ordinal", | | | "2005-01-01 Gregorian" or "2004-W53-6 Weekly" and thus | | | would match ``years="2005"`` or ``weekyears="2004"`` | +---------------+-----------------------------------------------------------+ | moon | .. index:: | | | pair: moon; date_spec | | | | | | Allowed values are 0-7 (where 0 is the new moon and 4 is | | | full moon). Seriously, you can use this. This was | | | implemented to demonstrate the ease with which new | | | comparisons could be added. | +---------------+-----------------------------------------------------------+ For example, ``monthdays="1"`` matches the first day of every month, and ``hours="09-17"`` matches the hours between 9 a.m. and 5 p.m. (inclusive). At this time, multiple ranges (e.g. ``weekdays="1,2"`` or ``weekdays="1-2,5-6"``) are not supported. .. note:: Pacemaker can calculate when evaluation of a ``date_expression`` with an ``operation`` of ``gt``, ``lt``, or ``in_range`` will next change, and schedule a cluster re-check for that time. However, it does not do this for ``date_spec``. Instead, it evaluates the ``date_spec`` whenever a cluster re-check naturally happens via a cluster event or the ``cluster-recheck-interval`` cluster option. For example, if you have a ``date_spec`` enabling a resource from 9 a.m. to 5 p.m., and ``cluster-recheck-interval`` has been set to 5 minutes, then sometime between 9 a.m. and 9:05 a.m. the cluster would notice that it needs to start the resource, and sometime between 5 p.m. and 5:05 p.m. it would realize that it needs to stop the resource. The timing of the actual start and stop actions will further depend on factors such as any other actions the cluster may need to perform first, and the load of the machine. .. index:: single: duration pair: XML element; duration Durations _________ A ``duration`` is used to calculate a value for ``end`` when one is not supplied to ``in_range`` operations. It contains one or more attributes each containing a single number. Any attribute not supplied is ignored. .. table:: **Attributes of a duration Element** :widths: 1 3 +---------------+-----------------------------------------------------------+ | Attribute | Description | +===============+===========================================================+ | id | .. index:: | | | pair: id; duration | | | | | | A unique name for this element (required) | +---------------+-----------------------------------------------------------+ | seconds | .. index:: | | | pair: seconds; duration | | | | | | This many seconds will be added to the total duration | +---------------+-----------------------------------------------------------+ | minutes | .. index:: | | | pair: minutes; duration | | | | | | This many minutes will be added to the total duration | +---------------+-----------------------------------------------------------+ | hours | .. index:: | | | pair: hours; duration | | | | | | This many hours will be added to the total duration | +---------------+-----------------------------------------------------------+ + | days | .. index:: | + | | pair: days; duration | + | | | + | | This many days will be added to the total duration | + +---------------+-----------------------------------------------------------+ | weeks | .. index:: | | | pair: weeks; duration | | | | | | This many weeks will be added to the total duration | +---------------+-----------------------------------------------------------+ | months | .. index:: | | | pair: months; duration | | | | | | This many months will be added to the total duration | +---------------+-----------------------------------------------------------+ | years | .. index:: | | | pair: years; duration | | | | | | This many years will be added to the total duration | +---------------+-----------------------------------------------------------+ Example Time-Based Expressions ______________________________ A small sample of how time-based expressions can be used: .. topic:: True if now is any time in the year 2005 .. code-block:: xml or equivalently: .. code-block:: xml .. topic:: 9 a.m. to 5 p.m. Monday through Friday .. code-block:: xml Note that the ``16`` matches all the way through ``16:59:59``, because the numeric value of the hour still matches. .. topic:: 9 a.m. to 6 p.m. Monday through Friday or anytime Saturday .. code-block:: xml .. topic:: 9 a.m. to 5 p.m. or 9 p.m. to 12 a.m. Monday through Friday .. code-block:: xml .. topic:: Mondays in March 2005 .. code-block:: xml .. note:: Because no time is specified with the above dates, 00:00:00 is implied. This means that the range includes all of 2005-03-01 but none of 2005-04-01. You may wish to write ``end`` as ``"2005-03-31T23:59:59"`` to avoid confusion. .. topic:: A full moon on Friday the 13th .. code-block:: xml .. index:: single: rule; resource expression single: resource; rule expression pair: XML element; rsc_expression Resource Expressions #################### An ``rsc_expression`` *(since 2.0.5)* is a rule condition based on a resource agent's properties. This rule is only valid within an ``rsc_defaults`` or ``op_defaults`` context. None of the matching attributes of ``class``, ``provider``, and ``type`` are required. If one is omitted, all values of that attribute will match. For instance, omitting ``type`` means every type will match. .. table:: **Attributes of a rsc_expression Element** :widths: 1 3 +---------------+-----------------------------------------------------------+ | Attribute | Description | +===============+===========================================================+ | id | .. index:: | | | pair: id; rsc_expression | | | | | | A unique name for this element (required) | +---------------+-----------------------------------------------------------+ | class | .. index:: | | | pair: class; rsc_expression | | | | | | The standard name to be matched against resource agents | +---------------+-----------------------------------------------------------+ | provider | .. index:: | | | pair: provider; rsc_expression | | | | | | If given, the vendor to be matched against resource | | | agents (only relevant when ``class`` is ``ocf``) | +---------------+-----------------------------------------------------------+ | type | .. index:: | | | pair: type; rsc_expression | | | | | | The name of the resource agent to be matched | +---------------+-----------------------------------------------------------+ Example Resource-Based Expressions __________________________________ A small sample of how resource-based expressions can be used: .. topic:: True for all ``ocf:heartbeat:IPaddr2`` resources .. code-block:: xml .. topic:: Provider doesn't apply to non-OCF resources .. code-block:: xml .. index:: single: rule; operation expression single: operation; rule expression pair: XML element; op_expression Operation Expressions ##################### An ``op_expression`` *(since 2.0.5)* is a rule condition based on an action of some resource agent. This rule is only valid within an ``op_defaults`` context. .. table:: **Attributes of an op_expression Element** :widths: 1 3 +---------------+-----------------------------------------------------------+ | Attribute | Description | +===============+===========================================================+ | id | .. index:: | | | pair: id; op_expression | | | | | | A unique name for this element (required) | +---------------+-----------------------------------------------------------+ | name | .. index:: | | | pair: name; op_expression | | | | | | The action name to match against. This can be any action | | | supported by the resource agent; common values include | | | ``monitor``, ``start``, and ``stop`` (required). | +---------------+-----------------------------------------------------------+ | interval | .. index:: | | | pair: interval; op_expression | | | | | | The interval of the action to match against. If not given,| | | only the name attribute will be used to match. | +---------------+-----------------------------------------------------------+ Example Operation-Based Expressions ___________________________________ A small sample of how operation-based expressions can be used: .. topic:: True for all monitor actions .. code-block:: xml .. topic:: True for all monitor actions with a 10 second interval .. code-block:: xml .. index:: pair: location constraint; rule Using Rules to Determine Resource Location ########################################## A location constraint may contain one or more top-level rules. The cluster will act as if there is a separate location constraint for each rule that evaluates as true. Consider the following simple location constraint: .. topic:: Prevent resource ``webserver`` from running on node ``node3`` .. code-block:: xml The same constraint can be more verbosely written using a rule: .. topic:: Prevent resource ``webserver`` from running on node ``node3`` using a rule .. code-block:: xml The advantage of using the expanded form is that one could add more expressions (for example, limiting the constraint to certain days of the week), or activate the constraint by some node attribute other than node name. Location Rules Based on Other Node Properties _____________________________________________ The expanded form allows us to match on node properties other than its name. If we rated each machine's CPU power such that the cluster had the following nodes section: .. topic:: Sample node section with node attributes .. code-block:: xml then we could prevent resources from running on underpowered machines with this rule: .. topic:: Rule using a node attribute (to be used inside a location constraint) .. code-block:: xml Using ``score-attribute`` Instead of ``score`` ______________________________________________ When using ``score-attribute`` instead of ``score``, each node matched by the rule has its score adjusted differently, according to its value for the named node attribute. Thus, in the previous example, if a rule inside a location constraint for a resource used ``score-attribute="cpu_mips"``, ``c001n01`` would have its preference to run the resource increased by ``1234`` whereas ``c001n02`` would have its preference increased by ``5678``. .. index:: pair: cluster option; rule pair: instance attribute; rule pair: meta-attribute; rule pair: resource defaults; rule pair: operation defaults; rule pair: node attribute; rule Using Rules to Define Options ############################# Rules may be used to control a variety of options: * :ref:`Cluster options ` (``cluster_property_set`` elements) * :ref:`Node attributes ` (``instance_attributes`` or ``utilization`` elements inside a ``node`` element) * :ref:`Resource options ` (``utilization``, ``meta_attributes``, or ``instance_attributes`` elements inside a resource definition element or ``op`` , ``rsc_defaults``, ``op_defaults``, or ``template`` element) * :ref:`Operation properties ` (``meta_attributes`` elements inside an ``op`` or ``op_defaults`` element) .. note:: Attribute-based expressions for meta-attributes can only be used within ``operations`` and ``op_defaults``. They will not work with resource configuration or ``rsc_defaults``. Additionally, attribute-based expressions cannot be used with cluster options. Using Rules to Control Resource Options _______________________________________ Often some cluster nodes will be different from their peers. Sometimes, these differences -- e.g. the location of a binary or the names of network interfaces -- require resources to be configured differently depending on the machine they're hosted on. By defining multiple ``instance_attributes`` objects for the resource and adding a rule to each, we can easily handle these special cases. In the example below, ``mySpecialRsc`` will use eth1 and port 9999 when run on ``node1``, eth2 and port 8888 on ``node2`` and default to eth0 and port 9999 for all other nodes. .. topic:: Defining different resource options based on the node name .. code-block:: xml The order in which ``instance_attributes`` objects are evaluated is determined by their score (highest to lowest). If not supplied, the score defaults to zero. Objects with an equal score are processed in their listed order. If the ``instance_attributes`` object has no rule, or a ``rule`` that evaluates to ``true``, then for any parameter the resource does not yet have a value for, the resource will use the parameter values defined by the ``instance_attributes``. For example, given the configuration above, if the resource is placed on ``node1``: * ``special-node1`` has the highest score (3) and so is evaluated first; its rule evaluates to ``true``, so ``interface`` is set to ``eth1``. * ``special-node2`` is evaluated next with score 2, but its rule evaluates to ``false``, so it is ignored. * ``defaults`` is evaluated last with score 1, and has no rule, so its values are examined; ``interface`` is already defined, so the value here is not used, but ``port`` is not yet defined, so ``port`` is set to ``9999``. Using Rules to Control Resource Defaults ________________________________________ Rules can be used for resource and operation defaults. The following example illustrates how to set a different ``resource-stickiness`` value during and outside work hours. This allows resources to automatically move back to their most preferred hosts, but at a time that (in theory) does not interfere with business activities. .. topic:: Change ``resource-stickiness`` during working hours .. code-block:: xml Rules may be used similarly in ``instance_attributes`` or ``utilization`` blocks. Any single block may directly contain only a single rule, but that rule may itself contain any number of rules. ``rsc_expression`` and ``op_expression`` blocks may additionally be used to set defaults on either a single resource or across an entire class of resources with a single rule. ``rsc_expression`` may be used to select resource agents within both ``rsc_defaults`` and ``op_defaults``, while ``op_expression`` may only be used within ``op_defaults``. If multiple rules succeed for a given resource agent, the last one specified will be the one that takes effect. As with any other rule, boolean operations may be used to make more complicated expressions. .. topic:: Default all IPaddr2 resources to stopped .. code-block:: xml .. topic:: Default all monitor action timeouts to 7 seconds .. code-block:: xml .. topic:: Default the timeout on all 10-second-interval monitor actions on ``IPaddr2`` resources to 8 seconds .. code-block:: xml .. index:: pair: rule; cluster option Using Rules to Control Cluster Options ______________________________________ Controlling cluster options is achieved in much the same manner as specifying different resource options on different nodes. The following example illustrates how to set ``maintenance_mode`` during a scheduled maintenance window. This will keep the cluster running but not monitor, start, or stop resources during this time. .. topic:: Schedule a maintenance window for 9 to 11 p.m. CDT Sept. 20, 2019 .. code-block:: xml .. important:: The ``cluster_property_set`` with an ``id`` set to "cib-bootstrap-options" will *always* have the highest priority, regardless of any scores. Therefore, rules in another ``cluster_property_set`` can never take effect for any properties listed in the bootstrap set.