= Advanced Configuration =

[[s-remote-connection]]
== Connecting from a Remote Machine ==
indexterm:[Cluster,Remote connection]
indexterm:[Cluster,Remote administration]

Provided Pacemaker is installed on a machine, it is possible to
connect to the cluster even if the machine itself is not in the same
cluster.  To do this, one simply sets up a number of environment
variables and runs the same commands as when working on a cluster
node.

.Environment Variables Used to Connect to Remote Instances of the CIB
[width="95%",cols="1m,1,3<",options="header",align="center"]
|=========================================================

|Environment Variable
|Default
|Description

|CIB_user
|$USER
|The user to connect as. Needs to be part of the +haclient+ group on
 the target host.
 indexterm:[Environment Variable,CIB_user]

|CIB_passwd
|
|The user's password. Read from the command line if unset.
 indexterm:[Environment Variable,CIB_passwd]

|CIB_server
|localhost
|The host to contact
 indexterm:[Environment Variable,CIB_server]

|CIB_port
|
|The port on which to contact the server; required.
 indexterm:[Environment Variable,CIB_port]

|CIB_encrypted
|TRUE
|Whether to encrypt network traffic
 indexterm:[Environment Variable,CIB_encrypted]

|=========================================================

So, if *c001n01* is an active cluster node and is listening on port 1234
for connections, and *someuser* is a member of the *haclient* group,
then the following would prompt for *someuser*'s password and return
the cluster's current configuration:

----
# export CIB_port=1234; export CIB_server=c001n01; export CIB_user=someuser;
# cibadmin -Q
----

For security reasons, the cluster does not listen for remote
connections by default.  If you wish to allow remote access, you need
to set the +remote-tls-port+ (encrypted) or +remote-clear-port+
(unencrypted) CIB properties (i.e., those kept in the +cib+ tag, like
+num_updates+ and +epoch+).

.Extra top-level CIB properties for remote access
[width="95%",cols="1m,1,3<",options="header",align="center"]
|=========================================================

|Field
|Default
|Description

|remote-tls-port
|_none_
|Listen for encrypted remote connections on this port.
 indexterm:[remote-tls-port,Remote Connection Option]
 indexterm:[Remote Connection,Option,remote-tls-port]

|remote-clear-port
|_none_
|Listen for plaintext remote connections on this port.
 indexterm:[remote-clear-port,Remote Connection Option]
 indexterm:[Remote Connection,Option,remote-clear-port]

|=========================================================

[[s-recurring-start]]
== Specifying When Recurring Actions are Performed ==


By default, recurring actions are scheduled relative to when the
resource started.  So if your resource was last started at 14:32 and
you have a backup set to be performed every 24 hours, then the backup
will always run in the middle of the business day -- hardly
desirable.

To specify a date and time that the operation should be relative to, set
the operation's +interval-origin+.  The cluster uses this point to
calculate the correct +start-delay+ such that the operation will occur
at _origin + (interval * N)_.

So, if the operation's interval is 24h, its interval-origin is set to
02:00 and it is currently 14:32, then the cluster would initiate
the operation with a start delay of 11 hours and 28 minutes.  If the
resource is moved to another node before 2am, then the operation is
cancelled.

The value specified for +interval+ and +interval-origin+ can be any
date/time conforming to the
http://en.wikipedia.org/wiki/ISO_8601[ISO8601 standard].  By way of
example, to specify an operation that would run on the first Monday of
2009 and every Monday after that, you would add:

.Specifying a Base for Recurring Action Intervals
=====
[source,XML]
<op id="my-weekly-action" name="custom-action" interval="P7D" interval-origin="2009-W01-1"/> 
=====

[[s-failure-handling]]
== Handling Resource Failure ==

By default, Pacemaker will attempt to recover failed resources by restarting
them. However, failure recovery is highly configurable.

=== Failure Counts ===

Pacemaker tracks resource failures for each combination of node, resource, and
operation (start, stop, monitor, etc.).

You can query the fail count for a particular node, resource, and/or operation
using the `crm_failcount` command. For example, to see how many times the
10-second monitor for +myrsc+ has failed on +node1+, run:

----
# crm_failcount --query -r myrsc -N node1 -n monitor -I 10s
----

If you omit the node, `crm_failcount` will use the local node. If you omit the
operation and interval, `crm_failcount` will display the sum of the fail counts
for all operations on the resource.

You can use `crm_resource --cleanup` or `crm_failcount --delete` to clear
fail counts. For example, to clear the above monitor failures, run:

----
# crm_resource --cleanup -r myrsc -N node1 -n monitor -I 10s
----

If you omit the resource, `crm_resource --cleanup` will clear failures for all
resources. If you omit the node, it will clear failures on all nodes. If you
omit the operation and interval, it will clear the failures for all operations
on the resource.

[NOTE]
====
Even when cleaning up only a single operation, all failed operations will
disappear from the status display. This allows us to trigger a re-check of the
resource's current status.
====

Higher-level tools may provide other commands for querying and clearing
fail counts.

The `crm_mon` tool shows the current cluster status, including any failed
operations. To see the current fail counts for any failed resources, call
`crm_mon` with the `--failcounts` option. This shows the fail counts per
resource (that is, the sum of any operation fail counts for the resource).

=== Failure Response ===

Normally, if a running resource fails, pacemaker will try to stop it and start
it again. Pacemaker will choose the best location to start it each time, which
may be the same node that it failed on.

However, if a resource fails repeatedly, it is possible that there is an
underlying problem on that node, and you might desire trying a different node
in such a case. Pacemaker allows you to set your preference via the
+migration-threshold+ resource meta-attribute.
footnote:[
The naming of this option was perhaps unfortunate as it is easily
confused with live migration, the process of moving a resource from
one node to another without stopping it.  Xen virtual guests are the
most common example of resources that can be migrated in this manner.
]

If you define +migration-threshold=pass:[<replaceable>N</replaceable>]+ for a
resource, it will be banned from the original node after 'N' failures.

[NOTE]
====
The +migration-threshold+ is per 'resource', even though fail counts are
tracked per 'operation'. The operation fail counts are added together
to compare against the +migration-threshold+.
====

By default, fail counts remain until manually cleared by an administrator
using `crm_resource --cleanup` or `crm_failcount --delete` (hopefully after
first fixing the failure's cause). It is possible to have fail counts expire
automatically by setting the +failure-timeout+ resource meta-attribute.

[IMPORTANT]
====
A successful operation does not clear past failures. If a recurring monitor
operation fails once, succeeds many times, then fails again days later, its
fail count is 2. Fail counts are cleared only by manual intervention or
falure timeout.
====

For example, a setting of +migration-threshold=2+ and +failure-timeout=60s+
would cause the resource to move to a new node after 2 failures, and
allow it to move back (depending on stickiness and constraint scores) after one
minute.

[NOTE]
====
+failure-timeout+ is measured since the most recent failure. That is, older
failures do not individually time out and lower the fail count. Instead, all
failures are timed out simultaneously (and the fail count is reset to 0) if
there is no new failure for the timeout period.
====

There are two exceptions to the migration threshold concept:
when a resource either fails to start or fails to stop.

If the cluster property +start-failure-is-fatal+ is set to +true+ (which is the
default), start failures cause the fail count to be set to +INFINITY+ and thus
always cause the resource to move immediately.

Stop failures are slightly different and crucial.  If a resource fails
to stop and STONITH is enabled, then the cluster will fence the node
in order to be able to start the resource elsewhere.  If STONITH is
not enabled, then the cluster has no way to continue and will not try
to start the resource elsewhere, but will try to stop it again after
the failure timeout.

[IMPORTANT]
Please read <<s-rules-recheck>> to understand how timeouts work
before configuring a +failure-timeout+.

== Moving Resources ==
indexterm:[Moving,Resources] 
indexterm:[Resource,Moving]

=== Moving Resources Manually ===

There are primarily two occasions when you would want to move a
resource from its current location: when the whole node is under
maintenance, and when a single resource needs to be moved.

==== Standby Mode ====

Since everything eventually comes down to a score, you could create
constraints for every resource to prevent them from running on one
node.  While pacemaker configuration can seem convoluted at times, not even
we would require this of administrators.

Instead, one can set a special node attribute which tells the cluster
"don't let anything run here".  There is even a helpful tool to help
query and set it, called `crm_standby`.  To check the standby status
of the current machine, run:

----
# crm_standby -G
----

A value of +on+ indicates that the node is _not_ able to host any
resources, while a value of +off+ says that it _can_.

You can also check the status of other nodes in the cluster by
specifying the `--node` option:

----
# crm_standby -G --node sles-2
----

To change the current node's standby status, use `-v` instead of `-G`:

----
# crm_standby -v on
----

Again, you can change another host's value by supplying a hostname with `--node`.

==== Moving One Resource ====

When only one resource is required to move, we could do this by creating
location constraints.  However, once again we provide a user-friendly
shortcut as part of the `crm_resource` command, which creates and
modifies the extra constraints for you.  If +Email+ were running on
+sles-1+ and you wanted it moved to a specific location, the command
would look something like:
        
----
# crm_resource -M -r Email -H sles-2
----

Behind the scenes, the tool will create the following location constraint:

[source,XML]
<rsc_location rsc="Email" node="sles-2" score="INFINITY"/>

It is important to note that subsequent invocations of `crm_resource
-M` are not cumulative. So, if you ran these commands

----
# crm_resource -M -r Email -H sles-2
# crm_resource -M -r Email -H sles-3
----

then it is as if you had never performed the first command.

To allow the resource to move back again, use:

----
# crm_resource -U -r Email
----

Note the use of the word _allow_.  The resource can move back to its
original location but, depending on +resource-stickiness+, it might
stay where it is.  To be absolutely certain that it moves back to
+sles-1+, move it there before issuing the call to `crm_resource -U`:
        
----
# crm_resource -M -r Email -H sles-1
# crm_resource -U -r Email
----

Alternatively, if you only care that the resource should be moved from
its current location, try:

----
# crm_resource -B -r Email
----

Which will instead create a negative constraint, like

[source,XML]
<rsc_location rsc="Email" node="sles-1" score="-INFINITY"/>

This will achieve the desired effect, but will also have long-term
consequences.  As the tool will warn you, the creation of a
+-INFINITY+ constraint will prevent the resource from running on that
node until `crm_resource -U` is used.  This includes the situation
where every other cluster node is no longer available!

In some cases, such as when +resource-stickiness+ is set to
+INFINITY+, it is possible that you will end up with the problem
described in <<node-score-equal>>.  The tool can detect
some of these cases and deals with them by creating both
positive and negative constraints. E.g.

+Email+ prefers +sles-1+ with a score of +-INFINITY+

+Email+ prefers +sles-2+ with a score of +INFINITY+

which has the same long-term consequences as discussed earlier.

=== Moving Resources Due to Connectivity Changes ===

You can configure the cluster to move resources when external connectivity is
lost in two steps.

==== Tell Pacemaker to Monitor Connectivity ====

First, add an *ocf:pacemaker:ping* resource to the cluster.  The
*ping* resource uses the system utility of the same name to a test whether
list of machines (specified by DNS hostname or IPv4/IPv6 address) are
reachable and uses the results to maintain a node attribute called +pingd+
by default.
footnote:[
The attribute name is customizable, in order to allow multiple ping groups to be defined.
]

[NOTE]
===========
Older versions of Heartbeat required users to add ping nodes to +ha.cf+, but
this is no longer required.

Older versions of Pacemaker used a different agent *ocf:pacemaker:pingd* which
is now deprecated in favor of *ping*. If your version of Pacemaker does not
contain the *ping* resource agent, download the latest version from
https://github.com/ClusterLabs/pacemaker/tree/master/extra/resources/ping
===========

Normally, the ping resource should run on all cluster nodes, which means that
you'll need to create a clone.  A template for this can be found below
along with a description of the most interesting parameters.
          
.Common Options for a 'ping' Resource
[width="95%",cols="1m,4<",options="header",align="center"]
|=========================================================

|Field
|Description

|dampen
|The time to wait (dampening) for further changes to occur. Use this
 to prevent a resource from bouncing around the cluster when cluster
 nodes notice the loss of connectivity at slightly different times.
 indexterm:[dampen,Ping Resource Option]
 indexterm:[Ping Resource,Option,dampen]

|multiplier
|The number of connected ping nodes gets multiplied by this value to
 get a score. Useful when there are multiple ping nodes configured.
 indexterm:[multiplier,Ping Resource Option]
 indexterm:[Ping Resource,Option,multiplier]

|host_list
|The machines to contact in order to determine the current
 connectivity status. Allowed values include resolvable DNS host
 names, IPv4 and IPv6 addresses.
 indexterm:[host_list,Ping Resource Option]
 indexterm:[Ping Resource,Option,host_list]

|=========================================================

.An example ping cluster resource that checks node connectivity once every minute
=====
[source,XML]
------------
<clone id="Connected">
   <primitive id="ping" provider="pacemaker" class="ocf" type="ping">
    <instance_attributes id="ping-attrs">
      <nvpair id="pingd-dampen" name="dampen" value="5s"/>
      <nvpair id="pingd-multiplier" name="multiplier" value="1000"/>
      <nvpair id="pingd-hosts" name="host_list" value="my.gateway.com www.bigcorp.com"/>
    </instance_attributes>
    <operations>
      <op id="ping-monitor-60s" interval="60s" name="monitor"/>
    </operations>
   </primitive>
</clone>
------------
=====

[IMPORTANT]
===========
You're only half done.  The next section deals with telling Pacemaker
how to deal with the connectivity status that +ocf:pacemaker:ping+ is
recording.
===========

==== Tell Pacemaker How to Interpret the Connectivity Data ====

[IMPORTANT]
======
Before attempting the following, make sure you understand
<<ch-rules>>.
======

There are a number of ways to use the connectivity data.

The most common setup is for people to have a single ping
target (e.g. the service network's default gateway), to prevent the cluster
from running a resource on any unconnected node.

.Don't run a resource on unconnected nodes
=====
[source,XML]
-------
<rsc_location id="WebServer-no-connectivity" rsc="Webserver">
   <rule id="ping-exclude-rule" score="-INFINITY" >
    <expression id="ping-exclude" attribute="pingd" operation="not_defined"/>
   </rule>
</rsc_location>
-------
=====

A more complex setup is to have a number of ping targets configured.
You can require the cluster to only run resources on nodes that can
connect to all (or a minimum subset) of them.

.Run only on nodes connected to three or more ping targets.
=====
[source,XML]
-------
<primitive id="ping" provider="pacemaker" class="ocf" type="ping">
... <!-- omitting some configuration to highlight important parts -->
      <nvpair id="pingd-multiplier" name="multiplier" value="1000"/>
...
</primitive>
...
<rsc_location id="WebServer-connectivity" rsc="Webserver">
   <rule id="ping-prefer-rule" score="-INFINITY" >
      <expression id="ping-prefer" attribute="pingd" operation="lt" value="3000"/>
   </rule>
</rsc_location>
-------
=====

Alternatively, you can tell the cluster only to _prefer_ nodes with the best
connectivity.  Just be sure to set +multiplier+ to a value higher than
that of +resource-stickiness+ (and don't set either of them to
+INFINITY+).

.Prefer the node with the most connected ping nodes
=====
[source,XML]
-------
<rsc_location id="WebServer-connectivity" rsc="Webserver">
   <rule id="ping-prefer-rule" score-attribute="pingd" >
    <expression id="ping-prefer" attribute="pingd" operation="defined"/>
   </rule>
</rsc_location>
-------
=====

It is perhaps easier to think of this in terms of the simple
constraints that the cluster translates it into.  For example, if
*sles-1* is connected to all five ping nodes but *sles-2* is only
connected to two, then it would be as if you instead had the following
constraints in your configuration:

.How the cluster translates the above location constraint
=====
[source,XML]
-------
<rsc_location id="ping-1" rsc="Webserver" node="sles-1" score="5000"/>
<rsc_location id="ping-2" rsc="Webserver" node="sles-2" score="2000"/>
-------
=====

The advantage is that you don't have to manually update any
constraints whenever your network connectivity changes.

You can also combine the concepts above into something even more
complex.  The example below shows how you can prefer the node with the
most connected ping nodes provided they have connectivity to at least
three (again assuming that +multiplier+ is set to 1000).

.A more complex example of choosing a location based on connectivity
=====
[source,XML]
-------
<rsc_location id="WebServer-connectivity" rsc="Webserver">
   <rule id="ping-exclude-rule" score="-INFINITY" >
    <expression id="ping-exclude" attribute="pingd" operation="lt" value="3000"/>
   </rule>
   <rule id="ping-prefer-rule" score-attribute="pingd" >
    <expression id="ping-prefer" attribute="pingd" operation="defined"/>
   </rule>
</rsc_location>
-------
=====

[[s-migrating-resources]]
=== Migrating Resources ===

Normally, when the cluster needs to move a resource, it fully restarts
the resource (i.e. stops the resource on the current node
and starts it on the new node).

However, some types of resources, such as Xen virtual guests, are able to move to
another location without loss of state (often referred to as live migration
or hot migration). In pacemaker, this is called resource migration.
Pacemaker can be configured to migrate a resource when moving it,
rather than restarting it.

Not all resources are able to migrate; see the Migration Checklist
below, and those that can, won't do so in all situations.
Conceptually, there are two requirements from which the other
prerequisites follow:

* The resource must be active and healthy at the old location; and
* everything required for the resource to run must be available on
  both the old and new locations.

The cluster is able to accommodate both 'push' and 'pull' migration models
by requiring the resource agent to support two special actions:
+migrate_to+ (performed on the current location) and +migrate_from+
(performed on the destination).

In push migration, the process on the current location transfers the
resource to the new location where is it later activated.  In this
scenario, most of the work would be done in the +migrate_to+ action
and, if anything, the activation would occur during +migrate_from+.

Conversely for pull, the +migrate_to+ action is practically empty and
+migrate_from+ does most of the work, extracting the relevant resource
state from the old location and activating it.

There is no wrong or right way for a resource agent to implement migration,
as long as it works.

.Migration Checklist
* The resource may not be a clone.
* The resource must use an OCF style agent.
* The resource must not be in a failed or degraded state.
* The resource agent must support +migrate_to+ and
  +migrate_from+ actions, and advertise them in its metadata.
* The resource must have the +allow-migrate+ meta-attribute set to
  +true+ (which is not the default).

If an otherwise migratable resource depends on another resource
via an ordering constraint, there are special situations in which it will be
restarted rather than migrated.

For example, if the resource depends on a clone, and at the time the resource
needs to be moved, the clone has instances that are stopping and instances
that are starting, then the resource will be restarted.
The Policy Engine is not yet able to model this
situation correctly and so takes the safer (if less optimal) path.

In pacemaker 1.1.11 and earlier, a migratable resource will be restarted
when moving if it directly or indirectly depends on 'any' primitive or group
resources.

Even in newer versions, if a migratable resource depends on a non-migratable
resource, and both need to be moved, the migratable resource will be restarted.

[[s-node-health]]
== Tracking Node Health ==

A node may be functioning adequately as far as cluster membership is concerned,
and yet be "unhealthy" in some respect that makes it an undesirable location
for resources. For example, a disk drive may be reporting SMART errors, or the
CPU may be highly loaded.

Pacemaker offers a way to automatically move resources off unhealthy nodes.

=== Node Health Attributes ===

Pacemaker will treat any node attribute whose name starts with +#health+ as an
indicator of node health. Node health attributes may have one of the following
values:

.Allowed Values for Node Health Attributes
[width="95%",cols="1,3<",options="header",align="center"]
|=========================================================

|Value
|Intended significance

|+red+
|This indicator is unhealthy
 indexterm:[Node health,red]

|+yellow+
|This indicator is becoming unhealthy
 indexterm:[Node health,yellow]

|+green+
|This indicator is healthy
 indexterm:[Node health,green]

|'integer'
|A numeric score to apply to all resources on this node
 (0 or positive is healthy, negative is unhealthy)
 indexterm:[Node health,score]

|=========================================================

=== Node Health Strategy ===

Pacemaker assigns a node health score to each node, as the sum of the values of
all its node health attributes. This score will be used as a location
constraint applied to this node for all resources.

The +node-health-strategy+ cluster option controls how Pacemaker responds to
changes in node health attributes, and how it translates +red+, +yellow+, and
+green+ to scores.

Allowed values are:

.Node Health Strategies
[width="95%",cols="1m,3<",options="header",align="center"]
|=========================================================

|Value
|Effect

|none
|Do not track node health attributes at all.
 indexterm:[Node health,none]

|migrate-on-red
|Assign the value of +-INFINITY+ to +red+, and 0 to +yellow+ and +green+.
 This will cause all resources to move off the node if any attribute is +red+.
 indexterm:[Node health,migrate-on-red]

|only-green
|Assign the value of +-INFINITY+ to +red+ and +yellow+, and 0 to +green+.
 This will cause all resources to move off the node if any attribute is +red+
 or +yellow+.
 indexterm:[Node health,only-green]

|progressive
|Assign the value of the +node-health-red+ cluster option to +red+, the value
 of +node-health-yellow+ to +yellow+, and the value of +node-health-green+ to
 +green+. Each node is additionally assigned a score of +node-health-base+
 (this allows resources to start even if some attributes are +yellow+). This
 strategy gives the administrator finer control over how important each value
 is.
 indexterm:[Node health,progressive]

|custom
|Track node health attributes using the same values as +progressive+ for
 +red+, +yellow+, and +green+, but do not take them into account.
 The administrator is expected to implement a policy by defining rules
 (see <<ch-rules>>) referencing node health attributes.
 indexterm:[Node health,custom]

|=========================================================

=== Measuring Node Health ===

Since Pacemaker calculates node health based on node attributes,
any method that sets node attributes may be used to measure node
health. The most common ways are resource agents or separate daemons.

Pacemaker provides examples that can be used directly or as a basis for
custom code. The +ocf:pacemaker:HealthCPU+ and +ocf:pacemaker:HealthSMART+
resource agents set node health attributes based on CPU and disk parameters.
The +ipmiservicelogd+ daemon sets node health attributes based on IPMI
values (the +ocf:pacemaker:SystemHealth+ resource agent can be used to manage
the daemon as a cluster resource).

== Reloading Services After a Definition Change ==

The cluster automatically detects changes to the definition of
services it manages.  The normal response is to stop the
service (using the old definition) and start it again (with the new
definition).  This works well, but some services are smarter and can
be told to use a new set of options without restarting.

To take advantage of this capability, the resource agent must:

. Accept the +reload+ operation and perform any required actions.
  _The actions here depend completely on your application!_
+
.The DRBD agent's logic for supporting +reload+
=====
[source,Bash]
-------
case $1 in
    start)
        drbd_start
        ;;
    stop)
        drbd_stop
        ;;
    reload)
        drbd_reload
        ;;
    monitor)
        drbd_monitor
        ;;
    *)
        drbd_usage
        exit $OCF_ERR_UNIMPLEMENTED
        ;;
esac
exit $?
-------
=====
. Advertise the +reload+ operation in the +actions+ section of its metadata
+
.The DRBD Agent Advertising Support for the +reload+ Operation
=====
[source,XML]
-------
<?xml version="1.0"?>
  <!DOCTYPE resource-agent SYSTEM "ra-api-1.dtd">
  <resource-agent name="drbd">
    <version>1.1</version>
    
    <longdesc lang="en">
      Master/Slave OCF Resource Agent for DRBD
    </longdesc>
    
    ...
    
    <actions>
      <action name="start"   timeout="240" />
      <action name="reload"  timeout="240" />
      <action name="promote" timeout="90" />
      <action name="demote"  timeout="90" />
      <action name="notify"  timeout="90" />
      <action name="stop"    timeout="100" />
      <action name="meta-data"    timeout="5" />
      <action name="validate-all" timeout="30" />
    </actions>
  </resource-agent>
-------
=====
. Advertise one or more parameters that can take effect using +reload+.
+
Any parameter with the +unique+ set to 0 is eligible to be used in this way.
+
.Parameter that can be changed using reload
=====
[source,XML]
-------
<parameter name="drbdconf" unique="0">
    <longdesc lang="en">Full path to the drbd.conf file.</longdesc>
    <shortdesc lang="en">Path to drbd.conf</shortdesc>
    <content type="string" default="${OCF_RESKEY_drbdconf_default}"/>
</parameter>
-------
=====

Once these requirements are satisfied, the cluster will automatically
know to reload the resource (instead of restarting) when a non-unique
field changes.
      
[NOTE]
======
Metadata will not be re-read unless the resource needs to be started. This may
mean that the resource will be restarted the first time, even though you
changed a parameter with +unique=0+.
======

[NOTE]
======
If both a unique and non-unique field are changed simultaneously, the
resource will still be restarted.
======
