containers. One basic idea here is that we can bundle related software
into such VM or container, so there is no need to compose one big
service from other services, like it was done with `rgmanager`. In
-general, a HA enabled resource should not depend on other resources.
+general, a HA managed resource should not depend on other resources.
How It Works
The CRM lost its lock, this means a failure happened and quorum was lost.
It main task is to manage the services which are configured to be highly
-available and try to always enforce them to the wanted state, e.g.: a
-enabled service will be started if its not running, if it crashes it will
-be started again. Thus it dictates the LRM the actions it needs to execute.
+available and try to always enforce the requested state. For example, a
+service with the requested state 'started' will be started if its not
+already running. If it crashes it will be automatically started again.
+Thus the CRM dictates the actions which the LRM needs to execute.
When an node leaves the cluster quorum, its state changes to unknown.
If the current CRM then can secure the failed nodes lock, the services
the same HA configuration.
+[[ha_manager_resource_config]]
Resources
~~~~~~~~~
recovered services move straight back to the fenced node.
-Node Power Status
------------------
-
-If a node needs maintenance you should migrate and or relocate all
-services which are required to run always on another node first.
-After that you can stop the LRM and CRM services. But note that the
-watchdog triggers if you stop it with active services.
-
-
-[[ha_manager_package_updates]]
-Package Updates
----------------
-
-When updating the ha-manager you should do one node after the other, never
-all at once for various reasons. First, while we test our software
-thoughtfully, a bug affecting your specific setup cannot totally be ruled out.
-Upgrading one node after the other and checking the functionality of each node
-after finishing the update helps to recover from an eventual problems, while
-updating all could render you in a broken cluster state and is generally not
-good practice.
-
-Also, the {pve} HA stack uses a request acknowledge protocol to perform
-actions between the cluster and the local resource manager. For restarting,
-the LRM makes a request to the CRM to freeze all its services. This prevents
-that they get touched by the Cluster during the short time the LRM is restarting.
-After that the LRM may safely close the watchdog during a restart.
-Such a restart happens on a update and as already stated a active master
-CRM is needed to acknowledge the requests from the LRM, if this is not the case
-the update process can be too long which, in the worst case, may result in
-a watchdog reset.
-
-
[[ha_manager_fencing]]
Fencing
-------
NOTE: The relocate count state will only reset to zero when the
service had at least one successful start. That means if a service is
-re-enabled without fixing the error only the restart policy gets
+re-started without fixing the error only the restart policy gets
repeated.
If after all tries the service state could not be recovered it gets
placed in an error state. In this state the service won't get touched
-by the HA stack anymore. To recover from this state you should follow
-these steps:
+by the HA stack anymore. The only way out is disabling a service:
+
+----
+# ha-manager set vm:100 --state disabled
+----
+
+This can also be done in the web interface.
+
+To recover from the error state you should do the following:
-* bring the resource back into a safe and consistent state (e.g.,
-killing its process)
+* bring the resource back into a safe and consistent state (e.g.:
+kill its process if the service could not be stopped)
-* disable the ha resource to place it in an stopped state
+* disable the resource to remove the error flag
* fix the error which led to this failures
-* *after* you fixed all errors you may enable the service again
+* *after* you fixed all errors you may request that the service starts again
+
+
+[[ha_manager_package_updates]]
+Package Updates
+---------------
+
+When updating the ha-manager you should do one node after the other, never
+all at once for various reasons. First, while we test our software
+thoughtfully, a bug affecting your specific setup cannot totally be ruled out.
+Upgrading one node after the other and checking the functionality of each node
+after finishing the update helps to recover from an eventual problems, while
+updating all could render you in a broken cluster state and is generally not
+good practice.
+
+Also, the {pve} HA stack uses a request acknowledge protocol to perform
+actions between the cluster and the local resource manager. For restarting,
+the LRM makes a request to the CRM to freeze all its services. This prevents
+that they get touched by the Cluster during the short time the LRM is restarting.
+After that the LRM may safely close the watchdog during a restart.
+Such a restart happens on a update and as already stated a active master
+CRM is needed to acknowledge the requests from the LRM, if this is not the case
+the update process can be too long which, in the worst case, may result in
+a watchdog reset.
+
+
+Node Maintenance
+----------------
+
+It is sometimes possible to shutdown or reboot a node to do
+maintenance tasks. Either to replace hardware, or simply to install a
+new kernel image.
+
+
+Shutdown
+~~~~~~~~
+
+A shutdown ('poweroff') is usually done if the node is planned to stay
+down for some time. The LRM stops all managed services in that
+case. This means that other nodes will take over those service
+afterwards.
+
+NOTE: Recent hardware has large amounts of RAM. So we stop all
+resources, then restart them to avoid online migration of all that
+RAM. If you want to use online migration, you need to invoke that
+manually before you shutdown the node.
+
+
+Reboot
+~~~~~~
+
+Node reboots are initiated with the 'reboot' command. This is usually
+done after installing a new kernel. Please note that this is different
+from ``shutdown'', because the node immediately starts again.
+
+The LRM tells the CRM that it wants to restart, and waits until the
+CRM puts all resources into the `freeze` state (same mechanism is used
+for xref:ha_manager_package_updates[Pakage Updates]). This prevents
+that those resources are moved to other nodes. Instead, the CRM start
+the resources after the reboot on the same node.
+
+
+Manual Resource Movement
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+Last but not least, you can also move resources manually to other
+nodes before you shutdown or restart a node. The advantage is that you
+have full control, and you can decide if you want to use online
+migration or not.
+
+NOTE: Please do not 'kill' services like `pve-ha-crm`, `pve-ha-lrm` or
+`watchdog-mux`. They manage and use the watchdog, so this can result
+in a node reboot.
[[ha_manager_service_operations]]
This are how the basic user-initiated service operations (via
`ha-manager`) work.
-enable::
+set state::
-The service will be started by the LRM if not already running.
+Request the service state.
+See xref:ha_manager_resource_config[Resource Configuration] for possible
+request states.
++
+----
+# ha-manager set SID -state REQUEST_STATE
+----
disable::
-The service will be stopped by the LRM if running.
+The service will be placed in the stopped state, even if it was in the error
+state. The service will not be recovered on a node failure and will stay
+stopped while it is in this state.
migrate/relocate::
projects / pve-docs.git / blobdiff