import ha-manager docs

[pve-docs.git] / ha-manager.adoc

[[chapter-ha-manager]]
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NAME
----

ha-manager - Proxmox VE HA manager command line interface

SYNOPSYS
--------

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DESCRIPTION
-----------
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High Availability
=================
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'ha-manager' handles management of user-defined cluster services. This
includes handling of user requests including service start, service
disable, service relocate, and service restart. The cluster resource
manager daemon also handles restarting and relocating services in the
event of failures.

HOW IT WORKS
------------

The local resource manager ('pve-ha-lrm') is started as a daemon on
each node at system start and waits until the HA cluster is quorate
and locks are working.  After initialization, the LRM determines which
services are enabled and starts them. Also the watchdog gets
initialized.

The cluster resource manager ('pve-ha-crm') starts on each node and
waits there for the manager lock, which can only be held by one node
at a time.  The node which successfully acquires the manager lock gets
promoted to the CRM, it handles cluster wide actions like migrations
and failures.

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
will be 'stolen' and restarted on another node.

When a cluster member determines that it is no longer in the cluster
quorum, the LRM waits for a new quorum to form. As long as there is no
quorum the node cannot reset the watchdog. This will trigger a reboot
after 60 seconds.

CONFIGURATION
-------------

The HA stack is well integrated int the Proxmox VE API2. So, for
example, HA can be configured via 'ha-manager' or the PVE web
interface, which both provide an easy to use tool.

The resource configuration file can be located at
'/etc/pve/ha/resources.cfg' and the group configuration file at
'/etc/pve/ha/groups.cfg'. Use the provided tools to make changes,
there shouldn't be any need to edit them manually.

RESOURCES/SERVICES AGENTS
-------------------------

A resource or also called service can be managed by the
ha-manager. Currently we support virtual machines and container.

GROUPS
------

A group is a collection of cluster nodes which a service may be bound to.

GROUP SETTINGS
~~~~~~~~~~~~~~

nodes::

list of group node members

restricted::

resources bound to this group may only run on nodes defined by the
group. If no group node member is available the resource will be
placed in the stopped state.

nofailback::

the resource won't automatically fail back when a more preferred node
(re)joins the cluster.


RECOVERY POLICY
---------------

There are two service recover policy settings which can be configured
specific for each resource.

max_restart::

maximal number of tries to restart an failed service on the actual
node.  The default is set to one.

max_relocate::

maximal number of tries to relocate the service to a different node.
A relocate only happens after the max_restart value is exceeded on the
actual node. The default is set to one.

Note that 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
repeated.

ERROR RECOVERY
--------------

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:

* bring the resource back into an safe and consistent state (e.g:
killing its process)

* disable the ha resource to place it in an stopped state

* fix the error which led to this failures

* *after* you fixed all errors you may enable the service again


SERVICE OPERATIONS
------------------

This are how the basic user-initiated service operations (via
'ha-manager') work.

enable::

the service will be started by the LRM if not already running.

disable::

the service will be stopped by the LRM if running.

migrate/relocate::

the service will be relocated (live) to another node.

remove::

the service will be removed from the HA managed resource list. Its
current state will not be touched.

start/stop::

start and stop commands can be issued to the resource specific tools
(like 'qm' or 'pct'), they will forward the request to the
'ha-manager' which then will execute the action and set the resulting
service state (enabled, disabled).


SERVICE STATES
--------------

stopped::

Service is stopped (confirmed by LRM)

request_stop::

Service should be stopped. Waiting for confirmation from LRM.

started::

Service is active an LRM should start it ASAP if not already running.

fence::

Wait for node fencing (service node is not inside quorate cluster
partition).

freeze::

Do not touch the service state. We use this state while we reboot a
node, or when we restart the LRM daemon.

migrate::

Migrate service (live) to other node.

error::

Service disabled because of LRM errors. Needs manual intervention.


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