Synnefo » snf-ganeti » ganeti-local

Node auto-maintenance

+++++++++++++++++++++

If the cluster parameter ``maintain_node_health`` is enabled (see the

manpage for :command:`gnt-cluster`, the init and modify subcommands),

then the following will happen automatically:

- the watcher will shutdown any instances running on offline nodes

- the watcher will deactivate any DRBD devices on offline nodes

In the future, more actions are planned, so only enable this parameter

if the nodes are completely dedicated to Ganeti; otherwise it might be

possible to lose data due to auto-maintenance actions.

      status. It has two separate functions, one for the master node

      and another one that runs on every node.

    <refsect2>

      <title>Master operations</title>

      <para>

        Its primary function is to try to keep running all instances

        which are marked as <emphasis>up</emphasis> in the configuration

        file, by trying to start them a limited number of times.

      </para>

      <para>

        Its other function is to <quote>repair</quote> DRBD links by

        reactivating the block devices of instances which have

        secondaries on nodes that have been rebooted.

      </para>

    </refsect2>

    <refsect2>

      <title>Node operations</title>

      <para>

        The watcher will restart any down daemons that are appropriate

        for the current node.

      </para>

      <para>

        In addition, it will execute any scripts which exist under the

        <quote>watcher</quote> directory in the ganeti hooks directory

        (@SYSCONFDIR@/ganeti/hooks). This should be used for

        lightweight actions, like starting any extra daemons.

      </para>

      <para>

        If the cluster

        parameter <literal>maintain_node_health</literal> is enabled,

        then the watcher will also shutdown instances and DRBD devices

        if the node is declared as offline by known master candidates.

      </para>

      <para>

        The watcher does synchronous queries but will submit jobs for

        executing the changes. Due to locking, it could be that the jobs

        execute much later than the watcher executes them.

      </para>

    </refsect2>

  </refsect1>

  <refsect1>

    <title>FILES</title>

      <filename>@LOCALSTATEDIR@/lib/ganeti/watcher.data</filename>

      (only used on the master) and a log file at