ganeti-watcher¶
Name¶
ganeti-watcher - Ganeti cluster watcher
Synopsis¶
ganeti-watcher [--debug] [--job-age=*age* ] [--ignore-pause] [--rapi-ip=*IP*] [--no-verify-disks]
DESCRIPTION¶
The ganeti-watcher is a periodically run script which is responsible for keeping the instances in the correct status. It has two separate functions, one for the master node and another one that runs on every node.
If the watcher is disabled at cluster level (via the
gnt-cluster watcher pause command), it will exit without doing
anything. The cluster-level pause can be overridden via the
--ignore-pause option, for example if during a maintenance the
watcher needs to be disabled in general, but the administrator
wants to run it just once.
The --debug option will increase the verbosity of the watcher
and also activate logging to the standard error.
The --rapi-ip option needs to be set if the RAPI daemon was
started with a particular IP (using the -b option). The two
options need to be exactly the same to ensure that the watcher
can reach the RAPI interface.
Master operations¶
Its primary function is to try to keep running all instances which are marked as up in the configuration file, by trying to start them a limited number of times.
Another function is to “repair” DRBD links by reactivating the block devices of instances which have secondaries on nodes that have been rebooted.
Additionally, it will verify and repair degraded DRBD disks; this
will not happen, if the --no-verify-disks option is given.
The watcher will also archive old jobs (older than the age given
via the --job-age option, which defaults to 6 hours), in order
to keep the job queue manageable.
Node operations¶
The watcher will restart any down daemons that are appropriate for the current node.
In addition, it will execute any scripts which exist under the
“watcher” directory in the Ganeti hooks directory
(/usr/local/etc/ganeti/hooks). This should be used for lightweight
actions, like starting any extra daemons.
If the cluster parameter maintain_node_health is enabled, then the
watcher will also shutdown instances and DRBD devices if the node is
declared as offline by known master candidates.
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 submits them.
FILES¶
The command has a set of state files (one per group) located at
/usr/local/var/lib/ganeti/watcher.GROUP-UUID.data (only used on the
master) and a log file at
/usr/local/var/log/ganeti/watcher.log. Removal of either file(s)
will not affect correct operation; the removal of the state file will
just cause the restart counters for the instances to reset to zero, and
mark nodes as freshly rebooted (so for example DRBD minors will be
re-activated).
In some cases, it’s even desirable to reset the watcher state, for example after maintenance actions, or when you want to simulate the reboot of all nodes, so in this case, you can remove all state files:
rm -f /usr/local/var/lib/ganeti/watcher.*.data
rm -f /usr/local/var/lib/ganeti/watcher.*.instance-status
rm -f /usr/local/var/lib/ganeti/instance-status
And then re-run the watcher.