harep¶
NAME¶
harep - Ganeti auto-repair tool
DESCRIPTION¶
Harep is the Ganeti auto-repair tool. It is able to detect that an instance is
broken and to generate a sequence of jobs that will fix it, in accordance to the
policies set by the administrator. At the moment, only repairs for instances
using the disk templates plain or drbd are supported.
Harep is able to recognize what state an instance is in (healthy, suspended, needs repair, repair disallowed, pending repair, repair failed) and to lead it through a sequence of steps that will bring the instance back to the healthy state. Therefore, harep is mainly meant to be run regularly and frequently using a cron job, so that it can actually follow the instance along all the process. At every run, harep will update the tags it adds to instances that describe its repair status, and will submit jobs that actually perform the required repair operations.
By default, harep only reports on the health status of instances, but doesn’t perform any action, as they might be potentially dangerous. Therefore, harep will only touch instances that it has been explicitly authorized to work on.
The tags enabling harep, can be associated to single instances, or to a nodegroup or to the whole cluster, therefore affecting all the instances they contain. The possible tags share the common structure:
ganeti:watcher:autorepair:<type>
where <type> can have the following values:
fix-storage: allow disk replacement or fix the backend without affecting the instance itself (broken DRBD secondary)migrate: allow instance migration. Note, however, that current harep does not submit migrate jobs; so, currently, this permission level is equivalent tofix-storage.failover: allow instance reboot on the secondary; this action is taken, if the primary node is offline.reinstall: allow disks to be recreated and the instance to be reinstalled
Each element in the list of tags, includes all the authorizations of the
previous one, with fix-storage being the least powerful and reinstall
being the most powerful.
In case multiple autorepair tags act on the same instance, only one can actually be active. The conflict is solved according to the following rules:
if multiple tags are in the same object, the least destructive takes precedence.
if the tags are across objects, the nearest tag wins.
Example:
A cluster has instances I1 and I2, where I1 has the failover tag, and
the cluster has both fix-storage and reinstall.
The I1 instance will be allowed to failover, the I2 instance only to
fix-storage.
LIMITATIONS¶
Harep doesn’t do any hardware failure detection on its own, it relies on nodes being marked as offline by the administrator.
Also harep currently works only for instances with the drbd and
plain disk templates.
Using the data model of htools(1), harep cannot distinguish between drained and offline nodes. In particular, it will (permission provided) failover instances also in situations where a migration would have been enough. In particular, handling of node draining is better done using hbal(1), which will always submit migration jobs, however is the permission to fall back to failover.
These issues will be addressed by a new maintenance daemon in future Ganeti versions, which will supersede harep.
OPTIONS¶
The options that can be passed to the program are as follows:
- -L socket, --luxi=*socket*
collect data via Luxi, optionally using the given socket path.
- --job-delay=*seconds*
insert this much delay before the execution of repair jobs to allow the tool to continue processing instances.
- --dry-run
only show which operations would be carried out, but do nothing, even on instances where tags grant the appropriate permissions. Note that harep keeps the state of repair operations in instance tags; therefore, only the operations of the next round of actions can be inspected.