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From "Koushik Das (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CLOUDSTACK-8666) Put host in Alert state only after alert.wait timeout
Date Thu, 23 Jul 2015 12:13:04 GMT
Koushik Das created CLOUDSTACK-8666:
---------------------------------------

             Summary: Put host in Alert state only after alert.wait timeout
                 Key: CLOUDSTACK-8666
                 URL: https://issues.apache.org/jira/browse/CLOUDSTACK-8666
             Project: CloudStack
          Issue Type: Bug
      Security Level: Public (Anyone can view this level - this is the default.)
          Components: Management Server
    Affects Versions: 4.5.0, 4.6.0
            Reporter: Koushik Das
            Assignee: Koushik Das
             Fix For: 4.6.0


When there is a ping timeout on a host, investigators try to determine the state of a host.
If none of the investigators are able to determine the host state then the process is repeated
after some time. This works most of the time except some boundary scenarios. For e.g. if last
host or all host in a XS cluster are brought down then the investigators are not able to determine
the host state and the investigation process never completes. In such scenarios host state
always remain as Up.

In order to fix these boundary scenarios, a fix was made (refer to commit 4a13f81485c0f0664c60acafe534946e7428f080)
to immediately put the host in Alert state if investigators are not able to determine the
state after ping timeout.

The fix solved the boundary scenarios but introduced a new issue. Suppose there is a XS cluster
with 2 hosts and the master host is brought down. In this case XS elects a new master for
the cluster. Since master is down, investigators won't able to determine host state until
a new master is elected. If this master election takes more than ping timeout to complete
then the host is put to Alert based on the above fix. Once this happens, the host continues
to remain in Alert state and no actions are taken on the VMs on this host. In this case if
the investigators were allowed to run for 1 or 2 more times, possibly the new master election
would have completed and host state correctly determined.

In order to fix both these issues, instead of putting the host to Alert state immediately,
the investigators should be allowed to run for some time based on alert.wait global config.
At the end of this interval if the host state still cannot be determined then put the host
in Alert.



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