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From "John Vines (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ACCUMULO-3569) Automatically restart accumulo processes intelligently
Date Fri, 06 Feb 2015 19:51:35 GMT
John Vines created ACCUMULO-3569:
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             Summary: Automatically restart accumulo processes intelligently
                 Key: ACCUMULO-3569
                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3569
             Project: Accumulo
          Issue Type: Bug
          Components: scripts
            Reporter: John Vines


On occasion process will die, for a variety of reasons. Some reasons are critical whereas
others may be due to momentary blips. There are a variety of reasons, but not all of the reasons
warrant keeping the server down and requiring human attention.

With that, I would like to propose a watcher process, which is an option component that wraps
the calls to the various processes (tserver, master, etc.). This process can watch the processes,
get their exit codes, read their logs, etc. and make intelligent decisions about how to behave.
This behavior would include coarse detection of failure types (will discuss below) and a configurable
response behavior around how many attempts should be made in a given window before giving
up entirely.

As for failure types, there are a few arch ones that seem to be regularly repeating that I
think are prime candidates for an initial approach-
Zookeeper lock lost - this can happen for a variety of reasons, mostly related to network
issues or server (tserver or zk node) congestion. These are some of the most common errors
and are typically transient. However, if these occur with great frequency then it's a sign
of a larger issue that needs to be handled by an administrator.

Jvm OOM - There are two spaces where these really seem to occur - a system that's just poorly
configured and dies shortly after it starts up and then there is the case where the system
gets slammed in just the right way where objects in our code and/or the iterator stack may
push the JVM just over the limits. In the former case, this will fail quickly and relatively
rapidly when being restarted, whereas the latter case is something that will occur rarely
and will want attention, but doesn't warrant keeping the node offline in the meantime.

Standard shutdown - this is just a case that occurs where we don't want it to automatically
interact because we want it to go down. Just a design consideration.

Unexpected exceptions - this is a catch all for everything else. We can attempt to enumerate
them, but they're less common. This would be something configured to have less tolerance for,
but just because a server goes down due to a random software bug doesn't mean that server
should be removed from the cluster unless it happens repeatedly (because then it's a sign
of a hardware/system issue). But we should provide the ability to keep resources available
in this space.



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