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From "Paul Millar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2991) Server logs error on shutdown
Date Mon, 07 May 2018 07:58:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2991?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16465582#comment-16465582

Paul Millar commented on ZOOKEEPER-2991:

ZOOKEEPER-2795 is almost the same as this bug report

> Server logs error on shutdown
> -----------------------------
>                 Key: ZOOKEEPER-2991
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2991
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.4.10, 3.4.11
>            Reporter: Paul Millar
>            Priority: Major
> Commit d497aac4 introduced the ZooKeeperServer#registerServerShutdownHandler method and
corresponding ZooKeeperServerShutdownHandler class.  Both the method and class are package-protected,
resulting in the expectation that non-ZK code should not use either.
> However, if registerServerShutdownHandler is *not* called, then ZK will log an error:
> {quote}ZKShutdownHandler is not registered, so ZooKeeper server won't take any action
on ERROR or SHUTDOWN server state changes
> {quote}
> There are several problems here.  In order of importance (for me, at least!)
> First, (most important) this certainly should not be logged as an error.  Depending
on usage, there may be no need for a shutdown handler.  Always logging an error (with no
opportunity to silence it) is therefore wrong.
> Second, the ability to learn of state changes may be of general interest (monitoring,
etc); however, this is not possible if the method is protected.
> Third, the method accepts a concrete class that is designed to use a CountDownLatch.
This is not appropriate in all cases.  The method should be updated to accept an interface.

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