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Thread: Excessive NIO write buffering leads to mailboxd service outage

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    inqueue is offline Zimbra Employee
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    Default Excessive NIO write buffering leads to mailboxd service outage

    AFFECTED ZCS VERSIONS


    7.x, 8.0.0, 8.0.1, 8.0.2, 8.0.3, 8.0.4

    PROBLEM


    Excessive write buffering in NIO caused by slow clients can lead to mailboxd memory over-utilization which can result in a service outage. The write buffer fills the available heap allocated to mailboxd which can result in an endless loop of major garbage collection.

    IMPACT


    The issue occurs when NIO for IMAP is enabled on the mailbox server. In 7.x, NIO is disabled by default. In Zimbra 8, NIO is enabled by default. Client symptoms include sluggishness or lack of response (hangs) while communicating with an affected ZCS mailbox server. ZCS server to server traffic can also be affected.

    BUGS


    NIO imap, NIOSocketSession leaking - Fix targeted for the 8.0.5 release.

    WORKAROUND


    Disable IMAP NIO and restart mailboxd.
    Code:
    zmlocalconfig -e nio_imap_enabled=false
    zmmailboxdctl restart
    Last edited by inqueue; 07-10-2013 at 09:24 AM.
    --
    Jason Bryan
    Zimbra R&D

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