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Thread: IMAP server stop processing

  1. #1
    slaplante is offline Intermediate Member
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    Default IMAP server stop processing

    In the last 2 weeks, I have the imap server process that keep answering to TCP 143, as I am able to connect to it with telnet, but then after the connection; nothing. Like the process go zombie.

    I check the /var/log/maillog but aside the last transactions that been log there no error.

    However, everything else looks to work fine during the imap hang WebUI, mailbox, LDAP...

    Restarting Zimbra resumed the issue but it happened for the third time in 2 weeks, so I'm afraid of a degradation...

    I use Zimbra 6.0.6_GA_2330 on a RHEL 4 (Nahant Update 5)

    Any hint where I can look to identify what went wrong.

    Thanks!

    Steeve

  2. #2
    iway is offline Partner (VAR/HSP)
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    Have you had a look at imapmaxnumthreads?

  3. #3
    slaplante is offline Intermediate Member
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    Here's the setting;
    zimbraImapNumThreads: 200

    Is it too low? On big day, we have about 125 concurrent connections. What the implication to up it on memory ie?

    Thank very much for your help!

    Steeve

  4. #4
    iway is offline Partner (VAR/HSP)
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    Well, we have it set at 500 currently.

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    slaplante is offline Intermediate Member
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    Hi,

    Sorry for the delay of answer but I had to let run the suggested setting to see the result. Unfortunately, after two busy Mondays, it doesn't seem the increase to 500 concurrents connections helps.

    Any other suggestion or log I can look into to help?

    Thanks greatly guys!

    Steeve

  6. #6
    dalmate is offline Elite Member
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    When the imap service dies, did you check how many connections are connecting to your server:
    netstat -ant | grep 143 | wc -l
    as zimbra user.
    Please let's me know that information and I can help.

  7. #7
    slaplante is offline Intermediate Member
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    Dalmate,

    Connections ran as high as 300 in the peak hour. Server scaled well to 175 but start to crawl and became slow in the 200 connections.

    I also saw that the swap is almost not use but there was memory left so I guess it is normal.

    It worth notice that Zimbra main process went often over 100% CPU utilization?!?!

    PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
    22672 zimbra 16 0 2964m 2.6g 11m S 150 45.6 1314:59 java

    Wierd...

    Steeve

  8. #8
    y@w's Avatar
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    Quote Originally Posted by slaplante View Post
    Dalmate,

    Connections ran as high as 300 in the peak hour. Server scaled well to 175 but start to crawl and became slow in the 200 connections.

    I also saw that the swap is almost not use but there was memory left so I guess it is normal.

    It worth notice that Zimbra main process went often over 100% CPU utilization?!?!

    PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
    22672 zimbra 16 0 2964m 2.6g 11m S 150 45.6 1314:59 java

    Wierd...

    Steeve
    The workload is being spread across multiple cores/processors

    What's a little more interesting is that java is using 45% of your memory. It shouldn't need to be quite that high (and can cause problems if it is). How much memory is in this system? See: Performance Tuning Guidelines for Large Deployments - Zimbra :: Wiki

    Also, anything interesting in /opt/zimbra/log/mailbox.log when the problem occurs?

  9. #9
    dalmate is offline Elite Member
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    @slaplante:
    How many Imap concurrent connections did you set?
    Please check by this command:
    zmprov gs yourdomain.com | grep Threads
    if it is 200 threads, please increase to 500 threads (or any number you want).
    About your CPU, please let me know which version of zimbra did you use?

  10. #10
    slaplante is offline Intermediate Member
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    Thank y@w, dalmate,

    We are at about 6Gb of RAM and I'll upgrade it to 8Gb. I also have all settings referenced in the link provided and have the server rebooted tonight. I will see the outcome next monday.

    dalmate, As suggested I upped the imap threads from 200 to 500 with no concrete improvement.

    Thanks again guys, I'll keep you post with the results next monday...

    Steeve

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