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Thread: Breaks in oubound RTMP data

  1. Default Breaks in oubound RTMP data

    Recently, I'm having a problem on all of my Windows 2008 edge servers. It seems that from time to time, particularly when the server is handling more than a couple of hundred streams, Wowza will just stop sending data out to subscribing clients for a few seconds.

    The problem servers serve both live and vod (from separate applications of course). In the case of live, the Wowza server acts as edge, and pulls streams from FMIS origins using MediaCasters. In the case of VOD, the files are on the local hard drive.

    When the data dropout happens, all RTMP subscribers (both live and VOD) stop getting data, no connections are broken, and for the live streams, the incoming data from the origins remains constant.

    Based on what I can see from my tests, this seems to be mainly an RTMP problem. HTTP protocols seem unaffected, and RTSP streams don't break.

    Is anyone else having this issue on Windows 2008 Standard 64bit? Any ideas here? This is happening with Wowza versions 2.4.4 and 3.0.5, both running against Java 64 bit server 1.6 (build 17.0-b17)

    Last edited by jay_charles; 03-08-2012 at 11:40 AM.

  2. #2
    Join Date
    Dec 2007


    Sounds load related, according to the report. I assume the servers are all tuned?

    I would monitor with JConsole, network tools, see if you are saturating and maxing out the network perhaps.


  3. #3


    Sounds like a Java garbage collection issue. Out of the box the Wowza configs are not tuned for JVM garbage collection and once the memory buffer fills you will have a 'stop the world' event as is purges the active memory (eden) and moved it to older memory (old) or dumps it completely.

    The Wowza performance tuning guide will get you 80% of the way there. The rest of it really depends on your exact server config. For us we didn't need to use tenured memory space at all, so we shut it off and just used Eden and Old. This prevented any 'stop the world' memory scans and allowed us to run ~100 live HD cameras in extremely low latency. Your environment may be different.

    To test and see if this is the issue, open up the JConsole app in your Wowza folder (Windows would be Start -> Programs -> Wowza -> JConsole). Select the instance that has the Wowza name in it. Head on over to the memory tab. Watch your video and watch the memory graph. Usually easiest if you set it to 5 minutes. If you see the stuttering around the same time that the JVM is dumping the memory, then you know it is a garbage collection issue.

    For your reference, this is what we use in our setenv.bat file for Wowza:
    -Xmx8000M -Xms8000M -XX:+UseConcMarkSweepGC -XX:NewRatio=1 -XX:SurvivorRatio=4 -Xss256k -XX:+AlwaysPreTouch -XX:+CMSScavengeBeforeRemark -XX:+UseParNewGC -XX:ParallelCMSThreads=4 -XX:ParallelGCThreads=4 -XX:MaxTenuringThreshold=0 -XX:SurvivorRatio=4096
    Last edited by Bencredible; 03-08-2012 at 05:22 PM.

  4. #4


    Had to break in to two posts... Forum seemed to break otherwise...

    Some items are system specific. -Xmx and -Xms are set to 8GB because we have 12GB of RAM. That is as high as I would let it go, but if you only have say 6GB of ram you would want to set those to 4000. The -XX:ParallelCMSThreads and -XX:ParallelGCThreads are set to 4 which is 1/2 of my available CPU cores. If you had 16 cores in your system then you would set that to 8.

    Anyhow, that should at least get you started and help prevent the nasty garbage collection pauses, assuming that is the problem you're seeing.

  5. Default

    Thanks for in replies.

    I'm certain the problem isn't NIC saturation, as we see the problem when our 1Gbps interfaces are handling under 200Mbps. I'll try the suggestions on tuning garbage collection to see if that helps matters.

    Thanks again,

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