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Thread: Two questions about MediaCache

  1. #1
    Join Date
    Aug 2012

    Default Two questions about MediaCache


    I'm currently testing mediacache addon (ver. 2.0) with wowza 3 and have some confusing questions, hoping to get some help.

    1. Sometimes, the items in mediacache are not flushed when they have been cached overpass the time limit set in MaxTimeToLive property. For example, I set MaxTimeToLive defaultly to be 1200000 and played a video yesterday, it was cached in the cache store. But when I checked the cache store this morning, I found the data still remained in cache store and never updated. I'm sure that the video was not viewed at night. I tried to purge the data manually with simple deletion, then this caused a "item not in the cache" error when I replaying the video. A server reboot is needed for this error.
    I said "sometimes" because most of the time it works fine.

    2. For testing I set MinTimeToLive to be 60000 and a small MaxSize to 2G and stuff it full with several videos. When I continue playing another video a minute later I expecting an immediate update in cache store, like it does when it still has room, replacing the oldest data with new incoming one.
    But nothing happens.
    After a while, I play again, this time the cache updates.
    So I'm wondering the timing that cache updates, is there any events needed to trigger that?

    Relative config is attached below:
                            <!-- variables: ${com.wowza.wms.context.ServerConfigHome} -->
                            <!-- <Path>${com.wowza.wms.context.ServerConfigHome}/mediacache</Path> -->
                            <!-- Mechanical Disk: assuming 20% of 50MBps sustained I/O rate = 10MBps
                            <!-- SSD drive: assuming 20% of 150MBps sustained I/O rate = 30MBps -->
    Any suggestions? Or I've done something wrong?
    Please Advise,

    Thanks in advance,
    Last edited by weichung; 09-05-2012 at 03:58 AM.

  2. #2
    Join Date
    Dec 2007



    If you can reproduce the first problem, let us know: open a ticket at with steps to reproduce.

    I'm not sure about the timing question, I don't know. You can discover to some extent as you are doing.


  3. #3
    Join Date
    Aug 2012


    Thanks, Richard,
    I'll keep working on this.


  4. #4
    Join Date
    Aug 2012


    Hi Richard,

    About question 1, it seems that the cause would be the unexpected crash of the player or some un-usual behavior which make cache think the item is still in use, so it will not be flushed. I reboot wowza server and everything works fine.

    In my experience, every time a play request reaches the full-occupied cache, the cache checks if there are any items which exceed the MinTimeToLive limit. The expired ones will be flushed. Then the requesting item enters the cache only if there is enough space for it. No immediate update for items exceed MinTimeToLive unless there is a request coming or they exceed the MaxTimeToLive, I guess.

    Advise please if I'm wrong.


  5. #5
    Join Date
    Dec 2007


    Sounds right.


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