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Thread: Multiple instances sharing MediaCache

  1. #1
    Join Date
    Aug 2014
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    Default Multiple instances sharing MediaCache

    I have 2 Wowza Streaming Engine servers running (load balanced), both host a VOD Edge application that is configured to use a medicache that shares the same storeage. Generally this appears to work as expected however some files seem to be located in the cache:

    2014-08-27 12:05:22 UTC comment server ERROR 500 - MediaCacheReaderCached.openInternal[movie/1709046/03BPDS.mp4] : java.io.FileNotFoundException: /mnt/VOD/previews/mediacache/00/00/00000008.media (No such file or directory)|at java.io.RandomAccessFile.open(Native Method)|at java.io.RandomAccessFile.<init>(Unknown Source)|at com.wowza.io.WowzaRandomAccessFile.<init>(WowzaRandomAccessFile.java:12)|at com.wowza.wms.mediacache.model.MediaCacheReaderCached.a(MediaCacheReaderCached.java:47)|at com.wowza.wms.mediacache.model.MediaCacheReaderCached.open(MediaCacheReaderCached.java:22)| - - - 597698.024 - - - - - - - -

    which would be fine however it continues to throw the above error instead of trying to re-fetch the file from the source.

    My assumption is the 2 boxes are not able to share a single cache source for some reason, which would be unfortunate, but I'd like to know if that's the case before I reconfigure.

    Thx

  2. #2

    Default

    Hi there and welcome to the Wowza support forum.

    Yes, MediaCache is capable and designed to be accessed by multiple servers.

    Is it possible that you inadvertently(or deliberately) deleted the MediaCache store you are trying to access? As that is what it looks like according to the error message.

    Salvadore

  3. #3
    Join Date
    Aug 2014
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    Default

    Quote Originally Posted by salvadore View Post
    Hi there and welcome to the Wowza support forum.

    Yes, MediaCache is capable and designed to be accessed by multiple servers.

    Is it possible that you inadvertently(or deliberately) deleted the MediaCache store you are trying to access? As that is what it looks like according to the error message.

    Salvadore
    Thanks for the quick response.

    It's good to know that I can share a single cache drive across servers, that will save me a few TBs ;-}

    The MediaCache store is still active on both servers and works in many (most) cases. There are at least a few thousand videos cached and served without a problem however there are a handful that seem to be bad. One thing of note is I attempted to access the same file (movie/1709046/03BPDS.mp4) from each of the 2 servers directly and noticed that the cache filenames were different? /mnt/VOD/previews/mediacache/00/00/00000008.media vs /mnt/VOD/previews/mediacache/00/00/00000007.media

    One thing I don't understand is, if the MediaCacheReaderCached can't find the cached media file why does it keep trying? If, when it failed, it went back to the source then I could (probably live with it.

    Is there maybe a way I could purge an item from the cache and force it to re-fetch the source?

    TTFN

  4. #4

    Default

    I believe the .media files are actually chunks, not the entire file.

    Have a look at this guide:
    How to purge an item from the cache (MediaCache)

    Salvadore

  5. #5
    Join Date
    Aug 2014
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    3

    Default

    You are correct, the .media are chunks, my bad.

    I solved my problem. I fired up a test instance that was set to clear the cache on startup (unintentionally). That pretty much killed everything and forced me to reset my servers. Not the most graceful solution and I'm sure there are a couple hundred users wondering why their video stopped but it appears to have fixed the glitch so.... silver lining ;-}

    Thanks for your help.

  6. #6

    Default

    Thanks for the update and glad you got it working.

    Salvadore

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