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Thread: How to reduce the cancellation time of a query

  1. #1
    Join Date
    Mar 2015
    Posts
    8

    Default How to reduce the cancellation time of a query

    Hello

    When cancelling a Mondrian query through the Saiku UI, I notice that the JVM running Saiku & mondrian keeps on occupying my CPU for 30 seconds till 10 minutes. A screenshot of the profiler shows following stack:
    Name:  image2015-8-19 17-51-58.jpg
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    When running this on a single-cored server, it even take hours before the query execution is cancelled. Because I thought it might be due to multithreading (RolapResultShepherd class), I reduced the amount of SQL, MDX and Cache threads to 1 in the Mondrian.properties but to no prevail.

    Can someone explain the inner workings of the cancellation procedure? And do you know any options I can try to make sure the query is cancelled in a shorter period of time?

    Thank you.

  2. #2
    Join Date
    Jan 2013
    Posts
    796

    Default

    In general a cancellation should be picked up and handled immediately. There are some places where cancellation is not checked until an operation is completed, however, and if the operation is long running (like your tuple list merge) then cancellation can be delayed. I believe what you're seeing is captured here: http://jira.pentaho.com/browse/MONDRIAN-2279

    Some work has been done over the past year to clean up some places where cancellation is not handled correctly, but 2279 is still outstanding. Vote for it-- that'll increase it's visibility.

  3. #3
    Join Date
    Mar 2015
    Posts
    8

    Default

    Thank you for your answer. I up-voted the issue and started watching it.

    We see that our server gets bogged down because of accumulation of cancelled user queries. You know any remedies?

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