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  1. MariaDB Server
  2. MDEV-20390

Parse command/tool for galera.cache ring buffer

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Details

    • New Feature
    • Status: Open (View Workflow)
    • Minor
    • Resolution: Unresolved
    • None
    • Galera
    • None

    Description

      When we are talking about gcache, I have questions like:
      - What is the lower seqnumber stored on gcache
      - Which query/event belongs to seqnumber X

      I would like to be able to somehow parse the gcache to be able to answer some of those questions. I believe this follows the InnoDB standard, where each information is stored in a specific offset. Like the first 100 bytes are the header of the file, where we store from 1st - 4th byte the version of the file, from 5th - 10th the cluster uuid, ... so on. Can you please point out what is the layout of the file or direct me to the source files where this mapping is defined?

      I tried strings but it does not work:

      # strings -t d -a -e s galera.cache |  more
            0 Version: 2
           11 GID: 4974e99f-c27a-11e9-842b-e7d05d4d0202
           53 synced: 0
         1434 lK\_
         1442 a?T/
         1506 test

      Note: People pointed me to check the binary logs, but for Galera, it is not frequent to have binary logs enabled, so I want a way to extract this information from Galera ring buffer file (aka gcache).

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            seppo Seppo Jaakola
            vgrippa Vinicius Malvestio Grippa
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              Updated:

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