Uploaded image for project: 'MariaDB MaxScale'
  1. MariaDB MaxScale
  2. MXS-1412

Performance issue with MaxRows filter

    XMLWordPrintable

    Details

    • Type: Bug
    • Status: Closed (View Workflow)
    • Priority: Critical
    • Resolution: Fixed
    • Affects Version/s: 2.1.7
    • Fix Version/s: 2.1.8
    • Component/s: maxrows
    • Labels:
      None

      Description

      There is a performance issue with the MaxRows filter. When simple SELECT * FROM table (where there are millions of rows) is executed to see if the filter would trigger correctly and provide a different error in the log, 1 of 4 cpu cores on the server hit 100% and stayed there. 100% on a core for a single query seems like a lot. When the same query is executed without the MaxRows filter enabled, cpu usage is negligible.

      Furthermore, while the core was at 100% like this, queries hitting the backend were taking several seconds to complete, stuck in a state of 'writing to net' and the user was labeled as 'unauthenticated user'. These same queries run in microseconds any other time.

      As this happened on a server with 4 cores and threads=4 in the configuration file, it is expected to have all other queries routed mostly to the 3 idle cores. Either MaxScale was not routing them to the 3 idle cores, or there is a bottleneck somewhere else.

      Relevant part of configuration file is:

      [maxscale]
      threads=4
      ...
       
      [Galera Monitor]
      type=monitor
      module=galeramon
      servers=N1, N2, N3
      ...
       
      [Splitter Service]
      type=service
      router=readwritesplit
      servers=N1, N2, N3
      ...
      max_slave_connections=100%
      connection_timeout=5400
      disable_sescmd_history=true
      max_sescmd_history=5
      strict_multi_stmt=false
      filters=Hint | MaxRows
       
      [Hint]
      type=filter
      module=hintfilter
       
      [MaxRows]
      type=filter
      module=maxrows
      max_resultset_rows=300000
      max_resultset_size=1T
      max_resultset_return=error
      ...
      

      This may be related/similar to https://jira.mariadb.org/browse/MXS-1212

        Attachments

          Activity

            People

            Assignee:
            markus makela markus makela
            Reporter:
            valerii Valerii Kravchuk
            Votes:
            0 Vote for this issue
            Watchers:
            2 Start watching this issue

              Dates

              Created:
              Updated:
              Resolved: