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  1. MariaDB ColumnStore
  2. MCOL-5163

Increase the stability of writing processes: WriteEngineServer, DMLProc, DDLProc

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    • 2021-17

    Description

      As of 6.4.1 MCS uses systemd to handle processing start and stop routine. It also handles the processes hierarchy restarts, e.g. if mcs-primproc(contains both EM and PP) crashes systemd restarts mcs-writeengineserver unit. If WE is in the middle of a write operation this potentially left the system in an unusable state. If mcs-writeengineserver is restarted systemd restarts both mcs-dmlproc and mcs-ddlproc so if DMLProc was doing some changes it left failed transactions behind. It is tedious to clean these stuck txns from the cluster.
      The suggested approach is to decouple pairs: mcs-primproc, mcs-writeengineserver and mcs-writeengineserver and mcs-dmlproc, mcs-writeengineserver and mcs-ddlproc systemd-wise.

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            drrtuy Roman added a comment - - edited

            4QA Try to crash ExeMgr or PP and it will force WE and DMLProc to restart even if they are in the middle of a txn. The current version doesn't restart WE or DMLProc if PP has crashed.

            drrtuy Roman added a comment - - edited 4QA Try to crash ExeMgr or PP and it will force WE and DMLProc to restart even if they are in the middle of a txn. The current version doesn't restart WE or DMLProc if PP has crashed.

            Build verified: 22.08-1 (#5324)

            Also verified 6.x (#5262) since it was also checked into develop-6.

            dleeyh Daniel Lee (Inactive) added a comment - Build verified: 22.08-1 (#5324) Also verified 6.x (#5262) since it was also checked into develop-6.

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              dleeyh Daniel Lee (Inactive)
              drrtuy Roman
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