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  1. MariaDB Server
  2. MDEV-7610

MariaDB Galera Cluster Table locking issue after mysqldump execution



    • Bug
    • Status: Closed (View Workflow)
    • Major
    • Resolution: Won't Fix
    • 5.5.41-galera
    • N/A
    • Galera
    • CentOS release 6.5 2.6.32-431.3.1.el6.x86_64
      VM, 4GB RAM
      MariaDB Galera Cluster consists of 3 nodes


      We updated MariaDB Galera Version to 5.5.41 on 19th of January.
      We start a daily mysqldump on 21:00 CET. This worked for ~ 1 year without any issues.
      Last night (18th of FEB), the following issue happend at 21:00 (9 p.m.):

      • mysqldump starts on Node 1 with the following parameters:
        mysqldump -uroot -p --create-options {DATABASE_NAME}


      • simultaneously, the following query did not complete on Node 1 and remains with the state "sql end" on the server:
        INSERT INTO ` {DBNAME}`.`{TABLE_NAME}` (isin, date, count )\n VALUES ('XXXX12345', CURDATE() , 1 )\n ON DUPLICATE KEY UPDATE count=count+1

        * full mysqldump on Node 1 completed with a duration of only a minute without any issues like every day, dumps are valid and complete

        * new incoming connections on Node 1 try to access the same table, but are waiting in state "Waiting for table level lock"



        ` (isin, date, count )\n VALUES ('YYYY67890', CURDATE() , 1 )\n ON DUPLICATE KEY UPDATE count=count+1

      • INSERT/UPDATE statements on the same table on Node 2/3 do also not complete. Sessions are haning with similar statements in states "update" and "query end", first sessions appeared on 21:00
      • Number of connections increases on all 3 nodes, since all nodes are waiting for first INSERT statement on Node 1 to complete, therefore replication stopped.
      • Nodes 2 and 3 ran out of free connections and resources at ~ 21:10
      • INSERT statement on Node 1 could not be killed, whole Cluster needed to be shut down and restarted
      • Errorlogs do not show any issues until the high amount of connections leads to service unavailability
      • Nodes did not write any Core Dumps
      • This Incident is (hopefully) not reproducable, as already mentioned the cluster ran wihtout any issues about a year, the mysqldump is made every day at the same time.




            jplindst Jan Lindström (Inactive)
            TK Tobias Kleinke
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