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  1. MariaDB Server
  2. MDEV-10530

Replication unable to catch up master, seconds behind master increase

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Details

    • Bug
    • Status: Open (View Workflow)
    • Major
    • Resolution: Unresolved
    • 10.0.26
    • 10.1
    • Replication
    • None
    • Debian 8.5

    Description

      I am using master-slave replication. Master and slave are the same mariadb versions.
      I am using only MyISAM tables and my default storage engine is MyISAM.
      I've installed mariadb using apt-get (that means, from official Debian repository).

      Replicatin is set up properly, using mixed format, and slave server replicates properly. But it is incredibly slow. Seconds behind master never reaches zero, and gradually increments. Replication is completely useless this way. There is no particular sql query which would block, the replication goes on, only very slow. SHOW PROCESSLIST does never show any sql query which would block the replication, all sql queries are very fast by themselves. Even if I set wild_ignore to %.% to ignore all tables in all databases, it still has a problem that it is delayed and the delay increases (by about 1 second each 2 seconds).

      But, when I mount the /var/lib/mysql directory to tmpfs, replication works fast. So it looks like it has something to do with syncing data to disk, or so. But, I do not see any high I/O on the disk at all.

      I fixed the problem by installing mysqld 5.5.50, this works without any issue at all.
      I also know the replication had no issues on some older version of mariadb (it was on the server before reinstall, unfortunately I do not remember the version). So it is something introduced in recent mariadb release.

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            Elkin Andrei Elkin
            TomasM Tomas Matejicek
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              Updated:

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