Uploaded image for project: 'MariaDB Server'
  1. MariaDB Server
  2. MDEV-33166

Misleading wsrep_cluster_size value immediately after starting mariadb service

    XMLWordPrintable

Details

    • Bug
    • Status: Open (View Workflow)
    • Minor
    • Resolution: Unresolved
    • 10.6.16
    • None
    • Galera
    • None
    • RHEL7

    Description

      I have a medium/large database running on MariaDB Galera with 3 nodes on RHEL7, and I just upgraded from 10.6.15 to 10.6.16.

      While upgrading, I noticed something a bit strange:

      Immediately after starting up the mariadb service (sudo systemctl start mariadb), after having upgraded the RPM packages, I ran the command/statement:

      mariadb -e "show status where variable_name in ('wsrep_ready', 'wsrep_local_state_comment', 'wsrep_connected', 'wsrep_cluster_size');"
      

      ... which gave the following output:

      +---------------------------+-----------------------------------+
      | Variable_name             | Value                             |
      +---------------------------+-----------------------------------+
      | wsrep_local_state_comment | Joining: receiving State Transfer |
      | wsrep_cluster_size        | 3                                 |
      | wsrep_connected           | ON                                |
      | wsrep_ready               | OFF                               |
      +---------------------------+-----------------------------------+
      

      The Knowledge Base defines the wsrep_cluster_size status variable as:

      Number of nodes currently in the cluster.

      I believe wsrep_cluster_size here is misleading. When I re-ran the command shortly after, it reported wsrep_cluster_size as 2, and it stayed at 2 (while the other status variables remained unchanged) until I finally got:

      +---------------------------+--------+
      | Variable_name             | Value  |
      +---------------------------+--------+
      | wsrep_local_state_comment | Synced |
      | wsrep_cluster_size        | 3      |
      | wsrep_connected           | ON     |
      | wsrep_ready               | ON     |
      +---------------------------+--------+
      

      I reproduced the issue on another node when I did the same there.

      Perhaps this is "as designed", but the value seems misleading to me. Or maybe I am just misunderstanding the purpose of this variable.

      Attachments

        Activity

          People

            Unassigned Unassigned
            karll Karl Levik
            Votes:
            0 Vote for this issue
            Watchers:
            1 Start watching this issue

            Dates

              Created:
              Updated:

              Git Integration

                Error rendering 'com.xiplink.jira.git.jira_git_plugin:git-issue-webpanel'. Please contact your Jira administrators.