Bug #77760 index stat setup failure should only print info warnings
Submitted: 17 Jul 2015 8:59 Modified: 12 Oct 2015 12:50
Reporter: Magnus Blåudd Email Updates:
Status: Closed Impact on me:
Category:MySQL Cluster: Cluster (NDB) storage engine Severity:S3 (Non-critical)
Version:7.2.22 OS:Any
Assigned to: CPU Architecture:Any

[17 Jul 2015 8:59] Magnus Blåudd
When the ndb_index_stat component in ha_ndbcluster is enabled it will try to create it's necessary system tables, events and event subscriptions. This operation is quite likely to fail when: 
- several mysqlds start at the same time
- the index stat component is enabled in more than one mysqld at a time
- the cluster is starting/restarting/stopping/node failure handling.

This is since all the msyqld's compete to create these resources.

The problem is not fatal and after a little while the mysqld will retry the operation and most likely succeed.

How to repeat:
Occassionally in testing we detect a "create index stats tables failed: error 701" warning.

Suggested fix:
Downgrade these warning printouts to information printouts. Thes problem is just informational and the mysqld's will retry the operation soon.
[12 Oct 2015 12:50] Jon Stephens
Documented fix in the NDB 7.2.22, 7.3.11, 7.4.8, and 7.5.0 changelogs as follows:

    When attempting to enable index statistics, creation of the
    required system tables, events and event subscriptions often
    fails when multiple mysqld processes using index statistics are
    started concurrently in conjucntion with starting, restarting,
    or stopping the cluster, or with node failure handling. This is
    normally recoverable, since the affected mysqld process or
    processes can and do retry these operations shortly thereafter.
    For this reason, such failures are no longer logged as warnings,
    but merely as informational events.