MySQL Bugs: #79214: MaxNoOfExecutionThreads documentation wrong for 7.3.3+

Bug #79214	MaxNoOfExecutionThreads documentation wrong for 7.3.3+
Submitted:	10 Nov 2015 21:39	Modified:	17 Nov 2015 11:42
Reporter:	Jesper wisborg Krogh	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Cluster: Documentation	Severity:	S2 (Serious)
Version:	7.3+	OS:	Any
Assigned to:	Jon Stephens	CPU Architecture:	Any

Description:
In MySQL 7.3.3 the maximum number of threads supported was increased to 72 (from 44)and the maximum number of LDM threads was increased from 16 to 32. This is documented in http://dev.mysql.com/doc/refman/5.6/en/mysql-cluster-ndbd-definition.html#ndbparam-ndbmtd-...

However, this change also included changes to the thread distribution for existing number of threads:

// {MaxNoOfExecutionThreads, LDM thread, TC, threads, Send threads, Receive threads}
-    { 12, 4, 3, 1, 2 },
-    { 13, 4, 3, 2, 2 },
-    { 14, 4, 4, 2, 2 },
-    { 15, 4, 5, 2, 2 },
+    { 12, 6, 2, 1, 1 },
+    { 13, 6, 3, 1, 1 },
+    { 14, 6, 3, 1, 2 },
+    { 15, 6, 3, 2, 2 },

This change is not reflected in http://dev.mysql.com/doc/refman/5.6/en/mysql-cluster-ndbd-definition.html#ndbparam-ndbmtd-...

Note: neither of the above changes are mentioned in the change history

How to repeat:
See

   * http://dev.mysql.com/doc/refman/5.6/en/mysql-cluster-ndbd-definition.html#ndbparam-ndbmtd-...
   * http://dev.mysql.com/doc/relnotes/mysql-cluster/7.3/en/mysql-cluster-news-7-3-3.html

Suggested fix:
Update the documentation and change history

Posted by developer:
 
Since changing the number of LDM threads requires at least a system restart (and possibly an initial system restart) this should also be mentioned as an online upgrade limitation.

Posted by developer:
 
The workaround for doing online upgrades is to change to use ThreadConfig instead of MaxNoOfExecutionThreads and set the ThreadConfig configuration to match the pre-upgrade thread distribution.

Posted by developer:
 
A similar online upgrade limitation exists for 7.4.3 where the number of LDM threads changed for:

   * MaxNoOfExecutionThreads = 20-23 (LDM changed from 8 to 10)
   * MaxNoOfExecutionThreads = 40-47 (LDM changed from 16 to 20)

http://dev.mysql.com/doc/refman/5.6/en/mysql-cluster-ndbd-definition.html#ndbparam-ndbmtd-... already reflects this change, but should also be noted in the upgrade documentation.

Thank you for your bug report. This issue has been addressed in the documentation. The updated documentation will appear on our website shortly.