MySQL Bugs: #91178: GTID restriction is missing details

Bug #91178	GTID restriction is missing details
Submitted:	7 Jun 2018 15:04	Modified:	10 Aug 2018 9:48
Reporter:	Daniël van Eeden (OCA)	Email Updates:
Status:	Won't fix	Impact on me:	None
Category:	MySQL Cluster: Documentation	Severity:	S3 (Non-critical)
Version:	7.6.6	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-limitations-unsupported.html

"Replication using global transaction identifiers (GTIDs) is not compatible with NDB Cluster, and is not supported in NDB Cluster 7.5 or NDB CLuster 7.6. Do not enable GTIDs when using the NDB storage engine, as this is very likely to cause problems up to and including failure of NDB Cluster Replication."

This makes some sense when replicating between NDB clusters.

However when migrating to NDB one might want to replicate from InnoDB to NDB.

Also setting GTID_MODE to OFF_PERMISSIVE / ON_PERMISSIVE / ON doesn't give a warning. It seems to work just fine.

I guess the limitation is that the list of processed GTID transactions is not shared in the cluster. 

So as long as all writes go to one SQL node things should work.

Probably the best advice is to set gtid_mode=OFF_PERMISSIVE when migrating.

How to repeat:
Read docs and try to use GTID with NDB

Hi Daniel,

Yes you are correct, documentation here lacks details. In general ndbcluster SE lacks any understanding of GTID (for now) so the safest thing is to "not use GTID when ndbclustering" as documentation states. There are some situations where it could work and can work, as you noticed yourself but that opens a new can of worm as it would require much detailed documentation. As I understand your report, it's exactly what you would like (more detailed documentation) so I'm verifying this.

Thanks for the report
Bogdan

To the best of my knowledge, we neither support nor even test any use of gtid_mode with NDB. I can't document what we don't officially support.

Please file a feature request bug to have you're proposing supported by Development; when they do, we'll document it.

Thanks!