andrei.elkin@pp.inet.fi writes:
And the above transition can be explained by MDEV-24654 GTID event falsely marked transactional, its patch is under review.
Oh, yes, this bug sounds like it could result in what Jan described. It was not clear to me from the bug description exactly under what conditions the bug occurs, but if the first slave marks the replicated transactions as "transactional" in its binlog, then the observed behaviour could occur. The question then is how the chained slaves manage to run MyISAM transactions in parallel without getting conflicts and hanging. One possibility is that these are mostly insert-only queries (as Jan mentioned in another mail), and I believe that MyISAM has the feature that MyISAM can handle insert-only queries in parallel without locks and conflicts. Would require a bit more research to be sure this is the explanation, but it seems a possibility. - Kristian.