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MySQL NDB Cluster 7.4 Release Notes  /  Release Series Changelogs: MySQL NDB Cluster 7.4  /  Changes in MySQL NDB Cluster 7.4.22 (5.6.42-ndb-7.4.22) (2018-10-23, General Availability)

Changes in MySQL NDB Cluster 7.4.22 (5.6.42-ndb-7.4.22) (2018-10-23, General Availability)

Bugs Fixed

  • When the SUMA kernel block receives a SUB_STOP_REQ signal, it executes the signal then replies with SUB_STOP_CONF. (After this response is relayed back to the API, the API is open to send more SUB_STOP_REQ signals.) After sending the SUB_STOP_CONF, SUMA drops the subscription if no subscribers are present, which involves sending multiple DROP_TRIG_IMPL_REQ messages to DBTUP. LocalProxy can handle up to 21 of these requests in parallel; any more than this are queued in the Short Time Queue. When execution of a DROP_TRIG_IMPL_REQ was delayed, there was a chance for the queue to become overloaded, leading to a data node shutdown with Error in short time queue.

    This issue is fixed by delaying the execution of the SUB_STOP_REQ signal if DBTUP is already handling DROP_TRIG_IMPL_REQ signals at full capacity, rather than queueing up the DROP_TRIG_IMPL_REQ signals. (Bug #26574003)

  • Having a large number of deferred triggers could sometimes lead to job buffer exhaustion. This could occur due to the fact that a single trigger can execute many operations—for example, a foreign key parent trigger may perform operations on multiple matching child table rows—and that a row operation on a base table can execute multiple triggers. In such cases, row operations are executed in batches. When execution of many triggers was deferred—meaning that all deferred triggers are executed at pre-commit—the resulting concurrent execution of a great many trigger operations could cause the data node job buffer or send buffer to be exhausted, leading to failure of the node.

    This issue is fixed by limiting the number of concurrent trigger operations as well as the number of trigger fire requests outstanding per transaction.

    For immediate triggers, limiting of concurrent trigger operations may increase the number of triggers waiting to be executed, exhausting the trigger record pool and resulting in the error Too many concurrently fired triggers (increase MaxNoOfFiredTriggers. This can be avoided by increasing MaxNoOfFiredTriggers, reducing the user transaction batch size, or both. (Bug #22529864)

    References: See also: Bug #18229003, Bug #27310330.