XDMP-DEADLOCK at Info message level

Question

Official MarkLogic documentation on XDMP-DEADLOCK (https://docs.marklogic.com/8.0/messages/XDMP-en/XDMP-DEADLOCK) talks about it at Debug and Notice message levels, however I couldn't find any information on XDMP-DEADLOCK at Info message level.

Can someone please explain what does a XDMP-DEADLOCK message mean at Info message level?

For example:

2020-03-02 22:00:00.763 Info: XDMP-DEADLOCK: Deadlock detected locking Security http://marklogic.com/xdmp/users/123456789101112131415

MarkLogic Version : 8.0-9.1 OS : RedHat Linux 7

Answer 1

The Debug and Notice level XDMP-DEADLOCK messages are reported on the e-node that is evaluating the query. The Info level messages are reported on the d-node.

If you are running your servers as blended E/D, instead of dedicated evaluator and data nodes, then you may see the different log levels for those meessages logged on the same server.

This knoledgebase article explains MarkLogic XDMP-DEADLOCK messages in more detail:

https://help.marklogic.com/Knowledgebase/Article/View/17/0/understanding-xdmp-deadlock

MarkLogic Server is designed to automatically detect and resolve deadlocks. When a deadlock is detected, one of the deadlocked transactions is retried, allowing the other to acquire the lock and continue. When this expected behavior occurs, an XDMP-DEADLOCK is written to the e-node error log as a ‘Debug’ message to indicate that a deadlock occurred and was resolved.

If the deadlock cannot be resolved by repeated retries, an XDMP-DEADLOCK message is written to the e-node error log as a ‘Notice’ message.

Deadlocks are also reported at ‘Info’ level on the d-node on which they occur.

Deadlock messages can be the source of performance issues. You should investigate how to adjust the application codebase to avoid them when possible. Especially if you are seeing them frequently and/or they are bubbling up to the Notice level.