Hi Folks, We recently encountered an error on a prod cluster where Nifi couldn't acquire an H2 database lock when the canvas UI was modified, 'Timeout trying to lock table "ACTION"'. I wasn't able to track down who held the lock, or even where the lock was at. Ended up restarting the cluster, which did clear the issue and restored modification ability.
Has anyone seen issues like this, H2 DB lock timeouts? I don't believe the issue was due to timeout, we made sure all users stopped modification attempts so we could debug, so the canvas should have been quiescent. I believe there was a lock held, either a stale lock or someone had a pending modification that wasn't committed. I'd really like to know where to look for this lock, to track. I see locks in Nifi's database_repository, like nifi-flow-audit.lock.db and nifi-user-keys.lock.db but don't believe these were at issue. Related, see some threads for H2 DB where use of mvcc settings were recommended to support multiple version concurrency, such as discussed in http://www.h2database.com/html/advanced.html#mvcc. Is this advisable for Nifi ? Thanks for any help or information regarding this. patw
