Hi Bingqin, When cdc_raw directory is full, Cassandra rejects new writes on this node with the following message in the log:
- Rejecting Mutation containing CDC-enabled table..... https://github.com/apache/cassandra/blob/cassandra-3.11.9/src/java/org/apache/cassandra/db/commitlog/CommitLogSegmentManagerCDC.java#L125 So, I'm not sorry if WriteTimeoutException is related to cdc feature in your case. For your issue with no commitLog flushed/copied into cdc_raw directory, can you try with an explicit nodetool flush and see if commitLog will be transferred ? For tables with a "very low" write rates, memtable can take a lot of time before be flushed on disk. Cheers, Ahmed Le jeu. 29 avr. 2021 à 00:23, Bingqin Zhou <bingq...@wepay.com.invalid> a écrit : > Hi all, > > We're working on a Kafka connector to capture data changes in Cassandra by > processing commit log files in the cdc_raw directory. After we enabled CDC > on a few tables, we didn't observe any commit log files getting flushed > into cdc_raw directory as expected, but got WriteTimeoutException in > Cassandra DB. > > Here's how we reproduce the issue: > > 1. Our Cassandra Settings: > > - Cassandra Version: 3.11.9 > - Related configs in Cassandra.yaml: > - cdc_enabled: true > - cdc_total_space_in_mb: 4096 > - commitlog_segment_size_in_mb: 32mb > - commitlog_total_space_in_mb: 8192 > - commitlog_sync: periodic > - commitlog_sync_period_in_ms: 10000 > > 2. Enable CDC on a few tables by CQL: > ALTER TABLE foo WITH cdc=true; > > 3. After a few days, we get *WriteTimeoutException* in Cassandra DB. > However at the same time, cdc_raw directory is still empty with no commit > log flushed/copied into it at all. > > I want to understand why there's no commit log file flushed into > cdc_raw directory at all even when the threshold cdc_total_space_in_mb has > been reached and write suspension has been triggered in Cassandra DB. This > sounds like a bug and currently makes the CDC feature useless. > > Thanks so much, > Bingqin Zhou > -- Cordialement; Ahmed ELJAMI
