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ritu.kumari1_180415 avatar image
ritu.kumari1_180415 asked ·

What does the log entry "No STCS compactions found for first window" mean?

While switching compaction strategy from Size tier to Time window with compaction window of size 1 day got below messages recorded:

No STCS compactions found for first window for few sstables. What does this means?

[EDIT] we are trying to change comapction stategy using below command:

nodetool sjk mx -ms -b org.apache.cassandra.db:type=Tables,keyspace=********,table=********** -f CompactionParametersJson -v "{\"class\": \"org.apache.cassandra.db.compaction.TimeWindowCompactionStrategy\", \"compaction_window_size\": \"1\", \"compaction_window_unit\": \"DAYS\", \"max_threshold\": \"32\", \"min_threshold\": \"4\"}"

In debug log can see above message being recorded for few sstables.

DEBUG [CompactionExecutor:615] 2021-06-01 22:41:59,322 TimeWindowCompactionStrategy.java:322 - No STCS compactions found for first window, data files [(TrieIndexSSTableReader(path='/data_dir/keyspace/table-f2b11ebbe1836e82cbc12/-bti-Data.db'),4596734), options Min sstable size: 52428800, bucket low: 0.500000, bucket high: 1.500000

Unable to understand why we are getting it.

twcs
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1 Answer

Erick Ramirez avatar image
Erick Ramirez answered ·

It means that there were no SSTables identified as candidates for STCS compaction.

This is normal behaviour since there needs to be min_threshold SSTables of similar size (within bucket_low and bucket_high) for those SSTables to be identified as candidates to trigger a STCS compaction. In your example above, there was only 1 SSTable in the bucket so there were no other candidates.

I noted that you've logged a ticket with DataStax Support and that is the right place for you to get help. If you have any follow up questions, please post it in the support ticket. Cheers!

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