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ritu.kumari1_180415 avatar image
ritu.kumari1_180415 asked Erick Ramirez edited

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 Erick Ramirez edited

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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