CNDB-13565: allow to set memtable shard lock fairness via JMX and a system property #1785
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…ystem property Prior to that change memtable shard lock was always non-fair. This change introduces cassandra.trie.memtable.shard.lock.fairness system property and LockFairness property of org.apache.cassandra.db:type=TrieMemtableConfig JMX object to configure it persistently or on-line. The on-line change is effective once a new memtable is created (i.e. after flush). If forcing flush is not desired one can watch BytesFlushed metric for the table
jtgrabowski
reviewed
May 30, 2025
| @@ -152,8 +151,10 @@ public class TrieMemtable extends AbstractAllocatorMemtable | |||
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| @VisibleForTesting | |||
| public static final String SHARD_COUNT_PROPERTY = "cassandra.trie.memtable.shard.count"; | |||
| public static final String SHARD_LOCK_FAIRNESS_PROPERTY = "cassandra.trie.memtable.shard.lock.fairness"; | |||
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maybe move both to CassandraRelevantProperties.java ?
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(SHARD_COUNT_PROPERTY and SHARD_LOCK_FAIRNESS_PROPERTY)
jtgrabowski
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May 30, 2025
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❌ Build ds-cassandra-pr-gate/PR-1785 rejected by Butler1 new test failure(s) in 3 builds Found 1 new test failures
Found 4 known test failures |
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What is the issue
Memtable shard lock (required for
put) is non-fair. We suspect this leads to elevated latencies in case of bursty load, as in #13565What does this PR fix and why was it fixed
This change introduces
cassandra.trie.memtable.shard.lock.fairness systemproperty andLockFairnesspropertyof
org.apache.cassandra.db:type=TrieMemtableConfigJMX object to configure it persistently or on-line.The on-line change is effective once a new memtable is created (i.e. after flush). If forcing flush is not desired one can watch
BytesFlushedmetric for the table