Configuring key cache settings
This content applies only to On-premises and Client-managed cloud environments
Maintain fast read access to Cassandra SSTables by tuning the use of the key cache separately for each table.
Cassandra’s key cache stores a map of partition keys to row index entries, which enables fast read access into SSTables.
- Check the current cache size by using Cassandra's nodetool info utility.The following nodetool info snippet shows sample key cache metrics:
root@ip-10-123-5-62:/usr/local/tomcat/cassandra/bin# ./nodetool info ID : 8ae22738-98eb-4ed1-8b15-0af50afc5943 Gossip active : true Thrift active : true Native Transport active: true Load : 230.73 GB Generation No : 1550753940 Uptime (seconds) : 634324 Heap Memory (MB) : 3151.44 / 10240.00 Off Heap Memory (MB) : 444.33 Data Center : us-east Rack : 1c Exceptions : 0 Key Cache : entries 1286950, size 98.19 MB, capacity 300 MB, 83295 hits, 83591 requests, 0.996 recent hit rate, 14400 save period in seconds Row Cache : entries 0, size 0 bytes, capacity 0 bytes, 0 hits, 0 requests, NaN recent hit rate, 0 save period in seconds Counter Cache : entries 0, size 0 bytes, capacity 50 MB, 0 hits, 0 requests, NaN recent hit rate, 7200 save period in seconds Token : (invoke with -T/--tokens to see all 256 tokens) - If the
sizeparameter roughly equals thecapacityparameter, increase the cache size in the prconfig/dnode/yaml/key_cache_size_in_mb/default dynamic system setting, depending on your needs.The key_cache_size_in_mb setting indicates the maximum amount of memory for the key cache across all tables. The default value is either 5% of the total JVM heap, or 100 MB, whichever is lower.
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