I am using cassandra 7.4 and getting these messages.
Heap is 0.7802529021498031 full. You may need to reduce memtable and/or
cache sizes Cassandra will now flush up to the two largest memtables to free
up memory. Adjust flush_largest_memtables_at threshold in cassandra.yaml if
you don't want Cassandra to do this automatically
How do I verify that I need to adjust any thresholds? And how to calculate
correct value?
When I got this message only reads were occuring.
create keyspace StressKeyspace
with replication_factor = 3
and placement_strategy = 'org.apache.cassandra.locator.SimpleStrategy';
use StressKeyspace;
drop column family StressStandard;
create column family StressStandard
with comparator = UTF8Type
and keys_cached = 1000000
and memtable_flush_after = 1440
and memtable_throughput = 128;
nodetool -h dsdb4 tpstats
Pool Name Active Pending Completed
ReadStage 32 281 456598
RequestResponseStage 0 0 797237
MutationStage 0 0 499205
ReadRepairStage 0 0 149077
GossipStage 0 0 217227
AntiEntropyStage 0 0 0
MigrationStage 0 0 201
MemtablePostFlusher 0 0 1842
StreamStage 0 0 0
FlushWriter 0 0 1841
FILEUTILS-DELETE-POOL 0 0 3670
MiscStage 0 0 0
FlushSorter 0 0 0
InternalResponseStage 0 0 0
HintedHandoff 0 0 15
cfstats
Keyspace: StressKeyspace
Read Count: 460988
Read Latency: 38.07654727454945 ms.
Write Count: 499205
Write Latency: 0.007409593253272703 ms.
Pending Tasks: 0
Column Family: StressStandard
SSTable count: 9
Space used (live): 247408645485
Space used (total): 247408645485
Memtable Columns Count: 0
Memtable Data Size: 0
Memtable Switch Count: 1878
Read Count: 460989
Read Latency: 28.237 ms.
Write Count: 499205
Write Latency: NaN ms.
Pending Tasks: 0
Key cache capacity: 1000000
Key cache size: 299862
Key cache hit rate: 0.6031833150384193
Row cache: disabled
Compacted row minimum size: 219343
Compacted row maximum size: 5839588
Compacted row mean size: 497474
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