Memory (Off-Heap)

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The Memory (Off-Heap) metrics groups contain metrics regarding Cassandra’s off-heap memory usage. There are two metrics groups: one for overall metrics and one for column-family-level metrics. The metrics available are:

  • Memtable
  • AllMemtables
  • Compression metadata
  • Index summary
  • Bloom filter

Memtable

The total amount of data stored in the memtable that resides off-heap, including column related overhead and partitions overwritten.

You can also get this metric through the Monitoring API with the query param metrics=n::offheapsizememtable for overall metrics and the query param cf::{keyspace}::{table}::offHeapSizeMemtable for column-family-level metrics.

AllMemtables

The total amount of data stored in the memtables, including secondary indexes and pending flush memtables, that resides off-heap.

You can also get this metric through the Monitoring API with the query param metrics=n::offheapsizeallmemtables for overall metrics and the query param cf::{keyspace}::{table}::offHeapSizeAllMemtables for column-family-level metrics.

Compression metadata

The off-heap memory used by compression metadata.

You can also get this metric through the Monitoring API with the query param metrics=n::offheapusedcompressionmetadata for overall metrics and the query param metrics=cf::{keyspace}::{table}::offHeapUsedCompressionMetadata for column-family-level metrics.

Index summary

The off-heap memory used by the index summary.

You can also get this metric through the Monitoring API with the query param metrics=n::offheapusedindexsummary for overall metrics and the query param metrics=cf::{keyspace}::{table}::offHeapUsedIndexSummary for column-family-level metrics.

Bloom filter

The off-heap memory used by the bloom filter.

You can also get this metric through the Monitoring API with the query param metrics=n::offheapusedbloomfilter for overall metrics and the query param metrics=cf::{keyspace}::{table}::offHeapUsedBloomFilter for column-family-level metrics.

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