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Johnny Miller edited this page Jul 25, 2016 · 22 revisions

Templates

You can choose the following templates for the dashboard:

  • Cluster - the Cassandra cluster name
  • DC - the Data Center
  • GroupBy - datacenter/instance/cluster (not relevant for all 'per Node' graphs)
  • Instance - the node name

Dashboard Description

Key Cache

The key cache holds the location of keys in memory on a per-column family basis. It is a cache of the partition index for a Cassandra table. Its goal is to reduce the disk seek time for reading data.

For column family level read optimizations, turning this value up can have an immediate impact as soon as the cache warms. Key caching is enabled by default and set to the smaller of 5% of the available heap, or 100MB.

Graphs:

  • KeyCache Hit Rate Per Node
  • KeyCache Size vs Capacity - Compares keyCache's currently allocated size vs the maximum configured capacity
  • KeyCache Number of Entries
  • KeyCache Requests Count per Second

Row Cache

Unlike the key cache, the row cache holds the entire contents of the row in memory.

It is best used when you have a small subset of data to keep hot and you frequently need most or all of the columns returned. For these use cases, row cache can have substantial performance benefits.

Graphs:

  • RowCache Hit Rate Per Node
  • RowCache Size vs Capacity - Compares RowCache currently allocated size vs the maximum configured capacity
  • RowCache Number of Entries
  • RowCache Requests Count per Second

Counter Cache

Because the implementation of counters post Cassandra 2.1 performs a mutexed read-before-write, latency would suffer with a naive implementation, particularly for many updates contenting for few counter objects. To mitigate this, Cassandra 2.1 introduces a new form of cache, counter cache, to keep hot counter values performant.

Graphs:

  • CounterCache Hit Rate Per Node
  • CounterCache Size vs Capacity - Compares CounterCache currently allocated size vs the maximum configured capacity
  • CounterCache Number of Entries
  • CounterCache Requests Count per Second

File Cache

This is used for the memory allocated for sstable-reading buffers. Graphs:

  • FileCache Size
  • FileCache HitRate
  • FileCache Requesta
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