nodetool cfstats

Provides statistics about tables.

Provides statistics about tables.

Synopsis

$ nodetool <options> cfstats -i -- <keyspace>.<table> ...  -H 
Options
Short Long Description
-h --host Hostname or IP address
-p --port Port number
-pwf --password-file Password file path
-pw --password Password
-u --username User name
-- Separates an option from an argument that could be mistaken for a option.
Other options are:
  • i ignores the following tables, providing only information about other Cassandra tables
  • keyspace.table is one or more keyspace and table names in dot notation.
  • H converts bytes to a human readable form: kilobytes (KB), megabytes (MB), gigabytes (GB), or terabytes (TB). (Cassandra 2.1.1)

Description

The nodetool cfstats command provides statistics about one or more tables. It's updated when SSTables change through compaction or flushing.

Use dot notation to specify one or more keyspace and table names. If you do not specify a keyspace and table, Cassandra provides statistics about all tables. If you use the -i option, Cassandra provides statistics about all tables except the given ones. The use of the metrics-core library in Cassandra 2.1 makes the output more informative and easier to understand.

This table describes the nodetool cfstats output.
nodetool cfstats output
Name of statistic Example value Brief description Related information
Keyspace libdata Name of the keyspace Keyspace and table
Read count 11207 Number of requests to read tables in the libdata keyspace since startup  
Read latency 0.047. . . ms Latency reading the tables in the libdata keyspace OpsCenter alert metrics
Write count 17598 Number of requests to update tables in the libdata keyspace since startup Same as above
Write latency 0.053. . . ms Latency writing tables in the libdata keyspace Same as above
Pending tasks 0 Tasks in the queue for reads, writes, and cluster operations of tables in the keyspace OpsCenter pending task metrics
Table libout Name of the Cassandra table  
SSTable count 3 Number of SSTable containing data from the table How to use the SSTable counts metric and OpsCenter alert metrics
Space used (live), bytes: 9592399 Space used by the table (depends on operating system) Advanced system alert metrics
Space used (total), bytes: 9592399 Same as above Same as above
Space used by snapshots (total), bytes: 0 Same occupied by backup data  
SSTable compression ratio 0.367. . . Fraction of data-representation size resulting from compression Types of compression option)
Memtable cell count 1022550 Number of cells (storage engine rows x columns) of data in the memtable Cassandra memtable structure in memory
Memtable data size, bytes 32028148 Size of the memtable data Same as above
Memtable switch count 3 Number of times a full memtable was swapped for an empty one (Increases each time the memtable for a table is flushed to disk) How memtables are measured article
Local read count 11207 Number of local read requests for the libout table since startup OpsCenter alert documentation
Local read latency 0.048 ms Round trip time in milliseconds to complete a request to read the libout table Factors that affect read latency
Local write count 17598 Number of local requests to update the libout the table since startup OpsCenter alert documentation
Local write latency 0.054 ms Round trip time in milliseconds to complete an update to the libout table Factors that affect write latency
Pending tasks 0 Number of read, write, and cluster operations that are pending OpsCenter pending task metrics documentation
Bloom filter false positives 0 Number of false positives, which occur when the bloom filter said the row existed, but it actually did not exist in absolute numbers Tuning bloom filters
Bloom filter false ratio 0.00000 Fraction of all bloom filter checks resulting in a false positive Same as above
Bloom filter space used, bytes 11688 Size of bytes of the bloom filter data Same as above
Compacted partition minimum bytes 1110 Lower size limit for the partition being compacted in memory Used to calculate what the approximate row cache size should be. Multiply the reported row cache size, which is the number of rows in the cache, by the compacted row mean size for every table and sum them.
Compacted partition maximum bytes 126934 Upper size limit for compacted table rows. Configurable in the cassandra.yaml in_memory_compaction _limit_in_mb
Compacted partition mean bytes 2730 The average size of compacted table rows  
Average live cells per slice (last five minutes) 0.0 Average of cells scanned by single key queries during the last five minutes  
Average tombstones per slice (last five minutes) 0.0 Average of tombstones scanned by single key queries during the last five minutes  

Examples

This example shows an excerpt of the output of the command after flushing a table of library data to disk.

$ nodetool cfstats libdata.libout
Keyspace: libdata
	Read Count: 11207
	Read Latency: 0.047931114482020164 ms.
	Write Count: 17598
	Write Latency: 0.053502954881236506 ms.
	Pending Flushes: 0
		Table: libout
		SSTable count: 3
		Space used (live), bytes: 9088955
		Space used (total), bytes: 9088955
		Space used by snapshots (total), bytes: 0
		SSTable Compression Ratio: 0.36751363892150946
		Memtable cell count: 0
		Memtable data size, bytes: 0
		Memtable switch count: 3
		Local read count: 11207
		Local read latency: 0.048 ms
		Local write count: 17598
		Local write latency: 0.054 ms
		Pending flushes: 0
		Bloom filter false positives: 0
		Bloom filter false ratio: 0.00000
		Bloom filter space used, bytes: 11688
		Compacted partition minimum bytes: 1110
		Compacted partition maximum bytes: 126934
		Compacted partition mean bytes: 2730
		Average live cells per slice (last five minutes): 0.0
		Average tombstones per slice (last five minutes): 0.0

Using the human-readable option

Using the human-readable -H option provides output in easier-to-read units than bytes. For example:

$ nodetool cfstats demodb.nhanes -H
Keyspace: demodb
	Read Count: 0
	Read Latency: NaN ms.
	Write Count: 20050
	Write Latency: 0.08548014962593516 ms.
	Pending Flushes: 0
		Table: nhanes
		SSTable count: 1
		Space used (live): 13.75 MB
		Space used (total): 13.75 MB
		Space used by snapshots (total): 0 bytes
		SSTable Compression Ratio: 0.3064650643762481
		Memtable cell count: 0
		Memtable data size: 0 bytes
		Memtable switch count: 1
		Local read count: 0
		Local read latency: NaN ms
		Local write count: 20050
		Local write latency: 0.085 ms
		Pending flushes: 0
		Bloom filter false positives: 0
		Bloom filter false ratio: 0.00000
		Bloom filter space used: 23.73 KB
		Compacted partition minimum bytes: 1.87 KB
		Compacted partition maximum bytes: 2.69 KB
		Compacted partition mean bytes: 2.26 KB
		Average live cells per slice (last five minutes): 0.0
		Maximum live cells per slice (last five minutes): 0.0
		Average tombstones per slice (last five minutes): 0.0
		Maximum tombstones per slice (last five minutes): 0.0

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The location of the cassandra.yaml file depends on the type of installation:
Package installations /etc/cassandra/cassandra.yaml
Tarball installations install_location/resources/cassandra/conf/cassandra.yaml