Database Reference
In-Depth Information
▪ Migration Stage
▪ Response Stage
▪ Row Mutation Stage (for deletes and updates)
▪ Row Read Stage
▪ Stream Stage
For each of these stages you can see the counts for active, completed, and pending tasks. Some
of the stages, such as for reading and writing data, maintain their own thread pools, and the
MBeans allow you to see the pool size. All of the stage objects expose only attributes and don't
allow you to perform any operations.
org.apache.cassandra.db
These are the Cassandra classes related to the core database itself that are exposed as MBeans.
They include Caches, Column Family Stores, the Commit Log, and the Compaction Manager.
You can view information about a variety of caches that Cassandra maintains—including the
caches for column family key and row hints—for location information of keys, rows, and migra-
tions. The cache information contains attributes for the cache's current size, capacity, number of
cache requests, cache hits, and recent cache activity.
Column Family Stores is another set of MBeans, but these give you a richer variety of attribute
values, and also allow you to perform some operations. These give you a view into your memt-
ables, SSTables, and Bloom filter usage. You can use the operations provided to force a flush of
the memtables, initiate a major compaction by calling the
forceMajorCompaction
method of
the
CompactionManager
class, or invalidate a row cache.
One useful set of statistics here relates to reading and writing data, included in the
ColumnFam-
ilyStores > system > Schema
bean:
Tottal R
d Countt
This is the number of reads Cassandra has performed, available from the
ReadCount
attrib-
ute.
l Read C
Recent R
t Read L
d Lattency
You get this number (in microseconds) from the
RecentReadLatencyMicros
attribute. You
can also see the
TotalReadLatencyMicros
; the total reads multiplied by the read latency
gives you that number.
