Database Reference
In-Depth Information
Cassandra also does a lot of work off-heap. Things like bloom filters in version
1.2 and forward are off-heap now. Keeping tabs on what the off-heap memory us-
age looks like is also very important.
Garbage collection is also one of the metrics that can be viewed from the
Memory tab. If needed (though typically not recommended unless you know what
you are doing), you can even force a GC from the Memory tab in JConsole. In
Cassandra 1.1 and later, there are even helpful bars that display the total memory
used versus memory available both on-heap and off-heap.
Threads
The Threads tab in JConsole is dedicated to showing the current and peak usage
patterns of various thread stages in Cassandra (see Figure 8.3 ). These include
everything that you would normally see in the logs from things like the Com-
mitLog handler and compaction scheduler all the way to garbage collection, Gos-
sip, and streaming. It is also helpful here to see how many threads your system
uses normally as well as under load.
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