Monitoring

Monitoring

Metrics in Cassandra are managed using the Dropwizard Metrics library. These metrics can be queried via JMX or pushed to external monitoring systems using a number of built in and third party reporter plugins.

Metrics are collected for a single node. It’s up to the operator to use an external monitoring system to aggregate them.

Metric Types

All metrics reported by cassandra fit into one of the following types.

Gauge

An instantaneous measurement of a value.

Counter

A gauge for an AtomicLong instance. Typically this is consumed by monitoring the change since the last call to see if there is a large increase compared to the norm.

Histogram

Measures the statistical distribution of values in a stream of data. + In addition to minimum, maximum, mean, etc., it also measures median, 75th, 90th, 95th, 98th, 99th, and 99.9th percentiles.

Timer

Measures both the rate that a particular piece of code is called and the histogram of its duration.

Latency

Special type that tracks latency (in microseconds) with a Timer plus a Counter that tracks the total latency accrued since starting. The former is useful if you track the change in total latency since the last check. Each metric name of this type will have ‘Latency’ and ‘TotalLatency’ appended to it.

Meter

A meter metric which measures mean throughput and one-, five-, and fifteen-minute exponentially-weighted moving average throughputs.

Table Metrics

Each table in Cassandra has metrics responsible for tracking its state and performance.

The metric names are all appended with the specific Keyspace and Table name.

Reported name format:

Metric Name

org.apache.cassandra.metrics.Table.<MetricName>.<Keyspace>.<Table>

JMX MBean

org.apache.cassandra.metrics:type=Table keyspace=<Keyspace> scope=<Table> name=<MetricName>

Note

There is a special table called ‘all’ without a keyspace. This represents the aggregation of metrics across all tables and keyspaces on the node. ====[cols=”,,”,options=”header”,]

Name	Type	Description
MemtableOnHeapSize	Gauge<Long>	Total amount of data stored in the memtable that resides on-heap, including column related overhead and partitions overwritten.
MemtableOffHeapSize	Gauge<Long>	Total amount of data stored in the memtable that resides off-heap, including column related overhead and partitions overwritten.
MemtableLiveDataSize	Gauge<Long>	Total amount of live data stored in the memtable, excluding any data structure overhead.
AllMemtablesOnHeapSize	Gauge<Long>	Total amount of data stored in the memtables (2i and pending flush memtables included) that resides on-heap.
AllMemtablesOffHeapSize	Gauge<Long>	Total amount of data stored in the memtables (2i and pending flush memtables included) that resides off-heap.
AllMemtablesLiveDataSize	Gauge<Long>	Total amount of live data stored in the memtables (2i and pending flush memtables included) that resides off-heap, excluding any data structure overhead.
MemtableColumnsCount	Gauge<Long>	Total number of columns present in the memtable.
MemtableSwitchCount	Counter	Number of times flush has resulted in the memtable being switched out.
CompressionRatio	Gauge<Double>	Current compression ratio for all SSTables.
EstimatedPartitionSizeHistogram	Gauge<long[]>	Histogram of estimated partition size (in bytes).
EstimatedPartitionCount	Gauge<Long>	Approximate number of keys in table.
EstimatedColumnCountHistogram	Gauge<long[]>	Histogram of estimated number of columns.
SSTablesPerReadHistogram	Histogram	Histogram of the number of sstable data files accessed per single partition read. SSTables skipped due to Bloom Filters, min-max key or partition index lookup are not taken into acoount.
ReadLatency	Latency	Local read latency for this table.
RangeLatency	Latency	Local range scan latency for this table.
WriteLatency	Latency	Local write latency for this table.
CoordinatorReadLatency	Timer	Coordinator read latency for this table.
CoordinatorWriteLatency	Timer	Coordinator write latency for this table.
CoordinatorScanLatency	Timer	Coordinator range scan latency for this table.
PendingFlushes	Counter	Estimated number of flush tasks pending for this table.
BytesFlushed	Counter	Total number of bytes flushed since server [re]start.
CompactionBytesWritten	Counter	Total number of bytes written by compaction since server [re]start.
PendingCompactions	Gauge<Integer>	Estimate of number of pending compactions for this table.
LiveSSTableCount	Gauge<Integer>	Number of SSTables on disk for this table.
LiveDiskSpaceUsed	Counter	Disk space used by SSTables belonging to this table (in bytes).
TotalDiskSpaceUsed	Counter	Total disk space used by SSTables belonging to this table, including obsolete ones waiting to be GC’d.
MinPartitionSize	Gauge<Long>	Size of the smallest compacted partition (in bytes).
MaxPartitionSize	Gauge<Long>	Size of the largest compacted partition (in bytes).
MeanPartitionSize	Gauge<Long>	Size of the average compacted partition (in bytes).
BloomFilterFalsePositives	Gauge<Long>	Number of false positives on table’s bloom filter.
BloomFilterFalseRatio	Gauge<Double>	False positive ratio of table’s bloom filter.
BloomFilterDiskSpaceUsed	Gauge<Long>	Disk space used by bloom filter (in bytes).
BloomFilterOffHeapMemoryUsed	Gauge<Long>	Off-heap memory used by bloom filter.
IndexSummaryOffHeapMemoryUsed	Gauge<Long>	Off-heap memory used by index summary.
CompressionMetadataOffHeapMemoryUsed	Gauge<Long>	Off-heap memory used by compression meta data.
KeyCacheHitRate	Gauge<Double>	Key cache hit rate for this table.
TombstoneScannedHistogram	Histogram	Histogram of tombstones scanned in queries on this table.
LiveScannedHistogram	Histogram	Histogram of live cells scanned in queries on this table.
ColUpdateTimeDeltaHistogram	Histogram	Histogram of column update time delta on this table.
ViewLockAcquireTime	Timer	Time taken acquiring a partition lock for materialized view updates on this table.
ViewReadTime	Timer	Time taken during the local read of a materialized view update.
TrueSnapshotsSize	Gauge<Long>	Disk space used by snapshots of this table including all SSTable components.
RowCacheHitOutOfRange	Counter	Number of table row cache hits that do not satisfy the query filter, thus went to disk.
RowCacheHit	Counter	Number of table row cache hits.
RowCacheMiss	Counter	Number of table row cache misses.
CasPrepare	Latency	Latency of paxos prepare round.
CasPropose	Latency	Latency of paxos propose round.
CasCommit	Latency	Latency of paxos commit round.
PercentRepaired	Gauge<Double>	Percent of table data that is repaired on disk.
BytesRepaired	Gauge<Long>	Size of table data repaired on disk
BytesUnrepaired	Gauge<Long>	Size of table data unrepaired on disk
BytesPendingRepair	Gauge<Long>	Size of table data isolated for an ongoing incremental repair
SpeculativeRetries	Counter	Number of times speculative retries were sent for this table.
SpeculativeFailedRetries	Counter	Number of speculative retries that failed to prevent a timeout
SpeculativeInsufficientReplicas	Counter	Number of speculative retries that couldn’t be attempted due to lack of replicas
SpeculativeSampleLatencyNanos	Gauge<Long>	Number of nanoseconds to wait before speculation is attempted. Value may be statically configured or updated periodically based on coordinator latency.
WaitingOnFreeMemtableSpace	Histogram	Histogram of time spent waiting for free memtable space, either on- or off-heap.
DroppedMutations	Counter	Number of dropped mutations on this table.
AnticompactionTime	Timer	Time spent anticompacting before a consistent repair.
ValidationTime	Timer	Time spent doing validation compaction during repair.
SyncTime	Timer	Time spent doing streaming during repair.
BytesValidated	Histogram	Histogram over the amount of bytes read during validation.
PartitionsValidated	Histogram	Histogram over the number of partitions read during validation.
BytesAnticompacted	Counter	How many bytes we anticompacted.
BytesMutatedAnticompaction	Counter	How many bytes we avoided anticompacting because the sstable was fully contained in the repaired range.
MutatedAnticompactionGauge	Gauge<Double>	Ratio of bytes mutated vs total bytes repaired.

== Keyspace Metrics

Each keyspace in Cassandra has metrics responsible for tracking its state and performance.

Most of these metrics are the same as the Table Metrics above, only they are aggregated at the Keyspace level. The keyspace specific metrics are specified in the table below.

Reported name format:

Metric Name

org.apache.cassandra.metrics.keyspace.<MetricName>.<Keyspace>

JMX MBean

org.apache.cassandra.metrics:type=Keyspace scope=<Keyspace> name=<MetricName>

Name	Type	Description
WriteFailedIdeaCL	Counter	Number of writes that failed to achieve the configured ideal consistency level or 0 if none is configured
IdealCLWriteLatency	Latency	Coordinator latency of writes at the configured ideal consistency level. No values are recorded if ideal consistency level is not configured
RepairTime	Timer	Total time spent as repair coordinator.
RepairPrepareTime	Timer	Total time spent preparing for repair.

== ThreadPool Metrics

Cassandra splits work of a particular type into its own thread pool. This provides back-pressure and asynchrony for requests on a node. It’s important to monitor the state of these thread pools since they can tell you how saturated a node is.

The metric names are all appended with the specific ThreadPool name. The thread pools are also categorized under a specific type.

Reported name format:

Metric Name

org.apache.cassandra.metrics.ThreadPools.<MetricName>.<Path>.<ThreadPoolName>

JMX MBean

org.apache.cassandra.metrics:type=ThreadPools path=<Path> scope=<ThreadPoolName> name=<MetricName>

Name	Type	Description
ActiveTasks	Gauge<Integer>	Number of tasks being actively worked on by this pool.
PendingTasks	Gauge<Integer>	Number of queued tasks queued up on this pool.
CompletedTasks	Counter	Number of tasks completed.
TotalBlockedTasks	Counter	Number of tasks that were blocked due to queue saturation.
CurrentlyBlockedTask	Counter	Number of tasks that are currently blocked due to queue saturation but on retry will become unblocked.
MaxPoolSize	Gauge<Integer>	The maximum number of threads in this pool.
MaxTasksQueued	Gauge<Integer>	The maximum number of tasks queued before a task get blocked.

The following thread pools can be monitored.

Name	Type	Description
Native-Transport-Requests	transport	Handles client CQL requests
CounterMutationStage	request	Responsible for counter writes
ViewMutationStage	request	Responsible for materialized view writes
MutationStage	request	Responsible for all other writes
ReadRepairStage	request	ReadRepair happens on this thread pool
ReadStage	request	Local reads run on this thread pool
RequestResponseStage	request	Coordinator requests to the cluster run on this thread pool
AntiEntropyStage	internal	Builds merkle tree for repairs
CacheCleanupExecutor	internal	Cache maintenance performed on this thread pool
CompactionExecutor	internal	Compactions are run on these threads
GossipStage	internal	Handles gossip requests
HintsDispatcher	internal	Performs hinted handoff
InternalResponseStage	internal	Responsible for intra-cluster callbacks
MemtableFlushWriter	internal	Writes memtables to disk
MemtablePostFlush	internal	Cleans up commit log after memtable is written to disk
MemtableReclaimMemory	internal	Memtable recycling
MigrationStage	internal	Runs schema migrations
MiscStage	internal	Misceleneous tasks run here
PendingRangeCalculator	internal	Calculates token range
PerDiskMemtableFlushWriter_0	internal	Responsible for writing a spec (there is one of these per disk 0-N)
Sampler	internal	Responsible for re-sampling the index summaries of SStables
SecondaryIndexManagement	internal	Performs updates to secondary indexes
ValidationExecutor	internal	Performs validation compaction or scrubbing
ViewBuildExecutor	internal	Performs materialized views initial build

== Client Request Metrics

Client requests have their own set of metrics that encapsulate the work happening at coordinator level.

Different types of client requests are broken down by RequestType.

Reported name format:

Metric Name

org.apache.cassandra.metrics.ClientRequest.<MetricName>.<RequestType>

JMX MBean

org.apache.cassandra.metrics:type=ClientRequest scope=<RequestType> name=<MetricName>

RequestType

CASRead

Description

Metrics related to transactional read requests.

Metrics

|Failures |Counter |Number of transaction failures encountered.

|  |Latency |Transaction read latency.

|Unavailables |Counter |Number of unavailable exceptions encountered.

|UnfinishedCommit |Counter |Number of transactions that were committed
on read.

|ConditionNotMet |Counter |Number of transaction preconditions did not
match current values.

|ContentionHistogram |Histogram |How many contended reads were
encountered
|===

RequestType

CASWrite

Description

Metrics related to transactional write requests.

Metrics

|Failures |Counter |Number of transaction failures encountered.

|  |Latency |Transaction write latency.

|UnfinishedCommit |Counter |Number of transactions that were committed
on write.

|ConditionNotMet |Counter |Number of transaction preconditions did not
match current values.

|ContentionHistogram |Histogram |How many contended writes were
encountered

|MutationSizeHistogram |Histogram |Total size in bytes of the requests
mutations.
|===

RequestType

Read

Description

Metrics related to standard read requests.

Metrics

RequestType

RangeSlice

Description

Metrics related to token range read requests.

Metrics

RequestType

Write

Description

Metrics related to regular write requests.

Metrics

|Failures |Counter |Number of write failures encountered.

|  |Latency |Write latency.

|Unavailables |Counter |Number of unavailable exceptions encountered.

|MutationSizeHistogram |Histogram |Total size in bytes of the requests
mutations.
|===

RequestType

ViewWrite

Description

Metrics related to materialized view write wrtes.

Metrics

[cols=”,,”,] |=== |Timeouts |Counter |Number of timeouts encountered.

|Failures |Counter |Number of transaction failures encountered.

|Unavailables |Counter |Number of unavailable exceptions encountered.

|ViewReplicasAttempted |Counter |Total number of attempted view
replica writes.

|ViewReplicasSuccess |Counter |Total number of succeded view replica
writes.

|ViewPendingMutations |Gauge<Long> |ViewReplicasAttempted -
ViewReplicasSuccess.

|ViewWriteLatency |Timer |Time between when mutation is applied to
base table and when CL.ONE is achieved on view.
|===

== Cache Metrics

Cassandra caches have metrics to track the effectivness of the caches. Though the Table Metrics might be more useful.

Reported name format:

Metric Name

org.apache.cassandra.metrics.Cache.<MetricName>.<CacheName>

JMX MBean

org.apache.cassandra.metrics:type=Cache scope=<CacheName> name=<MetricName>

Name	Type	Description
Capacity	Gauge<Long>	Cache capacity in bytes.
Entries	Gauge<Integer>	Total number of cache entries.
FifteenMinuteCacheHitRate	Gauge<Double>	15m cache hit rate.
FiveMinuteCacheHitRate	Gauge<Double>	5m cache hit rate.
OneMinuteCacheHitRate	Gauge<Double>	1m cache hit rate.
HitRate	Gauge<Double>	All time cache hit rate.
Hits	Meter	Total number of cache hits.
Misses	Meter	Total number of cache misses.
MissLatency	Timer	Latency of misses.
Requests	Gauge<Long>	Total number of cache requests.
Size	Gauge<Long>	Total size of occupied cache, in bytes.

The following caches are covered:

Name	Description
CounterCache	Keeps hot counters in memory for performance.
ChunkCache	In process uncompressed page cache.
KeyCache	Cache for partition to sstable offsets.
RowCache	Cache for rows kept in memory.

Misses and MissLatency are only defined for the ChunkCache ====== CQL Metrics

Metrics specific to CQL prepared statement caching.

Reported name format:

Metric Name

org.apache.cassandra.metrics.CQL.<MetricName>

JMX MBean

org.apache.cassandra.metrics:type=CQL name=<MetricName>

Name	Type	Description
PreparedStatementsCount	Gauge<Integer>	Number of cached prepared statements.
PreparedStatementsEvicted	Counter	Number of prepared statements evicted from the prepared statement cache
PreparedStatementsExecuted	Counter	Number of prepared statements executed.
RegularStatementsExecuted	Counter	Number of non prepared statements executed.
PreparedStatementsRatio	Gauge<Double>	Percentage of statements that are prepared vs unprepared.

DroppedMessage Metrics

Metrics specific to tracking dropped messages for different types of requests. Dropped writes are stored and retried by Hinted Handoff

Reported name format:

Metric Name

org.apache.cassandra.metrics.DroppedMessage.<MetricName>.<Type>

JMX MBean

org.apache.cassandra.metrics:type=DroppedMessage scope=<Type> name=<MetricName>

Name	Type	Description
CrossNodeDroppedLatency	Timer	The dropped latency across nodes.
InternalDroppedLatency	Timer	The dropped latency within node.
Dropped	Meter	Number of dropped messages.

The different types of messages tracked are:

Name	Description
BATCH_STORE	Batchlog write
BATCH_REMOVE	Batchlog cleanup (after succesfully applied)
COUNTER_MUTATION	Counter writes
HINT	Hint replay
MUTATION	Regular writes
READ	Regular reads
READ_REPAIR	Read repair
PAGED_SLICE	Paged read
RANGE_SLICE	Token range read
REQUEST_RESPONSE	RPC Callbacks
_TRACE	Tracing writes

Streaming Metrics

Metrics reported during Streaming operations, such as repair, bootstrap, rebuild.

These metrics are specific to a peer endpoint, with the source node being the node you are pulling the metrics from.

Reported name format:

Metric Name

org.apache.cassandra.metrics.Streaming.<MetricName>.<PeerIP>

JMX MBean

org.apache.cassandra.metrics:type=Streaming scope=<PeerIP> name=<MetricName>

Name	Type	Description
IncomingBytes	Counter	Number of bytes streamed to this node from the peer.
OutgoingBytes	Counter	Number of bytes streamed to the peer endpoint from this node.

Compaction Metrics

Metrics specific to Compaction work.

Reported name format:

Metric Name

org.apache.cassandra.metrics.Compaction.<MetricName>

JMX MBean

org.apache.cassandra.metrics:type=Compaction name=<MetricName>

Name	Type	Description
BytesCompacted	Counter	Total number of bytes compacted since server [re]start.
PendingTasks	Gauge<Integer>	Estimated number of compactions remaining to perform.
CompletedTasks	Gauge<Long>	Number of completed compactions since server [re]start.
TotalCompactionsCompleted	Meter	Throughput of completed compactions since server [re]start.
PendingTasksByTableName	Gauge<Map<String, Map<String, Integer>>>	Estimated number of compactions remaining to perform, grouped by keyspace and then table name. This info is also kept in `Table Metrics`.

CommitLog Metrics

Metrics specific to the CommitLog

Reported name format:

Metric Name

org.apache.cassandra.metrics.CommitLog.<MetricName>

JMX MBean

org.apache.cassandra.metrics:type=CommitLog name=<MetricName>

Name	Type	Description
CompletedTasks	Gauge<Long>	Total number of commit log messages written since [re]start.
PendingTasks	Gauge<Long>	Number of commit log messages written but yet to be fsync’d.
TotalCommitLogSize	Gauge<Long>	Current size, in bytes, used by all the commit log segments.
WaitingOnSegmentAllocation	Timer	Time spent waiting for a CommitLogSegment to be allocated - under normal conditions this should be zero.
WaitingOnCommit	Timer	The time spent waiting on CL fsync; for Periodic this is only occurs when the sync is lagging its sync interval.

Storage Metrics

Metrics specific to the storage engine.

Reported name format:

Metric Name

org.apache.cassandra.metrics.Storage.<MetricName>

JMX MBean

org.apache.cassandra.metrics:type=Storage name=<MetricName>

Name	Type	Description
Exceptions	Counter	Number of internal exceptions caught. Under normal exceptions this should be zero.
Load	Counter	Size, in bytes, of the on disk data size this node manages.
TotalHints	Counter	Number of hint messages written to this node since [re]start. Includes one entry for each host to be hinted per hint.
TotalHintsInProgress	Counter	Number of hints attemping to be sent currently.

HintedHandoff Metrics

Metrics specific to Hinted Handoff. There are also some metrics related to hints tracked in Storage Metrics

These metrics include the peer endpoint in the metric name

Reported name format:

Metric Name

org.apache.cassandra.metrics.HintedHandOffManager.<MetricName>

JMX MBean

org.apache.cassandra.metrics:type=HintedHandOffManager name=<MetricName>

Name	Type	Description
Hints_created-<PeerIP>	Counter	Number of hints on disk for this peer.
Hints_not_stored-<PeerIP>	Counter	Number of hints not stored for this peer, due to being down past the configured hint window.

HintsService Metrics

Metrics specific to the Hints delivery service. There are also some metrics related to hints tracked in Storage Metrics

These metrics include the peer endpoint in the metric name

Reported name format:

Metric Name

org.apache.cassandra.metrics.HintsService.<MetricName>

JMX MBean

org.apache.cassandra.metrics:type=HintsService name=<MetricName>

Name	Type	Description
HintsSucceeded	Meter	A meter of the hints successfully delivered
HintsFailed	Meter	A meter of the hints that failed deliver
HintsTimedOut	Meter	A meter of the hints that timed out
Hint_delays	Histogram	Histogram of hint delivery delays (in milliseconds)
Hint_delays-<PeerIP>	Histogram	Histogram of hint delivery delays (in milliseconds) per peer

SSTable Index Metrics

Metrics specific to the SSTable index metadata.

Reported name format:

Metric Name

org.apache.cassandra.metrics.Index.<MetricName>.RowIndexEntry

JMX MBean

org.apache.cassandra.metrics:type=Index scope=RowIndexEntry name=<MetricName>

Name	Type	Description
IndexedEntrySize	Histogram	Histogram of the on-heap size, in bytes, of the index across all SSTables.
IndexInfoCount	Histogram	Histogram of the number of on-heap index entries managed across all SSTables.
IndexInfoGets	Histogram	Histogram of the number index seeks performed per SSTable.

BufferPool Metrics

Metrics specific to the internal recycled buffer pool Cassandra manages. This pool is meant to keep allocations and GC lower by recycling on and off heap buffers.

Reported name format:

Metric Name

org.apache.cassandra.metrics.BufferPool.<MetricName>

JMX MBean

org.apache.cassandra.metrics:type=BufferPool name=<MetricName>

Name	Type	Description
Size	Gauge<Long>	Size, in bytes, of the managed buffer pool
Misses	Meter	The rate of misses in the pool. The higher this is the more allocations incurred.

Client Metrics

Metrics specifc to client managment.

Reported name format:

Metric Name

org.apache.cassandra.metrics.Client.<MetricName>

JMX MBean

org.apache.cassandra.metrics:type=Client name=<MetricName>

Name	Type	Description
connectedNativeClients	Gauge<Integer>	Number of clients connected to this nodes native protocol server
connections	Gauge<List<Map<String, String>>	List of all connections and their state information
connectedNativeClientsByUser	Gauge<Map<String, Int>	Number of connnective native clients by username

Batch Metrics

Metrics specifc to batch statements.

Reported name format:

Metric Name

org.apache.cassandra.metrics.Batch.<MetricName>

JMX MBean

org.apache.cassandra.metrics:type=Batch name=<MetricName>

Name	Type	Description
PartitionsPerCounterBatch	Histogram	Distribution of the number of partitions processed per counter batch
PartitionsPerLoggedBatch	Histogram	Distribution of the number of partitions processed per logged batch
PartitionsPerUnloggedBatch	Histogram	Distribution of the number of partitions processed per unlogged batch

JVM Metrics

JVM metrics such as memory and garbage collection statistics can either be accessed by connecting to the JVM using JMX or can be exported using Metric Reporters.

BufferPool

Metric Name

jvm.buffers.<direct|mapped>.<MetricName>

JMX MBean

java.nio:type=BufferPool name=<direct|mapped>

Name	Type	Description
Capacity	Gauge<Long>	Estimated total capacity of the buffers in this pool
Count	Gauge<Long>	Estimated number of buffers in the pool
Used	Gauge<Long>	Estimated memory that the Java virtual machine is using for this buffer pool

FileDescriptorRatio

Metric Name

jvm.fd.<MetricName>

JMX MBean

java.lang:type=OperatingSystem name=<OpenFileDescriptorCount|MaxFileDescriptorCount>

Name	Type	Description
Usage	Ratio	Ratio of used to total file descriptors

GarbageCollector

Metric Name

jvm.gc.<gc_type>.<MetricName>

JMX MBean

java.lang:type=GarbageCollector name=<gc_type>

Name	Type	Description
Count	Gauge<Long>	Total number of collections that have occurred
Time	Gauge<Long>	Approximate accumulated collection elapsed time in milliseconds

Memory

Metric Name

jvm.memory.<heap/non-heap/total>.<MetricName>

JMX MBean

java.lang:type=Memory

Committed	Gauge<Long>	Amount of memory in bytes that is committed for the JVM to use
Init	Gauge<Long>	Amount of memory in bytes that the JVM initially requests from the OS
Max	Gauge<Long>	Maximum amount of memory in bytes that can be used for memory management
Usage	Ratio	Ratio of used to maximum memory
Used	Gauge<Long>	Amount of used memory in bytes

MemoryPool

Metric Name

jvm.memory.pools.<memory_pool>.<MetricName>

JMX MBean

java.lang:type=MemoryPool name=<memory_pool>

Committed	Gauge<Long>	Amount of memory in bytes that is committed for the JVM to use
Init	Gauge<Long>	Amount of memory in bytes that the JVM initially requests from the OS
Max	Gauge<Long>	Maximum amount of memory in bytes that can be used for memory management
Usage	Ratio	Ratio of used to maximum memory
Used	Gauge<Long>	Amount of used memory in bytes

JMX

Any JMX based client can access metrics from cassandra.

If you wish to access JMX metrics over http it’s possible to download Mx4jTool and place mx4j-tools.jar into the classpath. On startup you will see in the log:

HttpAdaptor version 3.0.2 started on port 8081

To choose a different port (8081 is the default) or a different listen address (0.0.0.0 is not the default) edit conf/cassandra-env.sh and uncomment:

#MX4J_ADDRESS="-Dmx4jaddress=0.0.0.0"
#MX4J_PORT="-Dmx4jport=8081"

Metric Reporters

As mentioned at the top of this section on monitoring the Cassandra metrics can be exported to a number of monitoring system a number of built in and third party reporter plugins.

The configuration of these plugins is managed by the metrics reporter config project. There is a sample configuration file located at conf/metrics-reporter-config-sample.yaml.

Once configured, you simply start cassandra with the flag -Dcassandra.metricsReporterConfigFile=metrics-reporter-config.yaml. The specified .yaml file plus any 3rd party reporter jars must all be in Cassandra’s classpath.