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Cassandra Documentation

Version:

4.1

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

[cols=",,",options="header",] |=== |Name |Type |Description |Timeouts |Counter |Number of timeouts encountered.

|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

[cols=",,",options="header",] |=== |Name |Type |Description |Timeouts |Counter |Number of timeouts encountered.

|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

[cols=",,",options="header",] |=== |Name |Type |Description |Timeouts |Counter |Number of timeouts encountered. |Failures |Counter |Number of read failures encountered. |  |Latency |Read latency. |Unavailables |Counter |Number of unavailable exceptions encountered. |===

RequestType

RangeSlice

Description

Metrics related to token range read requests.

Metrics

[cols=",,",options="header",] |=== |Name |Type |Description |Timeouts |Counter |Number of timeouts encountered. |Failures |Counter |Number of range query failures encountered. |  |Latency |Range query latency. |Unavailables |Counter |Number of unavailable exceptions encountered. |===

RequestType

Write

Description

Metrics related to regular write requests.

Metrics

[cols=",,",options="header",] |=== |Name |Type |Description |Timeouts |Counter |Number of timeouts encountered.

|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.

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