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.

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.
ReadRepairRequests Meter Throughput for mutations generated by read-repair.
ShortReadProtectionRequests Meter Throughput for requests to get extra rows during short read protection.
ReplicaFilteringProtectionRequests Meter Throughput for row completion requests during replica filtering protection.
ReplicaFilteringProtectionRowsCachedPerQuery Histogram Histogram of the number of rows cached per query when replica filtering protection is engaged.

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:
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:
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:
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:
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:
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:
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.

Note

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.
IncomingProcessTime Timer The time spent on processing the incoming stream message from the peer.

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.
OverSizedMutations Meter Throughput for mutations that exceed limit.

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.

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
ClientsByProtocolVersion Gauge<List<Map<String, String>>> List of up to last 100 connections including protocol version. Can be reset with clearConnectionHistory operation in org.apache.cassandra.db:StorageService mbean.
RequestsSize Gauge<Long> How many concurrent bytes used in currently processing requests
RequestsSizeByIpDistribution Histogram How many concurrent bytes used in currently processing requests by different ips

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.