Diagnostics

EventStoreDB provides several ways to diagnose and troubleshoot issues.

• Logging: structured or plain-text logs on the console and in log files.
• Metrics: collect standard metrics using Prometheus or OpenTelemetry.
• Stats: stats collection and HTTP endpoint.
• Histograms: metrics collection and HTTP endpoints.

You can also use external tools to measure the performance of EventStoreDB and monitor the cluster health. Learn more on the Integrations page.

Statistics

EventStoreDB servers collect internal statistics and make it available via HTTP over the https://<host>:2113/stats in JSON format. Here, 2113 is the default HTTP port. Monitoring applications and metric collectors can use this endpoint to gather the information about the cluster node. The stats endpoint only exposes information about the node where you fetch it from and doesn't contain any cluster information.

What you see in the stats endpoint response is the last collected state of the server. The server collects this information using events that are appended to the statistics stream. Each node has one. We use a reserved name for the stats stream, $stats-<host:port>. For example, for a single node running locally the stream name would be $stats-127.0.0.1:2113.

As all other events, stats events are also linked in the $all stream. These events have a reserved event type $statsCollected.

Click here to see an example of a stats event

{
  "proc-startTime": "2020-06-25T10:13:26.8281750Z",
  "proc-id": 5465,
  "proc-mem": 118648832,
  "proc-cpu": 2.44386363,
  "proc-cpuScaled": 0.152741477,
  "proc-threadsCount": 10,
  "proc-contentionsRate": 0.9012223,
  "proc-thrownExceptionsRate": 0.0,
  "sys-cpu": 100.0,
  "sys-freeMem": 25100288,
  "proc-gc-allocationSpeed": 0.0,
  "proc-gc-gen0ItemsCount": 8,
  "proc-gc-gen0Size": 0,
  "proc-gc-gen1ItemsCount": 2,
  "proc-gc-gen1Size": 0,
  "proc-gc-gen2ItemsCount": 0,
  "proc-gc-gen2Size": 0,
  "proc-gc-largeHeapSize": 0,
  "proc-gc-timeInGc": 0.0,
  "proc-gc-totalBytesInHeaps": 0,
  "proc-tcp-connections": 0,
  "proc-tcp-receivingSpeed": 0.0,
  "proc-tcp-sendingSpeed": 0.0,
  "proc-tcp-inSend": 0,
  "proc-tcp-measureTime": "00:00:19.0534210",
  "proc-tcp-pendingReceived": 0,
  "proc-tcp-pendingSend": 0,
  "proc-tcp-receivedBytesSinceLastRun": 0,
  "proc-tcp-receivedBytesTotal": 0,
  "proc-tcp-sentBytesSinceLastRun": 0,
  "proc-tcp-sentBytesTotal": 0,
  "es-checksum": 1613144,
  "es-checksumNonFlushed": 1613144,
  "sys-drive-/System/Volumes/Data-availableBytes": 545628151808,
  "sys-drive-/System/Volumes/Data-totalBytes": 2000481927168,
  "sys-drive-/System/Volumes/Data-usage": "72%",
  "sys-drive-/System/Volumes/Data-usedBytes": 1454853775360,
  "es-queue-Index Committer-queueName": "Index Committer",
  "es-queue-Index Committer-groupName": "",
  "es-queue-Index Committer-avgItemsPerSecond": 0,
  "es-queue-Index Committer-avgProcessingTime": 0.0,
  "es-queue-Index Committer-currentIdleTime": "0:00:00:29.9895180",
  "es-queue-Index Committer-currentItemProcessingTime": null,
  "es-queue-Index Committer-idleTimePercent": 100.0,
  "es-queue-Index Committer-length": 0,
  "es-queue-Index Committer-lengthCurrentTryPeak": 0,
  "es-queue-Index Committer-lengthLifetimePeak": 0,
  "es-queue-Index Committer-totalItemsProcessed": 0,
  "es-queue-Index Committer-inProgressMessage": "<none>",
  "es-queue-Index Committer-lastProcessedMessage": "<none>",
  "es-queue-MainQueue-queueName": "MainQueue",
  "es-queue-MainQueue-groupName": "",
  "es-queue-MainQueue-avgItemsPerSecond": 14,
  "es-queue-MainQueue-avgProcessingTime": 0.0093527972027972021,
  "es-queue-MainQueue-currentIdleTime": "0:00:00:00.8050567",
  "es-queue-MainQueue-currentItemProcessingTime": null,
  "es-queue-MainQueue-idleTimePercent": 99.986616840364917,
  "es-queue-MainQueue-length": 0,
  "es-queue-MainQueue-lengthCurrentTryPeak": 3,
  "es-queue-MainQueue-lengthLifetimePeak": 6,
  "es-queue-MainQueue-totalItemsProcessed": 452,
  "es-queue-MainQueue-inProgressMessage": "<none>",
  "es-queue-MainQueue-lastProcessedMessage": "Schedule",
  "es-queue-MonitoringQueue-queueName": "MonitoringQueue",
  "es-queue-MonitoringQueue-groupName": "",
  "es-queue-MonitoringQueue-avgItemsPerSecond": 0,
  "es-queue-MonitoringQueue-avgProcessingTime": 1.94455,
  "es-queue-MonitoringQueue-currentIdleTime": "0:00:00:19.0601186",
  "es-queue-MonitoringQueue-currentItemProcessingTime": null,
  "es-queue-MonitoringQueue-idleTimePercent": 99.980537727681721,
  "es-queue-MonitoringQueue-length": 0,
  "es-queue-MonitoringQueue-lengthCurrentTryPeak": 0,
  "es-queue-MonitoringQueue-lengthLifetimePeak": 0,
  "es-queue-MonitoringQueue-totalItemsProcessed": 14,
  "es-queue-MonitoringQueue-inProgressMessage": "<none>",
  "es-queue-MonitoringQueue-lastProcessedMessage": "GetFreshTcpConnectionStats",
  "es-queue-PersistentSubscriptions-queueName": "PersistentSubscriptions",
  "es-queue-PersistentSubscriptions-groupName": "",
  "es-queue-PersistentSubscriptions-avgItemsPerSecond": 1,
  "es-queue-PersistentSubscriptions-avgProcessingTime": 0.010400000000000001,
  "es-queue-PersistentSubscriptions-currentIdleTime": "0:00:00:00.8052015",
  "es-queue-PersistentSubscriptions-currentItemProcessingTime": null,
  "es-queue-PersistentSubscriptions-idleTimePercent": 99.998954276430226,
  "es-queue-PersistentSubscriptions-length": 0,
  "es-queue-PersistentSubscriptions-lengthCurrentTryPeak": 0,
  "es-queue-PersistentSubscriptions-lengthLifetimePeak": 0,
  "es-queue-PersistentSubscriptions-totalItemsProcessed": 32,
  "es-queue-PersistentSubscriptions-inProgressMessage": "<none>",
  "es-queue-PersistentSubscriptions-lastProcessedMessage": "PersistentSubscriptionTimerTick",
  "es-queue-Projection Core #0-queueName": "Projection Core #0",
  "es-queue-Projection Core #0-groupName": "Projection Core",
  "es-queue-Projection Core #0-avgItemsPerSecond": 0,
  "es-queue-Projection Core #0-avgProcessingTime": 0.0,
  "es-queue-Projection Core #0-currentIdleTime": "0:00:00:29.9480513",
  "es-queue-Projection Core #0-currentItemProcessingTime": null,
  "es-queue-Projection Core #0-idleTimePercent": 100.0,
  "es-queue-Projection Core #0-length": 0,
  "es-queue-Projection Core #0-lengthCurrentTryPeak": 0,
  "es-queue-Projection Core #0-lengthLifetimePeak": 0,
  "es-queue-Projection Core #0-totalItemsProcessed": 2,
  "es-queue-Projection Core #0-inProgressMessage": "<none>",
  "es-queue-Projection Core #0-lastProcessedMessage": "SubComponentStarted",
  "es-queue-Projections Master-queueName": "Projections Master",
  "es-queue-Projections Master-groupName": "",
  "es-queue-Projections Master-avgItemsPerSecond": 0,
  "es-queue-Projections Master-avgProcessingTime": 0.0,
  "es-queue-Projections Master-currentIdleTime": "0:00:00:29.8467445",
  "es-queue-Projections Master-currentItemProcessingTime": null,
  "es-queue-Projections Master-idleTimePercent": 100.0,
  "es-queue-Projections Master-length": 0,
  "es-queue-Projections Master-lengthCurrentTryPeak": 0,
  "es-queue-Projections Master-lengthLifetimePeak": 3,
  "es-queue-Projections Master-totalItemsProcessed": 10,
  "es-queue-Projections Master-inProgressMessage": "<none>",
  "es-queue-Projections Master-lastProcessedMessage": "RegularTimeout",
  "es-queue-Storage Chaser-queueName": "Storage Chaser",
  "es-queue-Storage Chaser-groupName": "",
  "es-queue-Storage Chaser-avgItemsPerSecond": 94,
  "es-queue-Storage Chaser-avgProcessingTime": 0.0043385023898035047,
  "es-queue-Storage Chaser-currentIdleTime": "0:00:00:00.0002530",
  "es-queue-Storage Chaser-currentItemProcessingTime": null,
  "es-queue-Storage Chaser-idleTimePercent": 99.959003031702224,
  "es-queue-Storage Chaser-length": 0,
  "es-queue-Storage Chaser-lengthCurrentTryPeak": 0,
  "es-queue-Storage Chaser-lengthLifetimePeak": 0,
  "es-queue-Storage Chaser-totalItemsProcessed": 2835,
  "es-queue-Storage Chaser-inProgressMessage": "<none>",
  "es-queue-Storage Chaser-lastProcessedMessage": "ChaserCheckpointFlush",
  "es-queue-StorageReaderQueue #1-queueName": "StorageReaderQueue #1",
  "es-queue-StorageReaderQueue #1-groupName": "StorageReaderQueue",
  "es-queue-StorageReaderQueue #1-avgItemsPerSecond": 0,
  "es-queue-StorageReaderQueue #1-avgProcessingTime": 0.22461000000000003,
  "es-queue-StorageReaderQueue #1-currentIdleTime": "0:00:00:00.9863988",
  "es-queue-StorageReaderQueue #1-currentItemProcessingTime": null,
  "es-queue-StorageReaderQueue #1-idleTimePercent": 99.988756844383616,
  "es-queue-StorageReaderQueue #1-length": 0,
  "es-queue-StorageReaderQueue #1-lengthCurrentTryPeak": 0,
  "es-queue-StorageReaderQueue #1-lengthLifetimePeak": 0,
  "es-queue-StorageReaderQueue #1-totalItemsProcessed": 15,
  "es-queue-StorageReaderQueue #1-inProgressMessage": "<none>",
  "es-queue-StorageReaderQueue #1-lastProcessedMessage": "ReadStreamEventsBackward",
  "es-queue-StorageReaderQueue #2-queueName": "StorageReaderQueue #2",
  "es-queue-StorageReaderQueue #2-groupName": "StorageReaderQueue",
  "es-queue-StorageReaderQueue #2-avgItemsPerSecond": 0,
  "es-queue-StorageReaderQueue #2-avgProcessingTime": 8.83216,
  "es-queue-StorageReaderQueue #2-currentIdleTime": "0:00:00:00.8051068",
  "es-queue-StorageReaderQueue #2-currentItemProcessingTime": null,
  "es-queue-StorageReaderQueue #2-idleTimePercent": 99.557874170777851,
  "es-queue-StorageReaderQueue #2-length": 0,
  "es-queue-StorageReaderQueue #2-lengthCurrentTryPeak": 0,
  "es-queue-StorageReaderQueue #2-lengthLifetimePeak": 0,
  "es-queue-StorageReaderQueue #2-totalItemsProcessed": 16,
  "es-queue-StorageReaderQueue #2-inProgressMessage": "<none>",
  "es-queue-StorageReaderQueue #2-lastProcessedMessage": "ReadStreamEventsForward",
  "es-queue-StorageReaderQueue #3-queueName": "StorageReaderQueue #3",
  "es-queue-StorageReaderQueue #3-groupName": "StorageReaderQueue",
  "es-queue-StorageReaderQueue #3-avgItemsPerSecond": 0,
  "es-queue-StorageReaderQueue #3-avgProcessingTime": 6.4189888888888893,
  "es-queue-StorageReaderQueue #3-currentIdleTime": "0:00:00:02.8228372",
  "es-queue-StorageReaderQueue #3-currentItemProcessingTime": null,
  "es-queue-StorageReaderQueue #3-idleTimePercent": 99.710808119472517,
  "es-queue-StorageReaderQueue #3-length": 0,
  "es-queue-StorageReaderQueue #3-lengthCurrentTryPeak": 0,
  "es-queue-StorageReaderQueue #3-lengthLifetimePeak": 0,
  "es-queue-StorageReaderQueue #3-totalItemsProcessed": 14,
  "es-queue-StorageReaderQueue #3-inProgressMessage": "<none>",
  "es-queue-StorageReaderQueue #3-lastProcessedMessage": "ReadStreamEventsForward",
  "es-queue-StorageReaderQueue #4-queueName": "StorageReaderQueue #4",
  "es-queue-StorageReaderQueue #4-groupName": "StorageReaderQueue",
  "es-queue-StorageReaderQueue #4-avgItemsPerSecond": 0,
  "es-queue-StorageReaderQueue #4-avgProcessingTime": 0.36447,
  "es-queue-StorageReaderQueue #4-currentIdleTime": "0:00:00:01.8144419",
  "es-queue-StorageReaderQueue #4-currentItemProcessingTime": null,
  "es-queue-StorageReaderQueue #4-idleTimePercent": 99.981747643099709,
  "es-queue-StorageReaderQueue #4-length": 0,
  "es-queue-StorageReaderQueue #4-lengthCurrentTryPeak": 0,
  "es-queue-StorageReaderQueue #4-lengthLifetimePeak": 0,
  "es-queue-StorageReaderQueue #4-totalItemsProcessed": 14,
  "es-queue-StorageReaderQueue #4-inProgressMessage": "<none>",
  "es-queue-StorageReaderQueue #4-lastProcessedMessage": "ReadStreamEventsForward",
  "es-queue-StorageWriterQueue-queueName": "StorageWriterQueue",
  "es-queue-StorageWriterQueue-groupName": "",
  "es-queue-StorageWriterQueue-avgItemsPerSecond": 0,
  "es-queue-StorageWriterQueue-avgProcessingTime": 0.0,
  "es-queue-StorageWriterQueue-currentIdleTime": "0:00:00:29.9437790",
  "es-queue-StorageWriterQueue-currentItemProcessingTime": null,
  "es-queue-StorageWriterQueue-idleTimePercent": 100.0,
  "es-queue-StorageWriterQueue-length": 0,
  "es-queue-StorageWriterQueue-lengthCurrentTryPeak": 0,
  "es-queue-StorageWriterQueue-lengthLifetimePeak": 0,
  "es-queue-StorageWriterQueue-totalItemsProcessed": 6,
  "es-queue-StorageWriterQueue-inProgressMessage": "<none>",
  "es-queue-StorageWriterQueue-lastProcessedMessage": "WritePrepares",
  "es-queue-Subscriptions-queueName": "Subscriptions",
  "es-queue-Subscriptions-groupName": "",
  "es-queue-Subscriptions-avgItemsPerSecond": 1,
  "es-queue-Subscriptions-avgProcessingTime": 0.057019047619047622,
  "es-queue-Subscriptions-currentIdleTime": "0:00:00:00.8153708",
  "es-queue-Subscriptions-currentItemProcessingTime": null,
  "es-queue-Subscriptions-idleTimePercent": 99.993992971356,
  "es-queue-Subscriptions-length": 0,
  "es-queue-Subscriptions-lengthCurrentTryPeak": 0,
  "es-queue-Subscriptions-lengthLifetimePeak": 0,
  "es-queue-Subscriptions-totalItemsProcessed": 31,
  "es-queue-Subscriptions-inProgressMessage": "<none>",
  "es-queue-Subscriptions-lastProcessedMessage": "CheckPollTimeout",
  "es-queue-Timer-queueName": "Timer",
  "es-queue-Timer-groupName": "",
  "es-queue-Timer-avgItemsPerSecond": 14,
  "es-queue-Timer-avgProcessingTime": 0.038568989547038329,
  "es-queue-Timer-currentIdleTime": "0:00:00:00.0002752",
  "es-queue-Timer-currentItemProcessingTime": null,
  "es-queue-Timer-idleTimePercent": 99.94364205726194,
  "es-queue-Timer-length": 17,
  "es-queue-Timer-lengthCurrentTryPeak": 17,
  "es-queue-Timer-lengthLifetimePeak": 17,
  "es-queue-Timer-totalItemsProcessed": 419,
  "es-queue-Timer-inProgressMessage": "<none>",
  "es-queue-Timer-lastProcessedMessage": "ExecuteScheduledTasks",
  "es-queue-Worker #1-queueName": "Worker #1",
  "es-queue-Worker #1-groupName": "Workers",
  "es-queue-Worker #1-avgItemsPerSecond": 2,
  "es-queue-Worker #1-avgProcessingTime": 0.076058695652173922,
  "es-queue-Worker #1-currentIdleTime": "0:00:00:00.8050943",
  "es-queue-Worker #1-currentItemProcessingTime": null,
  "es-queue-Worker #1-idleTimePercent": 99.982484504768721,
  "es-queue-Worker #1-length": 0,
  "es-queue-Worker #1-lengthCurrentTryPeak": 0,
  "es-queue-Worker #1-lengthLifetimePeak": 0,
  "es-queue-Worker #1-totalItemsProcessed": 73,
  "es-queue-Worker #1-inProgressMessage": "<none>",
  "es-queue-Worker #1-lastProcessedMessage": "ReadStreamEventsForwardCompleted",
  "es-queue-Worker #2-queueName": "Worker #2",
  "es-queue-Worker #2-groupName": "Workers",
  "es-queue-Worker #2-avgItemsPerSecond": 2,
  "es-queue-Worker #2-avgProcessingTime": 0.19399347826086957,
  "es-queue-Worker #2-currentIdleTime": "0:00:00:00.8356863",
  "es-queue-Worker #2-currentItemProcessingTime": null,
  "es-queue-Worker #2-idleTimePercent": 99.955350254886739,
  "es-queue-Worker #2-length": 0,
  "es-queue-Worker #2-lengthCurrentTryPeak": 0,
  "es-queue-Worker #2-lengthLifetimePeak": 0,
  "es-queue-Worker #2-totalItemsProcessed": 69,
  "es-queue-Worker #2-inProgressMessage": "<none>",
  "es-queue-Worker #2-lastProcessedMessage": "PurgeTimedOutRequests",
  "es-queue-Worker #3-queueName": "Worker #3",
  "es-queue-Worker #3-groupName": "Workers",
  "es-queue-Worker #3-avgItemsPerSecond": 2,
  "es-queue-Worker #3-avgProcessingTime": 0.068475555555555567,
  "es-queue-Worker #3-currentIdleTime": "0:00:00:00.8356754",
  "es-queue-Worker #3-currentItemProcessingTime": null,
  "es-queue-Worker #3-idleTimePercent": 99.984583460721979,
  "es-queue-Worker #3-length": 0,
  "es-queue-Worker #3-lengthCurrentTryPeak": 0,
  "es-queue-Worker #3-lengthLifetimePeak": 0,
  "es-queue-Worker #3-totalItemsProcessed": 68,
  "es-queue-Worker #3-inProgressMessage": "<none>",
  "es-queue-Worker #3-lastProcessedMessage": "PurgeTimedOutRequests",
  "es-queue-Worker #4-queueName": "Worker #4",
  "es-queue-Worker #4-groupName": "Workers",
  "es-queue-Worker #4-avgItemsPerSecond": 2,
  "es-queue-Worker #4-avgProcessingTime": 0.040221428571428575,
  "es-queue-Worker #4-currentIdleTime": "0:00:00:00.8356870",
  "es-queue-Worker #4-currentItemProcessingTime": null,
  "es-queue-Worker #4-idleTimePercent": 99.99154911144629,
  "es-queue-Worker #4-length": 0,
  "es-queue-Worker #4-lengthCurrentTryPeak": 0,
  "es-queue-Worker #4-lengthLifetimePeak": 0,
  "es-queue-Worker #4-totalItemsProcessed": 65,
  "es-queue-Worker #4-inProgressMessage": "<none>",
  "es-queue-Worker #4-lastProcessedMessage": "PurgeTimedOutRequests",
  "es-queue-Worker #5-queueName": "Worker #5",
  "es-queue-Worker #5-groupName": "Workers",
  "es-queue-Worker #5-avgItemsPerSecond": 2,
  "es-queue-Worker #5-avgProcessingTime": 0.17759268292682928,
  "es-queue-Worker #5-currentIdleTime": "0:00:00:00.8052165",
  "es-queue-Worker #5-currentItemProcessingTime": null,
  "es-queue-Worker #5-idleTimePercent": 99.9635548548067,
  "es-queue-Worker #5-length": 0,
  "es-queue-Worker #5-lengthCurrentTryPeak": 0,
  "es-queue-Worker #5-lengthLifetimePeak": 0,
  "es-queue-Worker #5-totalItemsProcessed": 70,
  "es-queue-Worker #5-inProgressMessage": "<none>",
  "es-queue-Worker #5-lastProcessedMessage": "IODispatcherDelayedMessage",
  "es-writer-lastFlushSize": 0,
  "es-writer-lastFlushDelayMs": 0.0134,
  "es-writer-meanFlushSize": 0,
  "es-writer-meanFlushDelayMs": 0.0134,
  "es-writer-maxFlushSize": 0,
  "es-writer-maxFlushDelayMs": 0.0134,
  "es-writer-queuedFlushMessages": 0,
  "es-readIndex-cachedRecord": 676,
  "es-readIndex-notCachedRecord": 0,
  "es-readIndex-cachedStreamInfo": 171,
  "es-readIndex-notCachedStreamInfo": 32,
  "es-readIndex-cachedTransInfo": 0,
  "es-readIndex-notCachedTransInfo": 0
}

Stats stream has the max time-to-live set to 24 hours, so all the events that are older than 24 hours will be deleted.

Stats period

Using this setting you can control how often stats events are generated. By default, the node will produce one event in 30 seconds. If you want to decrease network pressure on subscribers to the $all stream, you can tell EventStoreDB to produce stats less often.

Format	Syntax
Command line	--stats-period-sec
YAML	StatsPeriodSec
Environment variable	EVENTSTORE_STATS_PERIOD_SEC

Default: 30

Write stats to database

As mentioned before, stats events are quite large and whilst it is sometimes beneficial to keep the stats history, it is most of the time not necessary. Therefore, we do not write stats events to the database by default. When this option is set to true, all the stats events will be persisted.

As mentioned before, stats events have a TTL of 24 hours and when writing stats to the database is enabled, you'd need to scavenge more often to release the disk space.

Format	Syntax
Command line	--write-stats-to-db
YAML	WriteStatsToDb
Environment variable	EVENTSTORE_WRITE_STATS_TO_DB

Default: false

Histograms

Histograms give a distribution in percentiles of the time spent on several metrics. This can be used to diagnose issues in the system. It is not recommended enabling this in production environment. When enabled, histogram stats are available at their corresponding http endpoints.

For example, you could ask for a stream reader histograms like this:

curl http://localhost:2113/histogram/reader-streamrange -u admin:changeit

That would give a response with the stats distributed across histogram buckets:

   Value     Percentile TotalCount 1/(1-Percentile)

   0.022 0.000000000000          1           1.00
   0.044 0.100000000000         30           1.11
   0.054 0.200000000000         59           1.25
   0.074 0.300000000000         88           1.43
   0.092 0.400000000000        118           1.67
   0.108 0.500000000000        147           2.00
   0.113 0.550000000000        162           2.22
   0.127 0.600000000000        176           2.50
   0.140 0.650000000000        191           2.86
   0.155 0.700000000000        206           3.33
   0.168 0.750000000000        220           4.00
   0.179 0.775000000000        228           4.44
   0.197 0.800000000000        235           5.00
   0.219 0.825000000000        242           5.71
   0.232 0.850000000000        250           6.67
   0.277 0.875000000000        257           8.00
   0.327 0.887500000000        261           8.89
   0.346 0.900000000000        264          10.00
   0.522 0.912500000000        268          11.43
   0.836 0.925000000000        272          13.33
   0.971 0.937500000000        275          16.00
   1.122 0.943750000000        277          17.78
   1.153 0.950000000000        279          20.00
   1.217 0.956250000000        281          22.86
   2.836 0.962500000000        283          26.67
   2.972 0.968750000000        284          32.00
   3.607 0.971875000000        285          35.56
   4.964 0.975000000000        286          40.00
   8.536 0.978125000000        287          45.71
  11.035 0.981250000000        288          53.33
  11.043 0.984375000000        289          64.00
  11.043 0.985937500000        289          71.11
  34.013 0.987500000000        290          80.00
  34.013 0.989062500000        290          91.43
  41.812 0.990625000000        292         106.67
  41.812 0.992187500000        292         128.00
  41.812 0.992968750000        292         142.22
  41.812 0.993750000000        292         160.00
  41.812 0.994531250000        292         182.86
  41.812 0.995312500000        292         213.33
  41.812 0.996093750000        292         256.00
  41.812 0.996484375000        292         284.44
  41.878 0.996875000000        293         320.00
  41.878 1.000000000000        293

#[Mean = 0.854, StdDeviation = 4.739]
#[Max = 41.878, Total count = 293]
#[Buckets = 20, SubBuckets = 2048]

Reading histograms

The histogram response tells you some useful metrics like mean, max, standard deviation and also that in 99% of cases reads take about 41.8ms, as in the example above.

Using histograms

You can enable histograms in a development environment and run a specific task to see how it affects the database, telling you where and how the time is spent.

Execute a GET HTTP call to a cluster node using the http://<node>:2113/histogram/<metric> path to get a response. Here 2113 is the default external HTTP port.

Available metrics

Endpoint	Measures time spent
reader-streamrange	ReadStreamEventsForward and ReadStreamEventsBackwards
writer-flush	Flushing to disk in the storage writer service
chaser-wait and chaser-flush	Storage chaser
reader-readevent	Checking the stream access and reading an event
reader-allrange	ReadAllEventsForward and ReadAllEventsBackward
request-manager	---
tcp-send	Sending messages over TCP
http-send	Sending messages over HTTP

Enabling histograms

Use the option described below to enable histograms. Because collecting histograms uses CPU resources, they are disabled by default.

Format	Syntax
Command line	--enable-histograms
YAML	EnableHistograms
Environment variable	EVENTSTORE_ENABLE_HISTOGRAMS

Default: false