db.collection.latencyStats()

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Definition

Compatibility
Output
Examples

Definition

db.collection.latencyStats(options)

Important

mongosh Method

This page documents a mongosh method. This is not the documentation for database commands or language-specific drivers, such as Node.js.

For the database command, see the latencyStats field returned by the collStats command.

For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.

db.collection.latencyStats() returns latency statistics for a given collection. It is a wrapper around $collStats.

This method has the form:

db.collection.latencyStats( { histograms: <boolean> } )

The histograms argument is an optional boolean. If histograms: true then latencyStats() adds latency histograms to the return document.

Tip

Compatibility

This method is available in deployments hosted in the following environments:

MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

Note

This command is supported in all MongoDB Atlas clusters. For information on Atlas support for all commands, see Unsupported Commands.

MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

Output

latencyStats() returns a document containing a field latencyStats, containing the following fields:

Field Name	Description
`reads`	Latency statistics for read requests.
`writes`	Latency statistics for write requests.
`commands`	Latency statistics for database commands.

Each of these fields contains an embedded document bearing the following fields:

Field Name

Description

latency

A 64-bit integer giving the total combined latency in microseconds.

ops

A 64-bit integer giving the total number of operations performed on the collection since startup.

histogram

An array of embedded documents, each representing a latency range. Each document covers twice the previous document's range. For lower values between 2048 microseconds and roughly 1 second, the histogram includes half-steps.

This field only exists given the latencyStats: { histograms: true } option. Empty ranges with a zero count are omitted from the output.

Each document bears the following fields:

Field Name	Description
`micros`	A 64-bit integer giving the inclusive lower time bound of the current latency range in microseconds. The document's range spans between the previous document's `micros` value, exclusive, and this document's `micros` value, inclusive.
`count`	A 64-bit integer giving the number of operations with latency less than or equal to `micros`.

For example, if collStats returns the following histogram:

histogram: [
  { micros: NumberLong(0), count: NumberLong(10) },
  { micros: NumberLong(2), count: NumberLong(1) },
  { micros: NumberLong(4096), count: NumberLong(1) },
  { micros: NumberLong(16384), count: NumberLong(1000) },
  { micros: NumberLong(49152), count: NumberLong(100) }
]

This indicates that there were:

10 operations taking 2 microsecond or less
1 operation in the range [2, 4) microseconds
1 operation in the range [4096, 6144) microseconds
1000 operations in the range [16384, 24576) microseconds
100 operations in the range [49152, 65536) microseconds

[1]	The `(` symbol notation on this page means the value is exclusive. The `]` symbol notation on this page means the value is inclusive.

Examples

You can run latencyStats() in mongosh as follows:

db.data.latencyStats( { histograms: true } ).pretty()

latencyStats() returns a document such as the following:

{
  "ns" : "test.data",
  "localTime" : ISODate("2016-11-01T21:56:28.962Z"),
  "latencyStats" : {
    "reads" : {
      "histogram" : [
        {
          "micros" : NumberLong(16),
          "count" : NumberLong(6)
        },
        {
          "micros" : NumberLong(512),
          "count" : NumberLong(1)
        }
      ],
      "latency" : NumberLong(747),
      "ops" : NumberLong(7)
    },
    "writes" : {
      "histogram" : [
        {
          "micros" : NumberLong(64),
          "count" : NumberLong(1)
        },
        {
          "micros" : NumberLong(24576),
          "count" : NumberLong(1)
        }
      ],
      "latency" : NumberLong(26845),
      "ops" : NumberLong(2)
    },
    "commands" : {
      "histogram" : [ ],
      "latency" : NumberLong(0),
      "ops" : NumberLong(0)
    }
  }
}

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