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db.collection.latencyStats()

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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.

For the legacy mongo shell documentation, refer to the documentation for the corresponding MongoDB Server release:

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

See also:

$collStats

Output

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

Field NameDescription
readsLatency statistics for read requests.
writesLatency statistics for write requests.
commandsLatency statistics for database commands.
transactionsLatency statistics for database transactions.

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

Field NameDescription
latencyA 64-bit integer giving the total combined latency in microseconds.
opsA 64-bit integer giving the total number of operations performed on the collection since startup.
histogramAn array of embedded documents, each representing a latency range. Each document covers twice the previous document's range. For upper 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 NameDescription
microsA 64-bit integer giving the inclusive upper 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.
countA 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(1), 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 [1]:

  • 10 operations taking 1 microsecond or less

  • 1 operation in the range (1, 2] microseconds

  • 1 operation in the range (3072, 4096] microseconds

  • 1000 operations in the range (12288, 16384] microseconds

  • 100 operations in the range (32768, 49152] 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)
    }
  }
}