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db.setProfilingLevel()

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Definition

db.setProfilingLevel(level, options)

Changed in version 4.4.2.

For a mongod instance, the method enables, disables, or configures the Database Profiler. The profiler captures and records data on the performance of write operations, cursors, and database commands on a running mongod instance. If the profiler is disabled, the method configures how slow operations are logged to the diagnostic log.

Note

Changes made to the profiling level with db.setProfilingLevel() do not persist. When the server restarts, it reverts to 0 (the default), or the value set by either the operationProfiling.mode setting or the --profile command-line option.

If the database profiler level is 1 or 2 (specifically, the database profiler is enabled), the slowms, sampleRate affect the behavior of both the profiler and the diagnostic log.

If the database profiler level is 0 (specifically, database profiler is disabled), the slowms and sampleRate, affect only the diagnostic log.

With mongos instances, the method sets the slowms, sampleRate and filter configuration settings, which configure how operations get written to the diagnostic log. You cannot enable the Database Profiler on a mongos instance because mongos does not have any collections that the profiler can write to. The profile level must be 0 for a mongos instance.

Starting in MongoDB 4.4.2, you can specify a filter on both mongod and mongos instances to control which operations are logged by the profiler. When you specify a filter for the profiler, the slowms, and sampleRate options are not used for profiling and slow-query log lines.

db.setProfilingLevel() provides a wrapper around the profile command.

Starting in MongoDB 4.4.2 (also available starting in 4.2.12), changes made to the database profiler level, slowms, sampleRate, or filter using the profile command or db.setProfilingLevel() wrapper method are recorded in the log file.

Syntax

The db.setProfilingLevel() method has the following form:

db.setProfilingLevel(<level>, <options>)

Parameters

Parameter

Type

Description

level

integer

Configures the database profiler level. The following profiler levels are available:

Level	Description
`0`	The profiler is off and does not collect any data. This is the default profiler level.
`1`	The profiler collects data for operations that take longer than the value of `slowms`.
`2`	The profiler collects data for all operations.

Because profiling is not available on mongos, db.setProfilingLevel() cannot be used to set the profiling level to a value other than 0 on a mongos instance.

options

document or integer

Optional. Accepts an integer or an options document. If an integer value is passed as the options argument instead of a document, the value is assigned to slowms. The following options are available:

slowms	Default: 100 Type: integer The slow operation time threshold, in milliseconds. Operations that run for longer than this threshold are considered slow. When `logLevel` is set to `0`, MongoDB records slow operations to the diagnostic log at a rate determined by `slowOpSampleRate`. At higher `logLevel` settings, all operations appear in the diagnostic log regardless of their latency with the following exception: the logging of slow oplog entry messages by the secondaries. The secondaries log only the slow oplog entries; increasing the `logLevel` does not log all oplog entries. For `mongod` instances, the setting affects both the diagnostic log and, if enabled, the profiler. For `mongos` instances, the setting affects the diagnostic log only and not the profiler because profiling is not available on `mongos`. Note This argument affects the same setting as the configuration file option `slowOpThresholdMs`.
sampleRate	Default: 1.0 Type: double The fraction of slow operations that should be profiled or logged. `sampleRate` accepts values between 0 and 1, inclusive. For `mongod` instances, the setting affects both the diagnostic log and, if enabled, the profiler. For `mongos` instances, the setting affects the diagnostic log only and not the profiler because profiling is not available on `mongos`. Note This argument affects the same setting as the configuration option `slowOpSampleRate`.
filter	Type: object A filter expression that controls which operations are profiled and logged. The field in the filter expression can be any field in the profiler output. For `mongod` instances, the setting affects both the diagnostic log and, if enabled, the profiler. For `mongos` instances, the setting affects the diagnostic log only and not the profiler because profiling is not available on `mongos`. For an example of a filter used to control logged operations, see Set a Filter to Determine Profiled Operations. New in version 4.4.2. Note When a profiling filter is set, the slowms and sampleRate options do not affect the diagnostic log or the profiler.

Returns

The method returns a document that contains the previous values of the settings.

{
   "was" : 2,
   "slowms" : 100,
   "sampleRate" : 1,
   "filter" : {
      "$and" : [
         {
            "op" : {
               "$eq" : "query"
            }
         },
         {
            "millis" : {
               "$gt" : 20000
            }
         }
      ]
   },
   "note" : "When a filter expression is set, slowms and sampleRate are not used for profiling and slow-query log lines.",
   "ok" : 1
}

{
   "was" : 0,
   "slowms" : 100,
   "sampleRate" : 1,
   "filter" : {
      "$and" : [
         {
            "op" : {
               "$eq" : "query"
            }
         },
         {
            "millis" : {
               "$gte" : 2000
            }
         }
      ]
   },
   "note" : "When a filter expression is set, slowms and sampleRate are not used for profiling and slow-query log lines.",
   "ok" : 1,
   "$clusterTime" : {
      "clusterTime" : Timestamp(1572991238, 1),
      "signature" : {
         "hash" : BinData(0,"hg6GnlrVhV9MAhwWdeHmHQ4T4qU="),
         "keyId" : NumberLong("6755945537557495811")
      }
   },
   "operationTime" : Timestamp(1572991238, 1)
}

{
   "was" : 0,
   "slowms" : 100,
   "sampleRate" : 1,
   "filter" : {
      "$and" : [
         {
            "op" : {
               "$eq" : "query"
            }
         },
         {
            "millis" : {
               "$gte" : 2000
            }
         }
      ]
   },
   "note" : "When a filter expression is set, slowms and sampleRate are not used for profiling and slow-query log lines.",
   "ok" : 1,
   "operationTime" : Timestamp(1572991499, 2),
   "$clusterTime" : {
      "clusterTime" : Timestamp(1572991499, 2),
      "signature" : {
         "hash" : BinData(0,"nhCquIxUw7thlrBudXe3PnsnvP0="),
         "keyId" : NumberLong("6755946491040235540")
      }
   }
}

Where:

was is the previous level setting.
slowms is the previous slowms setting.
sampleRate is the previous sampleRate setting.
filter is the previous filter setting. (New in MongoDB 4.4.2)
note is a string explaining the behavior of filter. This field only appears in the output when filter is also present. (New in MongoDB 4.4.2)

Note

The filter and note fields only appear in the output if they were present in the previous level setting.

To view the current profiling level, see db.getProfilingStatus().

Behavior

Warning

Profiling can degrade performance and expose unencrypted query data in the system log. Carefully consider any performance and security implications before configuring and enabling the profiler on a production deployment.

See Profiler Overhead for more information on potential performance degradation.

Examples

Enable Profiler and Set Slow Operation Threshold and Sample Rate

The following example sets for a mongod instance:

the profiling level to 1,
the slow operation threshold slowms to 20 milliseconds, and
the sampleRate to 0.42.

db.setProfilingLevel(1, { slowms: 20, sampleRate: 0.42 })

The method returns a document with the previous values for the settings.

To view the current profiling level, see db.getProfilingStatus().

Disable Profiler and Set Slow Operation Threshold and Sample Rate

The following example sets for a mongod or mongos instance:

the profiling level to 0,
the slow operation threshold slowms to 20 milliseconds, and
the sampleRate to 0.42.

db.setProfilingLevel(0, { slowms: 20, sampleRate: 0.42 })

The method returns a document with the previous values for the settings.

To view the current profiling level, see db.getProfilingStatus().

Set a Filter to Determine Profiled Operations

New in version 4.4.2.

The following example sets for a mongod instance:

the profiling level to 1,
a filter of { op: "query", millis: { $gt: 2000 } }, which causes the profiler to only record query operations that took longer than 2 seconds.

db.setProfilingLevel( 1, { filter: { op: "query", millis: { $gt: 2000 } } } )

The method returns a document with the previous values for the settings.

To view the current profiling level, see db.getProfilingStatus().

Back

db.setLogLevel()

db.shutdownServer()