Splunk® Enterprise

Search Reference

Splunk Enterprise version 8.0 is no longer supported as of October 22, 2021. See the Splunk Software Support Policy for details. For information about upgrading to a supported version, see How to upgrade Splunk Enterprise.
This documentation does not apply to the most recent version of Splunk® Enterprise. For documentation on the most recent version, go to the latest release.

mcollect

Description

Converts events into metric data points and inserts the metric data points into a metric index on the search head. A metric index must be present on the search head for mcollect to work properly, unless you are forwarding data to the indexer.

If you are forwarding data to the indexer, your data will be inserted on the indexer instead of the search head.

You can use the mcollect command only if your role has the run_mcollect capability. See Define roles on the Splunk platform with capabilities in Securing Splunk Enterprise.

Syntax

The required syntax is in bold.

| mcollect index=<string>
[ file=<string> ]
[ split=<bool> ]
[ spool=<bool> ]
[ prefix_field=<string> ]
[ host=<string> ]
[ source=<string> ]
[ sourcetype=<string> ]
[ <field-list> ]

Required arguments

index
Syntax: index=<string>
Description: Name of the metric index where the collected metric data is added.
field-list
Syntax: <field>, ...
Description: A list of dimension fields. Required if split=true. Optional if split=false. If unspecified, which implies that split=false, all fields are treated as dimensions for the data point except for the metric_name, prefix_field, and all internal fields.
Default: No default value

Optional arguments

file
Syntax: file=<string>
Description: The file name where you want the collected metric data to be written. Only applicable when spool=false. You can use a timestamp or a random number for the file name by specifying either file=$timestamp$ or file=$random$.
Default: $random$_metrics.csv
split
Syntax: split=<bool>
Description: Determines how mcollect identifies the measures in an event. See How to use the split argument.
Default: false
spool
Syntax: spool=<bool>
Description: If set to true, the metrics data file is written to the Splunk spool directory, $SPLUNK_HOME/var/spool/splunk, where the file is indexed. Once the file is indexed, it is removed. If set to false, the file is written to the $SPLUNK_HOME/var/run/splunk directory. The file remains in this directory unless further automation or administration is done.
Default: true
prefix_field
Syntax: prefix_field=<string>
Description: Only applicable when split=true. If specified, any data point with that field missing is ignored. Otherwise, the field value is prefixed to the metric name. See Set a prefix field
Default: No default value
host
Syntax: host=<string>
Description: The name of the host that you want to specify for the collected metrics data. Only applicable when spool=true.
Default: No default value
source
Syntax: source=<string>
Description: The name of the source that you want to specify for the collected metrics data.
Default: If the search is scheduled, the name of the search. If the search is ad-hoc, the name of the file that is written to the var/spool/splunk directory containing the search results.
sourcetype
Syntax: sourcetype=<string>
Description: The name of the source type that is specified for the collected metrics data. The Splunk platform does not calculate license usage for data indexed with mcollect_stash, the default source type. If you change the value of this setting to a different source type, the Splunk platform calculates license usage for any data indexed by the mcollect command.
Default: mcollect_stash

Do not change this setting without assistance from Splunk Professional Services or Splunk Support. Changing the source type requires a change to the props.conf file.

Usage

You use the mcollect command to convert events into metric data points to be stored in a metric index on the search head. The metrics data uses a specific format for the metrics fields. See Metrics data format in Metrics.

The mcollect command causes new data to be written to a metric index for every run of the search.

All metrics search commands are case sensitive. This means, for example, that mcollect treats as the following as three distinct values of metric_name: cap.gear, CAP.GEAR, and Cap.Gear.

If you are upgrading to version 8.0.0

After you upgrade your search head and indexer clusters to version 8.0.x of Splunk Enterprise, edit limits.conf on each search head cluster and set the always_use_single_value_output setting under the [mcollect] stanza to false. This lets these nodes use the "multiple measures per metric data point" schema when you convert logs to metrics with the mcollect command or use metrics rollups. This schema increases your data storage capacity and improves metrics search performance.

How to use the split argument

The split argument determines how mcollect identifies the measurement fields in your search. It defaults to false.

When split=false, your search needs to explicitly identify its measurement fields. If necessary it can use rename or eval conversions to do this.

  • If you have single-metric events, your mcollect search must produce results with a metric_name field that provides the name of the measure, and a _value field that provides the measure's numeric value.
  • If you have multiple-metric events, your mcollect search must produce results that follow this syntax: metric_name:<metric_name>=<numeric_value>. Each of these fields will be treated as a measurement. The remaining fields will be treated as dimensions.

When you set split=true, you use <field-list> to identify the dimensions in your search. mcollect converts any field that is not in the <field-list> into a measurement. The only exceptions are internal fields beginning with an underscore and the prefix_field, if you have set one.

Set a prefix field

Use the prefix_field argument to apply a prefix to the metric fields in your event data.

For example, if you have the following data:

type=cpu usage=0.78 idle=0.22

You have two metric fields, usage and idle.

Say you include the following in an mcollect search of that data:

...split=true prefix_field=type...

Because you have set split = true the Splunk software automatically converts those fields into measures, because they are not otherwise identified in a <field-list>. Then it applies the value of the specified prefix_field as a prefix to the metric field names. In this case, because you have specified the type field as the prefix field, its value, cpu, becomes the metric name prefix. The results look like this:

metric_name:cpu.usage metric_name:cpu.idle
0.78 0.22

Time

If the _time field is present in the results, the Splunk software uses it as the timestamp of the metric data point. If the _time field is not present, the current time is used.

field-list

If field-list is not specified, all fields are treated as dimensions for the data point, except for the prefix_field and internal fields (fields with an underscore '_' prefix). If field-list is specified, the list must appear at the end of the mcollect command arguments. If field-list is specified, all fields are treated as metric values, except for the fields in field-list, the prefix-field, and internal fields.

The name of each metric value is the field name prefixed with the prefix_field value.

Effectively, one metric data point is returned for each qualifying field that contains a numerical value. If one search result contains multiple qualifying metric name/value pairs, the result is split into multiple metric data points.

Examples

The following examples show how to use the mcollect command to convert events into multiple-value metric data points.

1: Generate metric data points that break out jobs and latency metrics by user

The following example specifies the metrics that should appear in the resulting metric data points, and splits them by user. Note that it does not use the split argument, so the search has to use a rename conversion to explicitly identify the measurements that will appear in the data points.

index="_audit" search_id info total_run_time | stats count(search_id) as jobs avg(total_run_time) as latency by user | rename jobs as metric_name:jobs latency as metric_name:latency | mcollect index=mcollect_test

Here are example results of that search:

_time user metric_name:jobs metric_name:latency
1563318689 admin 25 3.8105555555555575
1563318689 splunk-system-user 129 0.2951162790697676

2: Generate metric data points that break out event counts and total runtimes by user

This search sets split=true so it automatically converts fields not otherwise identified as dimensions by the <field-list> into metrics. The search identifies user as a dimension.

index="_audit" info=completed | stats max(total_run_time) as runtime max(event_count) as events by user | mcollect index=mcollect_test split=t user

Here are example results of that search:

_time user metric_name:runtime metric_name:events
1563318968 admin 0.29 293
1563318968 splunk-system-user 0.04 3

See also

Commands
collect
meventcollect
Last modified on 28 August, 2020
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This documentation applies to the following versions of Splunk® Enterprise: 8.0.0, 8.0.1, 8.0.2, 8.0.3, 8.0.4, 8.0.5, 8.0.6, 8.0.7, 8.0.8, 8.0.9, 8.0.10

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