# key

Names the JSON property whose values are counted on matching messages.

This parameter applies to mmcount.

Name:

  key

Scope:

  input

Type:

  word

Default:

  none (count messages per severity)

Required?:

  no

Introduced:

  7.5.0

## Description

Directs mmcount to evaluate a structured property on each message that matches appName. The value should be the RainerScript variable name used to access the JSON property (e.g., `!gf_code`).

If the named property is absent, mmcount leaves the message unchanged and no counter is modified. When the property exists, its value is converted into a string (JSON `null` becomes an empty string) and used to select which counter to increment. Without value, mmcount creates a distinct counter for every observed value and writes the running total for that value into the message’s `mmcount` property.

## Input usage

    action(type="mmcount" appName="glusterd" key="!gf_code")

## See also

See also mmcount.

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