:plugin: elapsed
:type: filter

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:version: %VERSION%
:release_date: %RELEASE_DATE%
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:include_path: ../../../../logstash/docs/include
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[id="plugins-{type}s-{plugin}"]

=== Elapsed filter plugin

include::{include_path}/plugin_header.asciidoc[]

==== Description

The elapsed filter tracks a pair of start/end events and uses their
timestamps to calculate the elapsed time between them.

The filter has been developed to track the execution time of processes and
other long tasks.

The configuration looks like this:
[source,ruby]
    filter {
      elapsed {
        start_tag => "start event tag"
        end_tag => "end event tag"
        unique_id_field => "id field name"
        timeout => seconds
        new_event_on_match => true/false
      }
    }

The events managed by this filter must have some particular properties.
The event describing the start of the task (the "start event") must contain
a tag equal to `start_tag`. On the other side, the event describing the end
of the task (the "end event") must contain a tag equal to `end_tag`. Both
these two kinds of event need to own an ID field which identify uniquely that
particular task. The name of this field is stored in `unique_id_field`.

You can use a Grok filter to prepare the events for the elapsed filter.
An example of configuration can be:
[source,ruby]
    filter {
      grok {
        match => { "message" => "%{TIMESTAMP_ISO8601} START id: (?<task_id>.*)" }
        add_tag => [ "taskStarted" ]
      }

      grok {
        match => { "message" => "%{TIMESTAMP_ISO8601} END id: (?<task_id>.*)" }
        add_tag => [ "taskTerminated" ]
      }

      elapsed {
        start_tag => "taskStarted"
        end_tag => "taskTerminated"
        unique_id_field => "task_id"
      }
    }

The elapsed filter collects all the "start events". If two, or more, "start
events" have the same ID, only the first one is recorded, the others are
discarded.

When an "end event" matching a previously collected "start event" is
received, there is a match. The configuration property `new_event_on_match`
tells where to insert the elapsed information: they can be added to the
"end event" or a new "match event" can be created. Both events store the
following information:

* the tags `elapsed` and `elapsed_match`
* the field `elapsed_time` with the difference, in seconds, between
  the two events timestamps
* an ID filed with the task ID
* the field `elapsed_timestamp_start` with the timestamp of the start event

If the "end event" does not arrive before "timeout" seconds, the
"start event" is discarded and an "expired event" is generated. This event
contains:

* the tags `elapsed` and `elapsed_expired_error`
* a field called `elapsed_time` with the age, in seconds, of the
  "start event"
* an ID filed with the task ID
* the field `elapsed_timestamp_start` with the timestamp of the "start event"


[id="plugins-{type}s-{plugin}-options"]
==== Elapsed Filter Configuration Options

This plugin supports the following configuration options plus the <<plugins-{type}s-{plugin}-common-options>> described later.

[cols="<,<,<",options="header",]
|=======================================================================
|Setting |Input type|Required
| <<plugins-{type}s-{plugin}-end_tag>> |<<string,string>>|Yes
| <<plugins-{type}s-{plugin}-new_event_on_match>> |<<boolean,boolean>>|No
| <<plugins-{type}s-{plugin}-start_tag>> |<<string,string>>|Yes
| <<plugins-{type}s-{plugin}-timeout>> |<<number,number>>|No
| <<plugins-{type}s-{plugin}-unique_id_field>> |<<string,string>>|Yes
| <<plugins-{type}s-{plugin}-keep_start_event>> |<<string,string>>|No
|=======================================================================

Also see <<plugins-{type}s-{plugin}-common-options>> for a list of options supported by all
filter plugins.

&nbsp;

[id="plugins-{type}s-{plugin}-end_tag"]
===== `end_tag` 

  * This is a required setting.
  * Value type is <<string,string>>
  * There is no default value for this setting.

The name of the tag identifying the "end event"

[id="plugins-{type}s-{plugin}-new_event_on_match"]
===== `new_event_on_match` 

  * Value type is <<boolean,boolean>>
  * Default value is `false`

This property manage what to do when an "end event" matches a "start event".
If it's set to `false` (default value), the elapsed information are added
to the "end event"; if it's set to `true` a new "match event" is created.

[id="plugins-{type}s-{plugin}-start_tag"]
===== `start_tag` 

  * This is a required setting.
  * Value type is <<string,string>>
  * There is no default value for this setting.

The name of the tag identifying the "start event"

[id="plugins-{type}s-{plugin}-timeout"]
===== `timeout` 

  * Value type is <<number,number>>
  * Default value is `1800`

The amount of seconds after an "end event" can be considered lost.
The corresponding "start event" is discarded and an "expired event"
is generated. The default value is 30 minutes (1800 seconds).

[id="plugins-{type}s-{plugin}-unique_id_field"]
===== `unique_id_field` 

  * This is a required setting.
  * Value type is <<string,string>>
  * There is no default value for this setting.

The name of the field containing the task ID.
This value must uniquely identify the task in the system, otherwise
it's impossible to match the couple of events.

[id="plugins-{type}s-{plugin}-keep_start_event"]
===== `keep_start_event`

  * Value type is <<string,string>>
  * Default value is `first`

This property manages what to do when several events matched as a start one
were received before the end event for the specified ID. There are two
supported values: `first` or `last`. If it's set to `first` (default value),
the first event matched as a start will be used; if it's set to `last`,
the last one will be used.


[id="plugins-{type}s-{plugin}-common-options"]
include::{include_path}/{type}.asciidoc[]