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Prune filter plugin

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Prune filter plugin

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Plugin version: v3.0.4
Released on: 2019-09-12
Changelog

For other versions, see the Versioned plugin docs.

Getting Help

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For questions about the plugin, open a topic in the Discuss forums. For bugs or feature requests, open an issue in Github. For the list of Elastic supported plugins, please consult the Elastic Support Matrix.

Description

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The prune filter is for removing fields from events based on whitelists or blacklist of field names or their values (names and values can also be regular expressions).

This can e.g. be useful if you have a json or kv filter that creates a number of fields with names that you don’t necessarily know the names of beforehand, and you only want to keep a subset of them.

Usage help: To specify a exact field name or value use the regular expression syntax ^some_name_or_value$. Example usage: Input data { "msg":"hello world", "msg_short":"hw" }

    filter {
      prune {
        whitelist_names => [ "msg" ]
      }
    }
Allows both `"msg"` and `"msg_short"` through.

While:

    filter {
      prune {
        whitelist_names => ["^msg$"]
      }
    }
Allows only `"msg"` through.

Logstash stores an event’s tags as a field which is subject to pruning. Remember to whitelist_names => [ "^tags$" ] to maintain tags after pruning or use blacklist_values => [ "^tag_name$" ] to eliminate a specific tag.

This filter currently only support operations on top-level fields, i.e. whitelisting and blacklisting of subfields based on name or value does not work.

Prune Filter Configuration Options

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This plugin supports the following configuration options plus the Common Options described later.

Setting	Input type	Required
`blacklist_names`	array	No
`blacklist_values`	hash	No
`interpolate`	boolean	No
`whitelist_names`	array	No
`whitelist_values`	hash	No

Also see Common Options for a list of options supported by all filter plugins.

`blacklist_names`

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Value type is array
Default value is ["%{[^}]+}"]

Exclude fields whose names match specified regexps, by default exclude unresolved %{field} strings.

    filter {
      prune {
        blacklist_names => [ "method", "(referrer|status)", "${some}_field" ]
      }
    }

`blacklist_values`

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Value type is hash
Default value is {}

Exclude specified fields if their values match one of the supplied regular expressions. In case field values are arrays, each array item is matched against the regular expressions and matching array items will be excluded.

    filter {
      prune {
        blacklist_values => [ "uripath", "/index.php",
                              "method", "(HEAD|OPTIONS)",
                              "status", "^[^2]" ]
      }
    }

`interpolate`

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Value type is boolean
Default value is false

Trigger whether configuration fields and values should be interpolated for dynamic values (when resolving %{some_field}). Probably adds some performance overhead. Defaults to false.

`whitelist_names`

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Value type is array
Default value is []

Include only fields only if their names match specified regexps, default to empty list which means include everything.

    filter {
      prune {
        whitelist_names => [ "method", "(referrer|status)", "${some}_field" ]
      }
    }

`whitelist_values`

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Value type is hash
Default value is {}

Include specified fields only if their values match one of the supplied regular expressions. In case field values are arrays, each array item is matched against the regular expressions and only matching array items will be included. By default all fields that are not listed in this setting are kept unless pruned by other settings.

    filter {
      prune {
        whitelist_values => [ "uripath", "/index.php",
                              "method", "(GET|POST)",
                              "status", "^[^2]" ]
      }
    }

Common Options

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The following configuration options are supported by all filter plugins:

Setting	Input type	Required
`add_field`	hash	No
`add_tag`	array	No
`enable_metric`	boolean	No
`id`	string	No
`periodic_flush`	boolean	No
`remove_field`	array	No
`remove_tag`	array	No

`add_field`

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Value type is hash
Default value is {}

If this filter is successful, add any arbitrary fields to this event. Field names can be dynamic and include parts of the event using the %{field}.

Example:

    filter {
      prune {
        add_field => { "foo_%{somefield}" => "Hello world, from %{host}" }
      }
    }

    # You can also add multiple fields at once:
    filter {
      prune {
        add_field => {
          "foo_%{somefield}" => "Hello world, from %{host}"
          "new_field" => "new_static_value"
        }
      }
    }

If the event has field "somefield" == "hello" this filter, on success, would add field foo_hello if it is present, with the value above and the %{host} piece replaced with that value from the event. The second example would also add a hardcoded field.

`add_tag`

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Value type is array
Default value is []

If this filter is successful, add arbitrary tags to the event. Tags can be dynamic and include parts of the event using the %{field} syntax.

Example:

    filter {
      prune {
        add_tag => [ "foo_%{somefield}" ]
      }
    }

    # You can also add multiple tags at once:
    filter {
      prune {
        add_tag => [ "foo_%{somefield}", "taggedy_tag"]
      }
    }

If the event has field "somefield" == "hello" this filter, on success, would add a tag foo_hello (and the second example would of course add a taggedy_tag tag).

`enable_metric`

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Value type is boolean
Default value is true

Disable or enable metric logging for this specific plugin instance. By default we record all the metrics we can, but you can disable metrics collection for a specific plugin.

`id`

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Value type is string
There is no default value for this setting.

Add a unique ID to the plugin configuration. If no ID is specified, Logstash will generate one. It is strongly recommended to set this ID in your configuration. This is particularly useful when you have two or more plugins of the same type, for example, if you have 2 prune filters. Adding a named ID in this case will help in monitoring Logstash when using the monitoring APIs.

    filter {
      prune {
        id => "ABC"
      }
    }

Variable substitution in the id field only supports environment variables and does not support the use of values from the secret store.

`periodic_flush`

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Value type is boolean
Default value is false

Call the filter flush method at regular interval. Optional.

`remove_field`

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Value type is array
Default value is []

If this filter is successful, remove arbitrary fields from this event. Fields names can be dynamic and include parts of the event using the %{field} Example:

    filter {
      prune {
        remove_field => [ "foo_%{somefield}" ]
      }
    }

    # You can also remove multiple fields at once:
    filter {
      prune {
        remove_field => [ "foo_%{somefield}", "my_extraneous_field" ]
      }
    }

If the event has field "somefield" == "hello" this filter, on success, would remove the field with name foo_hello if it is present. The second example would remove an additional, non-dynamic field.

`remove_tag`

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Value type is array
Default value is []

If this filter is successful, remove arbitrary tags from the event. Tags can be dynamic and include parts of the event using the %{field} syntax.

Example:

    filter {
      prune {
        remove_tag => [ "foo_%{somefield}" ]
      }
    }

    # You can also remove multiple tags at once:
    filter {
      prune {
        remove_tag => [ "foo_%{somefield}", "sad_unwanted_tag"]
      }
    }

If the event has field "somefield" == "hello" this filter, on success, would remove the tag foo_hello if it is present. The second example would remove a sad, unwanted tag as well.

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