Multiline filter plugin v3.0.4

  • Plugin version: v3.0.4
  • Released on: 2017-08-15
  • Changelog

For other versions, see the overview list.

To learn more about Logstash, see the Logstash Reference.

Getting Help

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

This filter will collapse multiline messages from a single source into one Logstash event.

The original goal of this filter was to allow joining of multi-line messages from files into a single event. For example - joining java exception and stacktrace messages into a single event.

Note

This filter will not work with multiple worker threads -w 2 on the logstash command line.

The config looks like this:

filter {
  multiline {
    pattern => "pattern, a regexp"
    negate => boolean
    what => "previous" or "next"
  }
}

The pattern should be a regexp (grok patterns are supported) which matches what you believe to be an indicator that the field is part of an event consisting of multiple lines of log data.

The what must be previous or next and indicates the relation to the multi-line event.

The negate can be true or false (defaults to false). If true, a message not matching the pattern will constitute a match of the multiline filter and the what will be applied. (vice-versa is also true)

For example, Java stack traces are multiline and usually have the message starting at the far-left, with each subsequent line indented. Do this:

filter {
  multiline {
    pattern => "^\s"
    what => "previous"
  }
}

This says that any line starting with whitespace belongs to the previous line.

Another example is C line continuations (backslash). Here’s how to do that:

filter {
  multiline {
    pattern => "\\$"
    what => "next"
  }
}

This says that any line ending with a backslash should be combined with the following line.

Multiline Filter Configuration Options

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

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

 

allow_duplicates

  • Value type is boolean
  • Default value is true

Allow duplcate values on the source field.

max_age

  • Value type is number
  • Default value is 5

The maximum age an event can be (in seconds) before it is automatically flushed.

negate

  • Value type is boolean
  • Default value is false

Negate the regexp pattern (if not matched)

pattern

  • This is a required setting.
  • Value type is string
  • There is no default value for this setting.

The expression to match. The same matching engine as the grok filter is used, so the expression can contain a plain regular expression or one that also contains grok patterns.

patterns_dir

  • Value type is array
  • Default value is []

Logstash ships by default with a bunch of patterns, so you don’t necessarily need to define this yourself unless you are adding additional patterns.

Pattern files are plain text with format:

NAME PATTERN

For example:

NUMBER \d+

source

  • Value type is string
  • Default value is "message"

The field name to execute the pattern match on.

stream_identity

  • Value type is string
  • Default value is "%{host}.%{path}.%{type}"

The stream identity is how the multiline filter determines which stream an event belongs to. This is generally used for differentiating, say, events coming from multiple files in the same file input, or multiple connections coming from a tcp input.

The default value here is usually what you want, but there are some cases where you want to change it. One such example is if you are using a tcp input with only one client connecting at any time. If that client reconnects (due to error or client restart), then logstash will identify the new connection as a new stream and break any multiline goodness that may have occurred between the old and new connection. To solve this use case, you can use %{@source_host}.%{@type} instead.

what

  • This is a required setting.
  • Value can be any of: previous, next
  • There is no default value for this setting.

If the pattern matched, does event belong to the next or previous event?

Common Options

The following configuration options are supported by all filter plugins:

add_field

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

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

  • 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

  • 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 multiline filters. Adding a named ID in this case will help in monitoring Logstash when using the monitoring APIs.

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

periodic_flush

  • Value type is boolean
  • Default value is false

Call the filter flush method at regular interval. Optional.

remove_field

  • Value type is array
  • Default value is []

If this filter is successful, remove arbitrary fields from this event. Example:

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

  • 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 {
  multiline {
    remove_tag => [ "foo_%{somefield}" ]
  }
}
# You can also remove multiple tags at once:
filter {
  multiline {
    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. :plugin: multiline :type: filter