multiline

Status: stable

multiline filter

This filter will collapse multiline messages into a single event.

The multiline filter is for combining multiple events from a single source into the same 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.

TODO(sissel): Document any issues? The config looks like this:

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

The 'regexp' should match what you believe to be an indicator that the field is part of a multi-line event

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

The 'negate' can be "true" or "false" (defaults 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, then each subsequent line indented. Do this:

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

Synopsis

This is what it might look like in your config file:

filter {
  multiline {
    add_field => ... # hash (optional), default: {}
    add_tag => ... # array (optional), default: []
    negate => ... # boolean (optional)
    pattern => ... # string (optional)
    stream_identity => ... # string (optional), default: "%{@source}.%{@type}"
    tags => ... # array (optional), default: []
    type => ... # string (optional), default: ""
    what => ... # ["previous", "next"] (optional)
  }
}

Details

add_field

• Value type is hash
• Default value is {}

If this filter is successful, add any arbitrary fields to this event. Example:

filter {
  myfilter {
    add_field => [ "sample", "Hello world, from %{@source}" ]
  }
}

On success, myfilter will then add field 'sample' with the value above and the %{@source} piece replaced with that value from the event.

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 {
  myfilter {
    add_tag => [ "foo_%{somefield}" ]
  }
}

If the event has field "somefield" == "hello" this filter, on success, would add a tag "foo_hello"

negate

• Value type is boolean
• There is no default value for this setting.

Negate the regexp pattern ('if not matched')

pattern

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

The regular expression to match

stream_identity

• Value type is string
• Default value is "%{@source}.%{@type}"

The stream identity is how the multiline filter determines which stream an event belongs. 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.

tags

• Value type is array
• Default value is []

Only handle events with all of these tags. Note that if you specify a type, the event must also match that type. Optional.

type

• Value type is string
• Default value is ""

The type to act on. If a type is given, then this filter will only act on messages with the same type. See any input plugin's "type" attribute for more. Optional.

what

• 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?

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This is documentation from lib/logstash/filters/multiline.rb