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Elastic Docs ›Filebeat Reference [1.2] ›Configuring Filebeat

Managing Multiline Messages

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Managing Multiline Messages

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You can specify multiline settings in the filebeat.yml file to control how Filebeat deals with messages that span multiple lines. At a minimum, you need to configure:

  • the pattern option, which specifies a regular expression. Depending on how you configure other multiline options, lines that match the specified regular expression are considered either continuations of a previous line or the start of a new multiline event. You can set the negate option to negate the pattern.
  • the match option, which specifies how Filebeat combines matching lines into an event. You can specify before or after.

See the full documentation for multiline to learn more about these options. Also read YAML Tips and Gotchas and Regular Expression Support to avoid common mistakes.

Testing Your Regexp Pattern for Multiline

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To make it easier for you to test the regexp patterns in your multiline config, we’ve created a Go Playground. You can simply plug in the regexp pattern along with the negate setting that you plan to use, and paste a sample message between the content backticks (` `). Then click Run, and you’ll see which lines in the message match your specified configuration. For example:

go playground

Examples of Multiline Configuration

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The examples in this section cover the following use cases:

  • Combining a Java stack trace into a single event
  • Combining C-style line continuations into a single event
  • Combining multiple lines from time-stamped events

Java Stack Traces

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Java stack traces consist of multiple lines, with each line after the initial line beginning with whitespace, as in this example:

Exception in thread "main" java.lang.NullPointerException
        at com.example.myproject.Book.getTitle(Book.java:16)
        at com.example.myproject.Author.getBookTitles(Author.java:25)
        at com.example.myproject.Bootstrap.main(Bootstrap.java:14)

To consolidate these lines into a single event in Filebeat, use the following multiline configuration:

multiline:
  pattern: '^[[:space:]]'
  negate: false
  match: after

This configuration merges any line that begins with whitespace up to the previous line.

Here’s a Java stack trace that presents a slightly more complex example:

Exception in thread "main" java.lang.IllegalStateException: A book has a null property
       at com.example.myproject.Author.getBookIds(Author.java:38)
       at com.example.myproject.Bootstrap.main(Bootstrap.java:14)
Caused by: java.lang.NullPointerException
       at com.example.myproject.Book.getId(Book.java:22)
       at com.example.myproject.Author.getBookIds(Author.java:35)
       ... 1 more

To consolidate these lines into a single event in Filebeat, use the following multiline configuration:

multiline:
    pattern: '^[[:space:]]+|^Caused by:'
    negate: false
    match: after

In this example, the pattern matches the following lines:

  • a line that begins with spaces followed by the word at or ...
  • a line that begins with the words Caused by:

Line Continuations

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Several programming languages use the backslash (\) character at the end of a line to denote that the line continues, as in this example:

printf ("%10.10ld  \t %10.10ld \t %s\
  %f", w, x, y, z );

To consolidate these lines into a single event in Filebeat, use the following multiline configuration:

multiline:
  pattern: '\\$'
  negate: false
  match: before

This configuration merges any line that ends with the \ character with the line that follows.

Timestamps

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Activity logs from services such as Elasticsearch typically begin with a timestamp, followed by information on the specific activity, as in this example:

[2015-08-24 11:49:14,389][INFO ][env                      ] [Letha] using [1] data paths, mounts [[/
(/dev/disk1)]], net usable_space [34.5gb], net total_space [118.9gb], types [hfs]

To consolidate these lines into a single event in Filebeat, use the following multiline configuration:

multiline:
  pattern: '^\[[0-9]{4}-[0-9]{2}-[0-9]{2}'
  negate: true
  match: after

This configuration uses the negate: true and match: after settings to specify that any line that does not match the specified pattern belongs to the previous line.

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