fluent-plugin-concat

Fluentd Filter plugin to concatenate multiline log separated in multiple events.

Requirements

fluent-plugin-concat	fluentd	ruby
>= 2.0.0	>= v0.14.0	>= 2.1
< 2.0.0	>= v0.12.0	>= 1.9

Installation

Add this line to your application's Gemfile:

gem 'fluent-plugin-concat'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fluent-plugin-concat

Configuration

key (string) (required)

The key for part of multiline log.

separator (string) (optional)

The separator of lines. Default value is "\n".

n_lines (integer) (optional)

The number of lines. This is exclusive with multiline_start_regex.

multiline_start_regexp (string) (optional)

The regexp to match beginning of multiline. This is exclusive with n_lines.

multiline_end_regexp (string) (optional)

The regexp to match ending of multiline. This is exclusive with n_lines.

continuous_line_regexp (string) (optional)

The regexp to match continuous lines. This is exclusive with n_lines.

stream_identity_key (string) (optional)

The key to determine which stream an event belongs to.

flush_interval (integer) (optional)

The number of seconds after which the last received event log will be flushed. If specified 0, wait for next line forever.

timeout_label (string) (optional)

The label name to handle events caused by timeout.

use_first_timestamp (bool) (optional)

Use timestamp of first record when buffer is flushed. Default value is false.

partial_key (string) (optional)

The field name that is the reference to concatenate records

partial_value (string) (optional)

The value stored in the field specified by partial_key that represent partial log

keep_partial_key (bool) (optional)

If true, keep partial_key in concatenated records Default value is false.

use_partial_metadata (bool) (optional)

Use partial metadata to concatenate multiple records

keep_partial_metadata (bool) (optional)

If true, keep partial metadata

partial_metadata_format (string) (optional)

Configure based on the input plugin, that is used. The docker fluentd and journald log drivers are behaving differently, so the plugin needs to know, what to look for. Use docker-journald-lowercase, if you have fields_lowercase true in the journald source config

Valid options: docker-fluentd, docker-journald, docker-journald-lowercase

Default value is docker-fluentd

Usage

Every 10 events will be concatenated into one event.

<filter docker.log>
  @type concat
  key message
  n_lines 10
</filter>

Specify first line of multiline by regular expression.

<filter docker.log>
  @type concat
  key message
  multiline_start_regexp /^Start/
</filter>

You can handle timeout events and remaining buffers on shutdown this plugin.

<label @ERROR>
  <match docker.log>
    @type file
    path /path/to/error.log
  </match>
</label>

Handle timeout log lines the same as normal logs.

<filter **>
  @type concat
  key message
  multiline_start_regexp /^Start/
  flush_interval 5
  timeout_label @NORMAL
</filter>

<match **>
  @type relabel
  @label @NORMAL
</match>

<label @NORMAL>
  <match **>
    @type stdout
  </match>
</label>

Handle single line JSON from Docker containers.

<filter **>
  @type concat
  key message
  multiline_end_regexp /\n$/
</filter>

Handle Docker logs splitted in several parts (using partial_message), and do not add new line between parts.

<filter>
  @type concat
  key log
  partial_key partial_message
  partial_value true
  separator ""
</filter>

(Docker v19.03+) Handle Docker logs splitted in several parts (using use_partial_metadata), and do not add new line between parts.

<filter>
  @type concat
  key log
  use_partial_metadata true
  separator ""
</filter>

(Docker v20.10+) Handle Docker logs splitted in several parts (using use_partial_metadata), and do not add new line between parts.

Docker v20.10 improved partial message handling by adding better metadata in the journald log driver, this works now similarily to the fluentd log driver, but requires one additional setting

<filter>
  @type concat
  key log
  use_partial_metadata true
  partial_metadata_format docker-journald
  separator ""
</filter>

Handle Docker logs splitted in several parts (using newline detection), and do not add new line between parts (prior to Docker 18.06).

<filter **>
  @type concat
  key log
  multiline_end_regexp /\\n$/
  separator ""
</filter>

Handle containerd/cri in Kubernetes.

<source>
  @type tail
  path /var/log/containers/*.log
  <parse>
    @type regexp
    expression /^(?<timestamp>\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d+Z) (?<output>\w+) (?<partial_flag>[FP]) (?<message>.+)$/
  </parse>
  tag k8s
  @label @CONCAT
</source>

<label @CONCAT>
  <filter k8s>
    @type concat
    key message
    partial_key partial_flag
    partial_value P
  </filter>
  <match k8s>
    @type relabel
    @label @OUTPUT
  </match>
</label>

<label @OUTPUT>
  <match>
    @type stdout
  </match>
</label>

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

License

The gem is available as open source under the terms of the MIT License.