The parser filter plugin "parses" string field in event records and mutates its event record with parsed result.

Example Configurations

filter_parser is included in Fluentd's core. No installation required.

<filter foo.bar>
  @type parser
  key_name log
  <parse>
    @type regexp
    expression /^(?<host>[^ ]*) [^ ]* (?<user>[^ ]*) \[(?<time>[^\]]*)\] "(?<method>\S+)(?: +(?<path>[^ ]*) +\S*)?" (?<code>[^ ]*) (?<size>[^ ]*)$/
    time_format %d/%b/%Y:%H:%M:%S %z
  </parse>
</filter>

filter_parser uses built-in parser plugins and your own customized parser plugin, so you can re-use pre-defined format like apache2, json and etc. See document page for more details: Parser Plugin Overview​

With this example, if you receive following event:

time:
injested time (depends on your input)
record:
{"log":"192.168.0.1 - - [05/Feb/2018:12:00:00 +0900] \"GET / HTTP/1.1\" 200 777"}

parsed result is below:

time
05/Feb/2018:12:00:00 +0900
record:
{"host":"192.168.0.1","user":"-","method":"GET","path":"/","code":"200","size":"777"}

Plugin helpers

• ​parser​

• ​record_accessor​

• ​compat_parameters​

Parameters

​Common Parameters​

<parse> section

This is required sub section. Specify parser type and related parameter.

For more details, see Parse section configurations.

key_name

Specify field name in the record to parse.

This parameter supports nested field access via record_accessor syntax.

reserve_time

Keep original event time in parsed result.

reserve_data

Keep original key-value pair in parsed result.

<filter foo.bar>
  @type parser
  key_name log
  reserve_data true
  <parse>
    @type json
  </parse>
</filter>

With above configuration, result is below:

# input data:  {"key":"value","log":"{\"user\":1,\"num\":2}"}
# output data: {"key":"value","log":"{\"user\":1,\"num\":2}","user":1,"num":2}

Without reserve_data, result is below

# input data:  {"key":"value","log":"{\"user\":1,\"num\":2}"}
# output data: {"user":1,"num":2}

remove_key_name_field

Remove key_name field when parsing is succeeded.

<filter foo.bar>
  @type parser
  key_name log
  reserve_data true
  remove_key_name_field true
  <parse>
    @type json
  </parse>
</filter>

With above configuration, result is below:

# input data:  {"key":"value","log":"{\"user\":1,\"num\":2}"}
# output data: {"key":"value","user":1,"num":2}

replace_invalid_sequence

If true, invalid string is replaced with safe characters and re-parse it.

inject_key_prefix

Store parsed values with specified key name prefix.

<filter foo.bar>
  @type parser
  key_name log
  reserve_data true
  inject_key_prefix data.
  <parse>
    @type json
  </parse>
</filter>

With above configuration, result is below:

# input data:  {"log": "{\"user\":1,\"num\":2}"}
# output data: {"log":"{\"user\":1,\"num\":2}","data.user":1, "data.num":2}

hash_value_field

Store parsed values as a hash value in a field.

<filter foo.bar>
  @type parser
  key_name log
  hash_value_field parsed
  <parse>
    @type json
  </parse>
</filter>

With above configuration, result is below:

# input data:  {"log": "{\"user\":1,\"num\":2}"}
# output data: {"parsed":{"user":1,"num":2}}

emit_invalid_record_to_error

Emit invalid record to @ERROR label. Invalid cases are

• key not exist

• format is not matched

• unexpected error

You can rescue unexpected format logs in @ERROR label.

If you want to ignore these errors, set false.

FAQ

suppress_parse_error_log is missing. What are the alternatives?

Since v1, parser filter doesn't support suppress_parse_error_log parameter because parser filter uses @ERROR feature instead of internal logging to rescue invalid records. If you want to simply ignore invalid records, set emit_invalid_record_to_error false.

See also emit_invalid_record_to_error parameter.

Learn More

• ​Filter Plugin Overview​

If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is a open source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.