The syslog parser plugin parses syslog generated logs. This plugin supports two RFC formats, rfc3164 and rfc5424.

Parameters

See Parse section configurations​

time_format

Specify time format for event time. Default is "%b %d %H:%M:%S" for rfc3164 protocol. If your log uses sub-second timestamp, change this parameter to like "%b %d %H:%M:%S.%N".

rfc5424_time_format

Specify time format for event time for rfc5424 protocol.

message_format

Specify protocol format. Supported values are rfc3164, rfc5424 and auto. Default is rfc3164. If your syslog uses rfc5424, use rfc5424 instead.

auto is useful when this parser receives both rfc3164 and rfc5424 message. syslog parser detects message format by using message prefix.

with_priority

If the incoming logs have priority prefix, e.g. <9>, set true. Default is false.

This parameter is used inside in_syslog plugin because the file logs via syslog don't have <9> like priority prefix.

parser_type

Specify internal parser type for rfc3164 format. Supported values are regexp and string. Both parsers generate same record for standard format.

We recommend to use string parser because it is 2x faster than regexp. The default is regexp for existing users, but fluentd v2 will change the default to string parser.

support_colonless_ident

This parameter is used when parser_type is string. If your message doesn't contain ident field, set false to avoid ident mismatch.

# No ident field log
Feb  5 17:32:18 10.0.0.99 Use the BFG!
​
# generated record with true is wrong
{"host":"10.0.0.99","ident":"Use","message":"the BFG!"}
​
# generated record with false is correct
{"host":"10.0.0.99","message":"Use the BFG!"}

Regexp patterns

rfc3164 pattern

expression /^\<(?<pri>[0-9]+)\>(?<time>[^ ]* {1,2}[^ ]* [^ ]*) (?<host>[^ ]*) (?<ident>[a-zA-Z0-9_\/\.\-]*)(?:\[(?<pid>[0-9]+)\])?(?:[^\:]*\:)? *(?<message>.*)$/
time_format "%b %d %H:%M:%S"

pri, host, ident, pid and message are included in the event record. time is used for the event time.

pri value is converted into integer type.

If with_priority is false, ^\<(?<pri>[0-9]+)\> is removed from the pattern.

rfc5424 pattern

expression /\A^\<(?<pri>[0-9]{1,3})\>[1-9]\d{0,2} (?<time>[^ ]+) (?<host>[^ ]+) (?<ident>[^ ]+) (?<pid>[-0-9]+) (?<msgid>[^ ]+) (?<extradata>(\[(.*)\]|[^ ])) (?<message>.+)$\z/
time_format "%Y-%m-%dT%H:%M:%S.%L%z"

pri, host, ident, pid, msgid, extradata and message are included in the event record. time is used for the event time.

pri value is converted into integer type.

Example

rfc3164 log

<6>Feb 28 12:00:00 192.168.0.1 fluentd[11111]: [error] Syslog test

This incoming event is parsed as:

time:
1362020400 (Feb 28 12:00:00)
​
record:
{
  "pri"    : 6,
  "host"   : "192.168.0.1",
  "ident"  : "fluentd",
  "pid"    : "11111",
  "message": "[error] Syslog test"
}

rfc5424 log

<16>1 2013-02-28T12:00:00.003Z 192.168.0.1 fluentd 11111 ID24224 [exampleSDID@20224 iut="3" eventSource="Application" eventID="11211"] Hi, from Fluentd!

This incoming event is parsed as:

time:
1362052800 (2013-02-28T12:00:00.003Z)
​
record:
{
  "pri"      : 16,
  "host"     : "192.168.0.1",
  "ident"    : "fluentd",
  "pid"      : "11111",
  "msgid"    : "ID24224",
  "extradata": "[exampleSDID@20224 iut=\"3\" eventSource=\"Application\" eventID=\"11211\"]",
  "message"  : "Hi, from Fluentd!"
}

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.