Syslog

The Syslog input plugin lets you collect syslog messages through a Unix socket server (UDP or TCP) or over the network using TCP or UDP.

Configuration parameters

The plugin supports the following configuration parameters:

Key	Description	Default
Mode	Defines transport protocol mode: UDP over Unix socket (unix_udp), TCP over Unix socket (unix_tcp), tcp, or udp	unix_udp
Listen	If Mode is set to tcp or udp, specify the network interface to bind.	0.0.0.0
Port	If Mode is set to tcp or udp, specify the TCP port to listen for incoming connections.	5140
Path	If Mode is set to unix_tcp or unix_udp, set the absolute path to the Unix socket file.	none
Unix_Perm	If Mode is set to unix_tcp or unix_udp, set the permission of the Unix socket file.	0644
Parser	Specify an alternative parser for the message. If Mode is set to tcp or udp then the default parser is syslog-rfc5424. Otherwise, syslog-rfc3164-local is used. If your syslogmessages have fractional seconds set this parser value tosyslog-rfc5424` instead.	none
Buffer_Chunk_Size	By default, the buffer to store the incoming syslog messages. Doesn't allocate the maximum memory allowed, instead it allocates memory when required. The rounds of allocations are set by Buffer_Chunk_Size. There are considerations when using udp or unix_udp mode.	32KB (set in code)
Buffer_Max_Size	Specify the maximum buffer size to receive a syslog message. If not set, the default size is the value of Buffer_Chunk_Size.	none
Receive_Buffer_Size	Specify the maximum socket receive buffer size. If not set, the default value is OS-dependant, but generally too low to accept thousands of syslog messages per second without loss on udp or unix_udp sockets. For Linux, the value is capped by sysctl net.core.rmem_max.	none
Source_Address_Key	Specify the key where the source address will be injected.	none
Threaded	Indicates whether to run this input in its own thread.	false

Considerations

• When using the Syslog input plugin, Fluent Bit requires access to the parsers configuration file. The path to this file can be specified with the option -R or through the parsers_file key in the service section.

• When using udp or unix_udp, the buffer size to receive messages is configurable only through the buffer_chunk_size option, which defaults to 32kb.

Get started

To receive syslog messages, you can run the plugin from the command line or through the configuration file:

Command line

From the command line you can let Fluent Bit listen for Forward messages with the following options:

# For YAML configuration
./fluent-bit -R /path/to/parsers.yaml -i syslog -p path=/tmp/in_syslog -o stdout

# For classic configuration.
./fluent-bit -R /path/to/parsers.conf -i syslog -p path=/tmp/in_syslog -o stdout

By default, the service will create and listen for Syslog messages on the Unix socket /tmp/in_syslog.

Configuration file

In your main configuration file append the following sections:

fluent-bit.yaml

service:
  flush: 1
  log_level: info
  parsers_file: parsers.yaml

pipeline:
  inputs:
    - name: syslog
      path: /tmp/in_syslog
      buffer_chunk_size: 32000
      buffer_max_size: 64000
      receive_buffer_size: 512000

  outputs:
    - name: stdout
      match: '*'

fluent-bit.conf

Testing

When Fluent Bit is running, you can send some messages using the logger tool:

logger -u /tmp/in_syslog my_ident my_message

Then run Fluent Bit using the following command:

# For YAML configuration.
./fluent-bit -R ../conf/parsers.yaml -i syslog -p path=/tmp/in_syslog -o stdout

# For classic configuration.
./fluent-bit -R ../conf/parsers.conf -i syslog -p path=/tmp/in_syslog -o stdout

You should see the following output:

...
[0] syslog.0: [1489047822, {"pri"=>"13", "host"=>"edsiper:", "ident"=>"my_ident", "pid"=>"", "message"=>"my_message"}]
...

Examples

The following configuration examples cover different use cases to integrate Fluent Bit and make it listen for Syslog messages from your systems.

rsyslog to Fluent Bit: Network mode over TCP

Fluent Bit configuration [#config-tcp]

Put the following content in your configuration file:

fluent-bit.yaml

service:
  flush: 1
  parsers_file: parsers.yaml

pipeline:
  inputs:
    - name: syslog
      parser: syslog-rfc3164
      listen: 0.0.0.0
      port: 5140
      mode: tcp

  outputs:
    - name: stdout
      match: '*'

fluent-bit.conf

Then, start Fluent Bit.

rsyslog configuration [#rsyslog-tcp]

Add a new file to your rsyslog configuration rules called 60-fluent-bit.conf inside the directory /etc/rsyslog.d/ and add the following content:

action(type="omfwd" Target="127.0.0.1" Port="5140" Protocol="tcp")

Then, restart your rsyslog daemon:

sudo service rsyslog restart

rsyslog to Fluent Bit: Unix socket mode over UDP

Fluent Bit configuration [#config-udp]

Put the following content in your Fluent Bit configuration:

fluent-bit.yaml

service:
  flush: 1
  parsers_file: parsers.yaml

pipeline:
  inputs:
    - name: syslog
      parser: syslog-rfc3164
      path: /tmp/fluent-bit.sock
      mode: unix_udp
      unix_perm: 0644

  outputs:
    - name: stdout
      match: '*'

fluent-bit.conf

Then, start Fluent Bit.

rsyslog configuration [#rsyslog-udp]

Add a new file to your rsyslog configuration rules called 60-fluent-bit.conf inside the directory /etc/rsyslog.d/ containing the following content:

$ModLoad omuxsock
$OMUxSockSocket /tmp/fluent-bit.sock
*.* :omuxsock:

Make sure that the socket file is readable by rsyslog by modifying Unix_Perm key.