Forward

Forward is the protocol used by Fluent Bit and Fluentd to route messages between peers. This plugin implements the input service to listen for Forward messages.

Configuration parameters

The plugin supports the following configuration parameters:

Key	Description	Default
buffer_chunk_size	By default the buffer to store the incoming Forward messages, don't allocate the maximum memory allowed, instead it allocate memory when it's required. The rounds of allocations are set by buffer_chunk_size. The value must be according to the Unit Size specification.	1024000
buffer_max_size	Specify the maximum buffer memory size used to receive a Forward message. The value must be according to the Unit Size specification.	6144000
empty_shared_key	Enable secure forward protocol with a zero-length shared key. Use this to enable user authentication without requiring a shared key, or to connect to Fluentd with a zero-length shared key.	false
listen	Listener network interface.	0.0.0.0
port	TCP port to listen for incoming connections.	24224
security.users	Specify the username and password pairs for secure forward authentication. Requires shared_key or empty_shared_key to be set.
self_hostname	Hostname for secure forward authentication.	none
shared_key	Shared key for secure forward authentication.	none
tag	Override the tag of the forwarded events with the defined value.	none
tag_prefix	Prefix incoming tag with the defined value.	none
threaded	Indicates whether to run this input in its own thread.	false
unix_path	Specify the path to Unix socket to receive a Forward message. If set, listen and port are ignored.	none
unix_perm	Set the permission of the Unix socket file. If unix_path isn't set, this parameter is ignored.	none

TLS / SSL

The Forward input plugin supports TLS/SSL. For more details about the properties available and general configuration, refer to Transport Security.

Get started

To receive Forward messages, you can run the plugin from the command line or through the configuration file as shown in the following examples.

Command line

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

fluent-bit -i forward -o stdout

By default, the service listens on all interfaces (0.0.0.0) through TCP port 24224. You can change this by passing parameters to the command:

fluent-bit -i forward -p listen="192.168.3.2" -p port=9090 -o stdout

In the example, the Forward messages arrive only through network interface 192.168.3.2 address and TCP Port 9090.

Configuration file

In your main configuration file append the following:

fluent-bit.yaml

pipeline:
  inputs:
    - name: forward
      listen: 0.0.0.0
      port: 24224
      buffer_chunk_size: 1M
      buffer_max_size: 6M

  outputs:
    - name: stdout
      match: '*'

fluent-bit.conf

Fluent Bit and secure forward setup

In Fluent Bit v3 or later, in_forward can handle secure forward protocol.

When using security.users for user-password authentication, you must also configure either shared_key or set empty_shared_key to true. The Forward input plugin will reject a configuration that has security.users set without one of these options.

For shared key authentication, specify shared_key in both forward output and forward input. For user-password authentication, specify security.users with at least one user-password pair along with a shared key. To use user authentication without requiring clients to know a shared key, set empty_shared_key to true.

The self_hostname value can't be the same between Fluent Bit servers and clients.

fluent-bit-secure-forward.yaml

pipeline:
  inputs:
    - name: forward
      listen: 0.0.0.0
      port: 24224
      buffer_chunk_size: 1M
      buffer_max_size: 6M
      security.users: fluentbit changeme
      shared_key: secret
      self_hostname: flb.server.local

  outputs:
    - name: stdout
      match: '*'

fluent-bit-secure-forward.conf

User authentication with empty_shared_key

To use username and password authentication without requiring clients to know a shared key, set empty_shared_key to true:

fluent-bit-user-auth.yaml

pipeline:
  inputs:
    - name: forward
      listen: 0.0.0.0
      port: 24224
      buffer_chunk_size: 1M
      buffer_max_size: 6M
      security.users: fluentbit changeme
      empty_shared_key: true
      self_hostname: flb.server.local

  outputs:
    - name: stdout
      match: '*'

fluent-bit-user-auth.conf

Testing

After Fluent Bit is running, you can send some messages using the fluent-cat tool, provided by Fluentd:

echo '{"key 1": 123456789, "key 2": "abcdefg"}' | fluent-cat my_tag

When you run the plugin with the following command:

fluent-bit -i forward -o stdout

In Fluent Bit you should see the following output:

...
[0] my_tag: [1475898594, {"key 1"=>123456789, "key 2"=>"abcdefg"}]
...