Forward is the protocol used by Fluentd to route messages between peers. The forward output plugin allows to provide interoperability between Fluent Bit and Fluentd. There are not configuration steps required besides to specify where Fluentd is located, it can be in the local host or a in a remote machine.

This plugin offers two different transports and modes:

  • Forward (TCP): It uses a plain TCP connection.
  • Secure Forward (TLS): when TLS is enabled, the plugin switch to Secure Forward mode.


Configuration Parameters

The following parameters are mandatory for eiter Forward for Secure Forward modes:

Key Description Default
Host Target host where Fluent-Bit or Fluentd are listening for Forward messages.
Port TCP Port of the target service. 24224
Time_as_Integer Set timestamps in integer format, it enable compatibility mode for Fluentd v0.12 series. False

Secure Forward Mode Configuration Parameters

When using Secure Forward mode, the TLS mode requires to be enabled. The following additional configuration parameters are available:

Key Description Default
Shared_Key A key string known by the remote Fluentd used for authorization.
Self_Hostname Default value of the auto-generated certificate common name (CN).
tls Enable or disable TLS support Off
tls.verify Force certificate validation On
tls.debug Set TLS debug verbosity level. It accept the following values: 0 (No debug), 1 (Error), 2 (State change), 3 (Informational) and 4 Verbose 1
tls.ca_file Absolute path to CA certificate file
tls.crt_file Absolute path to Certificate file.
tls.key_file Absolute path to private Key file.
tls.key_passwd Optional password for tls.key_file file.

Forward Setup

Before to proceed, make sure that Fluentd is installed in your system, if it's not the case please refer to the following Fluentd Installation document and go ahead with that.

Once Fluentd is installed, create the following configuration file example that will allow us to stream data into it:

  type forward
  port 24224

<match fluent_bit>
  type stdout

That configuration file specifies that will listen for TCP connections on the port 24224 through the forward input type. Then for every message with a fluent_bit TAG, will print the message to the standard output.

In one terminal launch Fluentd specifying the new configuration file created (in_fluent-bit.conf):

$ fluentd -c test.conf
2017-03-23 11:50:43 -0600 [info]: reading config file path="test.conf"
2017-03-23 11:50:43 -0600 [info]: starting fluentd-0.12.33
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-mixin-config-placeholders' version '0.3.1'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-docker' version '0.1.0'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-elasticsearch' version '1.4.0'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-flatten-hash' version '0.2.0'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-flowcounter-simple' version '0.0.4'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-influxdb' version '0.2.8'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-json-in-json' version '0.1.4'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-mongo' version '0.7.10'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-out-http' version '0.1.3'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-parser' version '0.6.0'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-record-reformer' version '0.7.0'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-rewrite-tag-filter' version '1.5.1'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-stdin' version '0.1.1'
2017-03-23 11:50:43 -0600 [info]: gem 'fluent-plugin-td' version '0.10.27'
2017-03-23 11:50:43 -0600 [info]: adding match pattern="fluent_bit" type="stdout"
2017-03-23 11:50:43 -0600 [info]: adding source type="forward"
2017-03-23 11:50:43 -0600 [info]: using configuration file: <ROOT>
    type forward
    port 24224
  <match fluent_bit>
    type stdout
2017-03-23 11:50:43 -0600 [info]: listening fluent socket on

Fluent Bit + Forward Setup

Now that Fluentd is ready to receive messages, we need to specify where the forward output plugin will flush the information using the following format:

bin/fluent-bit -i INPUT -o forward://HOST:PORT

If the TAG parameter is not set, the plugin will set the tag as fluent_bit. Keep in mind that TAG is important for routing rules inside Fluentd.

Using the CPU input plugin as an example we will flush CPU metrics to Fluentd:

$ bin/fluent-bit -i cpu -t fluent_bit -o forward://

Now on the Fluentd side, you will see the CPU metrics gathered in the last seconds:

2017-03-23 11:53:06 -0600 fluent_bit: {"cpu_p":0.0,"user_p":0.0,"system_p":0.0,"cpu0.p_cpu":0.0,"cpu0.p_user":0.0,"cpu0.p_system":0.0,"cpu1.p_cpu":0.0,"cpu1.p_user":0.0,"cpu1.p_system":0.0,"cpu2.p_cpu":0.0,"cpu2.p_user":0.0,"cpu2.p_system":0.0,"cpu3.p_cpu":1.0,"cpu3.p_user":1.0,"cpu3.p_system":0.0}
2017-03-23 11:53:07 -0600 fluent_bit: {"cpu_p":2.25,"user_p":2.0,"system_p":0.25,"cpu0.p_cpu":3.0,"cpu0.p_user":3.0,"cpu0.p_system":0.0,"cpu1.p_cpu":1.0,"cpu1.p_user":1.0,"cpu1.p_system":0.0,"cpu2.p_cpu":1.0,"cpu2.p_user":1.0,"cpu2.p_system":0.0,"cpu3.p_cpu":3.0,"cpu3.p_user":2.0,"cpu3.p_system":1.0}
2017-03-23 11:53:08 -0600 fluent_bit: {"cpu_p":1.75,"user_p":1.0,"system_p":0.75,"cpu0.p_cpu":2.0,"cpu0.p_user":1.0,"cpu0.p_system":1.0,"cpu1.p_cpu":3.0,"cpu1.p_user":1.0,"cpu1.p_system":2.0,"cpu2.p_cpu":3.0,"cpu2.p_user":2.0,"cpu2.p_system":1.0,"cpu3.p_cpu":2.0,"cpu3.p_user":1.0,"cpu3.p_system":1.0}
2017-03-23 11:53:09 -0600 fluent_bit: {"cpu_p":4.75,"user_p":3.5,"system_p":1.25,"cpu0.p_cpu":4.0,"cpu0.p_user":3.0,"cpu0.p_system":1.0,"cpu1.p_cpu":5.0,"cpu1.p_user":4.0,"cpu1.p_system":1.0,"cpu2.p_cpu":3.0,"cpu2.p_user":2.0,"cpu2.p_system":1.0,"cpu3.p_cpu":5.0,"cpu3.p_user":4.0,"cpu3.p_system":1.0}

So we gathered CPU metrics and flush them out to Fluentd properly.

Fluent Bit + Secure Forward Setup

DISCLAIMER: the following example do not consider the generation of certificates for a proper usage of production environments.

Secure Forward aims to provide a secure channel of communication with the remote Fluentd service using TLS. Above there is a minimalist configuration for testing purposes.

Fluent Bit

Paste this content in a file called flb.conf:

    Flush      5
    Daemon     off
    Log_Level  info

    Name       cpu
    Tag        cpu_usage

    Name          forward
    Match         *
    Port          24284
    Shared_Key    secret
    Self_Hostname flb.local
    tls           on
    tls.verify    off


Paste this content in a file called fld.conf:

  @type         secure_forward
  self_hostname myserver.local
  shared_key    secret
  secure no

<match **>
 @type stdout

Test Communication

Start Fluentd:

$ fluentd -c fld.conf

Start Fluent Bit:

$ fluent-bit -c flb.conf

After five seconds, Fluent Bit will write the records to Fluentd. In Fluentd output you will see a message like this:

2017-03-23 13:34:40 -0600 [info]: using configuration file: <ROOT>
    @type secure_forward
    self_hostname myserver.local
    shared_key xxxxxx
    secure no
  <match **>
    @type stdout
2017-03-23 13:34:41 -0600 cpu_usage: {"cpu_p":1.0,"user_p":0.75,"system_p":0.25,"cpu0.p_cpu":1.0,"cpu0.p_user":1.0,"cpu0.p_system":0.0,"cpu1.p_cpu":2.0,"cpu1.p_user":1.0,"cpu1.p_system":1.0,"cpu2.p_cpu":1.0,"cpu2.p_user":1.0,"cpu2.p_system":0.0,"cpu3.p_cpu":2.0,"cpu3.p_user":1.0,"cpu3.p_system":1.0}
2017-03-23 13:34:42 -0600 cpu_usage: {"cpu_p":1.75,"user_p":1.75,"system_p":0.0,"cpu0.p_cpu":3.0,"cpu0.p_user":3.0,"cpu0.p_system":0.0,"cpu1.p_cpu":2.0,"cpu1.p_user":2.0,"cpu1.p_system":0.0,"cpu2.p_cpu":0.0,"cpu2.p_user":0.0,"cpu2.p_system":0.0,"cpu3.p_cpu":1.0,"cpu3.p_user":1.0,"cpu3.p_system":0.0}
2017-03-23 13:34:43 -0600 cpu_usage: {"cpu_p":1.75,"user_p":1.25,"system_p":0.5,"cpu0.p_cpu":3.0,"cpu0.p_user":3.0,"cpu0.p_system":0.0,"cpu1.p_cpu":2.0,"cpu1.p_user":2.0,"cpu1.p_system":0.0,"cpu2.p_cpu":0.0,"cpu2.p_user":0.0,"cpu2.p_system":0.0,"cpu3.p_cpu":1.0,"cpu3.p_user":0.0,"cpu3.p_system":1.0}
2017-03-23 13:34:44 -0600 cpu_usage: {"cpu_p":5.0,"user_p":3.25,"system_p":1.75,"cpu0.p_cpu":4.0,"cpu0.p_user":2.0,"cpu0.p_system":2.0,"cpu1.p_cpu":8.0,"cpu1.p_user":5.0,"cpu1.p_system":3.0,"cpu2.p_cpu":4.0,"cpu2.p_user":3.0,"cpu2.p_system":1.0,"cpu3.p_cpu":4.0,"cpu3.p_user":2.0,"cpu3.p_system":2.0}

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