Variables

Fluent Bit supports the usage of environment variables in any value associated to a key when using a configuration file.
The variables are case sensitive and can be used in the following format:
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${MY_VARIABLE}
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When Fluent Bit starts, the configuration reader will detect any request for ${MY_VARIABLE} and will try to resolve its value.
Example
Create the following configuration file (fluent-bit.conf):
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[SERVICE]
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    Flush        1
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    Daemon       Off
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    Log_Level    info
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​
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[INPUT]
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    Name cpu
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    Tag  cpu.local
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​
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[OUTPUT]
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    Name  ${MY_OUTPUT}
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    Match *
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Open a terminal and set the environment variable:
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$ export MY_OUTPUT=stdout
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The above command set the 'stdout' value to the variable MY_OUTPUT.
Run Fluent Bit with the recently created configuration file:
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$ bin/fluent-bit -c fluent-bit.conf
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Fluent Bit v1.4.0
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* Copyright (C) 2019-2020 The Fluent Bit Authors
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* Copyright (C) 2015-2018 Treasure Data
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* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
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* https://fluentbit.io
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​
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[2020/03/03 12:25:25] [ info] [engine] started
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[0] cpu.local: [1491243925, {"cpu_p"=>1.750000, "user_p"=>1.750000, "system_p"=>0.000000, "cpu0.p_cpu"=>3.000000, "cpu0.p_user"=>2.000000, "cpu0.p_system"=>1.000000, "cpu1.p_cpu"=>0.000000, "cpu1.p_user"=>0.000000, "cpu1.p_system"=>0.000000, "cpu2.p_cpu"=>4.000000, "cpu2.p_user"=>4.000000, "cpu2.p_system"=>0.000000, "cpu3.p_cpu"=>1.000000, "cpu3.p_user"=>1.000000, "cpu3.p_system"=>0.000000}]
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As you can see the service worked properly as the configuration was valid.

Configuration File

Commands

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