Environment Variables

Beats support use of environment variables in config files to set values that need to be configurable during deployment. Environment variable expansion is introduced using ${VAR}, where VAR is the name of the environment variable.

Note: Only values can be set using environment variables. Environment variables usage in namespace and setting names are not supported.

Variable references are replaced when settings are read by beats. The replacement is case-sensitive and occurs after the YAML file itself has been parsed. References to undefined variables will lead to errors when dereferenced and no default value is specified. To specify a default value, use:

${VAR:default_value}

Where default_value is the value to use if the environment variable is undefined.

If you need to use a literal ${ in your configuration file then you can write $${ to escape the expansion. The $ symbol can be used to escape other characters in the default_value like using $} in order to generate a } character without closing the variable expansion.

After changing the value of an environment variable, the beat needs to be restarted to pick up the new value.

Here are some examples of configurations that use environment variables and what each configuration looks like after replacement: