Caution
Grafana Agent has reached End-of-Life (EOL) on November 1, 2025. Agent is no longer receiving vendor support and will no longer receive security or bug fixes. Current users of Agent Static mode, Agent Flow mode, and Agent Operator should proceed with migrating to Grafana Alloy. If you have already migrated to Alloy, no further action is required. Read more about why we recommend migrating to Grafana Alloy.
Function calls
You can use River function calls to build richer expressions.
Functions take zero or more arguments as their input and always return a single value as their output. You can’t construct functions. You can call functions from River’s standard library or export them from a component.
If a function fails, the expression isn’t evaluated, and an error is reported.
Standard library functions
River contains a standard library of functions. Some functions enable interaction with the host system, for example, reading from an environment variable. Some functions allow for more complex expressions, for example, concatenating arrays or decoding JSON strings into objects.
env("HOME")
json_decode(local.file.cfg.content)["namespace"]
