CEL variables

CEL expressions for agent status evaluation have access to variables that represent data collected by Telegraf since the last successful heartbeat message (unless noted otherwise).

Top-level variables

Agent statistics

The agent variable is a map containing aggregate statistics for the entire Telegraf instance. These fields correspond to the internal_agent metric from the Telegraf internal input plugin.

Example

agent.gather_errors > 0

Input plugin statistics (inputs)

The inputs variable is a map where each key is a plugin type (for example, cpu for inputs.cpu) and the value is a list of plugin instances. Each entry in the list represents one configured instance of that plugin type.

These fields correspond to the internal_gather metric from the Telegraf internal input plugin.

Access patterns

Access a specific plugin type and iterate over its instances:

// Check if any cpu input instance has errors
inputs.cpu.exists(i, i.errors > 0)

// Access the first instance of the cpu input
inputs.cpu[0].metrics_gathered

Use has() to safely check if a plugin type exists before accessing it:

// Safe access — returns false if no cpu input is configured
has(inputs.cpu) && inputs.cpu.exists(i, i.errors > 0)

Output plugin statistics (outputs)

The outputs variable is a map with the same structure as inputs. Each key is a plugin type (for example, influxdb_v3 for outputs.influxdb_v3) and the value is a list of plugin instances.

These fields correspond to the internal_write metric from the Telegraf internal input plugin.

Access patterns

// Access the first instance of the InfluxDB v3 output plugin
outputs.influxdb_v3[0].metrics_written

// Check if any InfluxDB v3 output has write errors
outputs.influxdb_v3.exists(o, o.errors > 0)

// Check buffer fullness across all instances of an output
outputs.influxdb_v3.exists(o, o.buffer_fullness > 0.8)

Use has() to safely check if a plugin type exists before accessing it:

// Safe access — returns false if no cpu input is configured
has(outputs.influxdb_v3) && outputs.influxdb_v3.exists(o, o.errors > 0)

Accumulation behavior

Unless noted otherwise, all variable values are accumulated since the last successful heartbeat message. Use the last_update variable with now() to calculate rates — for example:

// True if the error rate exceeds 1 error per minute
log_errors > 0 && duration.getMinutes(now() - last_update) > 0
  && log_errors / duration.getMinutes(now() - last_update) > 1