CEL functions and operators
CEL expressions for agent status evaluation support built-in CEL operators and the following function libraries.
Time functions
now()
Returns the current time.
Use with last_update to calculate durations or detect stale data.
// True if more than 10 minutes since last heartbeat
now() - last_update > duration('10m')// True if more than 5 minutes since last heartbeat
now() - last_update > duration('5m')Math functions
Math functions from the CEL math library are available for numeric calculations.
Commonly used functions
| Function | Description | Example |
|---|---|---|
math.greatest(a, b, ...) | Returns the greatest value. | math.greatest(log_errors, log_warnings) |
math.least(a, b, ...) | Returns the least value. | math.least(agent.metrics_gathered, 1000) |
Example
// Warn if either errors or warnings exceed a threshold
math.greatest(log_errors, log_warnings) > 5String functions
String functions from the
CEL strings library
are available for string operations.
These are useful when checking plugin alias or id fields.
Example
// Check if any input plugin has an alias containing "critical"
inputs.cpu.exists(i, has(i.alias) && i.alias.contains("critical"))Encoding functions
Encoding functions from the CEL encoder library are available for encoding and decoding values.
Operators
CEL supports standard operators for building expressions.
Comparison operators
| Operator | Description | Example |
|---|---|---|
== | Equal | metrics == 0 |
!= | Not equal | log_errors != 0 |
< | Less than | agent.metrics_gathered < 100 |
<= | Less than or equal | buffer_fullness <= 0.5 |
> | Greater than | log_errors > 10 |
>= | Greater than or equal | metrics >= 1000 |
Logical operators
| Operator | Description | Example |
|---|---|---|
&& | Logical AND | log_errors > 0 && metrics == 0 |
|| | Logical OR | log_errors > 10 || log_warnings > 50 |
! | Logical NOT | !(metrics > 0) |
Arithmetic operators
| Operator | Description | Example |
|---|---|---|
+ | Addition | log_errors + log_warnings |
- | Subtraction | agent.metrics_gathered - agent.metrics_dropped |
* | Multiplication | log_errors * 2 |
/ | Division | agent.metrics_dropped / agent.metrics_gathered |
% | Modulo | metrics % 100 |
Ternary operator
// Conditional expression
log_errors > 10 ? true : falseList operations
| Function | Description | Example |
|---|---|---|
exists(var, condition) | True if any element matches. | inputs.cpu.exists(i, i.errors > 0) |
all(var, condition) | True if all elements match. | outputs.influxdb_v2.all(o, o.errors == 0) |
size() | Number of elements. | inputs.cpu.size() > 0 |
has() | True if a field or key exists. | has(inputs.cpu) |
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