facetoe / promval

PromQL validator written in Python

promval

promval is a PromQL validator written in Python.

It can be used to validate PromQL expressions are written as expected.

Examples

Validate that we are grouping by certain metrics in by clauses

Here we validate that we are grouping by "job" and "host":

promql = """
    sum by (job) (
      rate(http_requests_total[5m])
    )
"""
validator = ByGroupValidator(expected={"job", "host"})
validator.validate(promql)

This fails with:

promval.error.ValidationError: 'line: 2:12 'by (job)' - missing required metric names {'host'}

Validate that labels containing a certain value are specified in by clause

Here we ensure that if we have a label with a particular value, it is specified in the by clause:

expr = """
max by (require, not_required)(foo_metric{required=~'important', something='else'})
"""
validator = ByLabelValueValidator(label_value="important")
validator.validate(expr)

This fails with:

'line: 2:4 'by (require, not_required)' - expected label name 'required' in by clause

Extending promval

It is easy to write custom validators, simply subclass promval.validators.Validator and implement a validating visitor. See examples in promval.validators for more information.