prometheus-absent-data-alert-rule-generator is a tool to generate alerts for missing data in time-series that we use in our other alerts and recordings.

This is a normal Rust project and can be managed using Cargo. For the most up-to-date usage, run:

cargo run -- --help

For normal usage you just need to pass in the directory containing your Prometheus rules files in as the first (and only) positional argument, e.g.

cargo run -- ./rules

This will generate an absent.rules.yml file in the rules directory containing all your absent alerts.

The high-level overview of how the alerts are generated is:

1. Parse all the *.rules.yml files in the given directory and pull out the expressions from the expr field
2. In each expression, pull out all the time-series selector used (e.g. stack:public_http_errors_5xx_non_L3:rate1m_sum or aws_firehose_delivery_to_redshift_success_minimum[1h])
3. Group the selectors into those that are all the same
4. For each group "merge" the selectors into a rule based on some rules

• "for" field is chosen based on the minimum of all the selectors' origin rules with a floor of 1h

4. For each selector generate a rule of the form:

- expr: "absent(<selector>)"
  alert: absent_<selector name>
  annotations:
    description: "No data for '<selector>'. This alert rule was generated by   prometheus-absent-data-alert-rule-generator."
    summary: "No data for '<selector>' data"
  for: <chosen for>
  labels:
    severity: business_hours_page

NOTE: For range-vector selectors (e.g. aws_firehose_delivery_to_redshift_success_minimum[1h]) the absent_over_time function is used because it's the range-vector equivalent of absent.

5. Dump all the rules to absent.rules.yml in the input directory or to the specified output file.

You can ignore selectors by listing their names, one line per name, in a text file. By default the text file is ignore_metrics.txt in this directory, or you can use the --ignore-file flag to pass in your own path.

Testing is done using the normal cargo test. The only external dependency that you need to have installed is promtool which you can get from the prometheus repository.