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# Ballista Scheduler Metrics

## Prometheus

> This is an optional scheduler feature, enabled with the `prometheus-metrics` Cargo feature.

When built with it, the scheduler collects and exposes a standard set of Prometheus metrics:

- _job_exec_time_seconds_ - Histogram of successful job execution time in seconds
- _planning_time_ms_ - Histogram of job planning time in milliseconds
- _job_failed_total_ - Counter of failed jobs
- _job_cancelled_total_ - Counter of cancelled jobs
- _job_completed_total_ - Counter of completed jobs
- _job_submitted_total_ - Counter of submitted jobs
- _pending_task_queue_size_ - Number of pending tasks

**NOTE** Currently the histogram buckets for the above metrics are set to reasonable defaults. If the defaults are not
appropriate for a given use case, the only workaround is to implement a custom `SchedulerMetricsCollector`. In the future
the buckets should be made configurable.

The metrics are then exported through the scheduler REST API at `GET /api/metrics`. It should be sufficient to ingest metrics
into an existing metrics system by point your chosen prometheus exporter at that endpoint.