.. _Telemetry:

Telemetry (Prometheus)
======================

Scout exposes a Prometheus-compatible metrics endpoint that publishes per-stream CMSD-MQA
quality scores. The endpoint is enabled by default for **Standard** and higher licenses.

Configuration
-------------

.. code-block:: yaml

   prometheusEnabled: true   # set to false to disable
   prometheusPort: 9090
   prometheusPath: /metrics

Accessing the metrics
---------------------

Metrics are served at::

   http://<your-server>:9090/metrics

The response uses the Prometheus text exposition format (``text/plain; version=0.0.4``).

Metrics reference
-----------------

.. list-table::
   :widths: 45 55
   :header-rows: 1

   * - Metric
     - Description
   * - ``scout_stream_psnr_db{stream="<id>"}``
     - PSNR of the most recently completed segment for this stream (dB). Omitted if MQA
       is not enabled for the stream or no segment has completed yet.
   * - ``scout_stream_ssim{stream="<id>"}``
     - SSIM of the most recently completed segment (0–1).
   * - ``scout_stream_vmaf{stream="<id>"}``
     - VMAF score of the most recently completed segment (0–100). Omitted unless
       ``cmsdVmafEnabled=true`` for the stream and libvmaf is available.
   * - ``scout_stream_bitrate_kbps{stream="<id>"}``
     - Current encoded bitrate for the stream (kbps), from the stream metadata cache.
   * - ``scout_headers_injected_total{stream="<id>"}``
     - Running count of ``CMSD-Static`` headers injected for this stream since plugin start.
   * - ``scout_alerts_fired_total{stream="<id>"}``
     - Running count of quality alerts fired for this stream since plugin start (Enterprise
       tier only; always zero on Standard and Integration).

Score sources
^^^^^^^^^^^^^

The Prometheus endpoint merges scores from two sources for each stream:

1. **Computed scores** — PSNR / SSIM / VMAF computed on-device from the AMS encoder pipeline
   (requires ``cmsdMqaEnabled=true`` per stream, configured via the MQA REST API).
2. **Injected scores** — pushed by an external tool via the MQA REST ingest endpoint
   (requires ``restApiEnabled: true``; see :ref:`MQA`).

Injected scores take precedence over computed scores for the same stream and metric.