# metrics

URL: /pounce/api/metrics/
Section: api
Description: Prometheus-compatible metrics collector.

Implements the ``LifecycleCollector`` protocol to track standard HTTP
server metrics from lifecycle events.  No external dependencies — uses
internal counters that can be exported in Prometheus text format.

Metrics:
    - ``http_requests_total`` — counter by method and status
    - ``http_request_duration_seconds`` — histogram of request durations
    - ``http_connections_active`` — gauge of open connections
    - ``http_requests_in_flight`` — gauge of in-progress requests
    - ``http_streams_active`` — gauge of open streaming responses
    - ``http_stream_duration_seconds`` — histogram of completed stream lifetimes

Label stability contract (``http_requests_total``):
    - ``method`` — the uppercase HTTP request method as parsed (e.g.
      ``"GET"``, ``"POST"``).  On error/early-out paths where the method
      was never parsed, the stable sentinel ``"unknown"`` is used.  The
      empty string is never emitted.
    - ``status`` — the numeric HTTP status code rendered as a string.

Thread-safe: all counters use ``threading.Lock`` for free-threading mode.

---

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Module

#
`metrics`

Prometheus-compatible metrics collector.

Implements the`LifecycleCollector`protocol to track standard HTTP
server metrics from lifecycle events. No external dependencies — uses
internal counters that can be exported in Prometheus text format.

Metrics:

- `http_requests_total`— counter by method and status

- `http_request_duration_seconds`— histogram of request durations

- `http_connections_active`— gauge of open connections

- `http_requests_in_flight`— gauge of in-progress requests

- `http_streams_active`— gauge of open streaming responses

- `http_stream_duration_seconds`— histogram of completed stream lifetimes

Label stability contract (`http_requests_total`):

- `method`— the uppercase HTTP request method as parsed (e.g.

```
``"GET"``, ``"POST"``).  On error/early-out paths where the method
```

```
was never parsed, the stable sentinel ``"unknown"`` is used.  The
```

```
empty string is never emitted.
```

- `status`— the numeric HTTP status code rendered as a string.

Thread-safe: all counters use`threading.Lock`for free-threading mode.

1Class

## Classes

`PrometheusCollector`

4

▼

Lifecycle collector that maintains Prometheus-compatible metrics.

Thread-safe — multiple workers c…

Lifecycle collector that maintains Prometheus-compatible metrics.

Thread-safe — multiple workers can call`record()`concurrently.

Example::

(/pounce/api/metrics/#PrometheusCollector)
```
collector = PrometheusCollector()
server = Server(config, app, lifecycle_collector=collector)

# Later: export metrics
text = collector.export()
```

#### Methods

`record`

1

▼

Process a lifecycle event and update metrics.

`def record(self, event: LifecycleEvent) -> None`

##### Parameters

Name
Type
Description

`event`
`—`

`snapshot`

0

`dict[str, object]`

▼

Return a snapshot of current metrics as a dict.

Useful for JSON export or prog…

`def snapshot(self) -> dict[str, object]`

Return a snapshot of current metrics as a dict.

Useful for JSON export or programmatic access.

##### Returns

`dict[str, object]`

`export`

0

`str`

▼

Export metrics in Prometheus text exposition format.

`def export(self) -> str`

##### Returns

`str`

String in Prometheus text format, ready to serve at ``/metrics``.

Internal Methods
1

▼

`__init__`

1

▼

`def __init__(self, *, duration_buckets: tuple[float, ...] = _DEFAULT_BUCKETS) -> None`

##### Parameters

Name
Type
Description

`duration_buckets`
`—`

Default:`_DEFAULT_BUCKETS`