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csmarchbanks merged 2 commits into from
May 4, 2026
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docs: follow-up fixes for collect() generator examples (#1169) #1172

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docs: clarify collect() generator usage and API Reference snippet con…
k1chik May 4, 2026
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docs: split InfoMetricFamily example into two separate blocks
k1chik May 4, 2026
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17 changes: 15 additions & 2 deletions docs/content/collector/custom.md
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Expand Up @@ -47,6 +47,11 @@ can also implement `describe`.
Returns an iterable of metric family objects (`GaugeMetricFamily`,
`CounterMetricFamily`, etc.). Called every time the registry is scraped.

Using `yield` is the idiomatic way to implement `collect()` — it turns the method
into a generator, which the registry iterates lazily without building an intermediate
list first. Each scrape calls `collect()` fresh, so no state carries over between
scrapes.

### `describe()`

Returns an iterable of metric family objects used only to determine the metric
Expand Down Expand Up @@ -76,6 +81,10 @@ g.add_metric(['eu-west-1'], 5)

## API Reference

The examples below show usage inside a `collect()` method body. Each snippet is
meant to be placed within a custom collector class as shown in the example at the
top of this page.

### GaugeMetricFamily

```python
Expand Down Expand Up @@ -232,11 +241,15 @@ InfoMetricFamily(name, documentation, value=None, labels=None)
| `value` | `Dict[str, str]` | Key-value label pairs that form the info payload. |
| `timestamp` | `float` or `Timestamp` | Optional Unix timestamp. |

Single unlabelled info metric:

```python
# single unlabelled info metric
yield InfoMetricFamily('build', 'Build metadata', value={'version': '1.2.3', 'commit': 'abc123'})
```

Labelled — one info metric per service:

# labelled: one info metric per service
```python
i = InfoMetricFamily('service_build', 'Per-service build info', labels=['service'])
i.add_metric(['auth'], {'version': '2.0.1', 'commit': 'def456'})
i.add_metric(['api'], {'version': '1.9.0', 'commit': 'ghi789'})
Expand Down