Add add_distribution_value method

Add an `add_distribution_value` custom instrumentation metrics
method, in the same line as the ones that currently exist for Ruby,
Elixir and Node.js.

src/appsignal/__init__.py

@@ -1,5 +1,5 @@
 from .client import Client as Appsignal
-from .metrics import increment_counter, set_gauge
+from .metrics import increment_counter, set_gauge, add_distribution_value
 from .tracing import (
     send_error,
     send_error_with_context,
@@ -36,6 +36,7 @@
     "send_error_with_context",
     "increment_counter",
     "set_gauge",
+    "add_distribution_value"
 ]
 
 

src/appsignal/metrics.py

@@ -2,7 +2,13 @@
 
 from typing import TYPE_CHECKING, Any, Iterable
 
-from opentelemetry.metrics import CallbackOptions, Observation, UpDownCounter, get_meter
+from opentelemetry.metrics import (
+    CallbackOptions,
+    Histogram,
+    Observation,
+    UpDownCounter,
+    get_meter,
+)
 
 
 if TYPE_CHECKING:
@@ -23,6 +29,19 @@ def increment_counter(name: str, value: int | float, tags: Tags = None) -> None:
     counter.add(value, tags)
 
 
+_histograms: dict[str, Histogram] = {}
+
+
+def add_distribution_value(name: str, value: int | float, tags: Tags = None) -> None:
+    if name in _histograms:
+        histogram = _histograms[name]
+    else:
+        histogram = _meter.create_histogram(name)
+        _histograms[name] = histogram
+
+    histogram.record(value, tags)
+
+
 _gauges: dict[str, dict[TagsKey, int | float]] = {}