fix: Fix regression multi app Prometheus registry (#220)

* chore: Enter regression with upgrade

* chore: Potential fix

* fix: Check for function being None before adding

This reflects that now the metric functions can either instrumentation
function closure or None.

Also add missing registry param to metrics functions.

* test: Adjust tests for multiple apps

* chore: Update deps in lock

Relevant because things started to fail with fastapi 0.92.0.

* chore: Improve metrics

* docs: Update CHANGELOG.md

CHANGELOG.md

@@ -7,7 +7,29 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0).
 
 ## Unreleased
 
-Nothing.
+### Fixed
+
+- Fixed `NameError` and "Duplicated timeseries..." errors that started to occur
+  with latest versions of Starlette / FastAPI in combination with multiple
+  middlewares. Instrumentation closures are now optional and the instrumentator
+  handles this accordingly. Thanks to [@alexted](https://github.com/alexted) and
+  others for reporting errors. Related to pull request
+  [#153](https://github.com/trallnag/prometheus-fastapi-instrumentator/pull/153)
+  and issue
+  [#214](https://github.com/trallnag/prometheus-fastapi-instrumentator/issues/214).
+  Closed issue
+  [#219](https://github.com/trallnag/prometheus-fastapi-instrumentator/issues/219).
+  Done in pull request
+  [#220](https://github.com/trallnag/prometheus-fastapi-instrumentator/pull/220).
+
+- Added missing `registry` parameter to remaining metrics functions. This
+  enables passing custom registry to other metrics functions than default.
+  Related to pull request
+  [#153](https://github.com/trallnag/prometheus-fastapi-instrumentator/pull/153).
+  Closed issue
+  [#219](https://github.com/trallnag/prometheus-fastapi-instrumentator/issues/219).
+  Done in pull request
+  [#220](https://github.com/trallnag/prometheus-fastapi-instrumentator/pull/220).
 
 ## [5.10.0](https://github.com/trallnag/prometheus-fastapi-instrumentator/compare/v5.9.1...v5.10.0) / 2023-02-26
 

pyproject.toml

@@ -16,6 +16,7 @@ keywords = ["prometheus", "instrumentation", "fastapi", "exporter", "metrics"]
 python = ">= 3.7.0, < 4.0.0"
 fastapi = ">= 0.38.1, < 1.0.0"
 prometheus-client = ">= 0.8.0, < 1.0.0"
+starlette = "0.25.0"
 
 [tool.poetry.group.dev.dependencies]
 httpx = "^0.23.1"

src/prometheus_fastapi_instrumentator/instrumentation.py

@@ -269,7 +269,9 @@ def metrics(request: Request):
 
     def add(
         self,
-        instrumentation_function: Callable[[metrics.Info], Union[None, Awaitable[None]]],
+        instrumentation_function: Optional[
+            Callable[[metrics.Info], Union[None, Awaitable[None]]]
+        ],
     ):
         """Adds function to list of instrumentations.
 
@@ -283,14 +285,18 @@ def add(
             self: Instrumentator. Builder Pattern.
         """
 
-        if asyncio.iscoroutinefunction(instrumentation_function):
-            self.async_instrumentations.append(
-                cast(Callable[[metrics.Info], Awaitable[None]], instrumentation_function)
-            )
-        else:
-            self.instrumentations.append(
-                cast(Callable[[metrics.Info], None], instrumentation_function)
-            )
+        if instrumentation_function:
+            if asyncio.iscoroutinefunction(instrumentation_function):
+                self.async_instrumentations.append(
+                    cast(
+                        Callable[[metrics.Info], Awaitable[None]],
+                        instrumentation_function,
+                    )
+                )
+            else:
+                self.instrumentations.append(
+                    cast(Callable[[metrics.Info], None], instrumentation_function)
+                )
 
         return self