Fix: Use MultiProcessCollector in PrometheusMiddleware for multi-worker support (#594)

Author: sergey-chek

taskiq/middlewares/prometheus_middleware.py

@@ -38,7 +38,6 @@ def __init__(
 
         logger.debug(f"Setting up multiproc dir to {metrics_path}")
 
-        os.environ["PROMETHEUS_MULTIPROC_DIR"] = str(metrics_path)
         os.environ["PROMETHEUS_MULTIPROC_DIR"] = str(metrics_path)
 
         logger.debug("Initializing metrics")
@@ -85,11 +84,23 @@ def startup(self) -> None:
         This function starts prometheus server.
         It starts it only in case if it's a worker process.
         """
-        from prometheus_client import start_http_server  # noqa: PLC0415
+        from prometheus_client import (  # noqa: PLC0415
+            CollectorRegistry,
+            start_http_server,
+        )
+        from prometheus_client.multiprocess import (  # noqa: PLC0415
+            MultiProcessCollector,
+        )
 
         if self.broker.is_worker_process:
             try:
-                start_http_server(port=self.server_port, addr=self.server_addr)
+                registry = CollectorRegistry()
+                MultiProcessCollector(registry)
+                start_http_server(
+                    port=self.server_port,
+                    addr=self.server_addr,
+                    registry=registry,
+                )
             except OSError as exc:
                 logger.debug("Cannot start prometheus server: %s", exc)