observers: introduce pipeline observers

src/pipecat/observers/base_observer.py

@@ -0,0 +1,38 @@
+#
+# Copyright (c) 2024–2025, Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+from abc import ABC, abstractmethod
+
+from pipecat.frames.frames import Frame
+from pipecat.processors.frame_processor import FrameDirection, FrameProcessor
+
+
+class BaseObserver(ABC):
+    """This is the base class for pipeline frame observers. Observers can view
+    all the frames that go through the pipeline without the need to inject
+    processors in the pipeline. This can be useful, for example, to implement
+    frame loggers or debuggers among other things.
+
+    """
+
+    @abstractmethod
+    async def on_push_frame(
+        self, src: FrameProcessor, dst: FrameProcessor, frame: Frame, direction: FrameDirection
+    ):
+        """Abstract method to handle the event when a frame is pushed from one
+        processor to another.
+
+        Args:
+            src (FrameProcessor): The source frame processor that is sending the frame.
+            dst (FrameProcessor): The destination frame processor that will receive the frame.
+            frame (Frame): The frame being transferred between processors.
+            direction (FrameDirection): The direction of the frame transfer.
+
+        This method should be implemented by subclasses to define specific behavior
+        when a frame is pushed.
+
+        """
+        pass