Python: Add A2A server sample (#4528)

* Python: Add A2A server sample and fix client streaming bug Add a pure Python A2A server sample so testing the A2A client no longer requires running the .NET server. The server uses the a2a-sdk's A2AStarletteApplication with uvicorn and supports three agent types (invoice, policy, logistics) backed by AzureOpenAIResponsesClient. New files: - a2a_server.py: Main server entry point with CLI args - agent_executor.py: Bridges a2a-sdk AgentExecutor to Agent Framework - agent_definitions.py: Agent and AgentCard factory definitions - invoice_data.py: Mock invoice data and query tool functions - a2a_server.http: REST Client requests for testing Also fixes a streaming bug in agent_with_a2a.py where async with was used on ResponseStream which does not support the async context manager protocol. Changed to async for to match all other samples. Closes #4045 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * Address PR review: handle CancelledError and fix end_date filtering - Re-raise asyncio.CancelledError before the broad exception handler so cooperative cancellation is not swallowed. - Make end_date filter inclusive of the full day by comparing with < end + timedelta(days=1) instead of <= midnight. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-06-16 21:04:09 +08:00 · 2026-03-09 17:00:49 -07:00
parent e2f0bc814e
commit ded32f3ff8
7 changed files with 709 additions and 25 deletions
@@ -0,0 +1,123 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+"""AgentExecutor bridge between the a2a-sdk server and Agent Framework agents.
+
+Implements the a2a-sdk ``AgentExecutor`` interface so that incoming A2A
+requests are forwarded to an Agent Framework agent and the response is
+published back through the a2a-sdk event queue.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import uuid
+from typing import TYPE_CHECKING
+
+from a2a.server.agent_execution.agent_executor import AgentExecutor
+from a2a.types import (
+    Message,
+    Part,
+    Role,
+    TaskState,
+    TaskStatus,
+    TaskStatusUpdateEvent,
+    TextPart,
+)
+
+if TYPE_CHECKING:
+    from a2a.server.agent_execution.context import RequestContext
+    from a2a.server.events.event_queue import EventQueue
+    from agent_framework import Agent
+
+
+class AgentFrameworkExecutor(AgentExecutor):
+    """Bridges A2A protocol requests to an Agent Framework agent.
+
+    For each incoming ``execute`` call the executor:
+    1. Extracts the user's text from the A2A ``RequestContext``.
+    2. Runs the Agent Framework agent (non-streaming).
+    3. Publishes the result as an A2A ``Message`` to the ``EventQueue``.
+    """
+
+    def __init__(self, agent: Agent) -> None:
+        self.agent = agent
+
+    async def execute(self, context: RequestContext, event_queue: EventQueue) -> None:
+        """Run the agent and publish the response."""
+        user_text = context.get_user_input()
+        if not user_text:
+            user_text = "Hello"
+
+        task_id = context.task_id or str(uuid.uuid4())
+        context_id = context.context_id or str(uuid.uuid4())
+
+        # Signal that the agent is working
+        await event_queue.enqueue_event(
+            TaskStatusUpdateEvent(
+                task_id=task_id,
+                context_id=context_id,
+                status=TaskStatus(state=TaskState.working),
+                final=False,
+            )
+        )
+
+        try:
+            response = await self.agent.run(user_text)
+
+            # Build response text from agent messages
+            response_parts: list[Part] = []
+            for msg in response.messages:
+                if msg.text:
+                    response_parts.append(TextPart(text=msg.text))
+
+            if not response_parts:
+                response_parts.append(TextPart(text=str(response)))
+
+            # Publish the agent's response as a completed message
+            await event_queue.enqueue_event(
+                TaskStatusUpdateEvent(
+                    task_id=task_id,
+                    context_id=context_id,
+                    status=TaskStatus(
+                        state=TaskState.completed,
+                        message=Message(
+                            message_id=str(uuid.uuid4()),
+                            role=Role.agent,
+                            parts=response_parts,
+                        ),
+                    ),
+                    final=True,
+                )
+            )
+        except asyncio.CancelledError:
+            raise
+        except Exception as e:
+            await event_queue.enqueue_event(
+                TaskStatusUpdateEvent(
+                    task_id=task_id,
+                    context_id=context_id,
+                    status=TaskStatus(
+                        state=TaskState.failed,
+                        message=Message(
+                            message_id=str(uuid.uuid4()),
+                            role=Role.agent,
+                            parts=[TextPart(text=f"Agent error: {e}")],
+                        ),
+                    ),
+                    final=True,
+                )
+            )
+
+    async def cancel(self, context: RequestContext, event_queue: EventQueue) -> None:
+        """Handle cancellation by publishing a canceled status."""
+        task_id = context.task_id or str(uuid.uuid4())
+        context_id = context.context_id or str(uuid.uuid4())
+
+        await event_queue.enqueue_event(
+            TaskStatusUpdateEvent(
+                task_id=task_id,
+                context_id=context_id,
+                status=TaskStatus(state=TaskState.canceled),
+                final=True,
+            )
+        )