feat(server): on_startup / on_shutdown hooks on serve(transport='both')#713
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…t='both') Closes #709. Adopters running the unified MCP+A2A binary needed an SDK-owned extension point for lifecycle-bound background work (schedulers, queue consumers, cache warmers). Previously they had to wire a custom ASGI middleware that intercepts the ``lifespan`` scope — fragile because positioning relative to the SDK's own lifespan composition was easy to get wrong. This threads ``on_startup`` / ``on_shutdown`` lists of zero-arg async callables through ``serve()`` -> ``_serve_mcp_and_a2a()`` -> ``_build_mcp_and_a2a_app()`` into ``_composed_lifespan``. Startup hooks fire after both inner framework lifespans have entered (so user code can rely on FastMCP / a2a-sdk being ready); shutdown hooks fire before either tears down. A failing startup hook propagates as ``lifespan.startup.failed`` and aborts boot. Shutdown hooks all run on a best-effort basis — the first failure re-raises, later failures land in ``logger.exception``. Single-transport paths (``streamable-http``, ``sse``, ``a2a``, ``stdio``) raise ``ValueError`` at boot when hooks are passed — those code paths don't construct an SDK-owned parent Starlette and adding the same composition would require mutating FastMCP / a2a-sdk internals. Fail closed instead of silently dropping. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
- Catch ``Exception`` rather than ``BaseException`` in the shutdown hook loop. ``CancelledError`` / ``KeyboardInterrupt`` / ``SystemExit`` are the signals uvicorn uses to drive shutdown — collecting them into ``first_error`` and re-raising as ordinary exceptions breaks the shutdown path. - Don't mask an upstream exception when a shutdown hook also raises. If the body raised (framework teardown, request handler escaping) the operator wants to see the upstream cause, not a secondary cleanup failure — log the shutdown error and let the original propagate. - Suppressed-hook errors log via ``logger.error(..., exc_info=False)`` instead of ``logger.exception``. Adopter closures capture DB DSNs, tokens, scheduler handles — tracebacks attached to log aggregators (Sentry, Datadog) would surface those verbatim. The re-raised ``first_error`` still carries the real traceback to Starlette. - Re-export ``LifespanHook`` from ``adcp.server`` so adopters can type their hook lists without reaching into a private path. - Document ``on_startup`` / ``on_shutdown`` in the ``serve()`` Args block, including the ``transport='both'``-only restriction. - Error message on non-``both`` transport now points at ``examples/scheduler_lifespan.py`` and the follow-up tracking. - ``test_shutdown_hooks_all_attempted_when_one_raises`` now captures the raised exception and asserts on its message; previously the ``try/except: pass`` swallowed exactly the re-raise the test claimed to verify. - Example uses ``ClassVar`` annotation on ``advertised_tools`` and shows where production code stashes hook-captured resources. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Closes #709.
Summary
on_startupandon_shutdownkwargs toserve()(and the mirror fields onServeConfig), threaded through_serve_mcp_and_a2a()→_build_mcp_and_a2a_app()→_composed_lifespan.lifespan.startup.failed; shutdown hooks all run best-effort, first failure re-raises, later failures log vialogger.exception.transport="both"only — single-transport paths raiseValueErrorat boot rather than silently drop hooks. Rationale documented in code and error message.LifespanHook = Callable[[], Awaitable[None]]alias inadcp.server.servewith its own docstring.examples/scheduler_lifespan.pyshows the salesagent pattern (start/stop a scheduler tied to lifecycle) — replaces the 61-LOCSchedulerLifespanMiddlewareadopters had to write before.Test plan
tests/test_serve_lifespan_hooks.pycovers happy-path ordering (startups before yield, shutdowns after), failure propagation (startup raise aborts boot), shutdown best-effort (all hooks run even if one raises), boot-time validation on non-bothtransports, no-op default, andServeConfigplumbing.tests/test_unified_mcp_a2a.pystill passes — the unified app builds the same way when no hooks are supplied.ruff check src/,mypy src/adcp/, pre-commit hooks all clean.🤖 Generated with Claude Code