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Add SSE polling support (SEP-1699) (#1654)

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Felix Weinberger 2025-12-02 11:44:49 +00:00 • committed by GitHub
commit 281fd4765e
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1 changed files with 1461 additions and 45 deletions
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35
src/mcp/server/fastmcp/server.py
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@ -153,6 +153,7 @@ class FastMCP(Generic[LifespanResultT]):
auth_server_provider: (OAuthAuthorizationServerProvider[Any, Any, Any] | None) = None,
token_verifier: TokenVerifier | None = None,
event_store: EventStore | None = None,
retry_interval: int | None = None,
*,
tools: list[Tool] | None = None,
debug: bool = False,
@ -221,6 +222,7 @@ class FastMCP(Generic[LifespanResultT]):
if auth_server_provider and not token_verifier: # pragma: no cover
self._token_verifier = ProviderTokenVerifier(auth_server_provider)
self._event_store = event_store
self._retry_interval = retry_interval
self._custom_starlette_routes: list[Route] = []
self.dependencies = self.settings.dependencies
self._session_manager: StreamableHTTPSessionManager | None = None
@ -940,6 +942,7 @@ class FastMCP(Generic[LifespanResultT]):
self._session_manager = StreamableHTTPSessionManager(
app=self._mcp_server,
event_store=self._event_store,
retry_interval=self._retry_interval,
json_response=self.settings.json_response,
stateless=self.settings.stateless_http, # Use the stateless setting
security_settings=self.settings.transport_security,
@ -1282,6 +1285,38 @@ class Context(BaseModel, Generic[ServerSessionT, LifespanContextT, RequestT]):
"""Access to the underlying session for advanced usage."""
return self.request_context.session
async def close_sse_stream(self) -> None:
"""Close the SSE stream to trigger client reconnection.
This method closes the HTTP connection for the current request, triggering
client reconnection. Events continue to be stored in the event store and will
be replayed when the client reconnects with Last-Event-ID.
Use this to implement polling behavior during long-running operations -
client will reconnect after the retry interval specified in the priming event.
Note:
This is a no-op if not using StreamableHTTP transport with event_store.
The callback is only available when event_store is configured.
"""
if self._request_context and self._request_context.close_sse_stream: # pragma: no cover
await self._request_context.close_sse_stream()
async def close_standalone_sse_stream(self) -> None:
"""Close the standalone GET SSE stream to trigger client reconnection.
This method closes the HTTP connection for the standalone GET stream used
for unsolicited server-to-client notifications. The client SHOULD reconnect
with Last-Event-ID to resume receiving notifications.
Note:
This is a no-op if not using StreamableHTTP transport with event_store.
Currently, client reconnection for standalone GET streams is NOT
implemented - this is a known gap.
"""
if self._request_context and self._request_context.close_standalone_sse_stream: # pragma: no cover
await self._request_context.close_standalone_sse_stream()
# Convenience methods for common log levels
async def debug(self, message: str, **extra: Any) -> None:
"""Send a debug log message."""