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mcp: add StreamableHTTPOptions.EventStore #593

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Merged
merged 1 commit into from
Oct 20, 2025
Merged

mcp: add StreamableHTTPOptions.EventStore #593

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11 changes: 6 additions & 5 deletions mcp/streamable.go
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Original file line number Diff line number Diff line change
Expand Up @@ -72,8 +72,11 @@ type StreamableHTTPOptions struct {
// If nil, do not log.
Logger *slog.Logger

// TODO(rfindley): file a proposal to export this option, or something equivalent.
configureTransport func(req *http.Request, transport *StreamableServerTransport)
// EventStore enables stream resumption.
//
// If set, EventStore will be used to persist stream events and replay them
// upon stream resumption.
EventStore EventStore
}

// NewStreamableHTTPHandler returns a new [StreamableHTTPHandler].
Expand Down Expand Up @@ -237,12 +240,10 @@ func (h *StreamableHTTPHandler) ServeHTTP(w http.ResponseWriter, req *http.Reque
transport = &StreamableServerTransport{
SessionID: sessionID,
Stateless: h.opts.Stateless,
EventStore: h.opts.EventStore,
jsonResponse: h.opts.JSONResponse,
logger: h.opts.Logger,
}
if h.opts.configureTransport != nil {
h.opts.configureTransport(req, transport)
}

// To support stateless mode, we initialize the session with a default
// state, so that it doesn't reject subsequent requests.
Expand Down
25 changes: 9 additions & 16 deletions mcp/streamable_test.go
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Expand Up @@ -95,14 +95,13 @@ func TestStreamableTransports(t *testing.T) {

// Start an httptest.Server with the StreamableHTTPHandler, wrapped in a
// cookie-checking middleware.
handler := NewStreamableHTTPHandler(func(req *http.Request) *Server { return server }, &StreamableHTTPOptions{
opts := &StreamableHTTPOptions{
JSONResponse: test.useJSON,
configureTransport: func(_ *http.Request, transport *StreamableServerTransport) {
if test.replay {
transport.EventStore = NewMemoryEventStore(nil)
}
},
})
}
if test.replay {
opts.EventStore = NewMemoryEventStore(nil)
}
handler := NewStreamableHTTPHandler(func(req *http.Request) *Server { return server }, opts)

var (
headerMu sync.Mutex
Expand Down Expand Up @@ -386,9 +385,7 @@ func testClientReplay(t *testing.T, test clientReplayTest) {
})

realServer := httptest.NewServer(mustNotPanic(t, NewStreamableHTTPHandler(func(*http.Request) *Server { return server }, &StreamableHTTPOptions{
configureTransport: func(_ *http.Request, t *StreamableServerTransport) {
t.EventStore = NewMemoryEventStore(nil) // necessary for replay
},
EventStore: NewMemoryEventStore(nil), // necessary for replay
})))
t.Cleanup(func() {
t.Log("Closing real HTTP server")
Expand Down Expand Up @@ -567,9 +564,7 @@ func TestServerInitiatedSSE(t *testing.T) {
// However, it shouldn't be necessary to use replay here, as we should be
// guaranteed that the standalone SSE stream is started by the time the
// client is connected.
configureTransport: func(_ *http.Request, transport *StreamableServerTransport) {
transport.EventStore = NewMemoryEventStore(nil)
},
EventStore: NewMemoryEventStore(nil),
}
httpServer := httptest.NewServer(mustNotPanic(t, NewStreamableHTTPHandler(func(*http.Request) *Server { return server }, opts)))
defer httpServer.Close()
Expand Down Expand Up @@ -942,9 +937,7 @@ func TestStreamableServerTransport(t *testing.T) {

opts := &StreamableHTTPOptions{}
if test.replay {
opts.configureTransport = func(_ *http.Request, t *StreamableServerTransport) {
t.EventStore = NewMemoryEventStore(nil)
}
opts.EventStore = NewMemoryEventStore(nil)
}
// Start the streamable handler.
handler := NewStreamableHTTPHandler(func(req *http.Request) *Server { return server }, opts)
Expand Down