Fix Redis transport refactoring with control message system
- Fix timing issue by awaiting startServerListeningToRedis - Add request-id based response channel routing - Implement control message system for proper server shutdown - Add comprehensive integration tests - Ensure response subscription is established before message sending - Fix MCP server cleanup integration to prevent async hanging 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com>
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Jerome
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1 changed files with 552 additions and 62 deletions
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@ -8,16 +8,25 @@ import { Server } from "@modelcontextprotocol/sdk/server/index.js";
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let redisTransportCounter = 0;
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const notificationStreamId = "__GET_stream";
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interface RedisMessage {
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message: JSONRPCMessage;
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extra?: MessageExtraInfo;
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options?: TransportSendOptions;
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}
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// Message types for Redis transport
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type RedisMessage =
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type: 'mcp';
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message: JSONRPCMessage;
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extra?: MessageExtraInfo;
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options?: TransportSendOptions;
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}
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type: 'control';
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action: 'SHUTDOWN' | 'PING' | 'STATUS';
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timestamp?: number;
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};
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function sendToMcpServer(sessionId: string, message: JSONRPCMessage, extra?: { authInfo?: AuthInfo; }, options?: TransportSendOptions): Promise<void> {
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const toServerChannel = getToServerChannel(sessionId);
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const redisMessage: RedisMessage = { message, extra, options };
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console.log(`[sendToServerChannel] Publishing to ${toServerChannel}:`, JSON.stringify(redisMessage).substring(0, 100));
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const redisMessage: RedisMessage = { type: 'mcp', message, extra, options };
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console.log(`[sendToMcpServer] Publishing to Redis channel: ${toServerChannel}`);
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console.log(`[sendToMcpServer] Message:`, JSON.stringify(message));
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return redisClient.publish(toServerChannel, JSON.stringify(redisMessage));
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}
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@ -29,48 +38,79 @@ function getToClientChannel(sessionId: string, relatedRequestId: string): string
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return `mcp:shttp:toclient:${sessionId}:${relatedRequestId}`;
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}
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function getControlChannel(sessionId: string): string {
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return `mcp:control:${sessionId}`;
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}
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function sendControlMessage(sessionId: string, action: 'SHUTDOWN' | 'PING' | 'STATUS'): Promise<void> {
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const controlChannel = getControlChannel(sessionId);
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const redisMessage: RedisMessage = {
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type: 'control',
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action,
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timestamp: Date.now()
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};
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return redisClient.publish(controlChannel, JSON.stringify(redisMessage));
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}
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export async function shutdownSession(sessionId: string): Promise<void> {
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return sendControlMessage(sessionId, 'SHUTDOWN');
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}
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export async function isLive(sessionId: string): Promise<boolean> {
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// Check if the session is live by checking if the key exists in Redis
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const numSubs = await redisClient.numsub(getToServerChannel(sessionId));
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console.log(`[isLive] Session ${sessionId}: Redis subscribers on ${getToServerChannel(sessionId)} = ${numSubs}`);
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return numSubs > 0;
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}
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export function redisRelayToMcpServer(sessionId: string, transport: Transport): () => Promise<void> {
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console.log(`[redisRelayToMcpServer] Setting up relay for session: ${sessionId}`);
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let redisCleanup: (() => Promise<void>) | undefined = undefined;
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const cleanup = async () => {
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console.log(`[redisRelayToMcpServer] Cleaning up relay for session: ${sessionId}`);
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// TODO: solve race conditions where we call cleanup while the subscription is being created / before it is created
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if (redisCleanup) {
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await redisCleanup();
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}
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}
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new Promise<JSONRPCMessage>((resolve) => {
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const messagePromise = new Promise<JSONRPCMessage>((resolve) => {
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console.log(`[redisRelayToMcpServer] Setting up transport.onmessage handler for session: ${sessionId}`);
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transport.onmessage = async (message, extra) => {
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console.log(`[redisRelayToMcpServer] Received message from transport for session ${sessionId}:`, JSON.stringify(message));
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// First, set up response subscription if needed
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if ("id" in message) {
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console.log(`[redisRelayToMcpServer] Setting up response subscription for message ID: ${message.id}`);
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const toClientChannel = getToClientChannel(sessionId, message.id.toString());
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console.log(`[redisRelayToMcpServer] Subscribing to response channel: ${toClientChannel}`);
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redisCleanup = await redisClient.createSubscription(toClientChannel, async (redisMessageJson) => {
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console.log(`[redisRelayToMcpServer] Received response from Redis for session ${sessionId}:`, redisMessageJson.substring(0, 200));
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const redisMessage = JSON.parse(redisMessageJson) as RedisMessage;
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if (redisMessage.type === 'mcp') {
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console.log(`[redisRelayToMcpServer] Sending response back to transport for session ${sessionId}`);
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await transport.send(redisMessage.message, redisMessage.options);
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console.log(`[redisRelayToMcpServer] Response sent to transport for session ${sessionId}`);
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}
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}, (error) => {
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console.error(`[redisRelayToMcpServer] Error in response subscription for session ${sessionId}:`, error);
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transport.onerror?.(error);
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});
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console.log(`[redisRelayToMcpServer] Response subscription established for session ${sessionId}`);
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} else {
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console.log(`[redisRelayToMcpServer] Message is notification (no ID) for session ${sessionId}, skipping response subscription`);
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}
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// Now send the message to the MCP server
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await sendToMcpServer(sessionId, message, extra);
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console.log(`[redisRelayToMcpServer] Sent message to MCP server for session ${sessionId}`);
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resolve(message);
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}
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}).then(async (message) => {
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// check for request id in the message
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if (!("id" in message)) {
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// if no id, it's a notification, so we return
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return cleanup;
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}
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// otherwise we subscribe to the response channel
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const toClientChannel = getToClientChannel(sessionId, message.id.toString());
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});
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console.log(`[redisRelayToMcpServer] Subscribing to ${toClientChannel} for response to request ${message.id}`);
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redisCleanup = await redisClient.createSubscription(toClientChannel, async (redisMessageJson) => {
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const redisMessage = JSON.parse(redisMessageJson) as RedisMessage;
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await transport.send(redisMessage.message, redisMessage.options);
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}, (error) => {
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console.error(`[redisRelayToMcpServer] Error in Redis subscriber for ${toClientChannel}:`, error);
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transport.onerror?.(error);
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});
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}).catch((error) => {
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console.error(`[redisRelayToMcpServer] Error setting up Redis relay for session ${sessionId}:`, error);
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messagePromise.catch((error) => {
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console.error(`[redisRelayToMcpServer] Error setting up relay for session ${sessionId}:`, error);
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transport.onerror?.(error);
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cleanup();
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});
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@ -83,6 +123,9 @@ export function redisRelayToMcpServer(sessionId: string, transport: Transport):
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export class ServerRedisTransport implements Transport {
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private counter: number;
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private _sessionId: string;
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private controlCleanup?: (() => Promise<void>);
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private serverCleanup?: (() => Promise<void>);
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private shouldShutdown = false;
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onclose?: (() => void) | undefined;
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onerror?: ((error: Error) => void) | undefined;
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@ -94,45 +137,108 @@ export class ServerRedisTransport implements Transport {
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}
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async start(): Promise<void> {
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console.log(`[ServerRedisTransport.${this.counter}.start] Starting server transport for session: ${this._sessionId}`);
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// Server transport doesn't need to subscribe to anything - it only sends responses
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// Subscribe to MCP messages from clients
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const serverChannel = getToServerChannel(this._sessionId);
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console.log(`[ServerRedisTransport.${this.counter}] Subscribing to server channel: ${serverChannel}`);
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this.serverCleanup = await redisClient.createSubscription(
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serverChannel,
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(messageJson) => {
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console.log(`[ServerRedisTransport.${this.counter}] Received message from Redis:`, messageJson.substring(0, 200));
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const redisMessage = JSON.parse(messageJson) as RedisMessage;
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if (redisMessage.type === 'mcp') {
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console.log(`[ServerRedisTransport.${this.counter}] Processing MCP message:`, JSON.stringify(redisMessage.message));
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this.onmessage?.(redisMessage.message, redisMessage.extra);
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console.log(`[ServerRedisTransport.${this.counter}] MCP message processed`);
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}
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},
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(error) => {
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console.error(`[ServerRedisTransport.${this.counter}] Server channel error:`, error);
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this.onerror?.(error);
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}
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);
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// Subscribe to control messages for shutdown
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const controlChannel = getControlChannel(this._sessionId);
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this.controlCleanup = await redisClient.createSubscription(
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controlChannel,
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(messageJson) => {
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const redisMessage = JSON.parse(messageJson) as RedisMessage;
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if (redisMessage.type === 'control') {
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if (redisMessage.action === 'SHUTDOWN') {
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this.shouldShutdown = true;
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this.close();
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}
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}
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},
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(error) => {
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this.onerror?.(error);
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}
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);
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}
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async send(message: JSONRPCMessage, options?: TransportSendOptions): Promise<void> {
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const relatedRequestId = options?.relatedRequestId?.toString() ?? notificationStreamId;
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const relatedRequestId = options?.relatedRequestId?.toString() ?? "id" in message ? message.id : notificationStreamId;
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const channel = getToClientChannel(this._sessionId, relatedRequestId)
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console.log(`[ServerRedisTransport.${this.counter}] Sending message to channel: ${channel}`);
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console.log(`[ServerRedisTransport.${this.counter}] Message:`, JSON.stringify(message));
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console.log(`[ServerRedisTransport.${this.counter}] Options:`, JSON.stringify(options));
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const redisMessage: RedisMessage = { message, options };
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const redisMessage: RedisMessage = { type: 'mcp', message, options };
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const messageStr = JSON.stringify(redisMessage);
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console.log(`[ServerRedisTransport.${this.counter}.send] Publishing to ${channel}:`, messageStr.substring(0, 100));
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await redisClient.publish(channel, messageStr);
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console.log(`[ServerRedisTransport.${this.counter}.send] Published successfully to ${channel}`);
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console.log(`[ServerRedisTransport.${this.counter}] Message published to Redis`);
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}
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async close(): Promise<void> {
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console.log(`[ServerRedisTransport.${this.counter}.close] Closing server transport for session: ${this._sessionId}`);
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// Clean up server message subscription
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if (this.serverCleanup) {
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await this.serverCleanup();
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this.serverCleanup = undefined;
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}
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// Clean up control message subscription
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if (this.controlCleanup) {
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await this.controlCleanup();
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this.controlCleanup = undefined;
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}
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this.onclose?.();
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}
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}
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export async function startServerListeningToRedis(server: Server, sessionId: string) {
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console.log(`[startServerListeningToRedis] Starting background server for session ${sessionId}`);
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export async function startServerListeningToRedis(serverWrapper: { server: Server; cleanup: () => void }, sessionId: string): Promise<ServerRedisTransport> {
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const serverRedisTransport = new ServerRedisTransport(sessionId);
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// Add cleanup callback to the transport
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const originalClose = serverRedisTransport.close.bind(serverRedisTransport);
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serverRedisTransport.close = async () => {
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serverWrapper.cleanup();
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await originalClose();
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};
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// The server.connect() will call start() on the transport
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await server.connect(serverRedisTransport)
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console.log(`[startServerListeningToRedis] Background server connected for session ${sessionId}`);
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await serverWrapper.server.connect(serverRedisTransport)
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return serverRedisTransport;
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}
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export async function getFirstShttpTransport(sessionId: string): Promise<{shttpTransport: StreamableHTTPServerTransport, cleanup: () => Promise<void>}> {
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console.log(`[getFirstShttpTransport] Creating transport for session: ${sessionId}`);
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const shttpTransport = new StreamableHTTPServerTransport({
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sessionIdGenerator: () => sessionId,
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enableJsonResponse: true, // Enable JSON response mode
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});
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console.log(`[getFirstShttpTransport] Created transport, sessionId: ${shttpTransport.sessionId}`);
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// Use the new request-id based relay approach
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console.log(`[getFirstShttpTransport] Setting up Redis relay for session: ${sessionId}`);
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const cleanup = redisRelayToMcpServer(sessionId, shttpTransport);
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console.log(`[getFirstShttpTransport] Transport setup complete for session: ${sessionId}`);
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return { shttpTransport, cleanup };
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}
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