Adding support for multiple instances of streamable http tracking the same MCP server. Needed for a multi-instance deployment of MCP using this transport

Author: jerome3o-anthropic

src/server/streamableHttp.ts

@@ -79,6 +79,11 @@ export interface StreamableHTTPServerTransportOptions {
    * Default is false for backwards compatibility.
    */
   enableDnsRebindingProtection?: boolean;
+
+  /**
+   * Enables support for multiple instances of the transport.
+   */
+  multiInstance?: boolean;
 }
 
 /**
@@ -130,6 +135,7 @@ export class StreamableHTTPServerTransport implements Transport {
   private _allowedHosts?: string[];
   private _allowedOrigins?: string[];
   private _enableDnsRebindingProtection: boolean;
+  private _multiInstance: boolean;
 
   sessionId?: string;
   onclose?: () => void;
@@ -144,6 +150,7 @@ export class StreamableHTTPServerTransport implements Transport {
     this._allowedHosts = options.allowedHosts;
     this._allowedOrigins = options.allowedOrigins;
     this._enableDnsRebindingProtection = options.enableDnsRebindingProtection ?? false;
+    this._multiInstance = options.multiInstance ?? false;
   }
 
   /**
@@ -674,6 +681,9 @@ export class StreamableHTTPServerTransport implements Transport {
     const streamId = this._requestToStreamMapping.get(requestId);
     const response = this._streamMapping.get(streamId!);
     if (!streamId) {
+      if (this._multiInstance) {
+        return; // If multi-instance is enabled, we can ignore messages without a stream
+      }
       throw new Error(`No connection established for request ID: ${String(requestId)}`);
     }
 
@@ -701,6 +711,10 @@ export class StreamableHTTPServerTransport implements Transport {
 
       if (allResponsesReady) {
         if (!response) {
+          if (this._multiInstance) {
+            // If multi-instance is enabled, we can ignore messages without a stream
+            return;
+          }
           throw new Error(`No connection established for request ID: ${String(requestId)}`);
         }
         if (this._enableJsonResponse) {