add support for SSE

Author: light4

README.md

@@ -70,6 +70,8 @@ The Elasticsearch MCP Server supports configuration options to connect to your E
 
 | Environment Variable | Description | Required |
 |---------------------|-------------|----------|
+| `SSE_ADDR` | Enable SSE and set the ADDR | No |
+| `ES_URL` | Your Elasticsearch instance URL | Yes |
 | `ES_URL` | Your Elasticsearch instance URL | Yes |
 | `ES_API_KEY` | Elasticsearch API key for authentication | No |
 | `ES_USERNAME` | Elasticsearch username for basic authentication | No |

index.ts

@@ -5,15 +5,23 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+import express, { Request, Response } from "express";
 import { z } from "zod";
 import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
+import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
 import { Client, estypes, ClientOptions } from "@elastic/elasticsearch";
 import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
 import fs from "fs";
 
 // Configuration schema with auth options
 const ConfigSchema = z
   .object({
+    sse_addr: z
+      .string()
+      .trim()
+      .optional()
+      .describe("Address for SSE server (optional)"),
+
     url: z
       .string()
       .trim()
@@ -403,23 +411,57 @@ export async function createElasticsearchMcpServer(
 }
 
 const config: ElasticsearchConfig = {
+  sse_addr: process.env.SSE_ADDR || "",
   url: process.env.ES_URL || "",
   apiKey: process.env.ES_API_KEY || "",
   username: process.env.ES_USERNAME || "",
   password: process.env.ES_PASSWORD || "",
   caCert: process.env.ES_CA_CERT || "",
 };
 
+async function create_sse_server(server: any) {
+  const app = express();
+
+  const transports: {[sessionId: string]: SSEServerTransport} = {};
+
+  app.get("/sse", async (_: Request, res: Response) => {
+    const transport = new SSEServerTransport('/messages', res);
+    transports[transport.sessionId] = transport;
+    res.on("close", () => {
+      delete transports[transport.sessionId];
+    });
+    await server.connect(transport);
+  });
+
+  app.post("/messages", async (req: Request, res: Response) => {
+    const sessionId = req.query.sessionId as string;
+    const transport = transports[sessionId];
+    if (transport) {
+      await transport.handlePostMessage(req, res);
+    } else {
+      res.status(400).send('No transport found for sessionId');
+    }
+  });
+
+  console.info("SSE server started on: ", process.env.SSE_ADDR);
+  app.listen(process.env.SSE_ADDR);
+}
+
 async function main() {
-  const transport = new StdioServerTransport();
+  console.info("Starting Elasticsearch MCP server...");
   const server = await createElasticsearchMcpServer(config);
 
-  await server.connect(transport);
+  if (process.env.SSE_ADDR) {
+    await create_sse_server(server);
+  } else {
+    const transport = new StdioServerTransport();
+    await server.connect(transport);
 
-  process.on("SIGINT", async () => {
-    await server.close();
-    process.exit(0);
-  });
+    process.on("SIGINT", async () => {
+      await server.close();
+      process.exit(0);
+    });
+  }
 }
 
 main().catch((error) => {

package.json

@@ -38,7 +38,9 @@
   },
   "dependencies": {
     "@elastic/elasticsearch": "^8.17.1",
-    "@modelcontextprotocol/sdk": "1.9.0"
+    "@modelcontextprotocol/sdk": "1.9.0",
+    "@types/express": "^5.0.1",
+    "express": "^5.1.0"
   },
   "engines": {
     "node": ">=18"