fix: Actorized MCP servers have 30 seconds timeout to connect #272

MichalKalita · 2025-09-11T15:14:26Z

Fixes: #250

When the connection to the Actorized MCP server is not completed in 30 seconds, this MCP server silently fails and opens a user session without this Actorized MCP server.

Potential improvements:

inside getMCPServersAsTools load all MCP servers in parallel
somehow write to client if MCP server is not connected, maybe create some resource with "startup errors?" @jirispilka @MQ37
- Not completed, there is no reliable way to return the MCP error when starting the session

MichalKalita · 2025-09-11T15:16:00Z

Or, theoretically, we can start the session without these tools and add them after the MCP server is connected. But it will probably be a problem for clients without the tool update feature.

MQ37 · 2025-09-11T18:13:30Z

Or, theoretically, we can start the session without these tools and add them after the MCP server is connected. But it will probably be a problem for clients without the tool update feature.

Yes, but we can use the https://github.com/apify/mcp-client-capabilities package and for the clients that support tools changed notification we can load that dynamically and connect them instantly and for those who do not we can let them wait or time out the proxy MCP connection.

MQ37 · 2025-09-11T18:14:26Z

@MichalKalita from my testing the LLM usually do not read the resources sadly, we could pass that in the initialize response instructions but the clients are not reading that either 😅

MQ37 · 2025-09-11T18:25:47Z

inside getMCPServersAsTools load all MCP servers in parallel

This is actually a great improvement, I wanted to do it but never finished that 😅

MichalKalita · 2025-09-17T16:43:56Z

Testing with:
mcp-servers/slidespeak-mcp-server ❌ error 500 in 8s

{"jsonrpc":"2.0","id":0,"error":{"code":-32001,"message":"Error POSTing to endpoint (HTTP 404): {\n \"error\": {\n \"type\": \"record-or-token-not-found\",\n \"message\": \"Actor or Actor task was not found or access denied\"\n }\n}","data":{}}}

direct connection works

mcp-servers/brave-search-mcp-server ✅ cold start in 11s

jiri.spilka/weather-mcp-server ❌ error 500 in 8s (direct connection works)

{
  "jsonrpc": "2.0",
  "id": 0,
  "error": {
    "code": -32001,
    "message": "Error POSTing to endpoint (HTTP 500): {\"jsonrpc\":\"2.0\",\"error\":{\"code\":-32603,\"message\":\"Internal server error\"},\"id\":null}",
    "data": {}
  }
}

apify/actors-mcp-server ✅
jakub.kopecky/browserbase-mcp-server 7.3s ✅
jakub.kopecky/arxiv-mcp-server 1.2s ❌ is loaded like normal Actor, not MCP
jiri.spilka/playwright-mcp-server 25s ❌
Error in request {"logMessage":"Error handling MCP request","error":{"name":"Error","message":"SSE error: Non-200 status code (400)","stack":"Error: SSE error: Non-200 status code (400) direct connection works

MichalKalita · 2025-09-18T09:58:30Z

There was simple bug, I fixed it.
But I found jakub.kopecky/browserbase-mcp-server have some issue to make more sessions @MQ37

 FAIL  tests/integration/actor.server-sse.test.ts > Apify MCP Server SSE > should connect to "jakub.kopecky/browserbase-mcp-server" MCP server and at least one tool is available
Error: SSE error: Non-200 status code (500)
 ❯ EventSource._eventSource.onerror node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:158:23
 ❯ EventSource.failConnection_fn node_modules/eventsource/src/EventSource.ts:535:5
 ❯ node_modules/eventsource/src/EventSource.ts:374:7

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 FAIL  tests/integration/actor.server-streamable.test.ts > Apify MCP Server Streamable HTTP > should connect to "jakub.kopecky/browserbase-mcp-server" MCP server and at least one tool is available
McpError: MCP error -32001: Request timed out
 ❯ Timeout.timeoutHandler node_modules/@modelcontextprotocol/sdk/src/shared/protocol.ts:625:43

MQ37 · 2025-09-18T11:50:25Z

jakub.kopecky/browserbase-mcp-server

Created issue for that https://github.com/apify/ai-team/issues/85

MQ37

Just a few nits/questions, otherwise LGTM

tests/integration/suite.ts

MQ37 · 2025-09-18T11:56:49Z

src/tools/actor.ts

+    });
+
+    // Wait for all actors to be processed in parallel
+    const actorToolsArrays = await Promise.all(actorToolPromises);


notice: for the most use cases it should be fine, but we should be aware of rate limits

I didn't find any rate limiting docs in the public docs on internal Notion. What type of limits do you mean?

src/mcp/client.ts

MQ37 · 2025-09-18T12:31:21Z

src/mcp/client.ts

+
+    try {
+        client = await createMCPSSEClient(url, token);
+        return client;
+    } catch (error) {
+        if (error instanceof TimeoutError) {
+            log.warning('Connection to MCP server using SSE transport timed out', { url });
+            return null;
+        }
+
+        log.error('Failed to connect to MCP server using SSE transport', { cause: error });
+        throw error;


nit/question: Why is the try block here? We are just catching and then re-throwing. I would remove the try block for the SSE.

If I throw exception, connection will not be opened.
When TimeoutError occurs, only warning will be logged to us and connection will be opened, but without this MCP server.

jirispilka

I left only a few comments. Can you please re-consider the number of mcp-servers u use for testing?

MichalKalita · 2025-09-19T14:29:35Z

@jirispilka I kept only a single MCP server.

jirispilka

Looks good, thanks!

fix: Actorized mcp server have 5 seconds timeout to connect

5f18d34

github-actions bot assigned MichalKalita Sep 11, 2025

github-actions bot added the t-ai Issues owned by the AI team. label Sep 11, 2025

MichalKalita changed the title ~~fix: Actorized mcp server have 5 seconds timeout to connect~~ fix: Actorized mcp server have 30 seconds timeout to connect Sep 11, 2025

MichalKalita changed the title ~~fix: Actorized mcp server have 30 seconds timeout to connect~~ fix: Actorized MCP servers have 30 seconds timeout to connect Sep 11, 2025

feat: get mcp server tools in parallel

4591042

Merge remote-tracking branch 'origin/master' into fix/mcp-timeout

693de47

fix: default stramable and backup SSE transport

22f4c9d

MichalKalita marked this pull request as ready for review September 18, 2025 10:03

MichalKalita requested review from MQ37 and jirispilka September 18, 2025 10:03

MQ37 approved these changes Sep 18, 2025

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jirispilka reviewed Sep 18, 2025

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MichalKalita added 3 commits September 19, 2025 16:09

fix: improve based on code review feedback

8ad0741

Merge remote-tracking branch 'origin/master' into fix/mcp-timeout

2ca73dd

fix: types after master merge

752021e

jirispilka approved these changes Sep 19, 2025

View reviewed changes

MichalKalita merged commit cdffc3e into master Sep 22, 2025
4 checks passed

MichalKalita deleted the fix/mcp-timeout branch September 22, 2025 07:56

fix: Actorized MCP servers have 30 seconds timeout to connect #272

fix: Actorized MCP servers have 30 seconds timeout to connect #272

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