[BUG] Unable to get remote mcp server running using streamable-http protocol

[sachinmalanki]

Describe the bug
Unable to connect to remote mcp server using streamable-http transport protocol when running this as a docker image in k8s.

To Reproduce
Steps to reproduce the behavior:
Running as deployment -

  - apiVersion: apps/v1  
    kind: Deployment
    metadata:
      name: atlan-mcp-server
      namespace: ai
      labels:
        app: atlan-mcp-server
    spec:
      replicas: 1
      selector:   
        matchLabels:
          app: atlan-mcp-server
      template:  
        metadata:
          labels:
            app: atlan-mcp-server
        spec:
          containers:
          - name: atlan-mcp-server
            image: ghcr.io/atlanhq/atlan-mcp-server:latest
            imagePullPolicy: IfNotPresent
            # Add command and args based on server.py
            command: ["python"]
            args: 
            - "server.py"
            - "--host=0.0.0.0"
            - "--port=8080"  
            - "--path=/atlan"
            - "--transport=streamable-http"
            ports:
            - containerPort: 8080  
              name: http
              protocol: TCP
            env:
            # Required environment variables based on server.py
            - name: ATLAN_BASE_URL
              value: "https://xxx.atlan.com"
            - name: ATLAN_API_KEY
              valueFrom:
                secretKeyRef:
                  name: mcp-token
                  key: atlan_token
            # Transport configuration
            # - name: MCP_TRANSPORT
            #   value: "sse"
            # - name: MCP_HOST
            #   value: "0.0.0.0"
            # - name: MCP_PORT
            #   value: "8080"
            # - name: MCP_PATH
            #   value: "/atlan"
            # Logging configuration
            - name: LOG_LEVEL
              value: "DEBUG"  
            - name: FASTMCP_LOG_LEVEL
              value: "DEBUG"
            resources:
              requests:
                memory: "128Mi"
                cpu: "100m"
              limits:
                memory: "512Mi"
                cpu: "500m"
            securityContext:
              allowPrivilegeEscalation: false
              runAsNonRoot: true
              runAsUser: 1000
              # Remove readOnlyRootFilesystem as Python may need to write temp files
              # readOnlyRootFilesystem: true
              capabilities:
                drop:
                - ALL
          restartPolicy: Always
          securityContext:
            fsGroup: 1000

  - apiVersion: v1
    kind: Service
    metadata:
      name: atlan-mcp-server-service
      namespace: ai
      labels:
        app: atlan-mcp-server
    spec:
      selector:
        app: atlan-mcp-server
      ports:
      - name: http
        port: 8080
        targetPort: 8080
        protocol: TCP
      type: ClusterIP

Environment Information

• OS: Linux
• Package versions: [e.g. python-dotenv==1.0.0, pydantic==2.0.0]

Error Message

│                                                                                    Autoscroll:On      FullScreen:Off     Timestamps:Off     Wrap:Off                                                                                    │
│ /appuser/.venv/lib/python3.12/site-packages/pydantic/_internal/_config.py:295: PydanticDeprecatedSince20: Support for class-based `config` is deprecated, use ConfigDict instead. Deprecated in Pydantic V2.0 to be removed in V3.0. Se │
│   warnings.warn(DEPRECATION_MESSAGE, DeprecationWarning)                                                                                                                                                                                │
│ [07/30/25 09:18:21] INFO     Starting MCP server 'Atlan MCP       server.py:1219                                                                                                                                                        │
│                              Server' with transport                                                                                                                                                                                     │
│                              'streamable-http' on                                                                                                                                                                                       │
│                              http://0.0.0.0:8080/atlan                                                                                                                                                                                  │
│ INFO:     Started server process [1]                                                                                                                                                                                                    │
│ INFO:     Waiting for application startup.                                                                                                                                                                                              │
│ INFO:     Application startup complete.                                                                                                                                                                                                 │
│ INFO:     Uvicorn running on http://0.0.0.0:8080 (Press CTRL+C to quit)                                                                                                                                                                 │
│ INFO:     10.160.193.80:25864 - "GET / HTTP/1.1" 404 Not Found                                                                                                                                                                          │
│ INFO:     10.160.196.26:12972 - "GET / HTTP/1.1" 404 Not Found                                                                                                                                                                          │
│ INFO:     10.160.193.80:53270 - "GET / HTTP/1.1" 404 Not Found                                                                                                                                                                          │
│ INFO:     10.160.196.26:37374 - "GET / HTTP/1.1" 404 Not Found                                                                                                                                                                          │
│ INFO:     10.160.193.80:12414 - "GET / HTTP/1.1" 404 Not Found                                                                                                                                                                          │
│ INFO:     10.160.196.26:6902 - "GET / HTTP/1.1" 404 Not Found  

Also getting this in the UI when port-forward -

{"jsonrpc":"2.0","id":"server-error","error":{"code":-32600,"message":"Not Acceptable: Client must accept text/event-stream"}}

Expected behavior
Expect to connect to localhost:8080/atlan endpoint when port-forward. I can confirm I can connect to it when I run it locally on stdio transport protocol

[abhinavmathur-atlan]

Thanks for raising this! To help troubleshoot, could you share a few more details?

How are you accessing the MCP server?

Are you using kubectl port-forward, Ingress, or something else?

What kind of client are you using?
For example, a browser, curl, Cursor, or a custom app?

Can you share your Ingress/port forwarding if possible?

or any other

[sachinmalanki]

I have created an ingress to access the MCP server.
I'm using VSCode with Github Copilot as the client but I do get the same when portforwarding and hitting the endpoint using curl

  - apiVersion: networking.k8s.io/v1
    kind: Ingress
    metadata:
      name: mcp-server-ingress
      namespace: ai
      labels:
        app: mcp-server
      annotations:
        # AWS Load Balancer Controller annotations
        alb.ingress.kubernetes.io/scheme: internal
        kubernetes.io/ingress.class: alb
        alb.ingress.kubernetes.io/load-balancer-name: xxx
        alb.ingress.kubernetes.io/backend-protocol: HTTP
        alb.ingress.kubernetes.io/subnets: xxx
        alb.ingress.kubernetes.io/target-type: ip
        alb.ingress.kubernetes.io/certificate-arn: "xxx"
        alb.ingress.kubernetes.io/listen-ports: '[{"HTTPS":443}]'  
    spec:
      ingressClassName: alb
      rules:
      - host: xxx.mcpserver.com
        http:
          paths:
          - path: /sse
            pathType: Prefix
            backend:
              service:
                name: mcp-github-proxy
                port:
                  number: 8080
          - path: /grafana
            pathType: Prefix
            backend:
              service:
                name: mcp-grafana-proxy
                port:
                  number: 9090 
          - path: /mcp
            pathType: Prefix
            backend:
              service:
                name: mcp-terraform-proxy
                port:
                  number: 8085   
          - path: /atlan
            pathType: Prefix
            backend:
              service:
                name: atlan-mcp-server-service
                # name: mcp-atlan-proxy                
                port:
                  number: 8080                                                 
      # Optional: Default backend for unmatched requests
      defaultBackend:
        service:
          name: mcp-grafana-proxy
          port:
            number: 9090    

[sachinmalanki]

Hi @SatabrataPaul-GitAc @Hk669 @abhinavmathur-atlan
I also see that when I run this as mentioned in the documentation in sse mode - INFO: 10.160.192.47:38232 - "POST /atlan HTTP/1.1" 405 Method Not Allowed
and when I run in streamable-http mode - INFO: 10.160.192.47:61484 - "POST /atlan HTTP/1.1" 307 Temporary Redirect
Any idea what could be the issue?

[abhinavmathur-atlan]

Hi @sachinmalanki , can you please try to do it with cursor once , need to see if this is a copilot issue or not

[abhinavmathur-atlan]

{"jsonrpc":"2.0","id":"server-error","error":{"code":-32600,"message":"Not Acceptable: Client must accept text/event-stream"}}

this is expected for browsers since header doesnt contain text/event-stream

[sachinmalanki]

I get the same in cursor as well. Also I don't believe it is a copilot issue cause I have multiple other mcp running fine.

[abhinavmathur-atlan]

can you try with a trailing slash
localhost:8000/atlan/

[sachinmalanki]

I get the same error and I see this in the logs - INFO: 10.160.196.103:29804 - "POST /atlan/ HTTP/1.1" 307 Temporary Redirect
terminal -

2025-09-01 11:05:09.210 [info] 405 status sending message to https://mcp.tec.dmn.we1.nexus.newday.co.uk/atlan, will attempt to fall back to legacy SSE
2025-09-01 11:05:09.444 [warning] 404 status sending message to [object Object]: 404 page not found

2025-09-01 11:05:14.662 [info] Waiting for server to respond to `initialize` request...
2025-09-01 11:05:19.070 [info] Waiting for server to respond to `initialize` request...
2025-09-01 11:05:24.071 [info] Waiting for server to respond to `initialize` request...

[abhinavmathur-atlan]

Would you be interested to take this up in a call?
@sachinmalanki