MCP Directory

title: "Fixing MCP Deployment Issues in Docker/Vercel" description: "Troubleshoot MCP deployment failures in Docker containers and Vercel serverless environments." slug: "deployment-errors" category: "testing" updatedAt: "2025-09-21T00:00:00.000Z" faqs:

  • q: "Why does my MCP crash on Vercel?" a: "Most MCP servers need persistent processes. Use Edge Functions or background jobs, set proper memory limits, and ensure the handler returns responses quickly."
  • q: "How do I debug a failing Docker container?" a: "Check docker logs, run an interactive shell with docker exec -it, and verify environment variables and exposed ports."
  • q: "Can I share the same Docker image across staging and production?" a: "Yes, but parameterise configuration via environment variables and secrets so each environment remains isolated."
Testing & Debugging
MCP SDK v2.1.0
Updated Sep 21, 20254 min read
deployment
docker
vercel
errors

Fixing MCP Deployment Issues in Docker/Vercel

Overview

Containerising MCP servers or running them on Vercel’s serverless platform offers convenient deployment, but misconfiguration can produce cold-start failures, timeouts, or missing environment variables. This guide covers the most frequent issues and their fixes.

Docker Deployment Checklist

# Dockerfile
FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --omit=dev
COPY . .
ENV PORT=8000
EXPOSE 8000
CMD ["node", "dist/server.js"]
  1. Ensure dependencies install (check network access, private registries).
  2. Expose the MCP port and map it when running: docker run -p 8000:8000 mcp-server.
  3. Set env vars through --env-file or your orchestrator.
  4. Health checks: add /health endpoint and configure Docker or Kubernetes readiness probes.

Vercel Deployment Checklist

  • Only lightweight MCP handlers work well in Edge Functions. For long-running tasks, use Vercel cron jobs or background functions.
  • Configure vercel.json:
{
  "functions": {
    "api/mcp.ts": {
      "memory": 1024,
      "maxDuration": 30
    }
  }
}
  • Set environment variables for each environment (Preview, Production).
  • Use next.config.js to mark MCP routes as dynamic: export const runtime = "edge"; when appropriate.

Debugging Techniques

Docker

# View logs
docker logs mcp-server

# Attach shell
docker exec -it mcp-server /bin/sh

# Inspect network
docker inspect mcp-server --format '{{json .NetworkSettings.Ports}}'

Vercel

  • Inspect deployment logs in the Vercel dashboard.
  • Run vercel env pull .env.local to keep local env vars in sync.
  • Use vercel logs <deployment-url> for realtime output.

Common Error Matrix

| Symptom | Docker Fix | Vercel Fix | | --- | --- | --- | | MODULE_NOT_FOUND | Rebuild image after adding files to COPY. | Verify vercel build uses the correct entry point. | | Timeout | Increase --timeout or optimize queries. | Move heavy work to background job. | | PORT already in use | Change host port mapping or use --init. | Let Vercel manage the port; remove hard-coded values. | | Environment variable missing | Pass via docker run --env. | Set in Vercel dashboard and redeploy. |

Logging & Monitoring

  • Ship container logs to CloudWatch, Datadog, or Logflare.
  • Enable OpenTelemetry (OTLP) exporters inside the MCP server for traces.
  • Tag logs with deployment version and commit SHA for traceability.

Related Guides

FAQ

Why does my MCP crash on Vercel?

Ensure the MCP handler finishes within the max duration and uses supported APIs. For long-running servers, deploy to a container or background worker instead.

How do I debug a failing Docker container?

Use docker logs, inspect the container with docker exec, and verify environment variables, network ports, and filesystem paths.

Can I share the same Docker image across staging and production?

Yes—tag the image once, then supply environment-specific configuration via secrets or environment variables.

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Last updated: September 21, 2025

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