Kubernetes环境下部署Rails+Unicorn+Nginx应用无法加载静态资源

Hey there, let's dig into why your Rails app's static assets aren't loading on Kubernetes—this is a super common gotcha when moving from Docker Compose to K8s, so let's break down targeted fixes and checks:

1. First, Confirm Rails Asset Precompilation is Working #

Rails doesn't serve static assets in production mode by default—you need to precompile them first, and make sure that step is baked into your Docker image.

• Double-check your Dockerfile includes this command (after installing gems and copying app code):

  RUN RAILS_ENV=production bundle exec rails assets:precompile
  

• Verify your Deployment sets the production environment via env vars:

  env:
    - name: RAILS_ENV
      value: "production"
  

• You can also exec into a running pod to check if assets exist:

  kubectl exec -it <your-app-pod-name> -- ls public/assets
  

  You should see hashed files like application-abc123.css—if not, precompilation failed.

2. Make Sure Your Web Server is Serving Static Assets #

Your choice of server (Unicorn, Passenger, Nginx) dictates how assets are handled:

• Unicorn: By default, Unicorn won't serve static assets. You can either:
  • Enable it temporarily in config/environments/production.rb (not ideal for performance):

    config.serve_static_assets = true
    # Or for Rails 5+, use:
    config.public_file_server.enabled = true
    

  • Or add an Nginx sidecar or combine Nginx with Unicorn in your image to serve assets directly (this is the production-grade approach).
• Combined Rails + Nginx Image: If you went this route, ensure your Nginx config has a block to serve assets:

  location ~ ^/assets/ {
    root /app/public;
    expires 1y;
    add_header Cache-Control public;
    add_header ETag "";
  }
  

• Passenger: It should handle static assets automatically, but confirm config.public_file_server.enabled = true is set in your production config.

3. Tweak Your Ingress Configuration (The Likely Culprit) #

Your existing tweaks might have missed a few key details:

• Ditch the ingress.kubernetes.io/add-base-url annotation unless your app is hosted under a subpath (like yourdomain.com/appx). This annotation can rewrite asset paths incorrectly.
• Use pathType: Prefix for your root path to ensure all requests (including assets) are forwarded to your service:

  spec:
    rules:
    - host: your-app-domain.com
      http:
        paths:
        - path: /
          pathType: Prefix
          backend:
            service:
              name: appX-cluster-ip-service
              port:
                number: 80
  

• Check your ingress controller logs for 404s related to assets:

  kubectl logs -n kube-system <your-ingress-controller-pod> | grep assets
  

4. Debug Pod-to-Service Connectivity #

Rule out issues inside your cluster:

• Exec into your app pod and test if assets load locally:

  kubectl exec -it <your-app-pod> -- curl localhost:<container-port>/assets/application-<hash>.css
  

  If this returns the asset content, the problem is in your Ingress or Service. If not, the issue is inside the pod (web server config or missing assets).
• Confirm your Service is targeting the correct container port (e.g., Unicorn usually listens on 8080, Nginx on 80).

5. Use Browser Dev Tools to Diagnose Request Issues #

Open your browser's dev tools (F12) and check the Network tab:

• Look for asset requests with 404/403 status codes. If the URL is something like yourdomain.com/assets/application.css (no hash), that means Rails isn't generating the hashed asset path correctly—double-check precompilation and RAILS_ENV.
• If the URL has the hash but returns 404, your server isn't routing the request to the correct asset file.

Quick Stable Setup Example (Rails + Unicorn + Nginx) #

If you want a reliable baseline, here's a simplified Dockerfile to combine both servers:

FROM ruby:2.5.5-slim

# Install system dependencies
RUN apt-get update && apt-get install -y --no-install-recommends \
  build-essential nginx \
  && rm -rf /var/lib/apt/lists/*

WORKDIR /app

# Install gems
COPY Gemfile Gemfile.lock ./
RUN bundle install --without development test --deployment

# Copy app code
COPY . .

# Precompile assets
RUN RAILS_ENV=production bundle exec rails assets:precompile

# Copy Nginx config
COPY nginx.conf /etc/nginx/nginx.conf

# Start both servers
CMD ["bash", "-c", "bundle exec unicorn -c config/unicorn.rb & nginx -g 'daemon off;'"]

And a basic nginx.conf:

events {
  worker_connections 1024;
}

http {
  server {
    listen 80;
    root /app/public;

    # Serve static assets directly
    location ~ ^/assets/ {
      expires 1y;
      add_header Cache-Control public;
    }

    # Forward dynamic requests to Unicorn
    location / {
      proxy_pass http://localhost:8080;
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
    }
  }
}

内容的提问来源于stack exchange，提问作者Alejandro Roble Gutiérrez