如何配置HAProxy实现Tomcat请求从localhost:8080/path转发至1.2.3.4:8080/path

Got it, let's walk through exactly how to set up HAProxy to forward requests coming to localhost:8080/path (and its subpaths) to 1.2.3.4:8080/path. The core here is preserving the request path while routing, which is easy with HAProxy's ACL and backend directives.

Here's a complete, ready-to-use configuration example (typically saved at /etc/haproxy/haproxy.cfg):

global
    log /dev/log local0
    log /dev/log local1 notice
    chroot /var/lib/haproxy
    stats socket /run/haproxy/admin.sock mode 660 level admin expose-fd listeners
    stats timeout 30s
    user haproxy
    group haproxy
    daemon

defaults
    log global
    mode http
    option httplog
    option dontlognull
    timeout connect 5000
    timeout client 50000
    timeout server 50000

frontend tomcat_path_frontend
    bind *:8080
    # Match requests starting with /path (covers /path, /path/sub, etc.)
    acl matches_path path_beg /path
    # Route matching requests to our backend
    use_backend remote_tomcat if matches_path

backend remote_tomcat
    # Define the target Tomcat server
    server tomcat_node 1.2.3.4:8080 check
    # Pass the client's real IP to Tomcat (optional but useful for logs)
    option forwardfor

Key Breakdown of the Configuration: #

• Global Section: These are base HAProxy settings (logging, permissions, daemon mode) – you can leave these as-is unless you have specific infrastructure needs.
• Defaults Section: Sets universal HTTP proxy rules: enables HTTP logging, sets reasonable timeouts for connections, clients, and servers.
• Frontend:
  • bind *:8080: Tells HAProxy to listen on all network interfaces at port 8080 (so localhost:8080 will hit this frontend).
  • acl matches_path path_beg /path: Creates an Access Control List (ACL) that triggers when the request path starts with /path. This matches both /path and any subpaths like /path/api or /path/page. If you need exact match only (just /path, no subpaths), replace path_beg with path /path.
  • use_backend remote_tomcat if matches_path: Routes any request matching the ACL to the remote_tomcat backend.
• Backend:
  • server tomcat_node 1.2.3.4:8080 check: Defines the target Tomcat server. The check flag enables health checks to ensure HAProxy only sends traffic to the server if it's online.
  • option forwardfor: Adds an X-Forwarded-For header to the request, so Tomcat can log the original client IP instead of HAProxy's IP.

To Apply the Configuration: #

1. Save the config to /etc/haproxy/haproxy.cfg (adjust path if your distro uses a different location).
2. Test the config for syntax errors: haproxy -c -f /etc/haproxy/haproxy.cfg
3. Restart HAProxy to apply changes:
   • For systemd-based systems: systemctl restart haproxy
   • For SysVinit: service haproxy restart

That's it! Now any request to localhost:8080/path (or its subpaths) will be forwarded to 1.2.3.4:8080/path with the full path preserved.

内容的提问来源于stack exchange，提问作者user5123481566