Apache proxy design

Doctrine

• Front-end trust must be explicit: proxy only to declared backend pools and documented protocols.
• Set end-to-end timeout, retry, and circuit-breaker policy centrally and review monthly.
• Strip untrusted headers, then add controlled forwarding context headers.
• Separate sticky routing from auth routing to avoid implicit session coupling.

Decision tree

1. Is the backend set static or dynamic?
   • Static → hardcode pool and validate with active health checks.
   • Dynamic → add registry and canary checks before rollout.
2. Is this a low-latency or secure-control route?
   • Secure-control → enforce stricter retries and short response deadlines.
   • Low-latency → conservative buffering and no speculative transforms.
3. Did backend failures exceed retry budget?
   • Yes → mark host unhealthy and route to fallback behavior.
   • No → continue with current pool and emit warning if increasing trend remains.

Diagnostics pathway

1. Confirm loaded modules and proxy flags:

   apachectl -M | rg -i "proxy|lb|rewrite"

2. Review backend membership and failover state:

   curl -sS http://127.0.0.1/server-status?auto | rg -i "busyworkers|scoreboard|starttime"

3. Check latency and retry patterns:

   curl -I -m 3 https://app.example.com/health

4. Verify header contract at boundary:

   curl -sS -H "X-Diagnostic: 1" https://app.example.com/headers | rg -i "x-forwarded|x-original"

Operational checks

• Before deployment, run at least one negative test for backend unavailable and one retry storm test.
• After deployment, verify all routes still emit identity context and correct host chain.
• Keep a documented rollback: disable `ProxyPass` route, reload Apache, and restore direct endpoint temporarily.

Related routes