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Apache

Apache rewrite strategy

Use deterministic, auditable rewrite behavior to avoid semantic drift, redirect loops, and canonicalization attacks.

Last updated: 2026-05-10. Owners: operations and service teams.

On this page

  1. Doctrine
  2. Decision tree
  3. Diagnostics pathway
  4. Decision checks
  5. Related routes

Doctrine

  • Prefer single canonical host + path ownership for each virtual host.
  • Keep rewrite logic in one block and gate every rule with explicit `RewriteRule`, `RewriteCond`, and comments.
  • Preserve query strings by default unless intentionally remapped.
  • Use HTTPS-aware conditions first, then canonicalization, then routing.

Decision tree

  1. Need to change user-visible path or query behavior?
    • Yes → define expected input/output pairs in a local test matrix before changing config.
    • No → keep existing rewrite contract and only add safety checks.
  2. Is request already normalized?
    • Yes → apply auth and cache handling; then routing rule.
    • No → normalize host, slash, and encoded path first.
  3. Any potential loop?
    • Yes → add terminal condition (`L`, `R=301`, and explicit exclusion matches) before rollout.
    • No → continue with staged enablement and live probes.

Diagnostics pathway

  1. Validate rule graph parsing: 
    apachectl configtest
  2. Track current effective rule chain: 
    tail -f /var/log/httpd/error_log | rg --line-buffered "rewrite|redirect|canonical"
  3. Reproduce rewrite path from a client: 
    curl -I -L https://example.com/path?x=1
  4. Check loop or double-hop signs: 
    curl -I -L -X GET "https://example.com/health?trace=1"

Operational checks

  • Before change: capture baseline HTTP status distribution for top 20 routes.
  • After change: confirm no new 3xx cycles or TLS downgrade transitions.
  • Every redirect decision must map to a documented business rationale and rollback command.

Rollback: disable affected RewriteRule blocks and reload once, keeping cache headers unchanged.