# Dispatcher Performance Tuning Patterns ## Cache Optimization Patterns ### Pattern 1: Extend TTL for Stable Content **Use Case:** Content that rarely changes (legal pages, terms, static content). **Before:** ```apache /cache { /enableTTL "1" /rules { /0000 { /glob "*" /type "allow" } } # Default TTL: short or not set } ``` **After:** ```apache /cache { /enableTTL "1" /rules { /0000 { /glob "*" /type "allow" } /0001 { /glob "/content/site/en/legal/*" /type "allow" } /0002 { /glob "/content/site/en/about/*" /type "allow" } } } # Apply TTL through response headers (respected by /enableTTL) Header set Cache-Control "public, s-maxage=86400, max-age=43200" ``` **Expected Impact:** +5-10% cache hit ratio, -20-30% backend requests for stable paths. --- ### Pattern 2: Add Cache-Control Headers for Static Assets **Use Case:** Images, CSS, JS, fonts should be cached aggressively. **Before:** ```apache # No caching headers ``` **After:** ```apache Header set Cache-Control "public, max-age=31536000, immutable" Header set Expires "1 year" ``` **Expected Impact:** CDN/browser cache offload, -15-25% dispatcher requests for assets. --- ### Pattern 3: Optimize Cache Invalidation (Reduce Over-Flushing) **Use Case:** Selective invalidation instead of full cache flush. **Before:** ```apache /invalidate { /0000 { /glob "*" /type "deny" } /0001 { /glob "*.html" /type "allow" } # Invalidates all HTML } ``` **After:** ```apache /invalidate { /0000 { /glob "*" /type "deny" } /0001 { /glob "/content/site/${specific-path}/*" /type "allow" } # Targeted } /cache { /statfileslevel "2" # Folder-level stat files } ``` **Expected Impact:** +10-15% cache persistence, faster cache recovery after publish. --- ### Pattern 4: Implement Query String Caching (Selectively) **Use Case:** API endpoints with cacheable query parameters. **Before:** ```apache /ignoreUrlParams { /0001 { /glob "*" /type "deny" } # Ignore all query params by default } ``` **After:** ```apache /ignoreUrlParams { /0001 { /glob "*" /type "deny" } /0002 { /glob "page" /type "allow" } # Allow caching with 'page' param /0003 { /glob "lang" /type "allow" } # Allow caching with 'lang' param } ``` **Expected Impact:** +20-30% cache hit ratio for API endpoints with common query patterns. --- ## Static Asset Optimization Patterns ### Pattern 5: Enable Compression **Before:** ```apache # No compression ``` **After:** ```apache AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css text/javascript application/javascript application/json DeflateCompressionLevel 6 ``` **Expected Impact:** -60-80% response size for compressible content, faster transfer times. --- ### Pattern 6: Asset Versioning for Cache Busting **Before:** ```html ``` **After:** ```html ``` ```apache # Rewrite versioned URLs to actual file RewriteRule ^(.*)\.(v[0-9]+)\.(css|js)$ $1.$3 [L] ``` **Expected Impact:** Safe long-term caching, no manual cache purging needed for assets. --- ## Request Processing Optimization Patterns ### Pattern 7: Simplify Filter Rules (Order & Specificity) **Before:** ```apache /filter { /0000 { /glob "*" /type "allow" } # Overly broad /0001 { /glob "/content/*" /type "allow" } /0002 { /glob "/content/site/*" /type "allow" } # Redundant # ... 50 more rules ... } ``` **After:** ```apache /filter { /0000 { /glob "*" /type "deny" } # Deny by default /0001 { /glob "/content/site/*/en/*" /type "allow" /method "GET" } # Specific allow /0002 { /glob "/etc/designs/site/*" /type "allow" /method "GET" } # Fewer, more specific rules } ``` **Expected Impact:** -10-20% filter evaluation time, clearer security posture. --- ### Pattern 8: Optimize Rewrite Rules (Minimize Redirects) **Before:** ```apache RewriteRule ^/old-path1/(.*)$ /new-path1/$1 [R=301,L] RewriteRule ^/old-path2/(.*)$ /new-path2/$1 [R=301,L] # ... many redirect chains ... RewriteRule ^/new-path1/(.*)$ /final-path/$1 [R=301,L] # Redirect chain! ``` **After:** ```apache # Eliminate redirect chains - go directly to final destination RewriteRule ^/old-path1/(.*)$ /final-path/$1 [R=301,L] RewriteRule ^/old-path2/(.*)$ /new-path2/$1 [R=301,L] # Use RewriteMap for many redirects RewriteMap redirects txt:/etc/httpd/conf.d/redirects.txt RewriteCond ${redirects:$1} !="" RewriteRule ^/(.*)$ ${redirects:$1} [R=301,L] ``` **Expected Impact:** -100-300ms latency per eliminated redirect, better UX. --- ### Pattern 9: Reduce Header Processing Overhead **Before:** ```apache # Setting many headers on every request Header always set X-Custom-Header-1 "value1" Header always set X-Custom-Header-2 "value2" Header always set X-Custom-Header-3 "value3" # ... 10 more headers ... ``` **After:** ```apache # Only set necessary headers, conditionally Header set X-Frame-Options "SAMEORIGIN" Header set X-Content-Type-Options "nosniff" # Only essential security headers ``` **Expected Impact:** -5-10ms per request, reduced processing overhead. --- ## AMS-Specific Patterns (AEM 6.5/AMS) ### Pattern 10: Apache MPM Tuning **Before:** ```apache StartServers 2 MaxRequestWorkers 150 MinSpareThreads 25 MaxSpareThreads 75 ThreadsPerChild 25 MaxRequestsPerChild 0 ``` **After:** ```apache StartServers 4 ServerLimit 16 MaxRequestWorkers 400 MinSpareThreads 50 MaxSpareThreads 150 ThreadsPerChild 25 MaxRequestsPerChild 1000 ``` **Expected Impact:** +30-50% concurrent request capacity, better resource utilization. --- ### Pattern 11: KeepAlive Optimization **Before:** ```apache KeepAlive On MaxKeepAliveRequests 100 KeepAliveTimeout 5 ``` **After:** ```apache KeepAlive On MaxKeepAliveRequests 200 # Higher for more reuse KeepAliveTimeout 2 # Lower to free up workers faster ``` **Expected Impact:** Better connection reuse, faster worker turnover under high load. --- ## Verification Pattern For every optimization applied: ```text # 1. Measure baseline BEFORE baseline_metrics = monitor_metrics({ "window_minutes": 10, "breakdown_by": "url_pattern" }) # 2. Apply optimization # (edit config files) # 3. Validate config lint({"mode":"directory","target":"/path/to/dispatcher/src","strict_mode":true}) sdk({"action":"check-files","config_path":"/path/to/dispatcher/src"}) validate({"config":"","type":"ams"}) # 4. Reload dispatcher (environment-specific) # 5. Measure impact AFTER post_metrics = monitor_metrics({ "window_minutes": 10, "breakdown_by": "url_pattern" }) # 6. Verify specific improvements inspect_cache({"url":"/sample/page.html","config_path":"/path/to/dispatcher/src"}) trace_request({"url":"/sample/page.html","method":"GET","config_path":"/path/to/dispatcher/src"}) ``` ## Anti-Patterns (Avoid These) ### Anti-Pattern 1: Overly Aggressive Caching ```apache # BAD: Apply 1-year TTL headers to all HTML pages Header set Cache-Control "public, s-maxage=31536000, max-age=31536000" ``` **Problem:** Personalized/dynamic content cached incorrectly, stale content issues. --- ### Anti-Pattern 2: No Cache Invalidation Strategy ```apache # BAD: No invalidation rules /invalidate { /0000 { /glob "*" /type "deny" } } ``` **Problem:** Manual cache clearing required, stale content persists indefinitely. --- ### Anti-Pattern 3: Allowing All Query Parameters ```apache # BAD: Cache with all query params /ignoreUrlParams { /0001 { /glob "*" /type "allow" } } ``` **Problem:** Cache fragmentation, low hit ratio, potential cache pollution attacks. --- ### Anti-Pattern 4: Excessive Redirect Chains ```apache # BAD: Multiple redirects RewriteRule ^/a$ /b [R=301,L] RewriteRule ^/b$ /c [R=301,L] RewriteRule ^/c$ /d [R=301,L] ``` **Problem:** 300-900ms added latency, poor user experience. --- ## Pattern Selection Guide | Optimization Goal | Recommended Patterns | Expected Impact | |-------------------|---------------------|-----------------| | Improve cache hit ratio | #1, #3, #4 | +10-25% hit ratio | | Reduce latency | #2, #6, #8, #9 | -50-200ms | | Reduce backend load | #1, #2, #3 | -20-40% backend requests | | Increase capacity | #5, #7, #10, #11 | +30-50% throughput | | Optimize static assets | #2, #5, #6 | -30-60% asset load time | ## References - Dispatcher Configuration: https://experienceleague.adobe.com/en/docs/experience-manager-dispatcher/using/configuring/dispatcher-configuration - AMS Dispatcher overview: https://experienceleague.adobe.com/en/docs/experience-manager-learn/ams/dispatcher/overview