Aem Dispatcher Configuration

AEM Dispatcher Configuration

Purpose

Configure, optimize, and troubleshoot the AEM Dispatcher module for Apache/IIS including caching rules, filter definitions, load balancing, and security hardening.

When to Use (Triggers)

• User mentions "dispatcher," "cache rules," "filter rules," or "Apache configuration"
• References to .any files, dispatcher.conf, or vanity URL handling
• Questions about cache invalidation, TTL, stat files, or auto-invalidation
• Requests involving URL rewriting, redirect management, or request filtering
• Discussion of CDN integration, load balancing, or dispatcher farm configuration

Core Capabilities

• Configure dispatcher farms with cache rules, filters, and render definitions
• Implement fine-grained cache invalidation strategies (stat file level, explicit flush)
• Design URL rewriting and redirect management with dispatcher rules
• Set up security filters blocking sensitive paths and parameters
• Optimize cache hit ratio through strategic caching configuration

Domain Knowledge Required

Technical Foundation

• Apache HTTP Server module architecture and configuration
• HTTP caching semantics (Cache-Control, Expires, ETag, Last-Modified)
• URL rewriting with mod_rewrite rules and conditions
• Load balancing algorithms and health check patterns

AEM-Specific Context

• Dispatcher module architecture (.any configuration hierarchy)
• Cache invalidation via stat files and auto-invalidation
• Flush agents and their interaction with dispatcher cache
• Dispatcher filter syntax (allow/deny, glob patterns, URL structure)
• Stat file level and its impact on invalidation granularity
• Grace period and serveStaleOnError behavior

Implementation Approach

Step 1: Farm Architecture

Design the dispatcher farm topology.

• Define farms per site/domain (author farm, publish farm(s))
• Configure renders (publish instance connections)
• Set up load balancing with health checks (stickyConnections, healthcheck URL)
• Define virtual hosts and domain routing

Step 2: Cache Configuration

Set up caching rules for optimal hit ratio.

• Define cache root directory and cache headers
• Configure cacheable paths and document types (/cache rules)
• Set stat file level for appropriate invalidation granularity
• Configure grace period for stale content serving during invalidation
• Implement TTL-based caching for API responses

Step 3: Filter Rules

Implement security and access filtering.

• Block access to system paths (/crx, /system, /libs)
• Filter query parameters that shouldn't reach AEM
• Block extension-based attacks (.json, .xml on sensitive paths)
• Allow only required HTTP methods per path
• Implement dispatcher-level CSRF validation

Step 4: URL Management

Configure rewrites and redirects.

• Implement vanity URL resolution
• Configure resource mapping (Sling mapping) integration
• Set up redirect rules for SEO and legacy URL handling
• Handle extension-less URLs and content path mapping

Step 5: Performance Tuning

Optimize dispatcher for high traffic.

• Tune cache hit ratio (target >95% for static, >80% for pages)
• Configure concurrent connections and timeouts
• Implement cache warming strategies
• Set up dispatcher clustering for high availability

Quality Checklist

• Cache hit ratio exceeds 90% for page content
• Security filters block all sensitive AEM paths
• Flush agents correctly invalidate changed content
• Load balancing distributes traffic evenly with failover
• URL rewrites handle all required patterns without loops
• Configuration validated with dispatcher validator tool
• Grace period configured for availability during cache misses
• No query string parameters leak to cache file paths incorrectly

Related Skills

• aem-caching-strategy (overall caching architecture)
• aem-security-access-control (dispatcher security layer)
• aem-replication-publishing (flush agent configuration)

Example Use Cases

1. Multi-Site Dispatcher: Configure a single dispatcher serving 5 domains with site-specific cache rules, shared static asset caching, and per-site filter policies with different security requirements.
2. API Gateway Pattern: Set up dispatcher as API gateway for headless content delivery with TTL-based caching, CORS header injection, and authentication token validation at the edge.
3. Zero-Downtime Deployment: Implement dispatcher-level blue/green deployment support with health-check-based render switching, cache warming of new instances, and automatic failback on health check failure.

Notes

• AEM Cloud Service manages dispatcher config via Cloud Manager — use the SDK dispatcher tools for local validation
• Always validate configuration with dispatcher-sdk-validator before deployment
• Stat file level is the single most impactful cache efficiency setting — set it thoughtfully
• Dispatcher does NOT cache responses with Set-Cookie headers — ensure AEM doesn't set cookies on cacheable responses