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Managing the Dispatcher Cache

The cmsw or Dispatcher tier of our AEM system is a cache layer that improves overall system performance by:

  • Cacheing rendered pages as plain html files

  • Shifts web serving load from Publishers (Java) to Apache

    • Apache is more efficient at serving static files
    • We can add as many Apache Dispatcher nodes as we need with no licence cost, little infrastructure cost.
    • Licensing additional Publisher instances is in the ballpark of $25,000.

Pruning the Dispatcher Cache

VTOC will gently warn us if the /apps volume on any machine gets above 90% utilization, and will become more assertive (read: page you in the middle of the night) if utilization gets above 96% or so.

Procudure

Script apps/local/VT/scripts/prune-aem-cache.sh will do all the work for you, and write the result in ${HOME}/var/logs/prune-aem-cache.log

In most cases, the default 180 days is reasonable, but you can change if necessary.

Prune AEM cache files

Usage: /apps/local/VT/scripts/prune-aem-cache.sh [options]

Options:
    -d DAYS     Remove files older than DAYS days. [Default 180]
    -v          List removed files. [Default: ]