Modes - csmig/stigman-watcher GitHub Wiki

STIG Manager Watcher implements two strategies, or modes, for discovering files under the watched path. The desired mode is set by the --mode option or the WATCHER_MODE environment variable.

Filesystem events (--mode events)

This mode depends on the underlying operating system providing a way to be notified of filesystem changes under --path. This varies by OS:

OS Technique
Linux inotify
OS X kqueue
Solaris event ports
Windows ReadDirectoryChangesW

Advantages

  • Very fast detection of added files (if well resourced, see Disadvantages)
  • Will process the same filename across delete/add cycles

Disadvantages

  • Resource limits.
    • In Windows, ReadDirectryChangesW is hard-coded by Microsoft to monitor a maximum of 64 directories per thread. Node.js is single-threaded.
    • In Linux/OS X, larger tress can be monitored but OS resources need to be allocated.
  • System utilization low-water mark is higher than --mode scan
  • Will not process files added between executions

Path scanning (--mode scan)

This mode scans the --path every--scan-interval milliseconds for files with extension .ckl or .xml. Each discovered file is passed to the parsing component, where it is processed asynchronously and potentially passed into the cargo queue.

Advantages

  • System utilization low-water mark is very low. Processor load is negligible between scans.
  • Can scan very large trees
  • Can process files added between executions while ignoring previously processed files, via --history-file <file>.

Disadvantages

  • Slower detection of added files
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