Optimize overall speed through parallelization, smarter ordering and other means:

1. faster start to debug ready
2. faster shutdown => this is critical for VS code debug stop which only gets very minimal time

Specific improvements:

• startup: avoid reading namespace list if not in wskprops, use from initial action GET

• startup: create backup action in parallel when debugger is already ready (this takes a lot of time for larger actions, depending on the openwhisk server, 1-10 sec), but has some risks if wskdebug gets killed quickly after being ready

• startup: parallelize container start and action code GET, this can save ~0.5 to 1 seconds (startup time of container, assuming that's slower than fetching the action code)

• startup: find ways to make agent installation faster (zip?), currently at 0.5 to 0.6 seconds for concurrency agent

  • unfortunately openhiwsk REST API does not support gzip encoding for header
  • unfortunately zipping it does not seem to be faster, even though 2 KB zipped vs. 4 KB js sources for agent-concurrency.js

• startup: move docker info check at start (OpenWhiskInvoker.checkIfAvailable()) out of critical path (saves 100-200ms)

• shutdown: keep action code in memory and use that on restore instead of reading it again from the backup action with another slow request (can be multiple seconds for larger actions, 4 sec for 1 MB)

• shutdown: 1. restore action, 2. stop container, 3. remove helper actions (more of a robustness improvement) not necessary since below was done

• shutdown: consider leaving helper actions behind to avoid delete cost??? (2-4 sec)
  for a ~1MB zip action:

   Shutting down...
   wskdebug restore: restored action with original (move step 2) +4s
   wskdebug restore: deleted backup copy (move step 3) +3s
   wskdebug restore: ensured removal of action worker-zip_wskdebug_invoked +355ms
   wskdebug restore: ensured removal of action worker-zip_wskdebug_completed +373ms
   wskdebug stopped container: wskdebug-worker-zip-1586825522274 +329ms
   wskdebug stopped source file watching +0ms
   Done (shutdown took 8.3s)