RFR: 1478: Add metrics and loggin measuring time before WorkItems start to run

Tue Jun 14 14:08:09 UTC 2022

In order to investigate and assess performance issues with the Skara bots, I need more data. One key class of data I'm missing is the time it takes from when a WorkItem is created or submitted to when it actually starts to run. This patch adds both metric gauges and log messages that include this information.

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Commit messages:
 - SKARA-1478

Changes: https://git.openjdk.org/skara/pull/1337/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1337&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1478
  Stats: 59 lines in 1 file changed: 39 ins; 1 del; 19 mod
  Patch: https://git.openjdk.org/skara/pull/1337.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1337/head:pull/1337

PR: https://git.openjdk.org/skara/pull/1337