Introduce cache.threads option to enable a custom cache executor

Since the introduction of Caffeine as alternative to Guava
in Change 244612, the execution of the cache event listeners moved
to a background thread, run by the ForkJoinPool's common pool [1].

The subtle difference has caused issues to the plugins that are
registering listeners, like the high-availability and multi-site:
the consequences have been quite serious because of the inability
to understand if the eviction was caused by a forwarded cache
eviction event or by an execution of Gerrit API or other internals
that caused the removal of the entry.

The use of the JVM common pool has several disadvantages and, under
certain conditions [2], it may even lead to deadlocks or unexpected

By introducing the cache.threads option, decouple the cache background
threads execution and allow to configure an explicit separate
thread pool which can be tuned and decoupled from the rest of the
JVM common threads.

Also, allow to restore the plugins' cache listeners legacy behaviour
without losing the ability to leverage the performance of Caffeine
cache vs. the traditional Guava.

By default, this change is a NO-OP because it preserves the current
behaviour of background execution tasks of the Caffeine cache.

Introduce DefaultMemoryCacheFactoryTest class from stable-3.4 for
avoiding further conflicts when merging upstream.


Release-Notes: introduce cache.threads option to allow custom executors for Caffeine caches
Bug: Issue 16565
Change-Id: I204abd1bdbf2bbed5b3d982d14cbc5549ac96ace
4 files changed
tree: 9f0833def4540a8f000bacd8fb2f16e39c1ad93a
  1. .settings/
  2. antlr3/
  3. contrib/
  4. Documentation/
  5. e2e-tests/
  6. java/
  7. javatests/
  8. lib/
  9. modules/
  10. plugins/
  11. polygerrit-ui/
  12. prolog/
  13. prologtests/
  14. proto/
  15. resources/
  16. tools/
  17. webapp/
  18. .bazelignore
  19. .bazelproject
  20. .bazelrc
  21. .bazelversion
  22. .editorconfig
  23. .git-blame-ignore-revs
  24. .gitignore
  25. .gitmodules
  26. .gitreview
  27. .mailmap
  28. .pydevproject
  29. .zuul.yaml
  30. BUILD
  33. Jenkinsfile
  34. package.json
  36. rules_nodejs-1.5.patch
  38. version.bzl
  40. yarn.lock

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