The 0x tool mentioned in ENG-5078 does not work with `node:cluster`. We can modify keyserver.js to launch a single process when `KEYSERVER_PROFILING_ENABLED` is set. This is what I did in my personal dev environment to get 0x working.
Basically if `KEYSERVER_PROFILING_ENABLED` is set, we avoid `cluster.fork()`ing and just "spill" into the else block that would usually only be executed by child processes (`cpid == 0`). Previous `cluster` `fork()`ing logic continues to work as expected when `KEYSERVER_PROFILING_ENABLED` is unset.
> Will users have to set `KEYSERVER_PROFILING_ENABLED` in their environment manually?
The `yarn` command for profiling will begin with `KEYSERVER=true KEYSERVER_PROFILING_ENABLED=true node...` to make this config "invisible" to the dev. As long as they run `yarn profile-*` things will work as expected.
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Depends on D9300