'yarn run' does not forward SIGTERM to process

[frank-weindel]

When running an application via 'yarn run' and a SIGTERM is signaled on it, yarn does not forward the SIGTERM to its child process(es). Hence an application's graceful shutdown code cannot run.

[bestander]

Send a PR :)

[GAumala]

Does yarn even handle SIGTERM? if so, where? It would have to keep a reference to every child process and call child.kill() on every one of them when SIGTERM is received.

[bestander]

@GAumala, would you send a PR?
The code is here https://github.com/yarnpkg/yarn/blob/master/src/util/execute-lifecycle-script.js

[GAumala]

I'd love to give it a shot, but I have some questions.

So execCommand is in execute-lifecycle-script.js, and then that function eventually calls spawn() in child.js, which uses Node's API for spawning child processes. A reference to the child process is needed to call kill(), but spawn() only returns the process STDOUT. So there are two options:

• Make spawn() return a reference to the child process instead of STDOUT. The child process object is then passed to whatever signal handler yarn has.
• Make spawn() attach a SIGTERM listener to the global process object in which child.kill() is executed. If yarn already handles SIGTERM somewhere else, that behavior will be overriden.

Does yarn already have a SIGTERM handler? Which choice should I use?

[OmgImAlexis]

@frank-weindel can you update the OP as this is an issue with yarn x as well as yarn run x.

[bestander]

@GAumala, sorry for a delay.

I don't think yarn has a SIGTERM handler except for onDeath() callback when Yarn is executed in mutex mode https://github.com/yarnpkg/yarn/blob/master/src/cli/index.js#L232.

I think returning reference should be a cleaner solution rather than attaching to global process.