[Bug] Unable to catch signals using Docker

[DRoet]

• I'd be willing to implement a fix

Describe the bug

To perform a graceful shutdown of containers we need a way to catch the signals (SIGTERM/SIGINT) that Docker sends when shutting down a container. In yarn v1 the workaround was to use node <script> directly instead of yarn run. However I can't seem to get this to work using yarn node <script> or yarn run in v2 with PnP enabled.

To Reproduce

Use a minimal Dockerfile:

FROM node:12.18.3

WORKDIR /opt/app

COPY . /opt/app

RUN yarn install

CMD ["yarn", "node", "./src"]

Inside src/index.js, listen for signals

const signals = [SIGHUP, SIGINT, SIGTERM]
for (const signal of signals) {
   process.on(signal, () => {
      console.log(`process received a ${signal} signal`)
   })
}

Then when the container kill it using:

docker kill -s SIGTERM <container name>

Environment if relevant (please complete the following information):

• OS: Docker
• Node version 12.18.3
• Yarn version 2.1.1

Additional context

I also tried using docker-init/tini to play around the PID 1 restriction after reading #991 but that doesn't seem to work either. It would be nice if there is some way to forward signals to the child processes so that yarn v2 works nicely with Docker.

[merceyz]

As a workaround you can use

node -r ./.pnp.js ./src

[arcanis]

Can you try master (yarn set version from sources)? Should be fixed with #1622

[DRoet]

@arcanis hmm no unfortunately it still doesn't work using master (2.1.1-git.20200822.133f4025)

[arcanis]

I confused it with #991, which you mentioned in your post, sorry. I think we intended to forward the signals, but it slipped past our radar after the issue got closed. If you're interested to add this logic, I'd be happy to review that. It shouldn't be too hard, there are only two places where we spawn child processes:

https://github.com/yarnpkg/berry/search?q=siginthandler&unscoped_q=siginthandler

[kevin-lindsay-1]

Was this ever fixed? I'm using yarn node ./script.js and I'm not seeing SIGTERM, but when I run node -r ./.pnp.cjs ./script.js it works. Wish the docs would have mentioned this if it was never fixed.

[merceyz]

Yes, see #2347 (comment)

[kevin-lindsay-1]

@merceyz so then, no, it wasn't fixed? That, or it's not planned to be fixed.

[merceyz]

Not sure how you interpreted my "Yes" to mean "no" but to be specific:
The issue was fixed and released in 3.0.0 and 1.22.11, your global and local Yarn version must satisfy ^1.22.11 || >= 3.0.0

[kevin-lindsay-1]

@merceyz I interpreted it as "no" because you pointed me to a specific comment that doesn't say it's fixed, it calls out a workaround, and the comments afterwards state they're still having issues. /shrug

[merceyz]

It was this part of that comment that was of interest

If you use yarn 1 to spawn yarn 2, note that bumping just v2 to sources isn't enough, because v1 has the same problem:
yarnpkg/yarn#8543

Following that leads you to yarnpkg/yarn#8543 (comment)

[kevin-lindsay-1]

@merceyz ah, I see. I looked at the docker image from node, and yeah it uses v1.22.5, so that was my issue. Thanks!

[bertho-zero]

@merceyz I have this issue with Yarn v4.0.0 + Yarn 1.22.19

edit: I'm using yarn workspace <package> <script> and I'm not getting the signal