Docker graceful shutdown on VM stop with GCE/Docker - docker

Question

I'd like to shutdown my docker app when the GCE VM stops.
I use a docker image on GCE:
FROM node:16-alpine
RUN apk add --no-cache tini
ENTRYPOINT ["/sbin/tini", "--"]
WORKDIR /usr/src/app
COPY dist/fetcher.js ./
CMD [ "node", "fetcher.js" ]
fetcher.js is:
console.log('## start');
setInterval(() => console.log('tick'), 10 * 1000);
for (const signal of ['SIGTERM', 'SIGINT', 'SIGHUP']) {
process.on(signal, async (signal) => {
console.info(`Got ${signal}. Graceful shutdown start at ${Date().toString()}`);
process.exit();
});
}
Locally I can see the log message when using docker kill -s 1 <container>:
## start
tick
tick
tick
Got SIGHUP. Graceful shutdown start at Mon Jan 03 2022 04:39:53 GMT+0000 (Coordinated Universal Time)
It works well when I SSH into the VM and run the same command (docker kill -s 1 <container>).
However I can not see the log when I stop the VM:
tick
...
tick
methodName: "v1.compute.instances.stop"
For some reason the signal handler does not seem to be executed.
I have tried different things:
with and without tini,
writing a file to google storage in the signal handle (in case the problem is the log).
But none of this works.
Any help would be appreciated.

Answer 1

I agree with #John Hanley and would like to add that Stopping an instance causes Compute Engine to send the ACPI Power Off signal to the instance and therefore I believe it is an intended behavior that log processing will be stopped when the shutdown or stopping signal is sent for a GCE VM. Getting the logs from the GCE VM, once the stop signal is processed, is fairly impossible. This could be the reason why you were not receiving further logs.