docker stop doesn't work for node process

Ok, I figured out a workaround myself, which I'll venture as an answer in the hope it helps others. It doesn't completely answer why the signals weren't working before, but it does give me the behaviour I want.

Using baseimage-docker seems to solve the issue. Here's what I did to get this working with the minimal test example above:

Keep test.js as is.

Modify Dockerfile to look like the following:

FROM phusion/baseimage:0.9.15

# disable SSH
RUN rm -rf /etc/service/sshd /etc/my_init.d/00_regen_ssh_host_keys.sh

# install curl and node as before
RUN apt-get update && apt-get install -y curl
RUN curl -sSL http://nodejs.org/dist/v0.11.14/node-v0.11.14-linux-x64.tar.gz | tar -xzf -

# the baseimage init process
CMD ["/sbin/my_init"]

# create a directory for the runit script and add it
RUN mkdir /etc/service/app
ADD run.sh /etc/service/app/run

# install the application
ADD test.js /

baseimage-docker includes an init process (/sbin/my_init) which handles starting other processes and dealing with zombie processes. It uses runit for service supervision. The Dockerfile therefore sets the my_init process as the command to run on boot, and adds a script /etc/service for runit to pick it up.

The run.sh script is simple:

#!/bin/sh
exec /node-v0.11.14-linux-x64/bin/node /test.js

Don't forget to chmod +x run.sh!

By default, runit will automatically restart the service if it goes down.

Following these steps (and build, run, and stop as before), the container properly responds to requests for it to shutdown, in a timely fashion.