adapter-node: systemd socket activation support

[lucasew]

Describe the problem

When running on premise, by default the application is running all the time and if it's not used often then you are always paying the cost to keep it running. Lambda services scale to zero if there is no activity for more than x minutes, and this is achievable with systemd socket activation if the programs are prepared for this.

Describe the proposed solution

Allow users to setup socket activation by passing PORT=systemd to the NodeJS bundle, or by checking for LISTEN_FDS.

Alternatives considered

Keep the application running all the time. Wasteful but doable.

Not running on premise is also an alternative.

Importance

would make my life easier

Additional Information

Documentation from systemd: https://www.freedesktop.org/software/systemd/man/systemd-socket-activate.html

This post has definitely better didactics than me in this case xD

https://rocketeer.be/articles/deploying-node-js-with-systemd/

I can do this, but I need to study the specifics of polka before that, someone else can get this more quickly.

[Rich-Harris]

adapter-node allows you to create custom servers to support exactly this sort of advanced use case — would that work?