feat: graceful shutdown and systemd socket activation in adapter-node

[karimfromjordan]

Closes #10134
Closes #9540

This is an alternative PR to #10977 that addresses all the points mentioned there, mainly:

1. simpler code by allowing only one file descriptor (fd 3)
2. handling the automatic shutdown of the server which is controlled by a new environment variable IDLE_TIMEOUT
3. add documentation

It also gracefully shuts down the app by default. A new SHUTDOWN_TIMEOUT environment variable controls how long the app should wait for all remaining requests to finish before the server is forcibly closed.

If you are on Linux or have access to a Linux server you can try this out yourself by installing the adapter into a new/existing SvelteKit project (requires npm, pnpm doesn't work) using:

npm install -D 'https://gitpkg.now.sh/karimfromjordan/sveltejs-kit/packages/adapter-node?systemd-socket-activation-build'

Then create a service and socket unit:

# /etc/systemd/system/myapp.service

[Service]
Environment=NODE_ENV=production IDLE_TIMEOUT=10
ExecStart=/usr/bin/node /usr/bin/myapp/build

# /etc/systemd/system/myapp.socket

[Socket]
ListenStream=3000

[Install]
WantedBy=sockets.target

Reload the daemon:

sudo systemctl daemon-reload

Start the socket:

sudo systemctl start myapp.socket

Navigate to localhost:3000. The app should then start as soon as the first request is made. If IDLE_TIMEOUT is set it will automatically terminate the app after being inactive for IDLE_TIMEOUT seconds. You can verify this behavior by following the logs using sudo journalctl -u myapp.service -f.

---

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[changeset-bot]

🦋 Changeset detected

Latest commit: d8c8a90

The changes in this PR will be included in the next version bump.

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Name	Type
@sveltejs/adapter-node	Major

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[Rich-Harris]

LGTM but I had one question

[Conduitry]

Thank you for your patience during the protracted review process - let's ship it!

[weepy]

I'm having issues with this - in particular when connecting to a database (mongodb). Out of the box it works fine via "npm run dev", but hangs if I build with adapter-node and run with node.
If I put in some code to close the db connection on SIGINT then it exits ok via adapter-node, but hangs on exit if use "npm run dev"

example code:
function closeMongoConnection() {
    client.close()
}
process.on('SIGINT', closeMongoConnection);
process.on('SIGTERM', closeMongoConnection);

Maybe I'm doing something dumb, but if there some best practice here ?

[karimfromjordan]

Let's please keep the conversation about this in one thread. I've already replied in the other thread and I saw your follow up comment but it can take a few days for me to get back. You can also ask on the Svelte Discord server and ping me there

[benmccann]

Just in case others come across this, here's the other thread: #9540 (comment)