Deno and Docker how to listen for the SIGTERM signal and close the server

Question

I'm trying to find a way to listen in Deno for the Docker SIGTERM signal to close my Oak server. I got this code from Oak website and it works fine when I call the controller.abort() function, using setTimeout or an end-point. However, I want to call it when I got a SIGTERM signal from Docker and I cannot figure out how to listen for it.

const controller = new AbortController();
const app = new Application();

app.addEventListener("listen", ({ hostname, port }) => {
  console.log(
    bold("Start listening on ") + yellow(`${hostname}:${port}`),
  );
});

// Utilise the signal from the controller
const { signal } = controller;
await app.listen({ hostname: "127.0.0.1", port: 8000, signal });
console.log(bold("Finished."));

I try to use this code from Deno GitHub discussions but also did not work

(() => {
  for await (const _ of Deno.signal(Deno.Signal.SIGINT)) {
    console.log("interrupt signal")
  }
})()
(() => {
  for await (const _ of Deno.signal(Deno.Signal.SIGQUIT)) {
    console.log("quit signal")
  }
})()
(() => {
  for await (const _ of Deno.signal(Deno.Signal.SIGTERM)) {
    console.log("terminate signal")
  }
})()

I don't see either the logs and abort does not get called

Answer 1

Your direction is right but you can simplify your solution.

Example of my application server handler. I am using Opine but it can be adapted by pasting anywhere into your server initialisation. You can try plug it into listener as well.

const handle = onSignal(Deno.Signal.SIGTERM, () => {
  mongoConnector.close()
  handle.dispose()
})

Reference to Signals Deno STD documentation.

Answer 2

Came across this while looking into the same thing! There's a relatively new unstable feature for adding listeners with addSignalListener.

A working example for Oak:

import { Application } from "https://deno.land/x/oak/mod.ts";

const controller = new AbortController();
const app = new Application();

app.use(() => void console.log('hello!'));
app.listen({port: 8080, signal: controller.signal});

Deno.addSignalListener('SIGTERM', () => {
  console.log('Aborting for SIGTERM')
  controller.abort();
});

Deno.addSignalListener('SIGINT', () => {
  console.log('Aborting for SIGINT')
  controller.abort();
});

Can be run with deno run --unstable --allow-net <file>.ts.