Test out scenarios with Node.js async hooks

test-async-hooks.js

/**
 * Test how async hooks works in various scenarios.
 * 
 * Call `hook.enable()` to start tracking async resources and `hook.disable()`
 * to stop or pause tracking. Then use `logAndResetHooks()` to print a log of
 * all the creation and destruction of async hooks.
 */

const asyncHooks = require("async_hooks");
const http = require("http");
const util = require("util");

// TOOLING FOR TESTING ASYNC HOOKS -----------------------------------------

let logs = [];
function log(...args) {
  logs.push(`${util.format(...args)}`);
}

class ErrorWithStack extends Error {
  constructor(message, callsite) {
    // Ensure we have a large stack length so we get full details.
    const stackLimit = Error.stackTraceLimit;
    Error.stackTraceLimit = Math.max(100, stackLimit || 10);

    super(message);
    if (Error.captureStackTrace) {
      Error.captureStackTrace(this, callsite);
    }

    Error.stackTraceLimit = stackLimit;
  }
}

const noStack = new Set(["TickObject", "Immediate"])
const handles = new Map();
const hook = asyncHooks.createHook({
  init: function initHook (asyncId, type, triggerAsyncId, resource) {
    const error = new ErrorWithStack(type, initHook);
    log(`init ( asyncId: ${asyncId}, type: "${type}", triggerAsyncId: ${triggerAsyncId} )`);
    if (!noStack.has(type)) log("  Stack:", error.stack);
    handles.set(asyncId, { asyncId, type, triggerAsyncId });
  },

  destroy(asyncId) {
    log(`destroy ( asyncId: ${asyncId} )`);
    handles.delete(asyncId);
  },
});

function logAndResetHooks() {
  console.log(logs.join("\n"));
  handles.clear();
  logs = [];
}

// ACTUAL TEST SCENARIOS --------------------------------------------------
const respondWithOk = (_, response) => response.end("ok");

// 1. `server.listen` with just a port creates TCPSERVERWRAP directly.
function userCode1 (done) {
  hook.enable();
  const server = http.createServer(respondWithOk);
  server.listen(0, () => {
    // Wait until after the server.listen callback is completed to stop hooks.
    setImmediate(() => {
      // Disable before closing the server to simulate a server left running
      hook.disable();
      server.close();

      logAndResetHooks();
      if (done) done();
    });
  });
}

// 2. `server.listen` with a host creates GETADDRINFOREQWRAP directly and
//    TCPSERVERWRAP indirectly.
function userCode2 (done) {
  hook.enable();
  const server = http.createServer(respondWithOk);
  server.listen({host: "localhost", port: 0}, () => {
    // Wait until after the server.listen callback is completed to stop hooks.
    setImmediate(() => {
      // Disable before closing the server to simulate a server left running
      hook.disable();
      server.close();
      
      logAndResetHooks();
      if (done) done();
    });
  });
}

// Run these!
console.log("TEST 1: `server.listen` with just a port");
console.log("----------------------------------------")
userCode1(() => {
  console.log("\n\n\n");
  console.log("TEST 2: `server.listen` with a host option");
  console.log("------------------------------------------")

  userCode2();
});