test: make test-perf-hooks more robust and work with workers

Previously the test makes several assumptions about the absolute
values of the nodeTiming fields, which can make the test flaky
on slow machines. This patch rewrites the test to check the
relative values instead. It also updates the test to make it
work with workers instead of directly skipping in workers.

PR-URL: #49197
Refs: nodejs/reliability#638
Reviewed-By: Debadree Chatterjee <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>

test/sequential/test-perf-hooks.js

@@ -1,84 +1,165 @@
 'use strict';
 
 const common = require('../common');
-const assert = require('assert');
 const { performance } = require('perf_hooks');
+// Get the start time as soon as possible.
+const testStartTime = performance.now();
+const assert = require('assert');
+const { writeSync } = require('fs');
 
-if (!common.isMainThread)
-  common.skip('bootstrapping workers works differently');
+// Use writeSync to stdout to avoid disturbing the loop.
+function log(str) {
+  writeSync(1, str + '\n');
+}
 
 assert(performance);
 assert(performance.nodeTiming);
 assert.strictEqual(typeof performance.timeOrigin, 'number');
+
+assert(testStartTime > 0, `${testStartTime} <= 0`);
 // Use a fairly large epsilon value, since we can only guarantee that the node
 // process started up in 15 seconds.
-assert(Math.abs(performance.timeOrigin - Date.now()) < 15000);
+assert(testStartTime < 15000, `${testStartTime} >= 15000`);
 
-const inited = performance.now();
-assert(inited < 15000);
+// Use different ways to calculate process uptime to check that
+// performance.timeOrigin and performance.now() are in reasonable range.
+const epsilon = 50;
+{
+  const uptime1 = Date.now() - performance.timeOrigin;
+  const uptime2 = performance.now();
+  const uptime3 = process.uptime() * 1000;
+  assert(Math.abs(uptime1 - uptime2) < epsilon,
+         `Date.now() - performance.timeOrigin (${uptime1}) - ` +
+         `performance.now() (${uptime2}) = ` +
+         `${uptime1 - uptime2} >= +- ${epsilon}`);
+  assert(Math.abs(uptime1 - uptime3) < epsilon,
+         `Date.now() - performance.timeOrigin (${uptime1}) - ` +
+         `process.uptime() * 1000 (${uptime3}) = ` +
+         `${uptime1 - uptime3} >= +- ${epsilon}`);
+}
 
 assert.strictEqual(performance.nodeTiming.name, 'node');
 assert.strictEqual(performance.nodeTiming.entryType, 'node');
 
-const delay = 250;
-function checkNodeTiming(props) {
-  console.log(props);
-
-  for (const prop of Object.keys(props)) {
-    if (props[prop].around !== undefined) {
-      assert.strictEqual(typeof performance.nodeTiming[prop], 'number');
-      const delta = performance.nodeTiming[prop] - props[prop].around;
-      assert(
-        Math.abs(delta) < (props[prop].delay || delay),
-        `${prop}: ${Math.abs(delta)} >= ${props[prop].delay || delay}`
-      );
-    } else {
-      assert.strictEqual(performance.nodeTiming[prop], props[prop],
-                         `mismatch for performance property ${prop}: ` +
-                         `${performance.nodeTiming[prop]} vs ${props[prop]}`);
-    }
-  }
+// Copy all the values from the getters.
+const initialTiming = { ...performance.nodeTiming };
+
+{
+  const {
+    startTime,
+    nodeStart,
+    v8Start,
+    environment,
+    bootstrapComplete,
+  } = initialTiming;
+
+  assert.strictEqual(startTime, 0);
+  assert.strictEqual(typeof nodeStart, 'number');
+  assert(nodeStart > 0, `nodeStart ${nodeStart} <= 0`);
+  // The whole process starts before this test starts.
+  assert(nodeStart < testStartTime,
+         `nodeStart ${nodeStart} >= ${testStartTime}`);
+
+  assert.strictEqual(typeof v8Start, 'number');
+  assert(v8Start > 0, `v8Start ${v8Start} <= 0`);
+  // V8 starts after the process starts.
+  assert(v8Start > nodeStart, `v8Start ${v8Start} <= ${nodeStart}`);
+  // V8 starts before this test starts.
+  assert(v8Start < testStartTime,
+         `v8Start ${v8Start} >= ${testStartTime}`);
+
+  assert.strictEqual(typeof environment, 'number');
+  assert(environment > 0, `environment ${environment} <= 0`);
+  // Environment starts after V8 starts.
+  assert(environment > v8Start,
+         `environment ${environment} <= ${v8Start}`);
+  // Environment starts before this test starts.
+  assert(environment < testStartTime,
+         `environment ${environment} >= ${testStartTime}`);
+
+  assert.strictEqual(typeof bootstrapComplete, 'number');
+  assert(bootstrapComplete > 0, `bootstrapComplete ${bootstrapComplete} <= 0`);
+  // Bootstrap completes after environment starts.
+  assert(bootstrapComplete > environment,
+         `bootstrapComplete ${bootstrapComplete} <= ${environment}`);
+  // Bootstrap completes before this test starts.
+  assert(bootstrapComplete < testStartTime,
+         `bootstrapComplete ${bootstrapComplete} >= ${testStartTime}`);
 }
 
-checkNodeTiming({
-  name: 'node',
-  entryType: 'node',
-  startTime: 0,
-  duration: { around: performance.now() },
-  nodeStart: { around: 0 },
-  v8Start: { around: 0 },
-  bootstrapComplete: { around: inited, delay: 2500 },
-  environment: { around: 0 },
-  loopStart: -1,
-  loopExit: -1
-});
+function checkNodeTiming(timing) {
+  // Calculate the difference between now() and duration as soon as possible.
+  const now = performance.now();
+  const delta = Math.abs(now - timing.duration);
+
+  log(JSON.stringify(timing, null, 2));
+  // Check that the properties are still reasonable.
+  assert.strictEqual(timing.name, 'node');
+  assert.strictEqual(timing.entryType, 'node');
+
+  // Check that duration is positive and practically the same as
+  // performance.now() i.e. measures Node.js instance up time.
+  assert.strictEqual(typeof timing.duration, 'number');
+  assert(timing.duration > 0, `timing.duration ${timing.duration} <= 0`);
+  assert(delta < 10,
+         `now (${now}) - timing.duration (${timing.duration}) = ${delta} >= 10`);
+
+  // Check that the following fields do not change.
+  assert.strictEqual(timing.startTime, initialTiming.startTime);
+  assert.strictEqual(timing.nodeStart, initialTiming.nodeStart);
+  assert.strictEqual(timing.v8Start, initialTiming.v8Start);
+  assert.strictEqual(timing.environment, initialTiming.environment);
+  assert.strictEqual(timing.bootstrapComplete, initialTiming.bootstrapComplete);
+
+  assert.strictEqual(typeof timing.loopStart, 'number');
+  assert.strictEqual(typeof timing.loopExit, 'number');
+}
+
+log('check initial nodeTiming');
+checkNodeTiming(initialTiming);
+assert.strictEqual(initialTiming.loopExit, -1);
 
-setTimeout(() => {
-  checkNodeTiming({
-    name: 'node',
-    entryType: 'node',
-    startTime: 0,
-    duration: { around: performance.now() },
-    nodeStart: { around: 0 },
-    v8Start: { around: 0 },
-    bootstrapComplete: { around: inited, delay: 2500 },
-    environment: { around: 0 },
-    loopStart: { around: inited, delay: 2500 },
-    loopExit: -1
-  });
-}, 1000);
+function checkValue(timing, name, min, max) {
+  const value = timing[name];
+  assert(value > 0, `${name} ${value} <= 0`);
+  // Loop starts after bootstrap completes.
+  assert(value > min,
+         `${name} ${value} <= ${min}`);
+  assert(value < max, `${name} ${value} >= ${max}`);
+}
+
+let loopStart = initialTiming.loopStart;
+if (common.isMainThread) {
+  // In the main thread, the loop does not start until we start an operation
+  // that requires it, e.g. setTimeout().
+  assert.strictEqual(initialTiming.loopStart, -1);
+  log('Start timer');
+  setTimeout(() => {
+    log('Check nodeTiming in timer');
+    const timing = { ...performance.nodeTiming };
+    checkNodeTiming(timing);
+    // Loop should start after we fire the timeout, and before we call
+    // performance.now() here.
+    loopStart = timing.loopStart;
+    checkValue(timing, 'loopStart', initialTiming.duration, performance.now());
+  }, 1000);
+} else {
+  // In the worker, the loop always starts before the user code is evaluated,
+  // and after bootstrap completes.
+  checkValue(initialTiming,
+             'loopStart',
+             initialTiming.bootstrapComplete,
+             testStartTime);
+}
 
 process.on('exit', () => {
-  checkNodeTiming({
-    name: 'node',
-    entryType: 'node',
-    startTime: 0,
-    duration: { around: performance.now() },
-    nodeStart: { around: 0 },
-    v8Start: { around: 0 },
-    bootstrapComplete: { around: inited, delay: 2500 },
-    environment: { around: 0 },
-    loopStart: { around: inited, delay: 2500 },
-    loopExit: { around: performance.now() }
-  });
+  log('Check nodeTiming in process exit event');
+  const timing = { ...performance.nodeTiming };
+  checkNodeTiming(timing);
+  // Check that loopStart does not change.
+  assert.strictEqual(timing.loopStart, loopStart);
+  checkValue(timing,
+             'loopExit',
+             loopStart,
+             performance.now());
 });