trace_events: add node.promises category, rejection counter

Allow the trace event log to include a count of unhandled rejections
and handled after rejections. This is useful primarily as a quick
check to see if rejections may be going unhandled (and unnoticed
in a process).

PR-URL: https://github.com/nodejs/node/pull/22124
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/test/parallel/test-trace-event-promises.js b/test/parallel/test-trace-event-promises.js
new file mode 100644
index 0000000000..69d35f25ec
--- /dev/null
+++ b/test/parallel/test-trace-event-promises.js
@@ -0,0 +1,48 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cp = require('child_process');
+const path = require('path');
+const fs = require('fs');
+const tmpdir = require('../common/tmpdir');
+
+common.disableCrashOnUnhandledRejection();
+
+if (!common.isMainThread)
+  common.skip('process.chdir is not available in Workers');
+
+if (process.argv[2] === 'child') {
+  const p = Promise.reject(1);  // Handled later
+  Promise.reject(2);  // Unhandled
+  setImmediate(() => {
+    p.catch(() => { /* intentional noop */ });
+  });
+} else {
+  tmpdir.refresh();
+  process.chdir(tmpdir.path);
+
+  const proc = cp.fork(__filename,
+                       [ 'child' ], {
+                         execArgv: [
+                           '--no-warnings',
+                           '--trace-event-categories',
+                           'node.promises.rejections'
+                         ]
+                       });
+
+  proc.once('exit', common.mustCall(() => {
+    const file = path.join(tmpdir.path, 'node_trace.1.log');
+
+    assert(common.fileExists(file));
+    fs.readFile(file, common.mustCall((err, data) => {
+      const traces = JSON.parse(data.toString()).traceEvents
+        .filter((trace) => trace.cat !== '__metadata');
+      traces.forEach((trace) => {
+        assert.strictEqual(trace.pid, proc.pid);
+        assert.strictEqual(trace.name, 'rejections');
+        assert(trace.args.unhandled <= 2);
+        assert(trace.args.handledAfter <= 1);
+      });
+    }));
+  }));
+}