src: trace_events: support for metadata events

Add support for metadata events. At this point they are added to the
main buffer. Emit a metadata event for the main thread.

PR-URL: https://github.com/nodejs/node/pull/20757
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/test/parallel/test-trace-events-metadata.js b/test/parallel/test-trace-events-metadata.js
new file mode 100644
index 0000000000..f8fcdcfe5b
--- /dev/null
+++ b/test/parallel/test-trace-events-metadata.js
@@ -0,0 +1,26 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cp = require('child_process');
+const fs = require('fs');
+
+const CODE =
+  'setTimeout(() => { for (var i = 0; i < 100000; i++) { "test" + i } }, 1)';
+const FILE_NAME = 'node_trace.1.log';
+
+const tmpdir = require('../common/tmpdir');
+tmpdir.refresh();
+process.chdir(tmpdir.path);
+
+const proc = cp.spawn(process.execPath,
+                      [ '--trace-events-enabled', '-e', CODE ]);
+proc.once('exit', common.mustCall(() => {
+  assert(common.fileExists(FILE_NAME));
+  fs.readFile(FILE_NAME, common.mustCall((err, data) => {
+    const traces = JSON.parse(data.toString()).traceEvents;
+    assert(traces.length > 0);
+    assert(traces.some((trace) =>
+      trace.cat === '__metadata' && trace.name === 'thread_name' &&
+        trace.args.name === 'JavaScriptMainThread'));
+  }));
+}));