trace_events: adds a new trace_events api

Removes the requirement to use `--trace-events-enabled` to enable
trace events. Tracing is enabled automatically if there are any
enabled categories.

Adds a new `trace_events` module with an API for enabling/disabling
trace events at runtime without a command line flag.

```js
const trace_events = require('trace_events');
const categories = [ 'node.perf', 'node.async_hooks' ];
const tracing = trace_events.createTracing({ categories });
tracing.enable();
// do stuff
tracing.disable();
```

Multiple `Tracing` objects may exist and be enabled at any point
in time. The enabled trace event categories is the union of all
enabled `Tracing` objects and the `--trace-event-categories`
flag.

PR-URL: https://github.com/nodejs/node/pull/19803
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/test/common/index.js b/test/common/index.js
index eaae0b53ac..7df3907f0e 100644
--- a/test/common/index.js
+++ b/test/common/index.js
@@ -30,6 +30,7 @@ const { exec, execSync, spawn, spawnSync } = require('child_process');
 const stream = require('stream');
 const util = require('util');
 const Timer = process.binding('timer_wrap').Timer;
+const { hasTracing } = process.binding('config');
 const { fixturesDir } = require('./fixtures');
 const tmpdir = require('./tmpdir');
 
@@ -201,6 +202,12 @@ Object.defineProperty(exports, 'hasCrypto', {
   }
 });
 
+Object.defineProperty(exports, 'hasTracing', {
+  get: function() {
+    return Boolean(hasTracing);
+  }
+});
+
 Object.defineProperty(exports, 'hasFipsCrypto', {
   get: function() {
     return exports.hasCrypto && require('crypto').fips;