lib: added logger api in node core

benchmark/logger/basic-json.js

@@ -0,0 +1,174 @@
+'use strict';
+
+const common = require('../common');
+const fs = require('node:fs');
+
+const bench = common.createBenchmark(main, {
+  n: [1e5],
+  scenario: [
+    'string-short',
+    'string-long',
+    'object-simple',
+    'object-nested',
+    'object-array',
+    'object-mixed',
+    'child-logger',
+    'disabled-level',
+    'error-object',
+  ],
+});
+
+function main({ n, scenario }) {
+  const { Logger, JSONConsumer } = require('node:logger');
+
+  const nullFd = fs.openSync('/dev/null', 'w');
+  const consumer = new JSONConsumer({ stream: nullFd, level: 'info' });
+  consumer.attach();
+
+  const logger = new Logger({ level: 'info' });
+
+  switch (scenario) {
+    case 'string-short': {
+      // Simple short string message
+      bench.start();
+      for (let i = 0; i < n; i++) {
+        logger.info('hello');
+      }
+      bench.end(n);
+      break;
+    }
+
+    case 'string-long': {
+      // Long string message (100 chars)
+      const longMsg = 'This is a much longer log message that contains ' +
+        'more text to serialize and process during logging operations';
+      bench.start();
+      for (let i = 0; i < n; i++) {
+        logger.info(longMsg);
+      }
+      bench.end(n);
+      break;
+    }
+
+    case 'object-simple': {
+      // Object with msg and a few string fields
+      bench.start();
+      for (let i = 0; i < n; i++) {
+        logger.info({
+          msg: 'user action',
+          userId: 'user-123',
+          action: 'login',
+        });
+      }
+      bench.end(n);
+      break;
+    }
+
+    case 'object-nested': {
+      // Object with nested structure
+      bench.start();
+      for (let i = 0; i < n; i++) {
+        logger.info({
+          msg: 'request completed',
+          request: {
+            method: 'POST',
+            path: '/api/users',
+            headers: {
+              'content-type': 'application/json',
+              'user-agent': 'Mozilla/5.0',
+            },
+          },
+          response: {
+            statusCode: 200,
+            body: { success: true },
+          },
+        });
+      }
+      bench.end(n);
+      break;
+    }
+
+    case 'object-array': {
+      // Object with array fields
+      const tags = ['web', 'api', 'auth', 'production'];
+      const ids = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+      bench.start();
+      for (let i = 0; i < n; i++) {
+        logger.info({
+          msg: 'batch operation',
+          tags,
+          processedIds: ids,
+          results: ['success', 'success', 'failed', 'success'],
+        });
+      }
+      bench.end(n);
+      break;
+    }
+
+    case 'object-mixed': {
+      // Mixed types: strings, numbers, booleans, null
+      bench.start();
+      for (let i = 0; i < n; i++) {
+        logger.info({
+          msg: 'mixed data',
+          stringField: 'value',
+          numberField: 42,
+          floatField: 3.14159,
+          booleanField: true,
+          nullField: null,
+          timestamp: 1704067200000,
+        });
+      }
+      bench.end(n);
+      break;
+    }
+
+    case 'child-logger': {
+      // Child logger with pre-bound context
+      const childLogger = logger.child({
+        service: 'api',
+        version: '1.0.0',
+        env: 'production',
+      });
+      bench.start();
+      for (let i = 0; i < n; i++) {
+        childLogger.info({
+          msg: 'request',
+          requestId: 'req-123',
+          duration: 150,
+        });
+      }
+      bench.end(n);
+      break;
+    }
+
+    case 'disabled-level': {
+      // Logging at disabled level (debug when level is info)
+      bench.start();
+      for (let i = 0; i < n; i++) {
+        logger.debug('this will be skipped');
+      }
+      bench.end(n);
+      break;
+    }
+
+    case 'error-object': {
+      // Logging with Error object
+      const error = new Error('Something went wrong');
+      error.code = 'ERR_SOMETHING';
+      bench.start();
+      for (let i = 0; i < n; i++) {
+        logger.error({
+          msg: 'operation failed',
+          err: error,
+          operation: 'database-query',
+        });
+      }
+      bench.end(n);
+      break;
+    }
+  }
+
+  consumer.flushSync();
+  fs.closeSync(nullFd);
+}

doc/api/cli.md

@@ -1255,6 +1255,17 @@ Specify the `module` containing exported [asynchronous module customization hook
 
 This feature requires `--allow-worker` if used with the [Permission Model][].
 
+### `--experimental-logger`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+> Stability: 1.1 - Active Development
+
+Enable the experimental `node:logger` module for structured logging.
+See the [Logger][] documentation for more details.
+
 ### `--experimental-network-inspection`
 
 <!-- YAML
@@ -3701,6 +3712,7 @@ one is included in the list below.
 * `--experimental-import-meta-resolve`
 * `--experimental-json-modules`
 * `--experimental-loader`
+* `--experimental-logger`
 * `--experimental-modules`
 * `--experimental-print-required-tla`
 * `--experimental-quic`
@@ -4294,6 +4306,7 @@ node --stack-trace-limit=12 -p -e "Error.stackTraceLimit" # prints 12
 [ExperimentalWarning: `vm.measureMemory` is an experimental feature]: vm.md#vmmeasurememoryoptions
 [File System Permissions]: permissions.md#file-system-permissions
 [Loading ECMAScript modules using `require()`]: modules.md#loading-ecmascript-modules-using-require
+[Logger]: logger.md
 [Module resolution and loading]: packages.md#module-resolution-and-loading
 [Navigator API]: globals.md#navigator
 [Node.js issue tracker]: https://github.com/nodejs/node/issues

doc/api/diagnostics_channel.md

@@ -1559,6 +1559,37 @@ passed to `console.warn()`.
 Emitted when `console.error()` is called. Receives and array of the arguments
 passed to `console.error()`.
 
+#### Logger
+
+> Stability: 1.1 - Active Development
+
+Published by the [`node:logger`][] module. Each log level has its own channel,
+allowing subscribers to filter by severity without matching on record contents.
+
+##### Event: `'log:trace'`
+
+* `record` {Object} Log record emitted at the `trace` level.
+
+##### Event: `'log:debug'`
+
+* `record` {Object} Log record emitted at the `debug` level.
+
+##### Event: `'log:info'`
+
+* `record` {Object} Log record emitted at the `info` level.
+
+##### Event: `'log:warn'`
+
+* `record` {Object} Log record emitted at the `warn` level.
+
+##### Event: `'log:error'`
+
+* `record` {Object} Log record emitted at the `error` level.
+
+##### Event: `'log:fatal'`
+
+* `record` {Object} Log record emitted at the `fatal` level.
+
 #### HTTP
 
 > Stability: 1 - Experimental
@@ -1934,6 +1965,7 @@ Emitted when a new thread is created.
 [`error` event]: #errorevent
 [`locks.request()`]: worker_threads.md#locksrequestname-options-callback
 [`net.Server.listen()`]: net.md#serverlisten
+[`node:logger`]: logger.md
 [`process.execve()`]: process.md#processexecvefile-args-env
 [`start` event]: #startevent
 [`worker_threads.locks`]: worker_threads.md#worker_threadslocks

doc/api/index.md

@@ -64,6 +64,7 @@
 * [UDP/datagram](dgram.md)
 * [URL](url.md)
 * [Utilities](util.md)
+* [Logger](logger.md)
 * [V8](v8.md)
 * [VM](vm.md)
 * [WASI](wasi.md)