[WIP] lib: added logger api in node core

benchmark/logger/basic-json.js

@@ -0,0 +1,53 @@
+'use strict';
+
+const common = require('../common');
+const { createLogger, JSONHandler } = require('node:logger');
+const fs = require('node:fs');
+
+const bench = common.createBenchmark(main, {
+  n: [1e5],
+  level: ['info', 'debug'],
+  fields: [0, 5],
+  type: ['simple', 'child', 'disabled'],
+});
+
+function main({ n, level, fields, type }) {
+  // Use /dev/null to avoid I/O overhead in benchmarks
+  const nullFd = fs.openSync('/dev/null', 'w');
+  const handler = new JSONHandler({ stream: nullFd, level: 'info' });
+  const logger = createLogger({ handler, level });
+
+  // Create test data based on fields count
+  const logData = { msg: 'benchmark test message' };
+  for (let i = 0; i < fields; i++) {
+    logData[`field${i}`] = `value${i}`;
+  }
+
+  let testLogger;
+  switch (type) {
+    case 'simple':
+      testLogger = logger;
+      break;
+    case 'child':
+      testLogger = logger.child({ requestId: 'bench-123', userId: 456 });
+      break;
+    case 'disabled': {
+      // When level is debug and handler is info, logs will be disabled
+      const nullFd2 = fs.openSync('/dev/null', 'w');
+
+      testLogger = createLogger({
+        handler: new JSONHandler({ stream: nullFd2, level: 'warn' }),
+        level: 'debug',
+      });
+      break;
+    }
+  }
+
+  bench.start();
+  for (let i = 0; i < n; i++) {
+    testLogger.info(logData);
+  }
+  bench.end(n);
+
+  handler.end();
+}

benchmark/logger/vs-pino.js

@@ -0,0 +1,146 @@
+'use strict';
+
+const common = require('../common');
+const fs = require('node:fs');
+
+const bench = common.createBenchmark(main, {
+  n: [1e5],
+  logger: ['node-logger', 'pino'],
+  scenario: ['simple', 'child', 'disabled', 'fields'],
+});
+
+function main({ n, logger, scenario }) {
+  const nullFd = fs.openSync('/dev/null', 'w');
+  let testLogger;
+  let consumer;
+
+  if (logger === 'node-logger') {
+    const { createLogger, JSONConsumer } = require('node:logger');
+
+    switch (scenario) {
+      case 'simple': {
+        consumer = new JSONConsumer({ stream: nullFd, level: 'info' });
+        consumer.attach();
+        testLogger = createLogger({ level: 'info' });
+
+        bench.start();
+        for (let i = 0; i < n; i++) {
+          testLogger.info('benchmark test message');
+        }
+        bench.end(n);
+        break;
+      }
+
+      case 'child': {
+        consumer = new JSONConsumer({ stream: nullFd, level: 'info' });
+        consumer.attach();
+        const baseLogger = createLogger({ level: 'info' });
+        testLogger = baseLogger.child({ requestId: 'req-123', userId: 456 });
+
+        bench.start();
+        for (let i = 0; i < n; i++) {
+          testLogger.info('benchmark test message');
+        }
+        bench.end(n);
+        break;
+      }
+
+      case 'disabled': {
+        consumer = new JSONConsumer({ stream: nullFd, level: 'warn' });
+        consumer.attach();
+        testLogger = createLogger({ level: 'warn' });
+
+        bench.start();
+        for (let i = 0; i < n; i++) {
+          testLogger.debug('benchmark test message');
+        }
+        bench.end(n);
+        break;
+      }
+
+      case 'fields': {
+        consumer = new JSONConsumer({ stream: nullFd, level: 'info' });
+        consumer.attach();
+        testLogger = createLogger({ level: 'info' });
+
+        bench.start();
+        for (let i = 0; i < n; i++) {
+          testLogger.info('benchmark test message', {
+            field1: 'value1',
+            field2: 'value2',
+            field3: 'value3',
+            field4: 'value4',
+            field5: 'value5',
+          });
+        }
+        bench.end(n);
+        break;
+      }
+    }
+
+    if (consumer) {
+      consumer.flushSync();
+    }
+    fs.closeSync(nullFd);
+
+  } else if (logger === 'pino') {
+    const pino = require('pino');
+    const destination = pino.destination({ dest: nullFd, sync: false });
+
+    switch (scenario) {
+      case 'simple': {
+        testLogger = pino({ level: 'info' }, destination);
+
+        bench.start();
+        for (let i = 0; i < n; i++) {
+          testLogger.info('benchmark test message');
+        }
+        bench.end(n);
+        break;
+      }
+
+      case 'child': {
+        const baseLogger = pino({ level: 'info' }, destination);
+        testLogger = baseLogger.child({ requestId: 'req-123', userId: 456 });
+
+        bench.start();
+        for (let i = 0; i < n; i++) {
+          testLogger.info('benchmark test message');
+        }
+        bench.end(n);
+        break;
+      }
+
+      case 'disabled': {
+        testLogger = pino({ level: 'warn' }, destination);
+
+        bench.start();
+        for (let i = 0; i < n; i++) {
+          testLogger.debug('benchmark test message');
+        }
+        bench.end(n);
+        break;
+      }
+
+      case 'fields': {
+        testLogger = pino({ level: 'info' }, destination);
+
+        bench.start();
+        for (let i = 0; i < n; i++) {
+          testLogger.info({
+            msg: 'benchmark test message',
+            field1: 'value1',
+            field2: 'value2',
+            field3: 'value3',
+            field4: 'value4',
+            field5: 'value5',
+          });
+        }
+        bench.end(n);
+        break;
+      }
+    }
+
+    destination.flushSync();
+  }
+}

doc/api/index.md

@@ -65,6 +65,7 @@
 * [UDP/datagram](dgram.md)
 * [URL](url.md)
 * [Utilities](util.md)
+* [Logger](logger.md)
 * [V8](v8.md)
 * [VM](vm.md)
 * [WASI](wasi.md)

doc/api/logger.md

@@ -0,0 +1,40 @@
+# Logger
+
+<!--introduced_in=v26.0.0-->
+
+> Stability: 1 - Experimental
+
+<!-- source_link=lib/logger.js -->
+
+The `node:logger` module provides structured logging capabilities for Node.js
+applications.
+
+## Class: `LogConsumer`
+
+### `consumer.enabled(level)`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `level` {string} The log level to check (e.g., `'debug'`, `'info'`, `'warn'`,
+  `'error'`, `'fatal'`).
+* Returns: {boolean} `true` if the level is enabled, `false` otherwise.
+
+Checks if a specific log level is enabled for this consumer.
+
+This method returns `false` for unknown log levels without throwing an error.
+Log levels are case-sensitive and must be one of the predefined levels:
+`'trace'`, `'debug'`, `'info'`, `'warn'`, `'error'`, `'fatal'`.
+
+```js
+const { LogConsumer } = require('node:logger');
+
+const consumer = new LogConsumer({ level: 'info' });
+
+console.log(consumer.enabled('debug')); // false (below threshold)
+console.log(consumer.enabled('info'));  // true
+console.log(consumer.enabled('error')); // true
+console.log(consumer.enabled('DEBUG')); // false (unknown level - case sensitive)
+console.log(consumer.enabled('unknown')); // false (unknown level)
+```

lib/internal/logger/serializers.js

@@ -0,0 +1,73 @@
+'use strict';
+const { isNativeError } = require('internal/util/types');
+
+/**
+ * Serializes an Error object
+ * @param {Error} error
+ * @returns {object}
+ */
+function serializeErr(error) {
+  if (!isNativeError(error)) {
+    return error;
+  }
+
+  const obj = {
+    type: error.constructor.name,
+    message: error.message,
+    stack: error.stack,
+  };
+
+  // Include additional error properties
+  for (const key in error) {
+    if (obj[key] === undefined) {
+      obj[key] = error[key];
+    }
+  }
+
+  // Handle error code if present
+  if (error.code !== undefined) {
+    obj.code = error.code;
+  }
+
+  // Handle error cause recursively
+  if (error.cause !== undefined) {
+    obj.cause = typeof error.cause === 'object' && error.cause !== null ?
+      serializeErr(error.cause) :
+      error.cause;
+  }
+
+  return obj;
+}
+
+/**
+ * Serializes HTTP request object
+ * @param {object} req - HTTP request
+ * @returns {object}
+ */
+function req(req) {
+  return {
+    method: req.method,
+    url: req.url,
+    headers: req.headers,
+    remoteAddress: req.socket?.remoteAddress,
+    remotePort: req.socket?.remotePort,
+  };
+}
+
+/**
+ * Serializes HTTP response object
+ * @param {object} res - HTTP response
+ * @returns {object}
+ */
+function res(res) {
+  return {
+    statusCode: res.statusCode,
+    headers: res.getHeaders ? res.getHeaders() : res.headers,
+  };
+}
+
+module.exports = {
+  err: serializeErr,
+  req,
+  res,
+};