feat(logging, ai): add log capture with native transport injection

docs/API.md

@@ -492,6 +492,38 @@ The Datadog SDK supports many of the configurations supported by the OpenTelemet
 
 For complete OTLP exporter configuration options, see the [OpenTelemetry OTLP Exporter documentation](https://opentelemetry.io/docs/languages/sdk-configuration/otlp-exporter/).
 
+<h3 id="log-capture">Log Capture</h3>
+
+dd-trace-js includes experimental support for automatic log capture via native transport injection. When enabled, the tracer automatically attaches an HTTP transport to Winston, Bunyan, and Pino loggers at creation time, forwarding log records to a configurable HTTP intake endpoint without any changes to application code.
+
+Enable by setting `DD_LOG_CAPTURE_ENABLED=true` and `DD_LOG_CAPTURE_METHOD=transport` along with a target host and port:
+
+```javascript
+const tracer = require('dd-trace').init({
+  logCaptureEnabled: true,
+  logCaptureMethod: 'transport',
+  logCaptureHost: 'localhost',
+  logCapturePort: 8080,
+})
+
+// Existing loggers are automatically instrumented — no changes needed
+const winston = require('winston')
+const logger = winston.createLogger({ level: 'debug' })
+logger.info('This log is forwarded to the intake endpoint automatically')
+```
+
+#### Supported Configuration
+
+- `DD_LOG_CAPTURE_ENABLED` - Enable log capture (default: `false`)
+- `DD_LOG_CAPTURE_METHOD` - Log capture method. Set to `transport` to enable native transport injection (default: `wrapper`)
+- `DD_LOG_CAPTURE_HOST` - Hostname of the log intake endpoint (required when transport injection is enabled)
+- `DD_LOG_CAPTURE_PORT` - Port of the log intake endpoint (required when transport injection is enabled)
+- `DD_LOG_CAPTURE_PROTOCOL` - Protocol for the log intake endpoint. Options: `http:`, `https:` (default: `http:`)
+- `DD_LOG_CAPTURE_PATH` - HTTP path for the log intake endpoint (default: `/logs`)
+- `DD_LOG_CAPTURE_FLUSH_INTERVAL_MS` - How often in milliseconds to flush buffered logs (default: `5000`)
+- `DD_LOG_CAPTURE_MAX_BUFFER_SIZE` - Maximum number of log records to buffer before a forced flush (default: `1000`)
+- `DD_LOG_CAPTURE_TIMEOUT_MS` - Timeout in milliseconds for each HTTP request to the intake endpoint (default: `5000`)
+
 <h2 id="advanced-configuration">Advanced Configuration</h2>
 
 <h3 id="tracer-settings">Tracer settings</h3>

index.d.ts

@@ -484,6 +484,69 @@ declare namespace tracer {
      */
     logInjection?: boolean,
 
+    /**
+     * Whether to enable native transport injection for log capture.
+     * When enabled with `logCaptureMethod: 'transport'`, automatically injects
+     * HTTP transports into Winston, Bunyan, and Pino loggers.
+     * @default false
+     * @env DD_LOG_CAPTURE_ENABLED
+     */
+    logCaptureEnabled?: boolean,
+
+    /**
+     * The hostname of the log intake endpoint.
+     * @env DD_LOG_CAPTURE_HOST
+     */
+    logCaptureHost?: string,
+
+    /**
+     * The port of the log intake endpoint.
+     * @env DD_LOG_CAPTURE_PORT
+     */
+    logCapturePort?: number,
+
+    /**
+     * The protocol for the log intake endpoint. Accepts `'http:'` or `'https:'`.
+     * @default 'http:'
+     * @env DD_LOG_CAPTURE_PROTOCOL
+     */
+    logCaptureProtocol?: string,
+
+    /**
+     * The HTTP path for the log intake endpoint.
+     * @default '/logs'
+     * @env DD_LOG_CAPTURE_PATH
+     */
+    logCapturePath?: string,
+
+    /**
+     * How often (in milliseconds) to flush buffered logs to the intake endpoint.
+     * @default 5000
+     * @env DD_LOG_CAPTURE_FLUSH_INTERVAL_MS
+     */
+    logCaptureFlushIntervalMs?: number,
+
+    /**
+     * Maximum number of log records to buffer before a forced flush.
+     * @default 1000
+     * @env DD_LOG_CAPTURE_MAX_BUFFER_SIZE
+     */
+    logCaptureMaxBufferSize?: number,
+
+    /**
+     * Timeout in milliseconds for each HTTP request to the log intake endpoint.
+     * @default 5000
+     * @env DD_LOG_CAPTURE_TIMEOUT_MS
+     */
+    logCaptureTimeoutMs?: number,
+
+    /**
+     * The log capture method. Set to `'transport'` to enable native transport injection.
+     * @default 'wrapper'
+     * @env DD_LOG_CAPTURE_METHOD
+     */
+    logCaptureMethod?: string,
+
     /**
      * Whether to enable startup logs.
      * @default false

integration-tests/network-transport-injection/benchmark-overhead.js

@@ -0,0 +1,166 @@
+#!/usr/bin/env node
+
+/**
+ * Benchmark to measure performance overhead of transport injection
+ * Compares logging performance with and without transport injection
+ */
+
+const { performance } = require('perf_hooks')
+
+// Test configurations
+const NUM_LOGS = 10000
+const WARMUP_LOGS = 1000
+
+console.log('\n=== Transport Injection Performance Benchmark ===\n')
+console.log(`Iterations: ${NUM_LOGS.toLocaleString()}`)
+console.log(`Warmup: ${WARMUP_LOGS.toLocaleString()}\n`)
+
+// Helper to measure performance
+function benchmark(name, fn) {
+  // Warmup
+  for (let i = 0; i < WARMUP_LOGS; i++) {
+    fn()
+  }
+
+  // Force GC if available
+  if (global.gc) global.gc()
+
+  // Actual benchmark
+  const start = performance.now()
+  for (let i = 0; i < NUM_LOGS; i++) {
+    fn()
+  }
+  const end = performance.now()
+
+  const totalMs = end - start
+  const perLogUs = (totalMs * 1000) / NUM_LOGS
+
+  console.log(`${name}:`)
+  console.log(`  Total: ${totalMs.toFixed(2)}ms`)
+  console.log(`  Per-log: ${perLogUs.toFixed(3)}μs`)
+  console.log(`  Rate: ${(NUM_LOGS / (totalMs / 1000)).toFixed(0)} logs/sec`)
+  console.log('')
+
+  return { totalMs, perLogUs }
+}
+
+// ==================== WINSTON ====================
+console.log('--- Winston ---\n')
+
+// Without transport injection
+const winston1 = require('winston')
+const winstonLoggerBaseline = winston1.createLogger({
+  level: 'info',
+  format: winston1.format.json(),
+  transports: [new winston1.transports.Console({ silent: true })]
+})
+
+const winstonBaseline = benchmark('Winston (baseline)', () => {
+  winstonLoggerBaseline.info('test message', { userId: 12345, action: 'test' })
+})
+
+// With transport injection
+process.env.DD_LOG_CAPTURE_ENABLED = 'true'
+process.env.DD_LOG_CAPTURE_METHOD = 'transport'
+process.env.DD_LOG_CAPTURE_HOST = 'localhost'
+process.env.DD_LOG_CAPTURE_PORT = '9999'  // Non-existent server (buffering only)
+process.env.DD_LOG_CAPTURE_FLUSH_INTERVAL_MS = '999999'  // Very long (no flushing during test)
+process.env.DD_LOGS_INJECTION = 'true'
+
+require('../../index').init({
+  service: 'benchmark-test',
+  env: 'test',
+  version: '1.0.0'
+})
+
+const winston2 = require('winston')
+const winstonLoggerWithTransport = winston2.createLogger({
+  level: 'info',
+  format: winston2.format.json(),
+  transports: [new winston2.transports.Console({ silent: true })]
+})
+
+const winstonWithTransport = benchmark('Winston (with transport)', () => {
+  winstonLoggerWithTransport.info('test message', { userId: 12345, action: 'test' })
+})
+
+const winstonOverheadUs = winstonWithTransport.perLogUs - winstonBaseline.perLogUs
+const winstonOverheadPct = ((winstonOverheadUs / winstonBaseline.perLogUs) * 100).toFixed(1)
+console.log(`Winston Overhead: ${winstonOverheadUs.toFixed(3)}μs (${winstonOverheadPct}%)\n`)
+
+// ==================== BUNYAN ====================
+console.log('--- Bunyan ---\n')
+
+// Without transport injection
+delete require.cache[require.resolve('bunyan')]
+const bunyan1 = require('bunyan')
+const bunyanLoggerBaseline = bunyan1.createLogger({
+  name: 'benchmark-baseline',
+  level: 'info',
+  streams: [{ stream: { write: () => {} } }]  // Null stream
+})
+
+const bunyanBaseline = benchmark('Bunyan (baseline)', () => {
+  bunyanLoggerBaseline.info({ userId: 12345, action: 'test' }, 'test message')
+})
+
+// With transport injection (already initialized tracer above)
+delete require.cache[require.resolve('bunyan')]
+const bunyan2 = require('bunyan')
+const bunyanLoggerWithTransport = bunyan2.createLogger({
+  name: 'benchmark-with-transport',
+  level: 'info',
+  streams: [{ stream: { write: () => {} } }]  // Null stream
+})
+
+const bunyanWithTransport = benchmark('Bunyan (with transport)', () => {
+  bunyanLoggerWithTransport.info({ userId: 12345, action: 'test' }, 'test message')
+})
+
+const bunyanOverheadUs = bunyanWithTransport.perLogUs - bunyanBaseline.perLogUs
+const bunyanOverheadPct = ((bunyanOverheadUs / bunyanBaseline.perLogUs) * 100).toFixed(1)
+console.log(`Bunyan Overhead: ${bunyanOverheadUs.toFixed(3)}μs (${bunyanOverheadPct}%)\n`)
+
+// ==================== PINO ====================
+console.log('--- Pino ---\n')
+
+// Without transport injection
+const pino1 = require('pino')
+const pinoLoggerBaseline = pino1({ level: 'info' }, { write: () => {} })  // Null destination
+
+const pinoBaseline = benchmark('Pino (baseline)', () => {
+  pinoLoggerBaseline.info({ userId: 12345, action: 'test' }, 'test message')
+})
+
+// With transport injection (already initialized tracer above)
+delete require.cache[require.resolve('pino')]
+const pino2 = require('pino')
+const pinoLoggerWithTransport = pino2({ level: 'info' }, { write: () => {} })
+
+const pinoWithTransport = benchmark('Pino (with transport)', () => {
+  pinoLoggerWithTransport.info({ userId: 12345, action: 'test' }, 'test message')
+})
+
+const pinoOverheadUs = pinoWithTransport.perLogUs - pinoBaseline.perLogUs
+const pinoOverheadPct = ((pinoOverheadUs / pinoBaseline.perLogUs) * 100).toFixed(1)
+console.log(`Pino Overhead: ${pinoOverheadUs.toFixed(3)}μs (${pinoOverheadPct}%)\n`)
+
+// ==================== SUMMARY ====================
+console.log('=== Summary ===\n')
+console.log('Per-Log Overhead:')
+console.log(`  Winston: ${winstonOverheadUs.toFixed(3)}μs (${winstonOverheadPct}% increase)`)
+console.log(`  Bunyan:  ${bunyanOverheadUs.toFixed(3)}μs (${bunyanOverheadPct}% increase)`)
+console.log(`  Pino:    ${pinoOverheadUs.toFixed(3)}μs (${pinoOverheadPct}% increase)`)
+console.log('')
+
+// Memory info
+const memUsage = process.memoryUsage()
+console.log('Memory Usage:')
+console.log(`  Heap Used: ${(memUsage.heapUsed / 1024 / 1024).toFixed(2)} MB`)
+console.log(`  External: ${(memUsage.external / 1024 / 1024).toFixed(2)} MB`)
+console.log('')
+
+console.log('Note: Run with --expose-gc for accurate memory measurements')
+console.log('Example: node --expose-gc benchmark-overhead.js\n')
+
+process.exit(0)

integration-tests/network-transport-injection/run-transport-tests.sh

@@ -0,0 +1,97 @@
+#!/bin/bash
+
+# Test runner for all three logger transport injection implementations
+#
+# Usage:
+#   From this directory: ./run-transport-tests.sh
+#   From repo root: ./integration-tests/network-transport-injection/run-transport-tests.sh
+#
+# Prerequisites:
+# 1. Start intake server in another terminal:
+#    node integration-tests/network-transport-injection/test-intake-server.js
+# 2. Logger dependencies will be checked and installed if needed
+
+set -e
+
+# Get the directory where this script is located
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
+
+# Change to repo root for npm commands
+cd "$REPO_ROOT"
+
+# Check and install logger dependencies if needed
+echo "Checking logger dependencies..."
+if ! npm list winston bunyan pino pino-pretty &>/dev/null; then
+    echo "Installing logger packages (winston, bunyan, pino, pino-pretty)..."
+    npm install --no-save winston bunyan pino pino-pretty
+    echo "✓ Dependencies installed"
+else
+    echo "✓ All dependencies present"
+fi
+echo ""
+
+# Change back to script directory to run tests
+cd "$SCRIPT_DIR"
+
+echo "=============================================="
+echo "  Logger Transport Injection Test Suite"
+echo "=============================================="
+echo ""
+
+# Check if intake server is running
+echo "Checking if intake server is running on port 8080..."
+if ! nc -z localhost 8080 2>/dev/null; then
+    echo "⚠️  WARNING: Intake server not detected on port 8080"
+    echo "   Start it with: node integration-tests/network-transport-injection/test-intake-server.js"
+    echo "   Or from this directory: node test-intake-server.js"
+    echo ""
+    read -p "Continue anyway? (y/N) " -n 1 -r
+    echo ""
+    if [[ ! $REPLY =~ ^[Yy]$ ]]; then
+        exit 1
+    fi
+else
+    echo "✓ Intake server is running"
+fi
+
+echo ""
+echo "=============================================="
+echo "  Test 1/3: Winston Transport Injection"
+echo "=============================================="
+node test-winston-transport.js
+
+echo ""
+echo "=============================================="
+echo "  Test 2/3: Bunyan Stream Injection"
+echo "=============================================="
+node test-bunyan-transport.js
+
+echo ""
+echo "=============================================="
+echo "  Test 3/4: Pino Simple (No User Transport)"
+echo "=============================================="
+node test-pino-simple.js
+
+echo ""
+echo "=============================================="
+echo "  Test 4/4: Pino with pino-pretty"
+echo "=============================================="
+node test-pino-transport.js
+
+echo ""
+echo "=============================================="
+echo "  All Tests Complete!"
+echo "=============================================="
+echo ""
+echo "Check the intake server output to verify:"
+echo "  ✓ All 20 logs received (5 per test × 4 tests)"
+echo "  ✓ Trace correlation present (trace_id, span_id)"
+echo "  ✓ Service metadata included (service, env, version)"
+echo ""
+echo "Test coverage:"
+echo "  ✓ Winston: Native HTTP transport"
+echo "  ✓ Bunyan: Custom stream with timing fix"
+echo "  ✓ Pino Simple: Basic HTTP injection"
+echo "  ✓ Pino Pretty: Multistream auto-combination"
+echo ""