Logger

HTTP request/response logging middleware.

Installation

dart pub add aim_server_logger

Quick Start

import 'dart:io';
import 'package:aim_server/aim_server.dart';
import 'package:aim_server_logger/aim_server_logger.dart';

void main() async {
  final app = Aim();

  // Add logger middleware
  app.use(logger());

  app.get('/', (c) async => c.text('Hello!'));

  await app.serve(host: InternetAddress.anyIPv4, port: 8080);
}

Output:

<-- GET /
--> GET / 200 2ms

Log Format

The default format includes:

• Request direction (<--)
• HTTP method (GET, POST, etc.)
• Request URI, including the query string if present (c.req.uri, not just c.req.path)
• Response direction (-->)
• Status code
• Response time in milliseconds

<-- POST /api/users
--> POST /api/users 201 15ms

<-- GET /search?q=dart
--> GET /search?q=dart 200 3ms

Custom Logging

Customize the log output with onRequest and onResponse callbacks:

app.use(logger(
  onResponse: (c, durationMs) async {
    print('[${c.req.method}] ${c.req.path} -> ${c.response?.statusCode} (${durationMs}ms)');
  },
));

Output:

[GET] / -> 200 (2ms)
[POST] /api/users -> 201 (15ms)

Complete Example

import 'dart:io';
import 'package:aim_server/aim_server.dart';
import 'package:aim_server_logger/aim_server_logger.dart';

void main() async {
  final app = Aim();

  // Add logger with custom format
  app.use(logger(
    onResponse: (c, durationMs) async {
      final timestamp = DateTime.now().toIso8601String();
      print('[$timestamp] ${c.req.method} ${c.req.path} ${c.response?.statusCode} ${durationMs}ms');
    },
  ));

  app.get('/', (c) async {
    return c.json({'message': 'Hello!'});
  });

  app.post('/users', (c) async {
    final body = await c.req.json();
    await Future.delayed(Duration(milliseconds: 50)); // Simulate work
    return c.json({'created': body}, statusCode: 201);
  });

  await app.serve(host: InternetAddress.anyIPv4, port: 8080);
  print('Server running on http://localhost:8080');
}

Output:

[2024-01-01T12:00:00.000Z] GET / 200 2ms
[2024-01-01T12:00:05.000Z] POST /users 201 52ms

Use Cases

Development Debugging

app.use(logger()); // See all requests during development

Production Monitoring

app.use(logger(
  onResponse: (c, durationMs) async {
    if ((c.response?.statusCode ?? 0) >= 400) {
      print('ERROR: ${c.req.method} ${c.req.path} ${c.response?.statusCode} ${durationMs}ms');
    }
    // Successful requests are simply not printed.
  },
));

Performance Tracking

app.use(logger(
  onResponse: (c, durationMs) async {
    if (durationMs > 1000) {
      print('SLOW: ${c.req.method} ${c.req.path} took ${durationMs}ms');
    }
    print('${c.req.method} ${c.req.path} ${c.response?.statusCode} ${durationMs}ms');
  },
));

JSON Logging

import 'dart:convert';

app.use(logger(
  onResponse: (c, durationMs) async {
    final log = {
      'timestamp': DateTime.now().toIso8601String(),
      'method': c.req.method,
      'path': c.req.path,
      'status': c.response?.statusCode,
      'duration_ms': durationMs,
    };
    print(jsonEncode(log));
  },
));

Output:

{"timestamp":"2024-01-01T12:00:00.000Z","method":"GET","path":"/","status":200,"duration_ms":2}

Best Practices

1. Place logger first - Capture all requests

   app.use(logger()); // First middleware
   app.use(cors());
   app.use(jwt());

2. Custom format for production - Include timestamps and metadata

   app.use(logger(
     onResponse: (c, durationMs) async {
       print('[${DateTime.now()}] ${c.req.method} ${c.req.path} ${c.response?.statusCode} ${durationMs}ms');
     },
   ));

3. Conditional logging - Log only errors or slow requests

   onResponse: (c, durationMs) async {
     if ((c.response?.statusCode ?? 0) >= 500 || durationMs > 5000) {
       print('ALERT: ${c.req.method} ${c.req.path} ${c.response?.statusCode} ${durationMs}ms');
     }
     // Normal requests are simply not printed.
   },

4. Structured logging - Use JSON for log aggregation

   onResponse: (c, durationMs) async {
     print(jsonEncode({
       'level': (c.response?.statusCode ?? 0) >= 500 ? 'error' : 'info',
       'method': c.req.method,
       'path': c.req.path,
       'status': c.response?.statusCode,
       'duration': durationMs,
     }));
   },

Next Steps

• Learn about Middleware patterns
• Explore Error handling
• Read about the Context API for request/response handling