Chapitre 4: Configuration Logback

Introduction

Logback est l'implémentation de logging par défaut de Spring Boot. Ce chapitre vous apprend à le configurer pour différents environnements.

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🎯 Objectifs du Chapitre

À la fin de ce chapitre, vous saurez:

1. ✅ Créer un fichier logback-spring.xml
2. ✅ Configurer les appenders (Console, File, Rolling)
3. ✅ Personnaliser les patterns de log
4. ✅ Utiliser les profils Spring
5. ✅ Configurer les logs JSON pour production

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1. Configuration de Base

Fichier logback-spring.xml

Créez src/main/resources/logback-spring.xml:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

    <!-- Import des valeurs Spring Boot -->
    <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
    
    <!-- Variable pour le nom de l'application -->
    <springProperty scope="context" name="APP_NAME" source="spring.application.name" defaultValue="myapp"/>

    <!-- Console Appender -->
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>

    <!-- Configuration par défaut -->
    <root level="INFO">
        <appender-ref ref="CONSOLE"/>
    </root>
    
    <!-- Niveau spécifique pour votre application -->
    <logger name="com.myapp" level="DEBUG"/>

</configuration>

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2. Patterns de Log

Syntaxe des Patterns

Pattern	Description	Exemple
%d\{format\}	Date/heure	2024-01-15 10:30:00
%thread	Nom du thread	http-nio-8080-exec-1
%level / %-5level	Niveau (padded)	INFO
%logger\{n\}	Nom du logger (n chars)	c.m.s.UserService
%msg	Message	User logged in
%n	Nouvelle ligne
%X\{key\}	Valeur MDC	abc-123
%highlight()	Couleurs (console)

Exemples de Patterns

<!-- Simple -->
<pattern>%d{HH:mm:ss} %-5level %logger{36} - %msg%n</pattern>
<!-- Output: 10:30:00 INFO  c.m.s.UserService - User logged in -->

<!-- Avec MDC -->
<pattern>%d{HH:mm:ss} [%X{requestId}] [%X{userId}] %-5level %logger{36} - %msg%n</pattern>
<!-- Output: 10:30:00 [abc-123] [42] INFO  c.m.s.UserService - User logged in -->

<!-- Coloré pour console -->
<pattern>%d{HH:mm:ss} %highlight(%-5level) %cyan(%logger{36}) - %msg%n</pattern>

<!-- Détaillé pour fichier -->
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] [%X{requestId:-N/A}] %-5level %logger{50} - %msg%n</pattern>

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3. Appenders

Console Appender

<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
        <pattern>%d{HH:mm:ss.SSS} %highlight(%-5level) %cyan(%logger{36}) - %msg%n</pattern>
    </encoder>
</appender>

File Appender (fichier simple)

<appender name="FILE" class="ch.qos.logback.core.FileAppender">
    <file>logs/application.log</file>
    <append>true</append>
    <encoder>
        <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
    </encoder>
</appender>

Rolling File Appender (avec rotation)

<appender name="ROLLING_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>logs/application.log</file>
    
    <!-- Politique de rotation -->
    <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
        <!-- Nom des fichiers archivés -->
        <fileNamePattern>logs/application.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>
        <!-- Taille max par fichier -->
        <maxFileSize>10MB</maxFileSize>
        <!-- Nombre de jours de rétention -->
        <maxHistory>30</maxHistory>
        <!-- Taille totale max -->
        <totalSizeCap>1GB</totalSizeCap>
    </rollingPolicy>
    
    <encoder>
        <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] [%X{requestId}] %-5level %logger{50} - %msg%n</pattern>
    </encoder>
</appender>

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4. Profils Spring

Configuration par Profil

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    
    <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
    
    <!-- Appender Console (toujours présent) -->
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} %highlight(%-5level) %cyan(%logger{36}) - %msg%n</pattern>
        </encoder>
    </appender>

    <!-- ===== PROFIL DEV ===== -->
    <springProfile name="dev">
        <root level="INFO">
            <appender-ref ref="CONSOLE"/>
        </root>
        <logger name="com.myapp" level="DEBUG"/>
        <logger name="org.hibernate.SQL" level="DEBUG"/>
    </springProfile>

    <!-- ===== PROFIL PROD ===== -->
    <springProfile name="prod">
        
        <!-- Fichier avec rotation -->
        <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
            <file>/var/log/myapp/application.log</file>
            <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
                <fileNamePattern>/var/log/myapp/application.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>
                <maxFileSize>50MB</maxFileSize>
                <maxHistory>30</maxHistory>
                <totalSizeCap>5GB</totalSizeCap>
            </rollingPolicy>
            <encoder>
                <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] [%X{requestId}] %-5level %logger{50} - %msg%n</pattern>
            </encoder>
        </appender>
        
        <root level="WARN">
            <appender-ref ref="FILE"/>
        </root>
        <logger name="com.myapp" level="INFO"/>
    </springProfile>

    <!-- ===== PROFIL TEST ===== -->
    <springProfile name="test">
        <root level="WARN">
            <appender-ref ref="CONSOLE"/>
        </root>
        <logger name="com.myapp" level="INFO"/>
    </springProfile>

</configuration>

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5. Logs JSON pour Production

Pourquoi JSON?

Logs texte:
2024-01-15 10:30:00 INFO UserService - User 42 logged in

Logs JSON (parseable par ELK, Datadog, etc.):
{"timestamp":"2024-01-15T10:30:00.000Z","level":"INFO","logger":"UserService","message":"User logged in","userId":42}

Dépendance

<dependency>
    <groupId>net.logstash.logback</groupId>
    <artifactId>logstash-logback-encoder</artifactId>
    <version>7.4</version>
</dependency>

Configuration JSON

<!-- Appender JSON -->
<appender name="JSON_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>/var/log/myapp/application.json</file>
    
    <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
        <fileNamePattern>/var/log/myapp/application.%d{yyyy-MM-dd}.%i.json.gz</fileNamePattern>
        <maxFileSize>50MB</maxFileSize>
        <maxHistory>7</maxHistory>
    </rollingPolicy>
    
    <!-- Encoder JSON -->
    <encoder class="net.logstash.logback.encoder.LogstashEncoder">
        <includeMdcKeyName>requestId</includeMdcKeyName>
        <includeMdcKeyName>userId</includeMdcKeyName>
        <customFields>{"app":"myapp","env":"prod"}</customFields>
    </encoder>
</appender>

<springProfile name="prod">
    <root level="INFO">
        <appender-ref ref="JSON_FILE"/>
    </root>
</springProfile>

Output JSON

{
    "@timestamp": "2024-01-15T10:30:00.000Z",
    "@version": "1",
    "message": "User logged in",
    "logger_name": "com.myapp.service.UserService",
    "thread_name": "http-nio-8080-exec-1",
    "level": "INFO",
    "requestId": "abc-123",
    "userId": "42",
    "app": "myapp",
    "env": "prod"
}

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6. Configuration Complète Professionnelle

<?xml version="1.0" encoding="UTF-8"?>
<configuration scan="true" scanPeriod="30 seconds">

    <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
    
    <springProperty scope="context" name="APP_NAME" source="spring.application.name" defaultValue="myapp"/>
    <property name="LOG_PATH" value="${LOG_PATH:-logs}"/>

    <!-- ===== CONSOLE APPENDER ===== -->
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%X{requestId:-}] %highlight(%-5level) %cyan(%logger{36}) - %msg%n</pattern>
        </encoder>
    </appender>

    <!-- ===== FILE APPENDER (Texte) ===== -->
    <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${LOG_PATH}/${APP_NAME}.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
            <fileNamePattern>${LOG_PATH}/archived/${APP_NAME}.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>
            <maxFileSize>50MB</maxFileSize>
            <maxHistory>30</maxHistory>
            <totalSizeCap>5GB</totalSizeCap>
        </rollingPolicy>
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] [%X{requestId:-N/A}] [%X{userId:-anonymous}] %-5level %logger{50} - %msg%n</pattern>
        </encoder>
    </appender>

    <!-- ===== ERROR FILE APPENDER ===== -->
    <appender name="ERROR_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${LOG_PATH}/${APP_NAME}-error.log</file>
        <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
            <level>ERROR</level>
        </filter>
        <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
            <fileNamePattern>${LOG_PATH}/archived/${APP_NAME}-error.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>
            <maxFileSize>50MB</maxFileSize>
            <maxHistory>90</maxHistory>
        </rollingPolicy>
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] [%X{requestId}] %-5level %logger{50} - %msg%n%ex</pattern>
        </encoder>
    </appender>

    <!-- ===== ASYNC APPENDER (Performance) ===== -->
    <appender name="ASYNC_FILE" class="ch.qos.logback.classic.AsyncAppender">
        <queueSize>512</queueSize>
        <discardingThreshold>0</discardingThreshold>
        <includeCallerData>false</includeCallerData>
        <appender-ref ref="FILE"/>
    </appender>

    <!-- ===== PROFIL DEV ===== -->
    <springProfile name="dev,local">
        <root level="INFO">
            <appender-ref ref="CONSOLE"/>
        </root>
        <logger name="com.myapp" level="DEBUG"/>
        <logger name="org.hibernate.SQL" level="DEBUG"/>
        <logger name="org.springframework.web" level="DEBUG"/>
    </springProfile>

    <!-- ===== PROFIL PROD ===== -->
    <springProfile name="prod">
        <root level="WARN">
            <appender-ref ref="ASYNC_FILE"/>
            <appender-ref ref="ERROR_FILE"/>
        </root>
        <logger name="com.myapp" level="INFO"/>
    </springProfile>

    <!-- ===== PROFIL TEST ===== -->
    <springProfile name="test">
        <root level="WARN">
            <appender-ref ref="CONSOLE"/>
        </root>
        <logger name="com.myapp" level="INFO"/>
    </springProfile>

    <!-- ===== DEFAULT (aucun profil) ===== -->
    <springProfile name="default">
        <root level="INFO">
            <appender-ref ref="CONSOLE"/>
            <appender-ref ref="FILE"/>
        </root>
        <logger name="com.myapp" level="DEBUG"/>
    </springProfile>

</configuration>

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7. Loggers Spécifiques Utiles

<!-- Requêtes SQL Hibernate -->
<logger name="org.hibernate.SQL" level="DEBUG"/>
<logger name="org.hibernate.type.descriptor.sql.BasicBinder" level="TRACE"/>

<!-- Spring Security -->
<logger name="org.springframework.security" level="DEBUG"/>

<!-- Requêtes HTTP entrantes -->
<logger name="org.springframework.web.filter.CommonsRequestLoggingFilter" level="DEBUG"/>

<!-- Connection Pool -->
<logger name="com.zaxxer.hikari" level="DEBUG"/>

<!-- Transactions -->
<logger name="org.springframework.transaction" level="DEBUG"/>

<!-- Désactiver les logs bruyants -->
<logger name="org.apache.catalina" level="WARN"/>
<logger name="org.apache.tomcat" level="WARN"/>

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8. Résumé

Fichiers de Configuration

Fichier	Usage
application.properties	Config simple
logback-spring.xml	Config avancée
logback.xml	Config sans Spring

Appenders Courants

Appender	Usage
ConsoleAppender	Console (dev)
FileAppender	Fichier simple
RollingFileAppender	Fichier avec rotation
AsyncAppender	Performance (prod)

Pattern Recommandé

%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] [%X{requestId}] %-5level %logger{50} - %msg%n

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🎯 Prochaine Étape

Place à la pratique! Implémentons un système complet de gestion d'erreurs et de logging.

➡️ TP10.1: Gestion Centralisée des Erreurs

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⬅️ Retour au Module 10