Change Logback Log Level Programmatically at Runtime via a REST API in Spring Boot
In this tutorial, we will show you how to change Logback log level programmatically at runtime via a REST API in Spring Boot.
The required Logback dependencies for this example are Logback Core, Logback Classic, SLF4J. However, these Logback dependencies are available by default if our Spring Boot project uses spring-boot-starter-web dependency.
Follow the steps below to complete this example:
- Spring Boot expects the logback.xml configuration file to be placed under the resources folder of the application. The configuration in the logback.xml file should be as follows:
- Create an interface named LoggingService with a method to change the log level:
- Create an implementation class named LoggingServiceImpl for the LoggingService interface:
- Create a controller with a REST API endpoint that allows changing the logging level for the application package, as shown in the example below:
- To test the API, you can run your application and make a PUT request, as shown in the example below:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<property name="LOG_FILE" value="LogFile" />
<appender name="FILE"
class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>/logs/application.log</file>
<rollingPolicy
class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!-- daily rollover -->
<fileNamePattern>${LOG_FILE}.%d{yyyy-MM-dd}.gz</fileNamePattern>
<!-- keep 30 days' worth of history capped at 3GB total size -->
<maxHistory>30</maxHistory>
<totalSizeCap>3GB</totalSizeCap>
</rollingPolicy>
<triggeringPolicy
class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
<maxFileSize>5GB</maxFileSize>
</triggeringPolicy>
</appender>
<logger name="com.example.logback.service.transaction.impl"
level="debug" additivity="false">
<appender-ref ref="FILE" />
</logger>
<root level="info">
<appender-ref ref="FILE" />
</root>
</configuration>package com.example.logback.service;
public interface LoggingService {
void changeLogLevel(String level, String packageName);
}package com.example.logback.service.impl;
import java.util.Arrays;
import java.util.List;
import org.slf4j.LoggerFactory;
import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.LoggerContext;
import com.example.logback.service.LoggingService;
public class LoggingServiceImpl implements LoggingService {
@Override
public void changeLogLevel(String level, String packageName) throws Exception {
List<String> validLevels = Arrays.asList("TRACE", "DEBUG", "INFO", "WARN", "ERROR", "OFF");
if (!validLevels.contains(level.toUpperCase())) {
throw new Exception("Invalid Log level");
}
LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();
ch.qos.logback.classic.Logger classicLogger = loggerContext.getLogger(packageName);
System.out.println(packageName + " current logger level: " + classicLogger.getLevel());
System.out.println(" You entered: " + level);
classicLogger.setLevel(Level.toLevel(level));
}
}package com.example.logback.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.PutMapping;
import com.example.logback.service.LoggingService;
@RestController
@RequestMapping(path = "/logging")
public class LoggingController {
@Autowired
private LoggingService loggingService;
@PutMapping(path = "/change-log-level")
public void changeLogLevel(@RequestParam(name = "level", defaultValue = "info") String level,
@RequestParam(name = "packageName",
defaultValue = "com.example.service.impl.TransactionServiceImpl")
String packageName) {
try {
loggingService.changeLogLevel(level, packageName);
} catch (Exception e) {
e.printStackTrace();
}
}
}