Question

How can I change a log file path on the fly in Logback?

In my web application user can change the place where some e-mail attachments will be saved and processed. The user can access this path and see if happened some errors after processing, so I want to create a log file in this path. To accomplish this I’ve tried use this Logback configuration:

<configuration debug="true" scan="true" scanPeriod="30 seconds">
    <property scope="context" resource="com/hrgi/configuracoes/recuperadorNFe.properties" />
    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%date{dd/MM/yyyy;HH:mm:ss} [%thread] %-5level %logger - %msg%n %ex{full}</pattern>
        </encoder>
    </appender>
    <appender name="importador" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${recuperadorNFe.diretorioDeArmazenamento}/logs/importador.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>${recuperadorNFe.diretorioDeArmazenamento}/logs/%d{yyyy/MM}/importador-%d{dd}.log</fileNamePattern>
        </rollingPolicy>
        <encoder>
            <pattern>(%date{dd/MM/yyyy;HH:mm:ss} [%-5level]) -> %msg%n %nopex</pattern>
        </encoder>
    </appender>
    <logger name="com.hrgi.nfe" level="info">
        <appender-ref ref="importador" />
    </logger>
    <root level="info">
        <appender-ref ref="console" />
    </root>
</configuration>

Like you can see, my hope was restart logger context so perhaps it could see that the properties file’s content was changed and load the right values. Doesn’t work:

private void restartLogContext(){
    LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();
    loggerContext.stop();
    loggerContext.start();
    StatusPrinter.print(loggerContext);
}

So I’ve tried remove logger appender and create a new one. At least the log file was created in the new path, but the logging is happening in console:

private void restartLog(){
    LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();

    Logger logbackLogger = loggerContext.getLogger("com.hrgi.nfe");
    logbackLogger.detachAndStopAllAppenders();

    TimeBasedRollingPolicy policy= new TimeBasedRollingPolicy();
    policy.setContext(loggerContext);
    policy.setFileNamePattern(modeloPopup.getConfiguracoes().getDiretorioDeArmazenamento()+"/logs/%d{yyyy/MM}/importador-%d{dd}.log");

    RollingFileAppender fileAppender = new RollingFileAppender();
    fileAppender.setContext(loggerContext);
    fileAppender.setName("importador");
    fileAppender.setFile(modeloPopup.getConfiguracoes().getDiretorioDeArmazenamento()+"/logs/importador.log");
    fileAppender.setRollingPolicy(policy);

    policy.setParent(fileAppender);

    PatternLayoutEncoder encoder = new PatternLayoutEncoder();
    encoder.setContext(loggerContext);
    encoder.setPattern("(%date{dd MMM yyyy;HH:mm:ss} [%-5level]) -> %msg%n %nopex");
    encoder.start();

    fileAppender.setEncoder(encoder);
    fileAppender.start();

    logbackLogger.addAppender(fileAppender);        
    StatusPrinter.print(loggerContext);
}

Could someone explain me what I’m doing wrong?

Answer 1

I’d just extend ch.qos.logback.core.rolling.TimeBasedRollingPolicy and pass it to RollingFileAppender.

It looks like appender can use it as a triggering and rolling policy. Just make it do rollover every time configuration changes somewhere and return next file name based on your configuration.
You should look at the methods isTriggeringEvent – this makes appender rollover, and rollover – this actually does a rollover, and getNewActiveFileName.

Look at (RollingFileAppender source)[http://grepcode.com/file/repo1.maven.org/maven2/ch.qos.logback/logback-core/0.9.3/ch/qos/logback/core/rolling/RollingFileAppender.java] to get the idea how to hook it up. It should be easier than struggling with configuration.