Add value from database to logback log message

Question

I have a Spring Boot application that is using logback for application logs. Now I've added support for logz.io to centralize the logs from multiple machines to one place. The problem is that I can't know which log is coming from which machine.

In the application database, I have a unique token that is unique for every machine where the application is running. My idea is to pre-append that token value to every log message so I can differentiate which client is sending which logs.

I can access the token value through a method in the repository that extends the JpaRepository. Logback configuration is done through the logback.xml

Edit: Each client uses its own H2 database where the value is stored.

Example of a message I currently have:

2020-03-26 07:58:13,702 [scheduling-1] INFO n.g.service.ScheduledBotService - Test message

To be:

UniqueToken123 2020-03-26 07:58:13,702 [scheduling-1] INFO n.g.service.ScheduledBotService - Test message

Answer 1

I try Thread Context in log4j2 and it seems work for me.

Test Code

public class AppTest {

    private Logger logger = LogManager.getLogger(AppTest.class);

    @Test
    public void testMaxFromIntegerList(){

        String uniqueToken = getTokenFromJpa();

        ThreadContext.put("uniqueToken", uniqueToken); 
        logger.info("Message Set uniqueToken");

        //remove after using
        ThreadContext.remove("uniqueToken");
        logger.info("Message Clear uniqueToken");
    }

    // dummy code.
    private String getTokenFromJpa() {
        return "UniqueToken123";
    }

}

Log4j2 Config.
Be notice that in your PatternLayout, use %X{key} to include the specified key.

appender.rolling.layout.pattern = %X{uniqueToken} %d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

Content in logFile.

UniqueToken123 2020-03-26 18:18:56 INFO  AppTest:30 - Message Set uniqueToken
 2020-03-26 18:18:56 INFO  AppTest:33 - Message Clear uniqueToken

You can get more about Thread Context from here

I hope it would help.