Log4j2 threadcontext log link tracking

summary

Log4j2 ThreadContext Allows you to mark log statements with multiple unique tags , In order to analyze logs when diagnosing problems at run time - Mainly in multithreaded applications , The application generates a large number of log records in a short time . for example , You may want to scan all logs for a specific user transaction or full session . This process is also known as fish marking （ That is, add some additional context information in each log statement ）. This fish marker can help you use Splunk And so on .

Let's see how we can log4j2 Use in ThreadContextclass Fish marking .

stay ThreadContext Add context information to

To uniquely mark each request , please ThreadContext Provide put(String key, String value) The method of accepting the key and its value . You can add as many tags as you need to capture the entire context . Please note that ,ThreadContext All methods of this class are static .

package com.howtodoinjava.log4j2.examples;
import java.util.UUID;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.ThreadContext;

public class Log4j2HelloWorldExample
{
    
    private static final Logger LOGGER = LogManager.getLogger(Log4j2HelloWorldExample.class.getName());
    public static void main(String[] args)
    {
    
        //Add context information
        ThreadContext.put("id", UUID.randomUUID().toString());
        ThreadContext.put("ipAddress", "192.168.21.9");
        LOGGER.debug("Debug Message Logged !!");
        LOGGER.info("Info Message Logged !!");
        LOGGER.debug("Another Debug Message !!");
        //Clear the map
        ThreadContext.clearMap(); 
        LOGGER.debug("Thread Context Cleaned up !!"); 
        LOGGER.debug("Log message with no context information !!"); 
    } 
}

Or you can put ThreadContext Of Stack Realization and ThreadContext.push（String value） Use it together , As shown below ：

//Add context information 
ThreadContext.push(UUID.randomUUID().toString()); 
ThreadContext.push("192.168.21.9"); 
LOGGER.debug("Debug Message Logged !!"); 
LOGGER.info("Info Message Logged !!"); 
LOGGER.debug("Another Debug Message !!"); 
//Clear the map 
ThreadContext.clearStack(); 
LOGGER.debug("Thread Context Cleaned up !!"); 
LOGGER.debug("Log message with no context information !!");

After the transaction ends or context information is no longer required , You can use ThreadContext.clearMap() Method clear information .

ThreadContext Of Stack and Map It is managed by thread ThreadLocal. By way of system Property settings isThreadContextMapInheritable by true, Pass the content of the context mapping to the child thread .

modify log4j2.xml Conversion mode in

<?xml version="1.0" encoding="UTF-8"?> 
<Configuration status="INFO"> 
    <Appenders> 
        <Console name="console" target="SYSTEM_OUT"> 
            <PatternLayout pattern="[%-5level] %d{yyyy-MM-dd HH:mm:ss.SSS} [%t] [%X{id}] [%X{ipAddress}] %c{1} - %msg%n" /> 
        </Console> 
    </Appenders> 
    <Loggers> 
        <Root level="debug" additivity="false"> 
            <AppenderRef ref="console" /> 
        </Root> 
    </Loggers> 
</Configuration>

• Use alone %X contain ThreadContext Everything added .
• Use %X{key} Include the specified key .
• Use %x Include the entire contents of the stack .

Log print results

Now when you run the above code - You will get the following output ：

[DEBUG] 2016-06-21 13:09:56.485 [main] [7cdd4cf0-2c26-4b81-b374-1adce3781499] [192.168.21.9] Log4j2HelloWorldExample - Debug Message Logged !! 
[INFO ] 2016-06-21 13:09:56.487 [main] [7cdd4cf0-2c26-4b81-b374-1adce3781499] [192.168.21.9] Log4j2HelloWorldExample - Info Message Logged !! 
[DEBUG] 2016-06-21 13:09:56.487 [main] [7cdd4cf0-2c26-4b81-b374-1adce3781499] [192.168.21.9] Log4j2HelloWorldExample - Another Debug Message !! 
[DEBUG] 2016-06-21 13:09:56.487 [main] [] [] Log4j2HelloWorldExample - Thread Context Cleaned up !! 
[DEBUG] 2016-06-21 13:09:56.487 [main] [] [] Log4j2HelloWorldExample - Log message with no context information !!

As you can see , Context information has been added to the first three log statements - The other two statements have no such information .

Reference resources

Log4j2 ThreadContext - Mark the log of the same transaction