Since the introduction of microservices architectures, the way applications are architected, developed, and monitored has changed a lot. The biggest issue with microservicse architectures is the need for centralized logging and tracing. 

All the logging libraries come up with diffrent appenders for pushing/publishing a message. For example:

1. Console Appender -> for console logging.

2. File Appender -> for logging in a file.

3. Etc.

In this post, I am going to share how to log an application's logs in a RabbitMQ server to achieve centralized logging. Using the RabbitMQ server, log messages can be fed to other downstream systems like an ELK stack-based app (Elasticsearch, Logstach, Kibana) or Splunk as well.

• Logstash - can pull messages from any source through its configured plugins for source and destination.

• Elasticsearch - Elasticsearch is a full-text search framework and has the ability to provide faster search using its indexing, which can get logs from Logstach.

• Kibana - UI application for searching and analyzing log data, etc.

In following steps, I am going to show you how to push application logs to a RabbitMQ server in Spring Boot using logback. Let's start.

1. The RabbitMQ server must be installed and running on your local machine at this URL, http://localhost:15672. 

RabbitMQ comes up with a default login credentials:

username: guest

password: guest

2. Create an exchange from the RabbitMQ console: exchangeName: my-exchange.

3. Create a queue from the RabbitMQ console: queueName: log-message-queue.

4. Bring the exchangename from the queue into the console from the exchange tab.

5. Create a Spring Boot project from spring.io, having these dependencies.

<dependency>   
<groupId>org.springframework.boot</groupId>   
    <artifactId>spring-boot-starter-amqp</artifactId>
</dependency>
<dependency>   
<groupId>org.springframework.boot</groupId>   
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

6. Create a logback.xml file in the src\main\resource folder with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>       
    <appender name="AMQP" class="org.springframework.amqp.rabbit.logback.AmqpAppender">        
        <layout>            
            <pattern><![CDATA[ %d %p %t [%c] - <%m>%n ]]></pattern>        
            </layout>        
            <exchangeName>my-exchange</exchangeName>        
            <host>localhost</host>        
            <port>5672</port>        
            <username>guest</username>        
            <password>guest</password>        
            <exchangeType>queue</exchangeType>        
            <applicationId>AmqpAppenderTest</applicationId>        
            <routingKeyPattern>logs-test</routingKeyPattern>        
            <generateId>true</generateId>        
            <charset>UTF-8</charset>        
            <durable>false</durable>        
            <deliveryMode>NON_PERSISTENT</deliveryMode>    
        </appender>    

          <root level="info">        
          <appender-ref ref="AMQP" />    
          </root>
</configuration

6. Create a simple controller in the src\main\java folder in your package:

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/api")
public class HomeController {    
  private  static final Logger logger = LoggerFactory.getLogger(HomeController.class);    

  @GetMapping("/hello")    
    public String hello(){        
      logger.info("***********Start Logging to rabbitMQ************");        
      logger.info("Publish Welcome Message to RabbitMQ");        
      return "Hello Shafique!";   
    }
}

OK, that is all we need to do. Let;s test the application.

7. Verify the log message in RabbitMQ Server's console.

Go to the Queue tab -> click on the queue name and the getMessages button.

2019-01-03 11:34:15,437 INFO http-nio-8080-exec-7 
  [com.shafique.springbootlogbackrabbitmq.controller.HomeController] - 
  <Publish Welcome Message to RabbitMQ>

You will see the following message, what we wrote in our controller hello() method: Hello Shafique!