There is one big issue when we are using microservices environment, that is sometimes we are unable to see messages goes from each microservice goes to which microservice and also unable to see latency for each microservices.
Luckily we have Jaeger to do that. According to its website, Jaeger is an open source, end-to-end distributed tracing for monitor and troubleshoot transactions in complex distributed systems. And it can also be installed easily on Openshift with a very simple oc command,
oc process -f https://raw.githubusercontent.com/jaegertracing/jaeger-openshift/master/all-in-one/jaeger-all-in-one-template.yml | oc create -f -
After installed, you will see Jaeger pod on Openshift project dashboard with several opened ports and a url for accessing query dashboard. See the red box on the image, it is the url for accessing zipkin api from other pods internally.
Next is creating two simple java app, one as backend, and another one as api gateway.
As usual, we’ll start with a simple maven file for our backend service,
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.edw.test</groupId>
<artifactId>HelloWorld</artifactId>
<version>1.0.1</version>
<name>Hello World</name>
<description>A Simple Hello World</description>
<properties>
<java.version>1.8</java.version>
<version.fabric8.plugin>3.5.38</version.fabric8.plugin>
<fabric8.generator.fromMode>istag</fabric8.generator.fromMode>
<fabric8.generator.from>redhat-openjdk18-openshift:1.0</fabric8.generator.from>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-sleuth</artifactId>
<version>2.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-zipkin</artifactId>
<version>2.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>io.fabric8</groupId>
<artifactId>fabric8-maven-plugin</artifactId>
<version>${version.fabric8.plugin}</version>
<executions>
<execution>
<id>fmp</id>
<goals>
<goal>resource</goal>
<goal>build</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
Create a simple java app,
package com.edw.test.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
package com.edw.test.demo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import java.util.HashMap;
@RestController
public class IndexController {
private Logger logger = LoggerFactory.getLogger(this.getClass());
@GetMapping("/")
public HashMap sayHelloApi(@RequestParam String id) {
logger.debug("say something, anything - {}", id);
return new HashMap(){{
put("Message", "Hello My World "+id);
}};
}
}
A logback.xml file for logging format,
<configuration>
<statusListener class="ch.qos.logback.core.status.NopStatusListener"/>
<springProperty scope="context" name="springAppName" source="spring.application.name"/>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%d{HH:mm:ss.SSS} %-5level [${springAppName},%X{X-B3-SpanId:-}] %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<logger name="com.edw" level="DEBUG" additivity="false">
<appender-ref ref="STDOUT"/>
</logger>
<root level="ERROR" additivity="false">
<appender-ref ref="STDOUT"/>
</root>
</configuration>
And finally, a properties file for storing our configuration.
spring.application.name=Hello World
spring.zipkin.baseUrl: http://zipkin:9411/
spring.sleuth.sampler.probability=1.0
Next is creating our Api Gateway class, we’ll start with a simple POM file.
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.6.RELEASE</version>
<relativePath/>
</parent>
<groupId>com.edw</groupId>
<artifactId>ApiGateway</artifactId>
<version>1.0</version>
<name>ApiGateway</name>
<description>Demo project for Api Gateway</description>
<properties>
<java.version>1.8</java.version>
<version.fabric8.plugin>3.5.38</version.fabric8.plugin>
<fabric8.generator.fromMode>istag</fabric8.generator.fromMode>
<fabric8.generator.from>redhat-openjdk18-openshift:1.0</fabric8.generator.from>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-sleuth</artifactId>
<version>2.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-zipkin</artifactId>
<version>2.1.3.RELEASE</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>io.fabric8</groupId>
<artifactId>fabric8-maven-plugin</artifactId>
<version>${version.fabric8.plugin}</version>
<executions>
<execution>
<id>fmp</id>
<goals>
<goal>resource</goal>
<goal>build</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
And several java classes,
package com.edw;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
package com.edw.controller;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.MDC;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import java.util.Date;
import java.util.UUID;
@RestController
public class IndexController {
@Autowired
private RestTemplate restTemplate;
private Logger logger = LoggerFactory.getLogger(this.getClass());
@GetMapping(value="/", produces = {MediaType.APPLICATION_JSON_UTF8_VALUE})
public String indexApi() throws Exception {
String result = "";
for (int i = 0; i< 3; i++) {
logger.debug("firing");
result = restTemplate.getForObject("http://helloworld:8080/?id="+ UUID.randomUUID().toString()+"×tamp="+new Date().getTime(), String.class);
logger.debug("response is {}, MDC is {}", result, MDC.get("X-B3-SpanId"));
}
return result;
}
}
package com.edw.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;
/**
* <pre>
* com.edw.config.RestTemplateConfig
* </pre>
*
* @author Muhammad Edwin < emuhamma at redhat dot com >
* 23 Sep 2019 10:47
*/
@Configuration
public class RestTemplateConfig {
@Bean
public RestTemplate getRestTemplate() {
RestTemplate restTemplate = new RestTemplate();
return restTemplate;
}
}
And a logback.xml, and application.properties.
<configuration>
<statusListener class="ch.qos.logback.core.status.NopStatusListener"/>
<springProperty scope="context" name="springAppName" source="spring.application.name"/>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%d{HH:mm:ss.SSS} %-5level [${springAppName},%X{X-B3-SpanId:-}] %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<logger name="com.edw" level="DEBUG" additivity="false">
<appender-ref ref="STDOUT"/>
</logger>
<root level="ERROR" additivity="false">
<appender-ref ref="STDOUT"/>
</root>
</configuration>
spring.application.name=API Gateway
spring.zipkin.baseUrl: http://zipkin:9411/
spring.sleuth.sampler.probability=1.0
We can deploy both project to Openshift using fabric8 command. And this is the result after deployed successfully and hitting Api Gateway url from browser,
And we can see the detail for each request by click on it,
To see a more detailed information, we can click more and see class and method name, and also information span.
And there is one good feature when using Jaeger, is that we can visualize how a message is delivered among different microservices,
And we can search the request SpanId on Kibana,
Well, hopefully it helps. 
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