OTel For Java

6min
In this guide, we will walk you through the process of setting up and using OpenTelemetry in Java. You will learn how to instrument a simple Java application to produce traces, metrics, and logs.
Step 1: Prerequisites
Before diving into OpenTelemetry, be sure that you have the following installed locally:
Java JDK
﻿Gradle﻿
Step 2: Example Application
For this tutorial, we will be using a basic Spring Boot application. However, OpenTelemetry Java is compatible with other web frameworks like Apache Wicket and Play as well. Feel free to adapt the instructions to your preferred framework.
Step 3: Installation
1. Set up an environment in a new directory called java-simple. Create a file build.gradle.kts in that directory and add the following content to it.
Java
plugins {
  id("java")
  id("org.springframework.boot") version "3.0.6"
  id("io.spring.dependency-management") version "1.1.0"
}

sourceSets {
  main {
    java.setSrcDirs(setOf("."))
  }
}

repositories {
  mavenCentral()
}

dependencies {
  implementation("org.springframework.boot:spring-boot-starter-web")
}

plugins {
  id("java")
  id("org.springframework.boot") version "3.0.6"
  id("io.spring.dependency-management") version "1.1.0"
}

sourceSets {
  main {
    java.setSrcDirs(setOf("."))
  }
}

repositories {
  mavenCentral()
}

dependencies {
  implementation("org.springframework.boot:spring-boot-starter-web")
}
﻿
2. Create another file called DiceApplication.java in the same directory and add the following content to it:

Java
package otel;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.Banner;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DiceApplication {
  public static void main(String[] args) {
    SpringApplication app = new SpringApplication(DiceApplication.class);
    app.setBannerMode(Banner.Mode.OFF);
    app.run(args);
  }
}

package otel;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.Banner;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DiceApplication {
  public static void main(String[] args) {
    SpringApplication app = new SpringApplication(DiceApplication.class);
    app.setBannerMode(Banner.Mode.OFF);
    app.run(args);
  }
}
﻿
3. Create another file called RollController.java in the same directory and add the following content to it:
Java
package otel;

import java.util.Optional;
import java.util.concurrent.ThreadLocalRandom;
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;

@RestController
public class RollController {
  private static final Logger logger = LoggerFactory.getLogger(RollController.class);

  @GetMapping("/rolldice")
  public String index(@RequestParam("player") Optional<String> player) {
    int result = this.getRandomNumber(1, 6);
    if (player.isPresent()) {
      logger.info("{} is rolling the dice: {}", player.get(), result);
    } else {
      logger.info("Anonymous player is rolling the dice: {}", result);
    }
    return Integer.toString(result);
  }

  public int getRandomNumber(int min, int max) {
    return ThreadLocalRandom.current().nextInt(min, max + 1);
  }
}

package otel;

import java.util.Optional;
import java.util.concurrent.ThreadLocalRandom;
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;

@RestController
public class RollController {
  private static final Logger logger = LoggerFactory.getLogger(RollController.class);

  @GetMapping("/rolldice")
  public String index(@RequestParam("player") Optional<String> player) {
    int result = this.getRandomNumber(1, 6);
    if (player.isPresent()) {
      logger.info("{} is rolling the dice: {}", player.get(), result);
    } else {
      logger.info("Anonymous player is rolling the dice: {}", result);
    }
    return Integer.toString(result);
  }

  public int getRandomNumber(int min, int max) {
    return ThreadLocalRandom.current().nextInt(min, max + 1);
  }
}
﻿
4. Run the application using the following command then open http://localhost:8080/rolldice in your web browser to ensure it is working.
Java
gradle assemble
java -jar ./build/libs/java-simple.jar
gradle assemble
java -jar ./build/libs/java-simple.jar
﻿
Step 4: Instrumentation
Now we are going to use Java agent to automatically instrument the application at launch time. We will configure the Java agent using environment variables.

1. Download the opentelemetry-javaagent.jar from Releases of the opentelemetry-java-instrumentation repository. The JAR file contains the agent and all automatic instrumentation packages:
text
https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases
https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases
﻿
2. Set and export variables that specify the Java agent JAR and a console exporter.﻿
Text
export JAVA_TOOL_OPTIONS="-javaagent:PATH/TO/opentelemetry-javaagent.jar" \
  OTEL_TRACES_EXPORTER=otlp \
  OTEL_METRICS_EXPORTER=otlp \
  OTEL_LOGS_EXPORTER=otlp \
  OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf \
  OTEL_EXPORTER_OTLP_ENDPOINT=https://otel.kloudmate.com:4318 \
  OTEL_EXPORTER_OTLP_HEADERS="Authorization=<YOUR_SECRET_KEY>"
  
export JAVA_TOOL_OPTIONS="-javaagent:PATH/TO/opentelemetry-javaagent.jar" \
  OTEL_TRACES_EXPORTER=otlp \
  OTEL_METRICS_EXPORTER=otlp \
  OTEL_LOGS_EXPORTER=otlp \
  OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf \
  OTEL_EXPORTER_OTLP_ENDPOINT=https://otel.kloudmate.com:4318 \
  OTEL_EXPORTER_OTLP_HEADERS="Authorization=<YOUR_SECRET_KEY>"
  
﻿
 The exporter URL mentioned above, along with the KloudMate API-Key as the Authorization header will send the data to KloudMate.
Replace PATH/TO above, with your path to the JAR file.
3. Run your application using the following command:
Java
$ java -jar ./build/libs/java-simple.jar
...
$ java -jar ./build/libs/java-simple.jar
...
﻿
Note the output from the otel.javaagent.
4. Send a request using curl from another terminal. You will see trace & log output from the server and client.
Java
curl localhost:8080/rolldice
curl localhost:8080/rolldice
﻿
5. Stop the server process to see an output of all the metrics collected.
﻿
﻿
﻿
Source URL for the example application: https://opentelemetry.io/docs/instrumentation/java/getting-started/﻿
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