OpenTelemetry provides a unified approach to collecting telemetry data from your Java applications. This page demonstrates how to configure OpenTelemetry in a Java app to send telemetry data to Axiom using the OpenTelemetry SDK.

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Prerequisites

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Create project

To create a Java project, run the Maven archetype command in the terminal:

mvn archetype:generate -DgroupId=com.example -DartifactId=MyProject -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

This command creates a new project in a directory named MyProject with a standard directory structure.

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Create core app

DiceRollerApp.java is the core of the sample app. It simulates rolling a dice and demonstrates the usage of OpenTelemetry for tracing. The app includes two methods: one for a simple dice roll and another that demonstrates the usage of span links to establish relationships between spans across different traces.

Create the DiceRollerApp.java in the src/main/java/com/example directory with the following content:

package com.example;

import io.opentelemetry.api.OpenTelemetry;
import io.opentelemetry.api.trace.Span;
import io.opentelemetry.api.trace.Tracer;
import io.opentelemetry.context.Scope;

import java.util.Random;

public class DiceRollerApp {
    private static final Tracer tracer;

    static {
        OpenTelemetry openTelemetry = OtelConfiguration.initializeOpenTelemetry();
        tracer = openTelemetry.getTracer(DiceRollerApp.class.getName());
    }

    public static void main(String[] args) {
        rollDice();
        rollDiceWithLink();
    }

    private static void rollDice() {
        Span span = tracer.spanBuilder("rollDice").startSpan();
        try (Scope scope = span.makeCurrent()) {
            int roll = 1 + new Random().nextInt(6);
            System.out.println("Rolled a dice: " + roll);
        } finally {
            span.end();
        }
    }

    private static void rollDiceWithLink() {
        Span parentSpan = tracer.spanBuilder("rollWithLink").startSpan();
        try (Scope parentScope = parentSpan.makeCurrent()) {
            Span childSpan = tracer.spanBuilder("rolldice")
                    .addLink(parentSpan.getSpanContext())
                    .startSpan();
            try (Scope childScope = childSpan.makeCurrent()) {
                int roll = 1 + new Random().nextInt(6);
                System.out.println("Dice roll result (with link): " + roll);
            } finally {
                childSpan.end();
            }
        } finally {
            parentSpan.end();
        }
    }
}

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Configure OpenTelemetry

OtelConfiguration.java sets up the OpenTelemetry SDK and configures the exporter to send data to Axiom. It initializes the tracer provider, sets up the Axiom exporter, and configures the resource attributes.

Create the OtelConfiguration.java file in the src/main/java/com/example directory with the following content:

package com.example;

import io.opentelemetry.api.OpenTelemetry;
import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.common.AttributeKey;
import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporter;
import io.opentelemetry.sdk.OpenTelemetrySdk;
import io.opentelemetry.sdk.resources.Resource;
import io.opentelemetry.sdk.trace.SdkTracerProvider;
import io.opentelemetry.sdk.trace.export.BatchSpanProcessor;

import java.util.concurrent.TimeUnit;

public class OtelConfiguration {
    private static final String SERVICE_NAME = "YOUR_SERVICE_NAME";
    private static final String SERVICE_VERSION = "YOUR_SERVICE_VERSION";
    private static final String OTLP_ENDPOINT = "https://api.axiom.co/v1/traces";
    private static final String BEARER_TOKEN = "Bearer API_TOKEN";
    private static final String AXIOM_DATASET = "DATASET_NAME";

    public static OpenTelemetry initializeOpenTelemetry() {
        Resource resource = Resource.getDefault()
                .merge(Resource.create(Attributes.of(
                        AttributeKey.stringKey("service.name"), SERVICE_NAME,
                        AttributeKey.stringKey("service.version"), SERVICE_VERSION
                )));

        OtlpHttpSpanExporter spanExporter = OtlpHttpSpanExporter.builder()
                .setEndpoint(OTLP_ENDPOINT)
                .addHeader("Authorization", BEARER_TOKEN)
                .addHeader("X-Axiom-Dataset", AXIOM_DATASET)
                .build();

        SdkTracerProvider sdkTracerProvider = SdkTracerProvider.builder()
                .addSpanProcessor(BatchSpanProcessor.builder(spanExporter)
                        .setScheduleDelay(100, TimeUnit.MILLISECONDS)
                        .build())
                .setResource(resource)
                .build();

        OpenTelemetrySdk openTelemetry = OpenTelemetrySdk.builder()
                .setTracerProvider(sdkTracerProvider)
                .buildAndRegisterGlobal();

        Runtime.getRuntime().addShutdownHook(new Thread(sdkTracerProvider::close));

        return openTelemetry;
    }
}
  • Replace API_TOKEN with the Axiom API token you have generated. For added security, store the API token in an environment variable.
  • Replace DATASET_NAME with the name of the Axiom dataset where you want to send data.

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Configure project

The pom.xml file defines the project structure and dependencies for Maven. It includes the necessary OpenTelemetry libraries and configures the build process.

Update the pom.xml file in the root of your project directory with the following content:

<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>

  <groupId>com.example</groupId>
  <artifactId>axiom-otel-java</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
    <opentelemetry.version>1.18.0</opentelemetry.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>io.opentelemetry</groupId>
      <artifactId>opentelemetry-api</artifactId>
      <version>${opentelemetry.version}</version>
    </dependency>
    <dependency>
      <groupId>io.opentelemetry</groupId>
      <artifactId>opentelemetry-sdk</artifactId>
      <version>${opentelemetry.version}</version>
    </dependency>
    <dependency>
      <groupId>io.opentelemetry</groupId>
      <artifactId>opentelemetry-exporter-otlp</artifactId>
      <version>${opentelemetry.version}</version>
    </dependency>
    <dependency>
      <groupId>io.grpc</groupId>
      <artifactId>grpc-netty-shaded</artifactId>
      <version>1.42.1</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.2</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.1</version>
        <configuration>
          <source>11</source>
          <target>11</target>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>3.0.0-M5</version>
        <configuration>
          <testFailureIgnore>true</testFailureIgnore>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>3.2.4</version>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>shade</goal>
            </goals>
            <configuration>
              <transformers>
                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                  <mainClass>com.example.DiceRollerApp</mainClass>
                </transformer>
              </transformers>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

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Run the instrumented app

To run your Java app with OpenTelemetry instrumentation, follow these steps:

  1. Clean the project and download dependencies:

    mvn clean

  2. Compile the code:

    mvn compile

  3. Package the app:

    mvn package

  4. Run the app:

    java -jar target/axiom-otel-java-1.0-SNAPSHOT.jar

The app executes the rollDice() and rollDiceWithLink() methods, generates telemetry data, and sends the data to Axiom.

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Observe telemetry data in Axiom

As the app runs, it sends traces to Axiom. To view the traces:

  1. In Axiom, click the Stream tab.
  2. Click your dataset.

Axiom provides a dynamic dashboard for visualizing and analyzing your OpenTelemetry traces. This dashboard offers insights into the performance and behavior of your app. To view the dashboard:

  1. In Axiom, click the Dashboards tab.
  2. Look for the OpenTelemetry traces dashboard or create a new one.
  3. Customize the dashboard to show the event data and visualizations most relevant to the app.

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Send data from an existing Java project

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Manual instrumentation

Manual instrumentation gives fine-grained control over which parts of the app are traced and what information is included in the traces. It requires adding OpenTelemetry-specific code to the app.

1

Set up OpenTelemetry

Set up OpenTelemetry. Create a configuration class to initialize OpenTelemetry with necessary settings, exporters, and span processors.

// OtelConfiguration.java
package com.example;

import io.opentelemetry.api.OpenTelemetry;
import io.opentelemetry.api.trace.Tracer;
import io.opentelemetry.context.Scope;
import io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporter;
import io.opentelemetry.sdk.OpenTelemetrySdk;
import io.opentelemetry.sdk.trace.SdkTracerProvider;
import io.opentelemetry.sdk.trace.export.BatchSpanProcessor;

public class OtelConfiguration {
    public static OpenTelemetry initializeOpenTelemetry() {
        OtlpGrpcSpanExporter spanExporter = OtlpGrpcSpanExporter.builder()
            .setEndpoint("https://api.axiom.co/v1/traces")
            .addHeader("Authorization", "Bearer API_TOKEN")
            .addHeader("X-Axiom-Dataset", "DATASET_NAME")
            .build();

        SdkTracerProvider tracerProvider = SdkTracerProvider.builder()
            .addSpanProcessor(BatchSpanProcessor.builder(spanExporter).build())
            .build();

        return OpenTelemetrySdk.builder()
            .setTracerProvider(tracerProvider)
            .buildAndRegisterGlobal();
    }
}
2

Create spans

Spans represent units of work in the app. They have a start time and duration and can be nested.

// DiceRollerApp.java
package com.example;

import io.opentelemetry.api.OpenTelemetry;
import io.opentelemetry.api.trace.Span;
import io.opentelemetry.api.trace.Tracer;
import io.opentelemetry.context.Scope;

public class DiceRollerApp {
    private static final Tracer tracer;

    static {
        OpenTelemetry openTelemetry = OtelConfiguration.initializeOpenTelemetry();
        tracer = openTelemetry.getTracer("com.example.DiceRollerApp");
    }

    public static void main(String[] args) {
        try (Scope scope = tracer.spanBuilder("Main").startScopedSpan()) {
            rollDice();
        }
    }

    private static void rollDice() {
        Span span = tracer.spanBuilder("rollDice").startSpan();
        try (Scope scope = span.makeCurrent()) {
            // Simulate dice roll
            int result = new Random().nextInt(6) + 1;
            System.out.println("Rolled a dice: " + result);
        } finally {
            span.end();
        }
    }
}

Custom spans are manually managed to provide detailed insights into specific functions or methods within the app.

3

Annotate spans

Spans can be annotated with attributes and events to provide more context about the operation being performed.

private static void rollDice() {
    Span span = tracer.spanBuilder("rollDice").startSpan();
    try (Scope scope = span.makeCurrent()) {
        int roll = 1 + new Random().nextInt(6);
        span.setAttribute("roll.value", roll);
        span.addEvent("Dice rolled");
        System.out.println("Rolled a dice: " + roll);
    } finally {
        span.end();
    }
}
4

Creating span links

Span links allow association of spans that aren’t in a parent-child relationship.

private static void rollDiceWithLink() {
    Span parentSpan = tracer.spanBuilder("rollWithLink").startSpan();
    try (Scope parentScope = parentSpan.makeCurrent()) {
        Span childSpan = tracer.spanBuilder("rolldice")
                .addLink(parentSpan.getSpanContext())
                .startSpan();
        try (Scope childScope = childSpan.makeCurrent()) {
            int roll = 1 + new Random().nextInt(6);
            System.out.println("Dice roll result (with link): " + roll);
        } finally {
            childSpan.end();
        }
    } finally {
        parentSpan.end();
    }
}

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Automatic instrumentation

Automatic instrumentation simplifies adding telemetry to a Java app by automatically capturing data from supported libraries and frameworks.

1

Set up dependencies

Ensure all necessary OpenTelemetry libraries are included in your Maven pom.xml.

<!-- pom.xml snippet -->
<dependencies>
    <dependency>
        <groupId>io.opentelemetry</groupId>
        <artifactId>opentelemetry-api</artifactId>
        <version>{opentelemetry_version}</version>
    </dependency>
    <dependency>
        <groupId>io.opentelemetry</groupId>
        <artifactId>opentelemetry-sdk</artifactId>
        <version>{opentelemetry_version}</version>
    </dependency>
    <dependency>
        <groupId>io.opentelemetry.instrumentation</groupId>
        <artifactId>opentelemetry-instrumentation-httpclient</artifactId>
        <version>{instrumentation_version}</version>
    </dependency>
</dependencies>

Dependencies include the OpenTelemetry SDK and instrumentation libraries that automatically capture data from common Java libraries.

2

Auto-instrument the app

Implement an initialization class to configure the OpenTelemetry SDK along with auto-instrumentation for frameworks used by the app.

// AutoInstrumentationSetup.java
package com.example;

import io.opentelemetry.instrumentation.httpclient.HttpClientInstrumentation;
import io.opentelemetry.api.OpenTelemetry;

public class AutoInstrumentationSetup {
    public static void setup() {
        OpenTelemetry openTelemetry = OtelConfiguration.initializeOpenTelemetry();
        HttpClientInstrumentation.instrument(openTelemetry);
    }
}

Auto-instrumentation is initialized early in the app lifecycle to ensure all relevant activities are automatically captured.

3

Integrate and run

// Main.java
package com.example;

public class Main {
    public static void main(String[] args) {
        AutoInstrumentationSetup.setup();  // Initialize OpenTelemetry auto-instrumentation
        DiceRollerApp.main(args);          // Start the application logic
    }
}

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Reference

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List of OpenTelemetry trace fields

Field categoryField nameDescription
General trace information
_rowIdUnique identifier for each row in the trace data.
_sysTimeSystem timestamp when the trace data was recorded.
_timeTimestamp when the actual event being traced occurred.
trace_idUnique identifier for the entire trace.
span_idUnique identifier for the span within the trace.
parent_span_idUnique identifier for the parent span within the trace.
Operational details
durationTime taken for the operation, typically in microseconds or milliseconds.
kindType of span. For example, server, internal.
nameName of the span, often a high-level title for the operation.
Scope and instrumentation
scope.nameInstrumentation scope, typically the Java package or app component. For example, com.example.DiceRollerApp.
Service attributes
service.nameName of the service generating the trace. For example, axiom-java-otel.
service.versionVersion of the service generating the trace. For example, 0.1.0.
Telemetry SDK attributes
telemetry.sdk.languageProgramming language of the SDK used for telemetry, typically java.
telemetry.sdk.nameName of the telemetry SDK. For example, opentelemetry.
telemetry.sdk.versionVersion of the telemetry SDK used in the tracing setup. For example, 1.18.0.

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List of imported libraries

The Java implementation of OpenTelemetry uses the following key libraries.

io.opentelemetry:opentelemetry-api

This package provides the core OpenTelemetry API for Java. It defines the interfaces and classes that developers use to instrument their apps manually. This includes the Tracer, Span, and Context classes, which are fundamental to creating and managing traces in your app. The API is designed to be stable and consistent, allowing developers to instrument their code without tying it to a specific implementation.

io.opentelemetry:opentelemetry-sdk

The opentelemetry-sdk package is the reference implementation of the OpenTelemetry API for Java. It provides the actual capability behind the API interfaces, including span creation, context propagation, and resource management. This SDK is highly configurable and extensible, allowing developers to customize how telemetry data is collected, processed, and exported. It’s the core component that brings OpenTelemetry to life in a Java app.

io.opentelemetry:opentelemetry-exporter-otlp

This package provides an exporter that sends telemetry data using the OpenTelemetry Protocol (OTLP). OTLP is the standard protocol for transmitting telemetry data in the OpenTelemetry ecosystem. This exporter allows Java applications to send their collected traces, metrics, and logs to any backend that supports OTLP, such as Axiom. The use of OTLP ensures broad compatibility and a standardized way of transmitting telemetry data across different systems and platforms.

io.opentelemetry:opentelemetry-sdk-extension-autoconfigure

This extension package provides auto-configuration capabilities for the OpenTelemetry SDK. It allows developers to configure the SDK using environment variables or system properties, making it easier to set up and deploy OpenTelemetry-instrumented applications in different environments. This is particularly useful for containerized applications or those running in cloud environments where configuration through environment variables is common.

io.opentelemetry:opentelemetry-sdk-trace

This package is part of the OpenTelemetry SDK and focuses specifically on tracing capability. It includes important classes like SdkTracerProvider and BatchSpanProcessor. The SdkTracerProvider is responsible for creating and managing tracers, while the BatchSpanProcessor efficiently processes and exports spans in batches, similar to its Node.js counterpart. This batching mechanism helps optimize the performance of trace data export in OpenTelemetry-instrumented Java applications.

io.opentelemetry:opentelemetry-sdk-common

This package provides common capability used across different parts of the OpenTelemetry SDK. It includes utilities for working with attributes, resources, and other shared concepts in OpenTelemetry. This package helps ensure consistency across the SDK and simplifies the implementation of cross-cutting concerns in telemetry data collection and processing.

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