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5. Honeycomb Distribution for Java

Send Data with the Honeycomb Distribution for Java

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Honeycomb provides the Honeycomb OpenTelemetry Distribution for Java to help you instrument your applications and send telemetry data to Honeycomb as quickly and easily as possible. Under the hood, the Honeycomb Distribution uses OpenTelemetry for Java, so advanced users or those who have already instrumented their applications with OpenTelemetry do not need to use this Distribution.

The Honeycomb Distribution reads variables you provide and translates them to variables understood by upstream OpenTelemetry. For example, the Honeycomb Distribution automatically converts the system property honeycomb.traces.endpoint to the OpenTelemetry system property otel.exporter.otlp.traces.endpoint. If you want to send data to Honeycomb using OpenTelemetry without the Honeycomb Distribution, you will need to configure your implementation to match variables expected by OpenTelemetry.

In this guide, we explain how to set up automatic and custom, or manual, instrumentation for a service written in Java. If you prefer learning by example, we provide several examples of applications configured to send OpenTelemetry data to Honeycomb using the Honeycomb OpenTelemetry Distribution for Java.

Before You Begin 

Before you can set up instrumentation for your Java application, you will need to do a few things.

Prepare Your Development Environment 

To complete the required steps, you will need:

• A working Java environment with Java version 8 or higher
• An application written in Java

Get Your Honeycomb API Key 

To send data to Honeycomb, you’ll need to sign up for a free Honeycomb account and create a Honeycomb Ingest API Key. To get started, you can create a key that you expect to swap out when you deploy to production. Name it something helpful, perhaps noting that it’s a getting started key. Make note of your API key; for security reasons, you will not be able to see the key again, and you will need it later!

If you want to use an API key you previously stored in a secure location, you can also look up details for Honeycomb API Keys any time in your Environment Settings, and use them to retrieve keys from your storage location.

Add Automatic Instrumentation 

Automatic instrumentation is handled with a Java Agent that runs alongside your application. Additional manual instrumentation can be added using the OpenTelemetry API, which is available when using our SDK as a dependency.

If you do not want to use automatic instrumentation, you will need to use the SDK Builder to instantiate an OpenTelemetryConfiguration instance. The Builder is not needed if you are using the Agent.

Acquire Dependencies 

The OpenTelemetry Java Agent supports many Java libraries and frameworks.

The automatic instrumentation agent for Honeycomb OpenTelemetry Java will automatically generate trace data from your application. The agent is packaged as a JAR file and is run alongside your app.

In order to use the automatic instrumentation agent, you must first download it:

curl -LO https://github.com/honeycombio/honeycomb-opentelemetry-java/releases/download/v1.7.0/honeycomb-opentelemetry-javaagent-1.7.0.jar

Configure 

Choose from one of the following configuration options:

Use environment variables:

# US instance
HONEYCOMB_API_ENDPOINT=https://api.honeycomb.io:443
# EU instance
#HONEYCOMB_API_ENDPOINT=https://api.eu1.honeycomb.io:443
SERVICE_NAME=my-favorite-service
HONEYCOMB_API_KEY=my-api-key
HONEYCOMB_METRICS_DATASET=my-metrics # optional

Or, use system properties:

# US instance
honeycomb.api.endpoint=https://api.honeycomb.io:443
# EU instance
#honeycomb.api.endpoint=https://api.eu1.honeycomb.io:443
sample.rate=2
service.name=my-favorite-service
honeycomb.api.key=my-api-key
honeycomb.metrics.dataset=my-metrics

and set an environment variable with a path to your properties file:

HONEYCOMB_CONFIG_FILE=/path/to/properties/file

# environment variable
HONEYCOMB_TRACES_DATASET=my-traces

# system property
honeycomb.traces.dataset=my-traces

Advanced Configuration 

You can configure the Honeycomb Agent using system properties or environment variables. If both are specified, system properties will take precedence over environment variables.

Explore all configuration options for the Honeycomb Agent:

To learn more about agent configuration, visit Java Agent Configuration in the OpenTelemetry documentation, which contains details about configuring and suppressing specific instrumentations.

Run 

Run your application with the automatic instrumentation agent as a sidecar:

java -javaagent:honeycomb-opentelemetry-javaagent-1.7.0.jar -jar /path/to/myapp.jar

You can also include configuration values with an invocation of your application:

java \
-Dhoneycomb.config.file=/path/to/properties/file \
-javaagent:honeycomb-opentelemetry-javaagent-1.7.0.jar -jar /path/to/myapp.jar

For more configuration options, visit our documentation on the OpenTelemetry Java Agent.

In Honeycomb’s UI, you should now see your application’s incoming requests and outgoing HTTP calls generate traces.

Add Custom Instrumentation 

Automatic instrumentation is the easiest way to get started with instrumenting your code. To get additional insight into your system, you should also add custom, or manual, instrumentation where appropriate. You can use manual instrumentation whether you are using the Agent or the Builder.

To learn more about custom, or manual, instrumentation, visit the comprehensive set of topics covered by Manual Instrumentation for Java, including the Annotations API, in OpenTelemetry’s documentation.

Add Dependencies 

To add custom instrumentation, add the Honeycomb OpenTelemetry SDK as a dependency in your project. This provides access to the OpenTelemetry APIs, which lets you access the currently executing span and add attributes to it, and/or to create new spans.

dependencies {
  implementation('io.honeycomb:honeycomb-opentelemetry-sdk:1.7.0')
}

<dependency>
  <groupId>io.honeycomb</groupId>
  <artifactId>honeycomb-opentelemetry-sdk</artifactId>
  <version>1.7.0</version>
</dependency>

Add Attributes to Spans 

Adding attributes to a currently executing span in a trace can be useful. For example, you may have an application or service that handles users and you want to associate the user with the span when querying your service in Honeycomb. To do this, get the current span from the context and set an attribute with the user ID.

In your code, import io.opentelemetry.api.trace.Span to get access to the span:

import io.opentelemetry.api.trace.Span;

...

Span span = Span.current();
span.setAttribute("user.id", user.getId());

This will add a user.id field to the current span so that you can use the field in WHERE, GROUP BY or ORDER clauses in the Honeycomb query builder.

Acquire a Tracer 

To create spans, you need to get a Tracer.

import io.opentelemetry.api.GlobalOpenTelemetry;
import io.opentelemetry.api.trace.Tracer;

//...

Tracer tracer = GlobalOpenTelemetry.getTracer("tracer.name.here");

When you create a Tracer, OpenTelemetry requires you to give it a name as a string. This string is the only required parameter.

When traces are sent to Honeycomb, the name of the Tracer is turned into the library.name field, which can be used to show all spans created from a particular tracer.

In general, pick a name that matches the appropriate scope for your traces. If you have one tracer for each service, then use the service name. If you have multiple tracers that live in different “layers” of your application, then use the name that corresponds to that “layer”.

The library.name field is also used with traces created from instrumentation libraries.

Create New Spans 

Automatic instrumentation can show the shape of requests to your system, but only you know the really important parts. To get the full picture of what’s happening, you will have to add custom, or manual, instrumentation and create some custom spans. To do this, create or re-use Tracer registered by the Agent and start a span.

In your code, import io.opentelemetry.api.GlobalOpenTelemetry, io.opentelemetry.api.trace.Span, and io.opentelemetry.api.trace.Tracer:

import io.opentelemetry.api.GlobalOpenTelemetry;
import io.opentelemetry.api.trace.Span;
import io.opentelemetry.api.trace.Tracer;

...

Tracer tracer = GlobalOpenTelemetry.getTracer("my-service");
Span span = tracer.spanBuilder("expensive-query").startSpan();

// ... do cool stuff

span.end();

Creating Spans Around Methods 

You can also use the annotation @WithSpan to wrap the execution of a method with a span. The span will be automatically closed once the method has completed. Unless explicitly specified, the span will be named className.methodName. To override the name of the span, add a name in parentheses as an argument.

In your code, import io.opentelemetry.instrumentation.annotations.WithSpan to allow usage of this annotation:

import io.opentelemetry.instrumentation.annotations.WithSpan;

...

@WithSpan("importantSpan")
public String getImportantInfo() {
    return importantInfo;
}

Add Multi-Span Attributes 

Sometimes you want to add the same attribute to many spans within the same trace. This attribute may include variables calculated during your program, or other useful values for correlation or debugging purposes.

To add this attribute, leverage the OpenTelemetry concept of baggage. Baggage allows you to add a key with a value as an attribute to every subsequent child span of the current application context.

In your code, import io.opentelemetry.api.baggage.Baggage to allow use of the Baggage class:

import io.opentelemetry.api.baggage.Baggage;
import io.opentelemetry.api.trace.Span;
import io.opentelemetry.context.Scope;

...

try (final Scope ignored = Baggage.current()
    .toBuilder()
    .put("app.username", name)
    .build()
    .makeCurrent()
) {
    // all subsequently created span in this block will have the `app.username` attribute
}

Note: Any Baggage attributes that you set in your application will be attached to outgoing network requests as a header. If your service communicates to a third party API, do NOT put sensitive information in the Baggage attributes.

Sampling 

You can use deterministic head sampling with the Java Agent, with or without custom instrumentation.

The agent will read these variables and expect an integer that represents the sample rate you would like to apply. For example, a value of 5 means that one out of every five traces will be sent to Honeycomb.

To add sampling to the agent, specify the SAMPLE_RATE environment variable or the -Dsample.rate system property when invoking the Java Virtual Machine (JVM), as shown in Advanced Configuration.

The value of your sample rate must be a positive integer.

If you have multiple services that communicate with each other, it is important that they have the same sampling configuration. Otherwise, each service might make a different sampling decision, resulting in incomplete or broken traces. You can sample using a standalone proxy as an alternative, like Honeycomb Refinery, or when you have more robust sampling needs.

Metrics Collection 

The JVM emits metrics at regular intervals that can be sent automatically to a Honeycomb dataset. These metrics will show up in data as runtime.jvm.gc.count, runtime.jvm.gc.time, runtime.jvm.memory.area, and so on. If an instrumentation library also supports emitting metrics, then those metrics will be sent as well.

Metrics are currently disabled by default. To enable metrics, set a HONEYCOMB_METRICS_DATASET environment variable. Optionally, set a specific HONEYCOMB_METRICS_APIKEY or HONEYCOMB_METRICS_ENDPOINT (if different from the traces API key and endpoint), as shown in Advanced Configuration.

Distributed Trace Propagation 

When a service calls another service, you want to ensure that the relevant trace information is propagated from one service to the other. This allows Honeycomb to connect the two services in a trace.

Distributed tracing enables you to trace and visualize interactions between multiple instrumented services. For example, your users may interact with a front-end API service, which talks to two internal APIs to fulfill their request. In order to have traces connect spans for all these services, it is necessary to propagate trace context between these services, usually by using an HTTP header.

Both the sending and receiving service must use the same propagation format, and both services must be configured to send data to the same Honeycomb environment.

Using the Honeycomb SDK Builder 

If you do not wish to use the automatic instrumentation agent, and/or wish to do more advanced instrumentation like adding other span processors or extensions, you can use the Honeycomb SDK to instantiate an OpenTelemetryConfiguration instance, which provides access to a Tracer and the rest of the OpenTelemetry API.

You should configure this as early as possible in the entry point of your application. This builder is not required if the agent is in use.

Aside from requiring this builder, setting up manual instrumentation will be the same as when using the agent.

The OpenTelemetryConfiguration builder provides convenient methods for configuration:

import io.honeycomb.opentelemetry.OpenTelemetryConfiguration;
import io.honeycomb.opentelemetry.sdk.trace.samplers.DeterministicTraceSampler; // optional
import io.honeycomb.opentelemetry.sdk.trace.spanprocessors.BaggageSpanProcessor; // optional

public OpenTelemetry honeycomb() {
  return OpenTelemetryConfiguration.builder()
    .setApiKey("your-api-key")
    .setServiceName("your-service-name")
    .setOtlpProtocol("http/protobuf") // optional - use HTTP instead of gRPC to transmit telemetry
    .setSampler(new DeterministicTraceSampler(2)) // optional - sends 1/2 of all traces generated
    .addSpanProcessor(new BaggageSpanProcessor()) // optional
    .buildAndRegisterGlobal();
}

When using the Honeycomb SDK builder, specify a span processor and/or a sampler with a sample rate as an argument to the constructor.

The BaggageSpanProcessor is available as part of the Honeycomb SDK; it is what allows for multi-span attributes. The DeterministicTraceSampler is available as part of the Honeycomb SDK that samples based on a common field, given a sample rate.

The setSampler method accepts any instance of a class that implements the io.opentelemetry.sdk.trace.samplers.Sampler interface. Look at the provided deterministic sampler as an example of how to create your own custom sampler, if needed.

Including the Java Agent as Part of Build Process 

Another option for using the agent is to include it when running Maven targets or Gradle tasks. For example, here is a possible configuration to attach the Java agent when running a Spring Boot app:

bootRun {
    environment = ["HONEYCOMB_API_KEY": System.getenv("HONEYCOMB_API_KEY"),
                   "OTEL_SERVICE_NAME": System.getenv("OTEL_SERVICE_NAME")]
    jvmArgs = ["-javaagent:honeycomb-opentelemetry-javaagent-1.7.0.jar"]
}

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <environmentVariables>
                        <OTEL_SERVICE_NAME>${env.OTEL_SERVICE_NAME}</OTEL_SERVICE_NAME>
                        <HONEYCOMB_API_KEY>${env.HONEYCOMB_API_KEY}</HONEYCOMB_API_KEY>
                    </environmentVariables>
                    <agents>
                        <agent>
                            honeycomb-opentelemetry-javaagent-1.7.0.jar
                        </agent>
                    </agents>
                </configuration>
            </plugin>
        </plugins>
    </build>

Be sure to set the environment variables for HONEYCOMB_API_KEY and OTEL_SERVICE_NAME as described in the Configure step above.

Using HTTP/protobuf instead of gRPC 

By default, the Honeycomb OpenTelemetry SDK uses the gRPC protocol to send telemetry data. To use HTTP instead of gRPC, update the protocol using one of the configuration methods:

• System property: -Dotel.exporter.otlp.protocol=http/protobuf
• Environment variable: export OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf

Troubleshooting 

To explore common issues when sending data, visit Common Issues with Sending Data in Honeycomb.

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