Java tracing installation

For the complete SDK reference, see the OpenTelemetry Java docs.

The zero-code Java agent is the recommended way to instrument a Java app. Download the latest agent jar:

curl -L -O https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/latest/download/opentelemetry-javaagent.jar

The agent instruments your application at runtime, so you don't need to add any dependencies to get started. If you'd rather instrument manually, see the SDK alternative in the configuration step.

You'll need your PostHog project token to authenticate trace requests. This is the same token you use for capturing events with the PostHog SDK.

Important: Use your project token which starts with phc_. Do not use a personal API key (which starts with phx_).

You can find your project token in Project settings.

Set the OpenTelemetry environment variables to export spans to PostHog over OTLP HTTP, then start your app with the agent attached.

OTEL_EXPORTER_OTLP_TRACES_ENDPOINT=https://us.i.posthog.com/i/v1/traces
OTEL_EXPORTER_OTLP_TRACES_HEADERS=Authorization=Bearer <ph_project_token>
OTEL_EXPORTER_OTLP_TRACES_PROTOCOL=http/protobuf
OTEL_SERVICE_NAME=my-service

java -javaagent:opentelemetry-javaagent.jar -jar myapp.jar

To instrument manually instead, add the SDK dependencies (opentelemetry-api, opentelemetry-sdk, and opentelemetry-exporter-otlp via the opentelemetry-bom) and build the exporter in code:

import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporter;
import io.opentelemetry.sdk.OpenTelemetrySdk;
import io.opentelemetry.sdk.trace.SdkTracerProvider;
import io.opentelemetry.sdk.trace.export.BatchSpanProcessor;

OtlpHttpSpanExporter spanExporter = OtlpHttpSpanExporter.builder()
    .setEndpoint("https://us.i.posthog.com/i/v1/traces")
    .addHeader("Authorization", "Bearer <ph_project_token>")
    .build();

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

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

The buildAndRegisterGlobal() call registers the SDK as the global instance, so GlobalOpenTelemetry.getTracer(...) in the next step works. (The Java agent does this for you, which is why the zero-code path needs no registration.)

Note: Pass the full /i/v1/traces path to the traces endpoint. OtlpHttpSpanExporter already sends OTLP over HTTP/protobuf, so no protocol setting is needed in code. If you configure via the environment variables above instead, set OTEL_EXPORTER_OTLP_TRACES_PROTOCOL=http/protobuf – the SDK's autoconfigure path defaults to gRPC.

Wrap the operations you want to measure in spans, and attach attributes for context.

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

Tracer tracer = GlobalOpenTelemetry.getTracer("my-service");

Span span = tracer.spanBuilder("checkout-order").startSpan();
try (Scope scope = span.makeCurrent()) {
    span.setAttribute("order.id", orderId);
    // ... do work ...
} catch (Exception e) {
    span.recordException(e);
    throw e;
} finally {
    span.end();
}

Once everything is configured, confirm spans are reaching PostHog:

1. Run your application and trigger the instrumented code
2. Open the PostHog Tracing interface
3. Confirm your spans and traces appear