Java

See what your Java application is doing in Logfire: the requests it handles, how long each one took, and which ones failed, without changing your code. It is one flag and about two minutes.

Java does not have a dedicated Logfire SDK, but Logfire is built on OpenTelemetry (OTel), the open industry standard for collecting traces, metrics, and logs. OpenTelemetry ships a Java agent that attaches to your running application and instruments common libraries (web servers, HTTP clients, database drivers) for you. You add one flag when you start the app and get traces (the full journey of one request, made of nested spans, where a span is one unit of work with a name, a start, and a duration) in the Logfire UI.

Before you start

You need:

• A Logfire project and a write token (the credential your app uses to send data to a Logfire project). Copy one from Project → Settings → Write tokens; see Create Write Tokens.
• A working Java runtime and an application you can run. The agent instruments a real app, so a program that does no work produces no spans.

This sends your data to Logfire

The steps below send your app’s data to Logfire, where it is stored. To keep data on your own infrastructure while you evaluate, send it to a local backend instead. Your write token is a secret, so keep it out of source control.

Send your first trace

1. Download the agent

Terminal

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

Note

This downloads the latest agent. For production, pin a specific release from the releases page and verify its checksum before running it.

2. Configure the agent

Terminal

export OTEL_SERVICE_NAME=hello-java
export OTEL_EXPORTER_OTLP_ENDPOINT=https://logfire-us.pydantic.dev
export OTEL_EXPORTER_OTLP_HEADERS='Authorization=your-write-token'
export OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf

The endpoint above is for the US data region. If your project is in the EU region, use https://logfire-eu.pydantic.dev instead.

3. Start your app with the agent attached

Terminal

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

Replace myapp.jar with your application’s jar, or add -javaagent:./opentelemetry-javaagent.jar to your normal start command. No code changes and no extra dependencies: the agent instruments the web server, HTTP clients, and database drivers your app already uses.

4. Exercise your app

The agent only records work your app actually does. Send it a request (open a page, call an endpoint, or run the code path you care about) so it produces spans.

Note

Version 2.x of the Java agent already uses http/protobuf by default, which matches Logfire. Setting OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf explicitly (as above) also makes older 1.x agents work, so it is safe to keep.

See it in the Live view

Open the Live view in Logfire. Traces arrive under the service name hello-java as your app handles work:

Each row is one span, with its service, name, and duration. The screenshot shows a busier app; your app’s spans appear as rows under service hello-java, which you can click to open their full traces.

Troubleshooting

Symptom	Likely cause	Fix
Nothing arrives	An older 1.x agent defaulted to gRPC	Upgrade to a 2.x agent, or keep OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf set
No spans appear at all	The app did no instrumented work	Trigger an HTTP request or database call, or add manual instrumentation for your own code
Can’t tell what the agent is doing	No visibility into what it instruments	Run with -Dotel.javaagent.debug=true to log what the agent instruments and why nothing exports
Connection or region errors	Wrong base URL	Give the bare base URL (https://logfire-us.pydantic.dev); the agent appends /v1/traces. Check the URL matches your data region
Nothing arrives from a self-hosted instance with a private certificate	The JVM has its own trust store and does not trust a private CA	Point the agent at the CA: OTEL_EXPORTER_OTLP_CERTIFICATE=/path/to/ca.pem

Next steps

• New to tracing? Core concepts explains spans and traces and how to read them.
• Want to add your own spans? Use the OpenTelemetry Java API on top of the automatic ones.
• Another language? See Language support, or Alternative clients for the generic pattern.