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Observability for Quarkus LangChain4j with Opik

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Quarkus LangChain4j uses Quarkus OpenTelemetry configuration in application.properties.

When this guide applies

Use this if your app is Quarkus + LangChain4j and you want OTEL traces to land in Opik.

Opik OTLP endpoint modes

For full endpoint/header details, see Opik OpenTelemetry overview.

  • Cloud endpoint: https://www.comet.com/opik/api/v1/private/otel
  • Enterprise endpoint: https://<comet-deployment-url>/opik/api/v1/private/otel
  • Self-hosted endpoint: http://localhost:5173/api/v1/private/otel

Example (application.properties)

Intent: Configure Quarkus OTEL trace exporter to target Opik directly.

Applies when: You are using Quarkus-native OTEL exporter settings.

Required fields:

  • quarkus.otel.enabled=true
  • quarkus.otel.traces.enabled=true
  • quarkus.otel.exporter.otlp.traces.endpoint
  • quarkus.otel.exporter.otlp.traces.protocol=http/protobuf

Recommended fields:

  • quarkus.langchain4j.tracing.include-prompt=true and quarkus.langchain4j.tracing.include-completion=true: without them, LLM spans arrive with model and token usage but no input or output (both default to false)
  • quarkus.langchain4j.tracing.include-tool-arguments=true and quarkus.langchain4j.tracing.include-tool-result=true if your AI services call tools

Optional fields:

  • quarkus.otel.exporter.otlp.traces.headers (projectName strongly recommended)
  • quarkus.application.name (for service.name attribution)

Minimal valid setup:

quarkus.otel.enabled=true
quarkus.otel.traces.enabled=true
quarkus.otel.exporter.otlp.traces.endpoint=https://www.comet.com/opik/api/v1/private/otel
quarkus.otel.exporter.otlp.traces.protocol=http/protobuf
quarkus.otel.exporter.otlp.traces.headers=Authorization=<your-api-key>,Comet-Workspace=<your-workspace>,projectName=<your-project-name>
# Send prompt and completion text, not just model and token counts
quarkus.langchain4j.tracing.include-prompt=true
quarkus.langchain4j.tracing.include-completion=true

Validation

  1. Start your Quarkus app with OTEL enabled.
  2. Trigger a LangChain4j-backed endpoint/action.
  3. Confirm spans with your configured service.name and project headers arrive in Opik.
  4. Open the completion <model> span: it should show the model, token usage, the prompt as input and the model response as output. If input and output are empty, check the include-prompt / include-completion settings above.

Source references