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Using OpenTelemetry Logging

This guide explains how your Quarkus application can utilize OpenTelemetry (OTel) to provide structured, contextual, vendor-neutral and centralised logging for interactive web applications.

Note

  • OpenTelemetry Logging is considered tech preview and is disabled by default.

  • The OpenTelemetry Guide is available with signal independent information about the OpenTelemetry extension.

Architecture

In this guide, we create a straightforward REST application to demonstrate OTel logging, in a similar way to the other OpenTelemetry signal guides.

Solution

We recommend that you follow the instructions in the next sections and create the application step by step. However, you can skip right to the completed example.

Clone the Git repository: git clone {quickstarts-clone-url}, or download an {quickstarts-archive-url}[archive].

The solution is located in the opentelemetry-quickstart directory.

Creating the Maven project

First, we need a new project. Create a new project with the following command:

This command generates the Maven project and imports the quarkus-opentelemetry extension, which includes the default OpenTelemetry support, and a gRPC span exporter for OTLP.

If you already have your Quarkus project configured, you can add the quarkus-opentelemetry extension to your project by running the following command in your project base directory:

This will add the following to your build file:

pom.xml
<dependency>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-opentelemetry</artifactId>
</dependency>
build.gradle
implementation("io.quarkus:quarkus-opentelemetry")

Examine the Jakarta REST resource

Create a src/main/java/org/acme/opentelemetry/TracedResource.java file with the following content:

package org.acme.opentelemetry;

import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;
import jakarta.ws.rs.Produces;
import jakarta.ws.rs.core.MediaType;
import org.jboss.logging.Logger;

@Path("/hello")
public class TracedResource {

    private static final Logger LOG = Logger.getLogger(TracedResource.class);

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello() {
        LOG.info("hello");
        return "hello";
    }
}

If you have followed the tracing guide, this class will seem familiar. The main difference is that now, the hello message logged with org.jboss.logging.Logger will end up in the OpenTelemetry logs.

Create the configuration

The only mandatory configuration for OpenTelemetry Logging is the one enabling it:

quarkus.otel.logs.enabled=true

To change any of the default property values, here is an example on how to configure the default OTLP gRPC Exporter within the application, using the src/main/resources/application.properties file:

quarkus.application.name=myservice // (1)
quarkus.otel.logs.enabled=true // (2)
quarkus.otel.exporter.otlp.logs.endpoint=http://localhost:4317 // (3)
quarkus.otel.exporter.otlp.logs.headers=authorization=Bearer my_secret // (4)

  1. All logs created from the application will include an OpenTelemetry Resource indicating the logs were created by the myservice application. If not set, it will default to the artifact id.

  2. Enable the OpenTelemetry logging. Must be set at build time.

  3. gRPC endpoint to send the logs. If not set, it will default to http://localhost:4317.

  4. Optional gRPC headers commonly used for authentication.

To configure the connection using the same properties for all signals, please check the base configuration section of the OpenTelemetry guide.

Setting the log level

By default all log levels are exported.

If the following configuration is created in the the application.properties file, only logs with a level of ERROR or higher will be exported:

quarkus.otel.logs.level=ERROR

As in other logs in Quarkus, log levels can be set to these values.

Run the application

First we need to start a system to visualise the OpenTelemetry data. We have 2 options:

  • Start an all-in-one Grafana OTel LGTM system for traces, metrics and logs.

See the data

Grafana OTel LGTM option

This features a Quarkus Dev service including a Grafana for visualizing data, Loki to store logs, Tempo to store traces and Prometheus to store metrics. Also provides and OTel collector to receive the data.

Logging exporter

You can output all logs to the console by setting the exporter to logging in the application.properties file:

quarkus.otel.logs.exporter=logging (1)

  1. Set the exporter to logging. Normally you don’t need to set this. The default is cdi.

Also add this dependency to your project:

<dependency>
    <groupId>io.opentelemetry</groupId>
    <artifactId>opentelemetry-exporter-logging</artifactId>
</dependency>

OpenTelemetry Configuration Reference

See the main OpenTelemetry Guide configuration reference.