SpringBootOpenTelemetryPrometheusExemplars - k8staz.com

application.yaml

# Enable Actuator endpoints including Prometheus
management:
  endpoints:
    web:
      exposure:
        include: health, info, prometheus
  metrics:
    # Exemplar metrics
    distribution:
      percentiles-histogram:
        http.server.requests: true
      minimum-expected-value:
        http.server.requests: 5ms
      maximum-expected-value:
        http.server.requests: 1000ms

# Add trace_id in log. OpenTelemetry set this value using logger-mdc.
# https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/docs/logger-mdc-instrumentation.md
logging:
  pattern:
    level: '%prefix(%mdc{trace_id:-0}) %5p'

build.gradle

plugins {
	id 'org.springframework.boot' version '2.7.0'
	id 'io.spring.dependency-management' version '1.0.11.RELEASE'
	id 'java'
}

repositories {
  maven {
    url = uri('https://repo.spring.io/libs-snapshot')
  }
	mavenCentral()
}

dependencyManagement {
  imports {
    mavenBom 'io.micrometer:micrometer-bom:1.9.0-SNAPSHOT'
  }
}

dependencies {
  implementation 'org.springframework.boot:spring-boot-starter-actuator'
  implementation 'io.micrometer:micrometer-registry-prometheus:1.9.0'
  implementation 'org.springframework.boot:spring-boot-starter-web'
  implementation 'io.opentelemetry:opentelemetry-api:1.12.0'
}

tasks.named('test') {
	useJUnitPlatform()
}

group = 'com.staz'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '11'

Controller.java

package com.staz.observability;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class Controller {

    @PostMapping("/fail")
    public String fail() {
        return "Fail!";
    }

    @GetMapping("/success")
    public String success() {

        return "Success!";
    }

}

Dockerfile

# Download OpenTelemetryAgent
FROM curlimages/curl:7.81.0 AS OTEL_AGENT
ARG OTEL_AGENT_VERSION="1.12.1"
RUN curl --silent --fail -L "https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/download/v${OTEL_AGENT_VERSION}/opentelemetry-javaagent.jar" \
    -o "/tmp/opentelemetry-javaagent.jar"

# Build .JAR file
FROM gradle:7.1.1-jdk11-hotspot AS BUILD_IMAGE
COPY --chown=gradle:gradle . /home/gradle/src
WORKDIR /home/gradle/src
RUN gradle build -x test --no-daemon 

# Final image copying OTEL Agent and .JAR File
FROM gradle:7.1.1-jdk11-hotspot
ENV TIME_ZONE America/Lima
ENV TZ=$TIME_ZONE
ENV JAVA_OPTS "-Dspring.config.location=src/main/resources/application.yaml"
COPY --from=OTEL_AGENT /tmp/opentelemetry-javaagent.jar /otel-javaagent.jar
COPY --from=BUILD_IMAGE home/gradle/src/build/libs/*.jar app.jar
ENTRYPOINT exec java -javaagent:/otel-javaagent.jar -jar app.jar 

PrometheusExemplarConfiguration.java

package com.staz.observability;

import io.micrometer.core.instrument.Clock;
import io.micrometer.prometheus.PrometheusConfig;
import io.micrometer.prometheus.PrometheusMeterRegistry;
import io.opentelemetry.api.trace.Span;
import io.prometheus.client.CollectorRegistry;
import io.prometheus.client.exemplars.DefaultExemplarSampler;
import io.prometheus.client.exemplars.tracer.otel_agent.OpenTelemetryAgentSpanContextSupplier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class PrometheusExemplarConfiguration {
    @Bean
    public PrometheusMeterRegistry prometheusMeterRegistryWithExemplar
    (PrometheusConfig prometheusConfig, CollectorRegistry collectorRegistry, 
    Clock clock) {
        return new PrometheusMeterRegistry(prometheusConfig, collectorRegistry, 
        clock, new DefaultExemplarSampler(new OpenTelemetryAgentSpanContextSupplier() {

                    @Override
                    public String getTraceId() {
                        if (!Span.current().getSpanContext().isSampled()) {
                            return null;
                        }
                        return super.getTraceId();
                    }
                })
        );
    }
}