improve javaagent declarative config example (#912)

Author: zeitlinger

README.md

@@ -86,6 +86,11 @@ To build the all of examples, run:
       OpenTelemetry SDK to use a Zipkin exporter and send spans to a
       Zipkin backend using the OpenTelemetry API.
     - Note: This example requires Docker to be installed.
+- [Declarative Configuration with the OpenTelemetry Java Agent](javaagent-declarative-configuration)
+    - This module demonstrates how to use declarative configuration with the
+      OpenTelemetry Java Agent to configure tracing behavior, including
+      excluding specific endpoints from tracing.
+    - Note: This example requires Java 17 or higher.
 
 ## Contributing
 

javaagent-declarative-configuration/README.md

@@ -11,7 +11,7 @@ This Spring Boot application includes two endpoints:
 ## End-to-End Instructions
 
 ### Prerequisites
-* Java 17 or higher
+* Java 17 or higher (due to Spring Boot 3 requirement, not because of declarative config support)
 * OpenTelemetry Java Agent JAR file (see next step)
 
 Download the OpenTelemetry Java Agent:

javaagent-declarative-configuration/build.gradle.kts

@@ -9,6 +9,12 @@ plugins {
 description = "OpenTelemetry Java Agent Declarative Configuration Example"
 val moduleName by extra { "io.opentelemetry.examples.javaagent.declarative" }
 
+java {
+    toolchain {
+        languageVersion.set(JavaLanguageVersion.of(17))
+    }
+}
+
 dependencies {
     implementation(platform(SpringBootPlugin.BOM_COORDINATES))
     implementation("org.springframework.boot:spring-boot-starter-web")

javaagent-declarative-configuration/oats/docker-compose.yml

@@ -7,12 +7,10 @@ services:
     environment:
       OTEL_SERVICE_NAME: "declarative-config-example-app"
       OTEL_EXPORTER_OTLP_ENDPOINT: http://lgtm:4318
-      OTEL_EXPORTER_OTLP_TRACES_ENDPOINT: http://lgtm:4318/v1/traces
-      OTEL_EXPORTER_OTLP_PROTOCOL: http/protobuf
     ports:
       - "8080:8080"
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:8080/actuator/health"]
       interval: 10s
       timeout: 5s
-      retries: 3
+      retries: 3

javaagent-declarative-configuration/otel-agent-config.yaml

@@ -1,23 +1,36 @@
-# See https://github.com/open-telemetry/opentelemetry-configuration for details on schema and examples
+# For schema documentation, including required properties, semantics, default behavior, etc,
+# see: https://github.com/open-telemetry/opentelemetry-configuration/blob/main/schema-docs.md
 
 file_format: "1.0-rc.2"
 
 resource:
   attributes:
     - name: service.name
       value: spring-boot-declarative-config-example
+  # Read resource attributes from the OTEL_RESOURCE_ATTRIBUTES environment variable.
+  # This aligns well with the OpenTelemetry Operator and other deployment methods.
+  attributes_list: ${OTEL_RESOURCE_ATTRIBUTES}
+  detection/development: # /development properties may not be supported in all SDKs
+    detectors:
+      - service: # will add "service.instance.id" and "service.name" from the OTEL_SERVICE_NAME env var
+      - host:
+      - process:
+      - container:
 
 propagator:
   composite:
     - tracecontext:
     - baggage:
 
+# Read backend endpoint from the OTEL_EXPORTER_OTLP_ENDPOINT environment variable.
+# This aligns well with the OpenTelemetry Operator and other deployment methods.
+
 tracer_provider:
   processors:
     - batch:
         exporter:
           otlp_http:
-            endpoint: ${OTEL_EXPORTER_OTLP_TRACES_ENDPOINT:-http://localhost:4318/v1/traces}
+            endpoint: ${OTEL_EXPORTER_OTLP_ENDPOINT:-http://localhost:4318}/v1/traces
 
     # Configure a console exporter for exploring without a collector/backend
     - batch:
@@ -45,11 +58,11 @@ meter_provider:
     - periodic:
         exporter:
           otlp_http:
-            endpoint: ${OTEL_EXPORTER_OTLP_METRICS_ENDPOINT:-http://localhost:4318/v1/metrics}
+            endpoint: ${OTEL_EXPORTER_OTLP_ENDPOINT:-http://localhost:4318}/v1/metrics
 
 logger_provider:
   processors:
     - batch:
         exporter:
           otlp_http:
-            endpoint: ${OTEL_EXPORTER_OTLP_LOGS_ENDPOINT:-http://localhost:4318/v1/logs}
+            endpoint: ${OTEL_EXPORTER_OTLP_ENDPOINT:-http://localhost:4318}/v1/logs