update the Jaeger example to cleanly separate SDK and API usage (#2531)

* update the Jaeger example to cleanly separate SDK and API usage

* formatting

examples/jaeger/src/main/java/io/opentelemetry/example/jaeger/ExampleConfiguration.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.example.jaeger;
+
+import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
+import io.opentelemetry.api.OpenTelemetry;
+import io.opentelemetry.exporter.jaeger.JaegerGrpcSpanExporter;
+import io.opentelemetry.sdk.OpenTelemetrySdk;
+import io.opentelemetry.sdk.trace.SdkTracerProvider;
+import io.opentelemetry.sdk.trace.export.SimpleSpanProcessor;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * All SDK management takes place here, away from the instrumentation code, which should only access
+ * the OpenTelemetry APIs.
+ */
+class ExampleConfiguration {
+
+  /**
+   * Initialize an OpenTelemetry SDK with a Jaeger exporter and a SimpleSpanProcessor.
+   *
+   * @param jaegerHost The host of your Jaeger instance.
+   * @param jaegerPort the port of your Jaeger instance.
+   * @return A ready-to-use {@link OpenTelemetry} instance.
+   */
+  static OpenTelemetry initOpenTelemetry(String jaegerHost, int jaegerPort) {
+    // Create a channel towards Jaeger end point
+    ManagedChannel jaegerChannel =
+        ManagedChannelBuilder.forAddress(jaegerHost, jaegerPort).usePlaintext().build();
+    // Export traces to Jaeger
+    JaegerGrpcSpanExporter jaegerExporter =
+        JaegerGrpcSpanExporter.builder()
+            .setServiceName("otel-jaeger-example")
+            .setChannel(jaegerChannel)
+            .setTimeout(30, TimeUnit.SECONDS)
+            .build();
+
+    // Set to process the spans by the Jaeger Exporter
+    OpenTelemetrySdk openTelemetry =
+        OpenTelemetrySdk.builder()
+            .setTracerProvider(
+                SdkTracerProvider.builder()
+                    .addSpanProcessor(SimpleSpanProcessor.create(jaegerExporter))
+                    .build())
+            .build();
+
+    // it's always a good idea to shut down the SDK cleanly at JVM exit.
+    Runtime.getRuntime()
+        .addShutdownHook(new Thread(() -> openTelemetry.getTracerManagement().shutdown()));
+
+    return openTelemetry;
+  }
+}

examples/jaeger/src/main/java/io/opentelemetry/example/jaeger/JaegerExample.java

@@ -1,48 +1,15 @@
 package io.opentelemetry.example.jaeger;
 
-import io.grpc.ManagedChannel;
-import io.grpc.ManagedChannelBuilder;
+import io.opentelemetry.api.OpenTelemetry;
 import io.opentelemetry.api.trace.Span;
 import io.opentelemetry.api.trace.Tracer;
-import io.opentelemetry.exporter.jaeger.JaegerGrpcSpanExporter;
-import io.opentelemetry.sdk.OpenTelemetrySdk;
-import io.opentelemetry.sdk.trace.SdkTracerManagement;
-import io.opentelemetry.sdk.trace.SdkTracerProvider;
-import io.opentelemetry.sdk.trace.export.SimpleSpanProcessor;
-import java.util.concurrent.TimeUnit;
 
 public class JaegerExample {
 
-  // OTel API
-  private final SdkTracerManagement sdkTracerManagement;
   private final Tracer tracer;
 
-  public JaegerExample(String ip, int port) {
-    OpenTelemetrySdk sdk = initOpenTelemetry(ip, port);
-    this.sdkTracerManagement = sdk.getTracerManagement();
-    tracer = sdk.getTracer("io.opentelemetry.example.JaegerExample");
-  }
-
-  private OpenTelemetrySdk initOpenTelemetry(String ip, int port) {
-    // Create a channel towards Jaeger end point
-    ManagedChannel jaegerChannel =
-        ManagedChannelBuilder.forAddress(ip, port).usePlaintext().build();
-    // Export traces to Jaeger
-    // Export traces to Jaeger
-    JaegerGrpcSpanExporter jaegerExporter =
-        JaegerGrpcSpanExporter.builder()
-            .setServiceName("otel-jaeger-example")
-            .setChannel(jaegerChannel)
-            .setTimeout(30, TimeUnit.SECONDS)
-            .build();
-
-    // Set to process the spans by the Jaeger Exporter
-    return OpenTelemetrySdk.builder()
-        .setTracerProvider(
-            SdkTracerProvider.builder()
-                .addSpanProcessor(SimpleSpanProcessor.create(jaegerExporter))
-                .build())
-        .build();
+  public JaegerExample(OpenTelemetry openTelemetry) {
+    tracer = openTelemetry.getTracer("io.opentelemetry.example.JaegerExample");
   }
 
   private void myWonderfulUseCase() {
@@ -63,33 +30,26 @@ public class JaegerExample {
     }
   }
 
-  // graceful shutdown
-  public void shutdown() {
-    // note: this doesn't wait for everything to get cleaned up. We need an SDK update to enable
-    // that.
-    sdkTracerManagement.shutdown();
-  }
-
   public static void main(String[] args) {
     // Parsing the input
     if (args.length < 2) {
       System.out.println("Missing [hostname] [port]");
       System.exit(1);
     }
-    String ip = args[0];
-    int port = Integer.parseInt(args[1]);
+    String jaegerHostName = args[0];
+    int jaegerPort = Integer.parseInt(args[1]);
+
+    // it is important to initialize your SDK as early as possible in your application's lifecycle
+    OpenTelemetry openTelemetry =
+        ExampleConfiguration.initOpenTelemetry(jaegerHostName, jaegerPort);
 
     // Start the example
-    JaegerExample example = new JaegerExample(ip, port);
-    example.initOpenTelemetry(ip, port);
+    JaegerExample example = new JaegerExample(openTelemetry);
     // generate a few sample spans
     for (int i = 0; i < 10; i++) {
       example.myWonderfulUseCase();
     }
 
-    // Shutdown example
-    example.shutdown();
-
     System.out.println("Bye");
   }
 }