Instrument NATS agent 'request' method

Author: AlixBa

instrumentation/nats/nats-2.21/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/nats/v2_21/CompletableFutureWrapper.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.instrumentation.nats.v2_21;
+
+import io.opentelemetry.context.Context;
+import io.opentelemetry.context.Scope;
+import java.util.concurrent.CompletableFuture;
+
+public final class CompletableFutureWrapper {
+
+  private CompletableFutureWrapper() {}
+
+  public static <T> CompletableFuture<T> wrap(CompletableFuture<T> future, Context context) {
+    CompletableFuture<T> result = new CompletableFuture<>();
+    future.whenComplete(
+        (T value, Throwable throwable) -> {
+          try (Scope ignored = context.makeCurrent()) {
+            if (throwable != null) {
+              result.completeExceptionally(throwable);
+            } else {
+              result.complete(value);
+            }
+          }
+        });
+
+    return result;
+  }
+}