Bound OkHttp sender dispatchers and surface rejections

exporters/sender/okhttp/src/main/java/io/opentelemetry/exporter/sender/okhttp/internal/OkHttpGrpcSender.java

@@ -41,6 +41,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
@@ -155,22 +156,26 @@ public void send(
     RequestBody requestBody = new GrpcRequestBody(messageWriter, compressor);
     requestBuilder.post(requestBody);
 
-    InstrumentationUtil.suppressInstrumentation(
-        () ->
-            client
-                .newCall(requestBuilder.build())
-                .enqueue(
-                    new Callback() {
-                      @Override
-                      public void onFailure(Call call, IOException e) {
-                        onError.accept(e);
-                      }
-
-                      @Override
-                      public void onResponse(Call call, Response response) {
-                        handleResponse(response, onResponse);
-                      }
-                    }));
+    try {
+      InstrumentationUtil.suppressInstrumentation(
+          () ->
+              client
+                  .newCall(requestBuilder.build())
+                  .enqueue(
+                      new Callback() {
+                        @Override
+                        public void onFailure(Call call, IOException e) {
+                          onError.accept(e);
+                        }
+
+                        @Override
+                        public void onResponse(Call call, Response response) {
+                          handleResponse(response, onResponse);
+                        }
+                      }));
+    } catch (RejectedExecutionException e) {
+      onError.accept(e);
+    }
   }
 
   private void handleResponse(Response response, Consumer<GrpcResponse> onResponse) {

exporters/sender/okhttp/src/main/java/io/opentelemetry/exporter/sender/okhttp/internal/OkHttpHttpSender.java

@@ -21,6 +21,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.RejectedExecutionException;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 import java.util.logging.Level;
@@ -138,22 +139,26 @@ public void send(
     requestBuilder.addHeader("Accept-Encoding", "gzip, identity");
     requestBuilder.post(new RequestBodyImpl(messageWriter, compressor, mediaType));
 
-    InstrumentationUtil.suppressInstrumentation(
-        () ->
-            client
-                .newCall(requestBuilder.build())
-                .enqueue(
-                    new Callback() {
-                      @Override
-                      public void onFailure(Call call, IOException e) {
-                        onError.accept(e);
-                      }
-
-                      @Override
-                      public void onResponse(Call call, Response response) {
-                        handleResponse(response, onResponse, onError);
-                      }
-                    }));
+    try {
+      InstrumentationUtil.suppressInstrumentation(
+          () ->
+              client
+                  .newCall(requestBuilder.build())
+                  .enqueue(
+                      new Callback() {
+                        @Override
+                        public void onFailure(Call call, IOException e) {
+                          onError.accept(e);
+                        }
+
+                        @Override
+                        public void onResponse(Call call, Response response) {
+                          handleResponse(response, onResponse, onError);
+                        }
+                      }));
+    } catch (RejectedExecutionException e) {
+      onError.accept(e);
+    }
   }
 
   private void handleResponse(

exporters/sender/okhttp/src/main/java/io/opentelemetry/exporter/sender/okhttp/internal/OkHttpUtil.java

@@ -20,6 +20,8 @@
  * at any time.
  */
 public final class OkHttpUtil {
+  private static final int DEFAULT_MAX_REQUESTS_PER_HOST = 5;
+
   @SuppressWarnings("NonFinalStaticField")
   private static boolean propagateContextForTestingInDispatcher = false;
 
@@ -30,14 +32,19 @@ public static void setPropagateContextForTestingInDispatcher(
 
   /** Returns a {@link Dispatcher} using daemon threads, otherwise matching the OkHttp default. */
   public static Dispatcher newDispatcher() {
-    return new Dispatcher(
-        new ThreadPoolExecutor(
-            0,
-            Integer.MAX_VALUE,
-            60,
-            TimeUnit.SECONDS,
-            new SynchronousQueue<>(),
-            createThreadFactory("okhttp-dispatch")));
+    int maxRequests = Math.max(Runtime.getRuntime().availableProcessors(), 5);
+    Dispatcher dispatcher =
+        new Dispatcher(
+            new ThreadPoolExecutor(
+                0,
+                maxRequests,
+                60,
+                TimeUnit.SECONDS,
+                new SynchronousQueue<>(),
+                createThreadFactory("okhttp-dispatch")));
+    dispatcher.setMaxRequests(maxRequests);
+    dispatcher.setMaxRequestsPerHost(DEFAULT_MAX_REQUESTS_PER_HOST);
+    return dispatcher;
   }
 
   private static DaemonThreadFactory createThreadFactory(String namePrefix) {

exporters/sender/okhttp/src/test/java/io/opentelemetry/exporter/sender/okhttp/internal/OkHttpGrpcSenderTest.java

@@ -5,11 +5,13 @@
 
 package io.opentelemetry.exporter.sender.okhttp.internal;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import io.opentelemetry.exporter.internal.RetryUtil;
 import io.opentelemetry.sdk.common.CompletableResultCode;
+import io.opentelemetry.sdk.common.export.GrpcResponse;
 import io.opentelemetry.sdk.common.export.GrpcStatusCode;
 import io.opentelemetry.sdk.common.export.MessageWriter;
 import java.io.IOException;
@@ -21,7 +23,10 @@
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
 import okhttp3.MediaType;
 import okhttp3.Protocol;
 import okhttp3.Request;
@@ -57,6 +62,34 @@ void isRetryable_NonRetryableGrpcStatus() {
     assertFalse(isRetryable);
   }
 
+  @Test
+  void send_rejectedExecution_callsOnError() {
+    ThreadPoolExecutor executor =
+        new ThreadPoolExecutor(0, 1, 0, TimeUnit.SECONDS, new SynchronousQueue<>());
+    executor.shutdown();
+
+    OkHttpGrpcSender sender =
+        new OkHttpGrpcSender(
+            "http://localhost",
+            null,
+            Duration.ofSeconds(10),
+            Duration.ofSeconds(10),
+            Collections::emptyMap,
+            null,
+            null,
+            null,
+            executor,
+            Long.MAX_VALUE);
+
+    AtomicReference<GrpcResponse> responseRef = new AtomicReference<>();
+    AtomicReference<Throwable> errorRef = new AtomicReference<>();
+
+    sender.send(new TestMessageWriter(), responseRef::set, errorRef::set);
+
+    assertThat(errorRef.get()).isNotNull();
+    assertThat(responseRef.get()).isNull();
+  }
+
   private static Response createResponse(int httpCode, String grpcStatus, String message) {
     return new Response.Builder()
         .request(new Request.Builder().url("http://localhost/").build())

exporters/sender/okhttp/src/test/java/io/opentelemetry/exporter/sender/okhttp/internal/OkHttpHttpSenderTest.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.exporter.sender.okhttp.internal;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.opentelemetry.sdk.common.export.HttpResponse;
+import io.opentelemetry.sdk.common.export.MessageWriter;
+import java.io.OutputStream;
+import java.net.URI;
+import java.time.Duration;
+import java.util.Collections;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+import org.junit.jupiter.api.Test;
+
+class OkHttpHttpSenderTest {
+
+  @Test
+  void send_rejectedExecution_callsOnError() {
+    ThreadPoolExecutor executor =
+        new ThreadPoolExecutor(0, 1, 0, TimeUnit.SECONDS, new SynchronousQueue<>());
+    executor.shutdown();
+
+    OkHttpHttpSender sender =
+        new OkHttpHttpSender(
+            URI.create("http://localhost"),
+            "text/plain",
+            null,
+            Duration.ofSeconds(10),
+            Duration.ofSeconds(10),
+            Collections::emptyMap,
+            null,
+            null,
+            null,
+            null,
+            executor,
+            Long.MAX_VALUE);
+
+    AtomicReference<HttpResponse> responseRef = new AtomicReference<>();
+    AtomicReference<Throwable> errorRef = new AtomicReference<>();
+
+    sender.send(new NoOpRequestBodyWriter(), responseRef::set, errorRef::set);
+
+    assertThat(errorRef.get()).isNotNull();
+    assertThat(responseRef.get()).isNull();
+  }
+
+  private static class NoOpRequestBodyWriter implements MessageWriter {
+    @Override
+    public void writeMessage(OutputStream output) {}
+
+    @Override
+    public int getContentLength() {
+      return 0;
+    }
+  }
+}

exporters/sender/okhttp/src/test/java/io/opentelemetry/exporter/sender/okhttp/internal/OkHttpUtilTest.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.exporter.sender.okhttp.internal;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.InstanceOfAssertFactories.type;
+
+import java.util.concurrent.ThreadPoolExecutor;
+import okhttp3.Dispatcher;
+import org.junit.jupiter.api.Test;
+
+class OkHttpUtilTest {
+  private static final int EXPECTED_MAX_REQUESTS =
+      Math.max(Runtime.getRuntime().availableProcessors(), 5);
+
+  @Test
+  void newDispatcher_isBounded() {
+    Dispatcher dispatcher = OkHttpUtil.newDispatcher();
+
+    try {
+      assertThat(dispatcher.getMaxRequests()).isEqualTo(EXPECTED_MAX_REQUESTS);
+      assertThat(dispatcher.getMaxRequestsPerHost()).isEqualTo(5);
+      assertThat(dispatcher.executorService())
+          .asInstanceOf(type(ThreadPoolExecutor.class))
+          .satisfies(
+              executor -> {
+                assertThat(executor.getMaximumPoolSize()).isEqualTo(EXPECTED_MAX_REQUESTS);
+                assertThat(executor.getRejectedExecutionHandler())
+                    .isInstanceOf(ThreadPoolExecutor.AbortPolicy.class);
+              });
+    } finally {
+      dispatcher.executorService().shutdownNow();
+    }
+  }
+}