Update to OkHttp 4 and use daemon threads in dispatcher. (#3946)

dependencyManagement/build.gradle.kts

@@ -16,6 +16,7 @@ val DEPENDENCY_BOMS = listOf(
   "com.google.guava:guava-bom:31.0.1-jre",
   "com.google.protobuf:protobuf-bom:3.18.1",
   "com.linecorp.armeria:armeria-bom:1.13.3",
+  "com.squareup.okhttp3:okhttp-bom:4.9.3",
   "io.grpc:grpc-bom:1.41.0",
   "io.zipkin.brave:brave-bom:5.13.3",
   "io.zipkin.reporter2:zipkin-reporter-bom:2.16.3",
@@ -73,11 +74,6 @@ val DEPENDENCIES = listOf(
   "com.google.code.findbugs:jsr305:3.0.2",
   "com.google.guava:guava-beta-checker:1.0",
   "com.lmax:disruptor:3.4.4",
-  // using old version of okhttp to avoid pulling in kotlin stdlib
-  // not using (old) okhttp bom because that is pulling in old guava version
-  // and overriding the guava bom
-  "com.squareup.okhttp3:okhttp:3.14.9",
-  "com.squareup.okhttp3:okhttp-tls:3.14.9",
   "com.sun.net.httpserver:http:20070405",
   "com.tngtech.archunit:archunit-junit5:0.21.0",
   "com.uber.nullaway:nullaway:0.9.2",

exporters/otlp/common/src/main/java/io/opentelemetry/exporter/otlp/internal/grpc/OkHttpGrpcExporterBuilder.java

@@ -10,6 +10,7 @@ import io.opentelemetry.api.metrics.MeterProvider;
 import io.opentelemetry.exporter.otlp.internal.Marshaler;
 import io.opentelemetry.exporter.otlp.internal.RetryPolicy;
 import io.opentelemetry.exporter.otlp.internal.TlsUtil;
+import io.opentelemetry.exporter.otlp.internal.okhttp.OkHttpUtil;
 import io.opentelemetry.exporter.otlp.internal.okhttp.RetryInterceptor;
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -121,7 +122,8 @@ public final class OkHttpGrpcExporterBuilder<T extends Marshaler>
 
   @Override
   public GrpcExporter<T> build() {
-    OkHttpClient.Builder clientBuilder = new OkHttpClient.Builder();
+    OkHttpClient.Builder clientBuilder =
+        new OkHttpClient.Builder().dispatcher(OkHttpUtil.newDispatcher());
 
     Headers.Builder headers = this.headers != null ? this.headers : new Headers.Builder();
 

exporters/otlp/common/src/main/java/io/opentelemetry/exporter/otlp/internal/okhttp/OkHttpExporterBuilder.java

@@ -93,7 +93,9 @@ public final class OkHttpExporterBuilder<T extends Marshaler> {
 
   public OkHttpExporter<T> build() {
     OkHttpClient.Builder clientBuilder =
-        new OkHttpClient.Builder().callTimeout(Duration.ofNanos(timeoutNanos));
+        new OkHttpClient.Builder()
+            .dispatcher(OkHttpUtil.newDispatcher())
+            .callTimeout(Duration.ofNanos(timeoutNanos));
 
     if (trustedCertificatesPem != null) {
       try {

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

@@ -0,0 +1,30 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.exporter.otlp.internal.okhttp;
+
+import io.opentelemetry.sdk.internal.DaemonThreadFactory;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import okhttp3.Dispatcher;
+
+/** Utilities for OkHttp. */
+public final class OkHttpUtil {
+
+  /** 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<>(),
+            new DaemonThreadFactory("okhttp-dispatch")));
+  }
+
+  private OkHttpUtil() {}
+}