[SPARK-54023][CORE] Support AUTO IO Mode

common/network-common/src/main/java/org/apache/spark/network/util/IOMode.java

@@ -32,5 +32,9 @@ public enum IOMode {
   /**
    * Native KQUEUE via JNI, MacOS/BSD only
    */
-  KQUEUE
+  KQUEUE,
+  /**
+   * Prefer to use native EPOLL on Linux (or KQUEUE on MacOS) if available. Then, fallback to NIO.
+   */
+  AUTO
 }

common/network-common/src/main/java/org/apache/spark/network/util/NettyUtils.java

@@ -21,9 +21,11 @@
 
 import io.netty.buffer.PooledByteBufAllocator;
 import io.netty.channel.*;
+import io.netty.channel.epoll.Epoll;
 import io.netty.channel.epoll.EpollIoHandler;
 import io.netty.channel.epoll.EpollServerSocketChannel;
 import io.netty.channel.epoll.EpollSocketChannel;
+import io.netty.channel.kqueue.KQueue;
 import io.netty.channel.kqueue.KQueueIoHandler;
 import io.netty.channel.kqueue.KQueueServerSocketChannel;
 import io.netty.channel.kqueue.KQueueSocketChannel;
@@ -35,7 +37,7 @@
 
 /**
  * Utilities for creating various Netty constructs based on whether we're using NIO, EPOLL,
- * or KQUEUE.
+ * , KQUEUE, or AUTO.
  */
 public class NettyUtils {
 
@@ -71,6 +73,15 @@ public static EventLoopGroup createEventLoop(IOMode mode, int numThreads, String
       case NIO -> NioIoHandler.newFactory();
       case EPOLL -> EpollIoHandler.newFactory();
       case KQUEUE -> KQueueIoHandler.newFactory();
+      case AUTO -> {
+        if (JavaUtils.isLinux && Epoll.isAvailable()) {
+          yield EpollIoHandler.newFactory();
+        } else if (JavaUtils.isMac && KQueue.isAvailable()) {
+          yield KQueueIoHandler.newFactory();
+        } else {
+          yield NioIoHandler.newFactory();
+        }
+      }
     };
     return new MultiThreadIoEventLoopGroup(numThreads, threadFactory, handlerFactory);
   }
@@ -81,6 +92,15 @@ public static Class<? extends Channel> getClientChannelClass(IOMode mode) {
       case NIO -> NioSocketChannel.class;
       case EPOLL -> EpollSocketChannel.class;
       case KQUEUE -> KQueueSocketChannel.class;
+      case AUTO -> {
+        if (JavaUtils.isLinux && Epoll.isAvailable()) {
+          yield EpollSocketChannel.class;
+        } else if (JavaUtils.isMac && KQueue.isAvailable()) {
+          yield KQueueSocketChannel.class;
+        } else {
+          yield NioSocketChannel.class;
+        }
+      }
     };
   }
 
@@ -90,6 +110,15 @@ public static Class<? extends ServerChannel> getServerChannelClass(IOMode mode)
       case NIO -> NioServerSocketChannel.class;
       case EPOLL -> EpollServerSocketChannel.class;
       case KQUEUE -> KQueueServerSocketChannel.class;
+      case AUTO -> {
+        if (JavaUtils.isLinux && Epoll.isAvailable()) {
+          yield EpollServerSocketChannel.class;
+        } else if (JavaUtils.isMac && KQueue.isAvailable()) {
+          yield KQueueServerSocketChannel.class;
+        } else {
+          yield NioServerSocketChannel.class;
+        }
+      }
     };
   }
 

common/network-common/src/main/java/org/apache/spark/network/util/TransportConf.java

@@ -87,7 +87,7 @@ public String getModuleName() {
     return module;
   }
 
-  /** IO mode: NIO, EPOLL, or KQUEUE */
+  /** IO mode: NIO, EPOLL, KQUEUE, or AUTO */
   public String ioMode() {
     String defaultIOMode = conf.get(SPARK_NETWORK_DEFAULT_IO_MODE_KEY, "NIO");
     return conf.get(SPARK_NETWORK_IO_MODE_KEY, defaultIOMode).toUpperCase(Locale.ROOT);

core/src/test/scala/org/apache/spark/ShuffleNettySuite.scala

@@ -55,3 +55,7 @@ class ShuffleNettyKQueueSuite extends ShuffleNettySuite {
   override def shouldRunTests: Boolean = Utils.isMac
   override def ioMode: IOMode = IOMode.KQUEUE
 }
+
+class ShuffleNettyAutoSuite extends ShuffleNettySuite {
+  override def ioMode: IOMode = IOMode.AUTO
+}