TINKERPOP 2498: Checks if Epoll is available and uses it instead of Nio

CHANGELOG.asciidoc

@@ -25,6 +25,7 @@ image::https://raw.githubusercontent.com/apache/tinkerpop/master/docs/static/ima
 
 * Prevented XML External Entity (XXE) style attacks via `GraphMLReader` by disabling DTD and external entities by default.
 * Fixed a `NullPointerException` that could occur during a failed `Connection` initialization due to uninstantiated `AtomicInteger`.
+* Added a check for when Epoll is available in the Java client and if so use it instead of Nio.
 
 [[release-3-4-12]]
 === TinkerPop 3.4.12 (Release Date: July 19, 2021)

gremlin-driver/src/main/java/org/apache/tinkerpop/gremlin/driver/Cluster.java

@@ -20,6 +20,9 @@
 
 import io.netty.buffer.PooledByteBufAllocator;
 import io.netty.channel.ChannelOption;
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.epoll.Epoll;
+import io.netty.channel.epoll.EpollEventLoopGroup;
 import io.netty.handler.ssl.SslContext;
 import io.netty.handler.ssl.SslContextBuilder;
 import io.netty.handler.ssl.SslProvider;
@@ -1103,11 +1106,14 @@ public Cluster create() {
     }
 
     static class Factory {
-        private final NioEventLoopGroup group;
+        private final EventLoopGroup group;
 
         public Factory(final int nioPoolSize) {
             final BasicThreadFactory threadFactory = new BasicThreadFactory.Builder().namingPattern("gremlin-driver-loop-%d").build();
-            group = new NioEventLoopGroup(nioPoolSize, threadFactory);
+            // Checks and uses Epoll if it is available. ref: http://netty.io/wiki/native-transports.html
+            System.out.println(Epoll.isAvailable() ? "epoll is available, using epoll" : "epoll is unavailable, using NIO.");
+            logger.warn(Epoll.isAvailable() ? "epoll is available, using epoll" : "epoll is unavailable, using NIO.");
+            group = Epoll.isAvailable() ? new EpollEventLoopGroup(nioPoolSize, threadFactory) : new NioEventLoopGroup(nioPoolSize, threadFactory);
         }
 
         Bootstrap createBootstrap() {

gremlin-driver/src/main/java/org/apache/tinkerpop/gremlin/driver/simple/AbstractClient.java

@@ -21,11 +21,15 @@
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.channel.epoll.Epoll;
+import io.netty.channel.epoll.EpollEventLoopGroup;
 import io.netty.channel.nio.NioEventLoopGroup;
 import org.apache.commons.lang3.concurrent.BasicThreadFactory;
 import org.apache.tinkerpop.gremlin.driver.message.RequestMessage;
 import org.apache.tinkerpop.gremlin.driver.message.ResponseMessage;
 import org.apache.tinkerpop.gremlin.driver.message.ResponseStatusCode;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -38,10 +42,14 @@
 public abstract class AbstractClient implements SimpleClient {
     protected final CallbackResponseHandler callbackResponseHandler = new CallbackResponseHandler();
     protected final EventLoopGroup group;
+    protected static final Logger logger = LoggerFactory.getLogger(AbstractClient.class);
 
     public AbstractClient(final String threadPattern) {
         final BasicThreadFactory threadFactory = new BasicThreadFactory.Builder().namingPattern(threadPattern).build();
-        group = new NioEventLoopGroup(Runtime.getRuntime().availableProcessors(), threadFactory);
+        // Checks and uses Epoll if it is available. ref: http://netty.io/wiki/native-transports.html
+        logger.warn(Epoll.isAvailable() ? "epoll is available, using epoll" : "epoll is unavailable, using NIO.");
+        group =  Epoll.isAvailable() ? new EpollEventLoopGroup(Runtime.getRuntime().availableProcessors(), threadFactory)
+                : new NioEventLoopGroup(Runtime.getRuntime().availableProcessors(), threadFactory);
     }
 
     public abstract void writeAndFlush(final RequestMessage requestMessage) throws Exception;

gremlin-driver/src/main/java/org/apache/tinkerpop/gremlin/driver/simple/WebSocketClient.java

@@ -20,6 +20,8 @@
 
 import io.netty.buffer.PooledByteBufAllocator;
 import io.netty.channel.ChannelOption;
+import io.netty.channel.epoll.Epoll;
+import io.netty.channel.epoll.EpollSocketChannel;
 import io.netty.handler.codec.http.EmptyHttpHeaders;
 import org.apache.tinkerpop.gremlin.driver.MessageSerializer;
 import org.apache.tinkerpop.gremlin.driver.handler.WebSocketClientHandler;
@@ -66,7 +68,9 @@ public WebSocketClient(final URI uri) {
             final WebSocketClientHandler wsHandler = new WebSocketClientHandler(WebSocketClientHandshakerFactory.newHandshaker(
                     uri, WebSocketVersion.V13, null, true, EmptyHttpHeaders.INSTANCE, 65536), 10000);
             final MessageSerializer serializer = new GryoMessageSerializerV3d0();
-            b.channel(NioSocketChannel.class)
+            // Checks and uses Epoll if it is available. ref: http://netty.io/wiki/native-transports.html
+            logger.info(Epoll.isAvailable() ? "epoll is available, using epoll" : "epoll is unavailable, using NIO.");
+            b.channel(Epoll.isAvailable() ? EpollSocketChannel.class : NioSocketChannel.class)
                     .handler(new ChannelInitializer<SocketChannel>() {
                         @Override
                         protected void initChannel(final SocketChannel ch) {

gremlin-driver/src/test/java/org/apache/tinkerpop/gremlin/driver/SimpleSocketServer.java

@@ -22,6 +22,9 @@
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelInitializer;
 import io.netty.channel.EventLoopGroup;
+import io.netty.channel.epoll.Epoll;
+import io.netty.channel.epoll.EpollEventLoopGroup;
+import io.netty.channel.epoll.EpollServerSocketChannel;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.socket.SocketChannel;
 import io.netty.channel.socket.nio.NioServerSocketChannel;
@@ -37,11 +40,12 @@ public class SimpleSocketServer {
     private EventLoopGroup workerGroup;
 
     public Channel start(final ChannelInitializer<SocketChannel> channelInitializer) throws InterruptedException {
-        bossGroup = new NioEventLoopGroup(1);
-        workerGroup = new NioEventLoopGroup();
+        // Checks and uses Epoll if it is available. ref: http://netty.io/wiki/native-transports.html
+        bossGroup = Epoll.isAvailable() ? new EpollEventLoopGroup(1) : new NioEventLoopGroup(1);
+        workerGroup =  Epoll.isAvailable() ? new EpollEventLoopGroup() : new NioEventLoopGroup();
         final ServerBootstrap b = new ServerBootstrap();
         b.group(bossGroup, workerGroup)
-                .channel(NioServerSocketChannel.class)
+                .channel(Epoll.isAvailable() ? EpollServerSocketChannel.class : NioServerSocketChannel.class)
                 .handler(new LoggingHandler(LogLevel.INFO))
                 .childHandler(channelInitializer);
         return b.bind(PORT).sync().channel();

gremlin-driver/src/test/java/org/apache/tinkerpop/gremlin/driver/WebSocketClientBehaviorIntegrateTest.java

@@ -18,6 +18,11 @@
  */
 package org.apache.tinkerpop.gremlin.driver;
 
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.epoll.Epoll;
+import io.netty.channel.epoll.EpollEventLoopGroup;
+import io.netty.channel.nio.NioEventLoopGroup;
+import org.apache.tinkerpop.gremlin.driver.simple.WebSocketClient;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Rule;
@@ -41,6 +46,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 
 public class WebSocketClientBehaviorIntegrateTest {
     @Rule
@@ -271,4 +277,22 @@ public void shouldNotCreateReplacementConnectionWhenClientClosesConnection() thr
                         .filter(str -> str.contains("Considering new connection on"))
                         .count());
     }
-}
+
+    // A mock client is made here, so we can test the protected field group
+    private static class MockClient extends WebSocketClient {
+        EventLoopGroup getEventLoopGroup() {
+            return group;
+        }
+    }
+
+    @Test
+    public void shouldUseEpollIfAvailable() throws Exception {
+        final MockClient client = new MockClient();
+        if (Epoll.isAvailable()) {
+            assertTrue(client.getEventLoopGroup() instanceof EpollEventLoopGroup);
+        } else {
+            assertTrue(client.getEventLoopGroup() instanceof NioEventLoopGroup);
+        }
+    }
+
+}