Separate netty boss and worker groups to improve the graceful shutdown process.

Author: mashhurs

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 3.9.0
+ - Netty boss and worker groups are separated [#178](https://github.com/logstash-plugins/logstash-input-http/pull/178)
+   As a result, when shutdown requested incoming connections are closed first and improved graceful shutdown
+
 ## 3.8.1
   - bump netty to 4.1.109 [#173](https://github.com/logstash-plugins/logstash-input-http/pull/173)
 

VERSION

@@ -1 +1 @@
-3.8.1
+3.9.0

src/main/java/org/logstash/plugins/inputs/http/NettyHttpServer.java

@@ -26,6 +26,7 @@ public class NettyHttpServer implements Runnable, Closeable {
     private final int port;
     private final int connectionBacklog = 128;
 
+    private final EventLoopGroup bossGroup;
     private final EventLoopGroup processorGroup;
     private final ThreadPoolExecutor executorGroup;
     private final HttpResponseStatus responseStatus;
@@ -37,8 +38,14 @@ public NettyHttpServer(String host, int port, IMessageHandler messageHandler,
         this.host = host;
         this.port = port;
         this.responseStatus = HttpResponseStatus.valueOf(responseCode);
+
+        // boss group is responsible for accepting incoming connections and sending to worker loop
+        // process group is channel handler, see the https://github.com/netty/netty/discussions/13305
+        // see the https://github.com/netty/netty/discussions/11808#discussioncomment-1610918 for why separation is good
+        bossGroup = new NioEventLoopGroup(1, daemonThreadFactory("http-input-connector"));
         processorGroup = new NioEventLoopGroup(threads, daemonThreadFactory("http-input-processor"));
 
+        // event handler group
         executorGroup = new ThreadPoolExecutor(threads, threads, 0, TimeUnit.MILLISECONDS,
                 new ArrayBlockingQueue<>(maxPendingRequests), daemonThreadFactory("http-input-handler-executor"),
                 new CustomRejectedExecutionHandler());
@@ -51,7 +58,7 @@ public NettyHttpServer(String host, int port, IMessageHandler messageHandler,
         }
 
         serverBootstrap = new ServerBootstrap()
-                .group(processorGroup)
+                .group(bossGroup, processorGroup)
                 .channel(NioServerSocketChannel.class)
                 .option(ChannelOption.SO_BACKLOG, connectionBacklog)
                 .childOption(ChannelOption.SO_KEEPALIVE, true)
@@ -73,7 +80,9 @@ public void run() {
     public void close() {
         try {
             // stop accepting new connections first
-            processorGroup.shutdownGracefully(0, 10, TimeUnit.SECONDS).sync();
+            bossGroup.shutdownGracefully().sync();
+            // stop the worker group
+            processorGroup.shutdownGracefully().sync();
             // then shutdown the message handler executor
             executorGroup.shutdown();
             try {