From b9baf36dc6c3bbdee8c673a0c4ed07211d289560 Mon Sep 17 00:00:00 2001
From: Radim Vansa <rvansa@azul.com>
Date: Thu, 8 Jun 2023 14:41:04 +0200
Subject: [PATCH] Register a resource for EPollEventLoopGroup

---
 pom.xml                                       |  5 +++
 .../net/impl/transport/EpollTransport.java    | 45 +++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/pom.xml b/pom.xml
index db991286e3f..994e68f6cf3 100644
--- a/pom.xml
+++ b/pom.xml
@@ -79,6 +79,11 @@
         <type>pom</type>
         <scope>import</scope>
       </dependency>
+      <dependency>
+        <groupId>io.netty</groupId>
+        <artifactId>netty-transport-classes-epoll</artifactId>
+        <version>4.1.96.Final</version>
+      </dependency>
     </dependencies>
   </dependencyManagement>
 
diff --git a/src/main/java/io/vertx/core/net/impl/transport/EpollTransport.java b/src/main/java/io/vertx/core/net/impl/transport/EpollTransport.java
index 83a1324870c..e3b2998ea38 100644
--- a/src/main/java/io/vertx/core/net/impl/transport/EpollTransport.java
+++ b/src/main/java/io/vertx/core/net/impl/transport/EpollTransport.java
@@ -18,6 +18,7 @@
 import io.netty.channel.epoll.EpollChannelOption;
 import io.netty.channel.epoll.EpollDatagramChannel;
 import io.netty.channel.epoll.EpollDomainSocketChannel;
+import io.netty.channel.epoll.EpollEventLoop;
 import io.netty.channel.epoll.EpollEventLoopGroup;
 import io.netty.channel.epoll.EpollServerDomainSocketChannel;
 import io.netty.channel.epoll.EpollServerSocketChannel;
@@ -25,12 +26,18 @@
 import io.netty.channel.socket.DatagramChannel;
 import io.netty.channel.socket.InternetProtocolFamily;
 import io.netty.channel.unix.DomainSocketAddress;
+import io.netty.util.concurrent.EventExecutor;
 import io.vertx.core.datagram.DatagramSocketOptions;
 import io.vertx.core.net.ClientOptionsBase;
 import io.vertx.core.net.NetServerOptions;
 import io.vertx.core.net.impl.SocketAddressImpl;
+import org.crac.Context;
+import org.crac.Core;
+import org.crac.Resource;
 
 import java.net.SocketAddress;
+import java.util.WeakHashMap;
+import java.util.concurrent.Phaser;
 import java.util.concurrent.ThreadFactory;
 
 /**
@@ -40,6 +47,10 @@ class EpollTransport extends Transport {
 
   private static volatile int pendingFastOpenRequestsThreshold = 256;
 
+  // Keeps the EpollResource alive until the EpollEventLoopGroup is GC'ed
+  @SuppressWarnings("MismatchedQueryAndUpdateOfCollection")
+  private final WeakHashMap<EpollEventLoopGroup, EpollResource> resources = new WeakHashMap<>();
+
   /**
    * Return the number of of pending TFO connections in SYN-RCVD state for TCP_FASTOPEN.
    *
@@ -95,6 +106,9 @@ public Throwable unavailabilityCause() {
   public EventLoopGroup eventLoopGroup(int type, int nThreads, ThreadFactory threadFactory, int ioRatio) {
     EpollEventLoopGroup eventLoopGroup = new EpollEventLoopGroup(nThreads, threadFactory);
     eventLoopGroup.setIoRatio(ioRatio);
+    synchronized (resources) {
+      resources.put(eventLoopGroup, new EpollResource(eventLoopGroup));
+    }
     return eventLoopGroup;
   }
 
@@ -155,4 +169,35 @@ public void configure(ClientOptionsBase options, boolean domainSocket, Bootstrap
     }
     super.configure(options, domainSocket, bootstrap);
   }
+
+  private static class EpollResource implements Resource {
+    private final EpollEventLoopGroup eventLoopGroup;
+    private final Phaser phaser;
+
+    public EpollResource(EpollEventLoopGroup eventLoopGroup) {
+      this.eventLoopGroup = eventLoopGroup;
+      // contrary to Barrier the Phaser supports uninterruptible waiting
+      this.phaser = new Phaser(eventLoopGroup.executorCount() + 1);
+      Core.getGlobalContext().register(this);
+    }
+
+    @Override
+    public void beforeCheckpoint(Context<? extends Resource> context) throws Exception {
+      for (EventExecutor executor : eventLoopGroup) {
+        EpollEventLoop eventLoop = (EpollEventLoop) executor;
+        executor.execute(() -> {
+          eventLoop.closeFileDescriptors();
+          phaser.arriveAndAwaitAdvance();
+          phaser.arriveAndAwaitAdvance();
+          eventLoop.openFileDescriptors();
+        });
+      }
+      phaser.arriveAndAwaitAdvance();
+    }
+
+    @Override
+    public void afterRestore(Context<? extends Resource> context) throws Exception {
+      phaser.arriveAndAwaitAdvance();
+    }
+  }
 }