Create a new HttpClient per connection (#1243)

* Create a new HttpClient for each connection

If the instance is using Java 21, the HttpClient resources will be cleaned using its AutoCloseable interface

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -595,8 +595,8 @@ public class VelocityServer implements ProxyServer, ForwardingAudience {
     this.cm.closeEndpoints(false);
   }
 
-  public HttpClient getHttpClient() {
+  public HttpClient createHttpClient() {
-    return cm.getHttpClient();
+    return cm.createHttpClient();
   }
 
   public Ratelimiter getIpAttemptLimiter() {

proxy/src/main/java/com/velocitypowered/proxy/connection/client/InitialLoginSessionHandler.java

@@ -43,6 +43,7 @@ import com.velocitypowered.proxy.protocol.packet.ServerLoginPacket;
 import io.netty.buffer.ByteBuf;
 import java.net.InetSocketAddress;
 import java.net.URI;
+import java.net.http.HttpClient;
 import java.net.http.HttpRequest;
 import java.net.http.HttpResponse;
 import java.security.GeneralSecurityException;
@@ -213,7 +214,8 @@ public class InitialLoginSessionHandler implements MinecraftSessionHandler {
                       server.getVersion().getName() + "/" + server.getVersion().getVersion())
               .uri(URI.create(url))
               .build();
-      server.getHttpClient().sendAsync(httpRequest, HttpResponse.BodyHandlers.ofString())
+      final HttpClient httpClient = server.createHttpClient();
+      httpClient.sendAsync(httpRequest, HttpResponse.BodyHandlers.ofString())
           .whenCompleteAsync((response, throwable) -> {
             if (mcConnection.isClosed()) {
               // The player disconnected after we authenticated them.
@@ -264,7 +266,18 @@ public class InitialLoginSessionHandler implements MinecraftSessionHandler {
                   response.statusCode(), login.getUsername(), playerIp);
               inbound.disconnect(Component.translatable("multiplayer.disconnect.authservers_down"));
             }
-          }, mcConnection.eventLoop());
+          }, mcConnection.eventLoop())
+          .thenRun(() -> {
+            if (httpClient instanceof final AutoCloseable closeable) {
+              try {
+                closeable.close();
+              } catch (Exception e) {
+                // In Java 21, the HttpClient does not throw any Exception
+                // when trying to clean its resources, so this should not happen
+                logger.error("An unknown error occurred while trying to close an HttpClient", e);
+              }
+            }
+          });
     } catch (GeneralSecurityException e) {
       logger.error("Unable to enable encryption", e);
       mcConnection.close(true);

proxy/src/main/java/com/velocitypowered/proxy/network/ConnectionManager.java

@@ -62,10 +62,9 @@ public final class ConnectionManager {
   public final BackendChannelInitializerHolder backendChannelInitializer;
 
   private final SeparatePoolInetNameResolver resolver;
-  private final HttpClient httpClient;
 
   /**
-   * Initalizes the {@code ConnectionManager}.
+   * Initializes the {@code ConnectionManager}.
    *
    * @param server a reference to the Velocity server
    */
@@ -79,9 +78,6 @@ public final class ConnectionManager {
     this.backendChannelInitializer = new BackendChannelInitializerHolder(
         new BackendChannelInitializer(this.server));
     this.resolver = new SeparatePoolInetNameResolver(GlobalEventExecutor.INSTANCE);
-    this.httpClient = HttpClient.newBuilder()
-            .executor(this.workerGroup)
-            .build();
   }
 
   public void logChannelInformation() {
@@ -238,8 +234,11 @@ public final class ConnectionManager {
     return this.serverChannelInitializer;
   }
 
-  public HttpClient getHttpClient() {
+  @SuppressWarnings("checkstyle:MissingJavadocMethod")
-    return this.httpClient;
+  public HttpClient createHttpClient() {
+    return HttpClient.newBuilder()
+            .executor(this.workerGroup)
+            .build();
   }
 
   public BackendChannelInitializerHolder getBackendChannelInitializer() {