From 426ee05e6947e9bbb5b3def5255b6e380a24a472 Mon Sep 17 00:00:00 2001
From: Edgar Espina <espina.edgar@gmail.com>
Date: Tue, 21 Apr 2026 16:11:40 -0300
Subject: [PATCH] fix(undertow): resolve buffer already freed exception during
 shutdown

Fixes an `IllegalStateException: UT000091: Buffer has already been freed` that occurs during server teardown in gRPC tests.

When raw request or response channels are acquired, Undertow shifts the exchange lifecycle management to the channels. Explicitly invoking `exchange.endExchange()` prematurely frees the pooled ByteBuffers. During server shutdown, the HTTP/2 `FrameCloseListener` attempts to gracefully close the connection and release the same buffers, resulting in a race condition and the subsequent exception.

Removed explicit `exchange.endExchange()` calls when streams are active in `UndertowGrpcExchange` and `UndertowGrpcInputBridge`. Replaced them with XNIO's `IoUtils.safeClose(channel)`, allowing Undertow's internal state machine to naturally flush, close, and terminate the exchange.
---
 .../internal/undertow/UndertowGrpcExchange.java    | 14 ++++++++++----
 .../internal/undertow/UndertowGrpcInputBridge.java |  2 --
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/modules/jooby-undertow/src/main/java/io/jooby/internal/undertow/UndertowGrpcExchange.java b/modules/jooby-undertow/src/main/java/io/jooby/internal/undertow/UndertowGrpcExchange.java
index b2508f2511..f46f7dce69 100644
--- a/modules/jooby-undertow/src/main/java/io/jooby/internal/undertow/UndertowGrpcExchange.java
+++ b/modules/jooby-undertow/src/main/java/io/jooby/internal/undertow/UndertowGrpcExchange.java
@@ -11,6 +11,7 @@
 import java.util.Map;
 import java.util.function.Consumer;
 
+import org.xnio.IoUtils;
 import org.xnio.channels.StreamSinkChannel;
 
 import io.jooby.rpc.grpc.GrpcExchange;
@@ -144,19 +145,19 @@ public void close(int statusCode, String description) {
                     try {
                       if (ch.flush()) {
                         ch.suspendWrites();
-                        exchange.endExchange();
+                        endExchange();
                       }
                     } catch (IOException ignored) {
                       ch.suspendWrites();
-                      exchange.endExchange();
+                      endExchange();
                     }
                   });
           responseChannel.resumeWrites();
         } else {
-          exchange.endExchange();
+          endExchange();
         }
       } catch (IOException e) {
-        exchange.endExchange();
+        endExchange();
       }
 
     } else {
@@ -170,4 +171,9 @@ public void close(int statusCode, String description) {
       exchange.endExchange();
     }
   }
+
+  private void endExchange() {
+    IoUtils.safeClose(responseChannel);
+    IoUtils.safeClose(exchange.getRequestChannel());
+  }
 }
diff --git a/modules/jooby-undertow/src/main/java/io/jooby/internal/undertow/UndertowGrpcInputBridge.java b/modules/jooby-undertow/src/main/java/io/jooby/internal/undertow/UndertowGrpcInputBridge.java
index 84d05a0293..2d68b31899 100644
--- a/modules/jooby-undertow/src/main/java/io/jooby/internal/undertow/UndertowGrpcInputBridge.java
+++ b/modules/jooby-undertow/src/main/java/io/jooby/internal/undertow/UndertowGrpcInputBridge.java
@@ -55,7 +55,6 @@ public void request(long n) {
   public void cancel() {
     demand.set(0);
     IoUtils.safeClose(channel);
-    exchange.endExchange();
   }
 
   @Override
@@ -90,7 +89,6 @@ public void handleEvent(StreamSourceChannel channel) {
     } catch (Throwable t) {
       subscriber.onError(t);
       IoUtils.safeClose(channel);
-      exchange.endExchange();
     }
   }
 }