[GitHub] [mina-sshd] tomaswolf commented on a diff in pull request #218: [SSHD-1261] Fixed possible pending unfinished pending write request if ChannelAsyncOutputStream closed prematurely

[GitBox <gi...@apache.org>]

tomaswolf commented on code in PR #218:
URL: https://github.com/apache/mina-sshd/pull/218#discussion_r854828577


##########
sshd-core/src/main/java/org/apache/sshd/common/channel/ChannelAsyncOutputStream.java:
##########
@@ -127,6 +129,28 @@ protected CloseFuture doCloseGracefully() {
         return builder().when(pendingWrite.get()).build().close(false);
     }
 
+    @Override
+    protected void doCloseImmediately() {
+        Channel channel = getChannel();
+        long channelId = (channel == null) ? -1L : channel.getChannelId();
+        abortCurrentWrite(() -> new SshChannelClosedException(channelId, "Channel closed before pending write completed"));
+
+        super.doCloseImmediately();
+    }
+
+    protected synchronized IoWriteFutureImpl abortCurrentWrite(Supplier<? extends Exception> errorProvider) {
+        IoWriteFutureImpl future = pendingWrite.get();
+        if ((future != null) && (!future.isDone())) {
+            Exception error = errorProvider.get();
+            log.debug("abortCurrentWrite({}) aborting pending write={} - {} : {}",
+                    this, future, error == null ? null : error.getClass().getSimpleName(),
+                    error == null ? null : error.getMessage());
+            future.setValue(error);
+        }
+
+        return future;
+    }

Review Comment:
   Terminating the current future is probably right, but still I don't think this will help in all situations. On a graceful shutdown, `AbstractCloseable.close` will call `doCloseGracefully()` *first*, which will block until the pending future is fulfilled.
   
   However, it also calls `preClose()` first, which will already close the `packetWriter`.
   
   I'm not sure a `ChannelAsyncOutputStream` *can* be closed gracefully in this situation.



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