Error flushing and closing an idle Connection

The normal mechanism to close a connection seems to be: (from: https://github.com/netty/netty/blob/master/example/src/main/java/io/netty/example/http/snoop/HttpSnoopServerHandler.java#L129)

ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);

Here is what is happening -

Channel established with a client goes idle after a successful HttpRequest/Response exchange. On detecting idle event after the configured idle timeout period, we attempt to close the channel using the above utility.

However, it seems like ctx.writeAndFlush(Unpooled.EMPTY_BUFFER) never completes and hence ChannelFutureListener.CLOSE is not invoked. Another idle event is fired after another idle timeout period and so on and this channel never gets closed.

We are suspecting that since the last request/response was successful there were no more buffers left to flush . So possibly the above statement is not achieving anything and the channel never gets closed.

Netty version Netty4-4.1.45.Final

[jsvd]

I added some more details to the scenario we’re seeing in Logstash (see here). Having the IdleStateHandler in the pipeline causes outbound messages to get stuck there until a write idle event is triggered, or something comes inbound. This causes synchronous clients that perform send(message); get(ack) to get stuck, while clients that send more than one message before requesting acks are still able to function.

[edit] to touch on @rishika728’s comment, in our case we are writing + flushing actual data, so the issue isn’t constrained to an empty buffer

[jsvd]

For us this change between .46 and .47 solved the issue, as we used a separate executor for the IdleStateHandler.