@amizurov its a bug :(
 
Fixed https://github.com/netty/netty/pull/7839 @normanmaurer Thanks a lot, It's really quickly as well as Netty :)
CorsHandler do writeAndFlush in override ChannelHandlerContext#write method
Do not really understand, why in `CorsHandler` invoked writeAndFlash ? It's strange side effect.
### Actual behavior

https://github.com/netty/netty/blob/473f6a6edb8353728ea8e711ac8241ddc21adf08/codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java#L198-L209
### Steps to reproduce
Add `CorsHandler` to pipeline then write response in your own handler, response flushed automatically.

### Netty version
4.1.22

codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java
codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java
diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java b/codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java
index f4b5552b724..9e7756521e9 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java
@@ -205,7 +205,7 @@ public void write(final ChannelHandlerContext ctx, final Object msg, final Chann
                 setExposeHeaders(response);
             }
         }
-        ctx.writeAndFlush(msg, promise);
+        ctx.write(msg, promise);
     }
 
     private static void forbidden(final ChannelHandlerContext ctx, final HttpRequest request) {
