netty 4 ChannelInboundHandlerAdapter.channelReadComplete called twice - client

Question

when you use netty (4.0.23, java 1.7u67, win8x64) as a client ChannelInboundHandlerAdapter.channelReadComplete(...) should be called 1 time once netty completes reading response, right?
Trying different sites, it's always called twice:
#Test
public void testDoubleReadComplete() throws Exception {
final String host = "www.google.de";
final CountDownLatch count = new CountDownLatch(20);
bootstrap = new Bootstrap()
.group(new NioEventLoopGroup())
.channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
#Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
String request = String.format(
"GET / HTTP/1.1\n" +
"Host: " + host +"\n" +
"\n\n"
);
System.out.println("sending...");
System.out.println(request);
ByteBuf req = Unpooled.wrappedBuffer(request.getBytes(Charset.defaultCharset()));
ctx.writeAndFlush(req);
}
#Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
System.err.println("777 read complete");
}
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
ByteBuf resp = (ByteBuf) msg;
count.countDown();
System.out.printf("****************************************************>>>>> %s%n", Thread.currentThread().getName());
System.out.println(resp.toString(Charset.defaultCharset()));
System.out.println("<<<<<****************************************************");
resp.release();
}
});
}
});
ChannelFuture future = bootstrap.connect(new InetSocketAddress(host, 80));
future.awaitUninterruptibly();
count.await(5, TimeUnit.SECONDS);
}
outputs 777 read complete 2 times, why?

Answer 1

I'm not sure that the channelReadComplete is intended for how you are trying to use it.
Read the javadoc for the method. The data is not guaranteed to arrive all at once and so netty reads the data as it arrives in a non-blocking manner. This methods notifies you when it has finished the current read operation which is not necessarily the last read operation.
I'm not exactly sure about your use case but here is some non-production code that may be closer to what you are trying to accomplish?
#Test
public void testDoubleReadComplete() throws Exception {
final String host = "www.google.de";
final CountDownLatch count = new CountDownLatch(20);
Bootstrap bootstrap = new Bootstrap()
.group(new NioEventLoopGroup())
.channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
#Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
String request = String.format(
"GET / HTTP/1.1\r\n" +
"Host: " + host +"\r\n" +
"Connection: close\r\n" +
"\r\n"
);
System.out.println("sending...");
System.out.println(request);
ByteBuf req = Unpooled.wrappedBuffer(request.getBytes(Charset.defaultCharset()));
ctx.writeAndFlush(req);
}
#Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
System.err.println("777 read complete");
}
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
ByteBuf resp = (ByteBuf) msg;
count.countDown();
System.out.printf("****************************************************>>>>> %s%n", Thread.currentThread().getName());
System.out.println(resp.toString(Charset.defaultCharset()));
System.out.println("<<<<<****************************************************");
resp.release();
}
});
}
});

Answer 2

found the cause and solution: ChannelOption.MAX_MESSAGES_PER_READ
So now I'm testing with .option(ChannelOption.MAX_MESSAGES_PER_READ, Integer.MAX_VALUE) and so far so good - channelReadComplete is called once at the end of response as I need