Adding a handler to capture response time in Netty

Question

I want to add a metricsHandler that measures the time taken for a request-response cycle.

@Sharable
public class MetricCalcHandler extends ChannelDuplexHandler {

private static final AttributeKey<Long> TIME_TAKEN = AttributeKey.newInstance("time");

@Override
public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
        ctx.channel().attr(TIME_TAKEN).set(System.currentTimeMillis());
        ctx.fireChannelRegistered();
    }

@Override
public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {

        Long ms = System.currentTimeMillis() - ctx.channel().attr(TIME_TAKEN).get());
        log.info("time taken " + ms);
        ctx.deregister(promise);
    }
}


public class MyInitializer extends ChannelInitializer<SocketChannel> {

@Override
    public void initChannel(SocketChannel ch) {
        ChannelPipeline p = ch.pipeline();
        p.addLast(new MetricCalcHandler());
        p.addLast(new LoggingHandler(LogLevel.INFO));

        p.addLast(new HttpServerCodec());
        p.addLast(new HttpObjectAggregator(1024 * 1024, true));
        p.addLast(new Handler1());
        p.addLast(new Handler2());

 }
}

Now the questions I have are

1. I added @Sharable but maintaining a state in the channel (per request). Is this right? Since a single channel is shared across multiple requests, wouldn't there be a collison/data-corruption.
2. I calculated the processing start time in ChannelRegistered and finished in deregister. Is that the right place to do? or use channelActive()/channelInActive() methods?
3. Does Netty provides any handler out of the box for these use-cases?
4. I am adding MetricCalcHandler first followed by other handlers in MyInitializer. so that handler is invoked first. is that correct?

Thanks