Mark stream-related request by RequestType

[drpmma]

1. Plan to add a RequestType in remoting protocol to indicate stream requests including requests driven by PullConsumer and LitePullConsumer.
2. Stream is an important part of rocketmq and it is not marked and distinguished with the messaging-related requests by now. It is helpful for observability and other features to mark it explicitly

[ni-ze]

I am sorry, I think we can put a key value pair in properties of Message, then we know what business the message comes from. Adding business attributes into remote protocol is not recommended.

[lizhanhui]

@drpmma Would you mind offering your use case story? Looks you and @ni-ze are talking about two completely different things.

[drpmma]

Stream is a totally different scenario compared with messaging. As I know, Many companies in industries develop rocketmq proxy to manage and distribute traffic. It is helpful to mark stream requests explicitly for traffic management and scalability like proxy scenarios.