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uber / tchannel

network multiplexing and framing protocol for RPC
MIT License
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Fragmentation: How to collect frame in the same message? #1412

Open nhattanmai opened 8 years ago

nhattanmai commented 8 years ago

When send large message that is bigger than 64KiB, the message is devide to some fragments. Please tell me how to receiving parse know fragments in the same message? Using header and fragment id?

abhinav commented 8 years ago

Hello. The library should take care of that for you. If you're trying to implement it yourself, https://github.com/uber/tchannel/blob/master/docs/protocol.md#fragmentation documents the fragmentation scheme for TChannel.

nhattanmai commented 8 years ago

Thanks for your answer, I see fragmentation scheme but I still misunderstand how to receiving parser can collect frames exactly of a message when have many frames come from other messages. Can you explain more detail? I don't realize something like fragmentation id or whatever to confirm the second frame is belong to the first frame...

abhinav commented 8 years ago

The frames are received in-order and have a message ID attached to them. Using the message ID and the in-order stream of frames, the library is able to reconstruct the original request/response. All frames that have a continuation frame have a continuation bit sit. When the last message in the stream is received, the bit is unset.

nhattanmai commented 8 years ago

It may be silly question. This is schema of "call req": flags:1 ttl:4 tracing:25 service~1 nh:1 (hk~1 hv~1){nh} csumtype:1 (csum:4){0,1} arg1~2 arg2~2 arg3~2 Schema of "call req continue": flags:1 csumtype:1 (csum:4){0,1} {continuation} I think the first frame is header + "call req" --> have message ID in header. The second frame is only "call req continue", have no message ID. Where is message ID?

jcorbin commented 8 years ago

All frames have a message id, including call continues; neither the call req nor call req continue frame bodies contain a message id, it is on the frame header.

nhattanmai commented 8 years ago

Oh. I see. Thank you very much!