Streaming support.

[wllenyj]

Introduce support for streaming(https://github.com/containerd/ttrpc/blob/main/PROTOCOL.md#streaming). This is already supported by Golang's TTRPC in https://github.com/containerd/ttrpc/pull/107. But currently only async is implemented. Related issues #144.

This pull request changes include:

1. Improved message encoding and decoding.
2. Added shutdown module to handle graceful shutdown.
3. Refactored connection handling.
4. Added streaming support, and added an example about streaming.

Usually, streaming supports 3 types:

• Server streaming
• Client streaming
• Bidirectional streaming ( or duplex streaming )

These 3 types are the same as GRPC, see https://grpc.io/docs/what-is-grpc/core-concepts/#server-streaming-rpc for details.

A general Bidirectional streaming process is as follows:

The Connection is an abstraction of a connection. One connection is handled as one Write async-task and one Read async-task.

• The Write task receives the message from the channel and writes it to the connection.
• The Read task receives the message from the connection and writes it to the channel.

[Tim-Zhang]

@wllenyj Awesome! Thanks a ton for introducing this so important feature. @jodh-intel @mxpv @lifupan @liubin Please take a look at this.

[wllenyj]

@dmcgowan Any time to help with this? Thanks a lot.

[dmcgowan]

@wllenyj thanks! I'll take a look

[codecov[bot]]

Codecov Report

Merging #146 (98d128d) into master (8f2bd91) will increase coverage by 14.34%. The diff coverage is 37.58%.

@@             Coverage Diff             @@
##           master     #146       +/-   ##
===========================================
+ Coverage   11.68%   26.02%   +14.34%     
===========================================
  Files          13       16        +3     
  Lines        1549     2413      +864     
===========================================
+ Hits          181      628      +447     
- Misses       1368     1785      +417     

Impacted Files	Coverage Δ
src/asynchronous/client.rs	0.00% <0.00%> (ø)
src/asynchronous/connection.rs	0.00% <0.00%> (ø)
src/asynchronous/server.rs	0.00% <0.00%> (ø)
src/asynchronous/stream.rs	0.00% <0.00%> (ø)
src/asynchronous/utils.rs	0.00% <ø> (ø)
src/common.rs	34.57% <ø> (-14.76%)	:arrow_down:
src/error.rs	55.55% <ø> (+55.55%)	:arrow_up:
src/lib.rs	100.00% <ø> (ø)
src/sync/channel.rs	0.00% <ø> (ø)
src/sync/client.rs	0.00% <0.00%> (ø)
... and 8 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.