Implement core functionalities of the IO component in scaler - YMQ

[gxuu]

READY FOR REVIEW.

Implements the C++ core of YMQ, the network part of scaler.

The initial design and implementation differs by about 10%, with majority comes from the idea of RecvMessageCallback should be placed in the IOSocket level.

General execution flow behaves like the following graph.

Limitations

Ability

• Current implementation does not allow listen on multiple addresses.
• Current implementation does not allow back-to-back connect to multiple addresses.
• Current implementation does not allow connect to remote end when an existing connection is retrying.
• Current implementation does not allow duplicate identity.
• Current implementation does not support NS lookup.

Performance

• Current implementation do sendMessage in O(n) time which can be reduced to O(lg n) easily.
• Current implementation do connection construction in O(n) time which can be reduced to O(lg n) not so easily.

Security

• Current implementation does not clear empty connection (ones that connect but never send anything).
• Current implementation does not clear connections with abnormal traffic (for example sending one bytes per 5 seconds).
• Current implementation does not set limits on package size.
• Current implementation does not differentiate true close and false close (based on the assumption that our use case don't close until the program finishes).

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: gxuu / name: gxu (2e17a4e, 4ca3b66, 5488320, 8d073fd, 849b952, c8c51cb, f22c87e, 734cc7b, 83cb911, 413673b, aab4c0f, d9dcb9b, 5c48a19, 12e938c, 20ad885, af10dcb, c114aad, d543515, 5ed6284, f3eeb9f, d96e506, fa51f60, b5395d8, 155aef1, 6ade637, fb2d15d, 5226fd6, 2f5e94a, 37206f8, 9d2c2cd, e32ac2a, 168e1b2, e658389, d12def6, a1b8926, 9145405, 0623285, 75e7938, 97c6291, ceecfc2, adb685c, c956839, b13ce76, bc4f33f, 8c4f494, 18f6cf3, b009c17, dc7ecad, cc483a6, fd33915)

This is not applicable