Use Case

As a driver engineer / CSOT engineer,
I want a connection layer that has easy to understand read / write semantics,
So that CSOT's connection layer timeouts can be easily reasoned about and implemented.

User Impact

• n/a

Dependencies

• n/a

Unknowns

• Should we also refactor to use async-await at this point? 
  • yes, we will refactor the internals of the connection layer to use promises but we will continue to prove a callback interface for `Connection.command()` to ensure compatibility throughout the driver

Acceptance Criteria

Implementation Requirements

Use subtasks as necessary. 

To allow development with subtasks for easier PR review and logical breakdown - create a copy of the Connection class (ModernConnection or a similar name) and make refactors on the copy.  Once refactors are complete, rename the new class to Connection and delete the old class.

• Remove the `MessageStream`
  • Introduce helpers for 
    • compression / decompression
    • serialization / deserialization 
    • buffering of server responses until we receive a full OP_MSG
  • Wrap the above helpers in generic "read", "write" and "readMany" helpers
  • Remove the message stream from the Connection class and listen to the socket for timeout and error events 
  • Adjust the `onMessage` handler to directly return a result or throw an error - no callbacks or async code is needed
  • adjust `Connection.command()` and write() to call the generic read/write helpers
  • Add a `readMany` helper specifically for use in monitoring and adjust the monitor to consume `hello`s using readMany

Testing Requirements

• Leave existing unit tests alone to provide coverage to the Connection class until the refactor is completed.
• Port any valuable connection-layer unit tests to a new test suite for the new socket layer implemenation
• Ensure all tests pass in the driver (integration and unit)

Documentation Requirements

• n/a

Follow Up Requirements

• n/a