Review of Control Systems guidelines and refactoring of implementation

A new release of the control system guidelines is imminent and the implementation of related aspects should be updated accordingly. This is phrased as a capability as it will have a slight impact on the SDHP train but it is expected that the OMC train will lead this effort. 

Design for implementation of long-running (asynchronous) commands) have been developed and reviewed in PI11 (outcome of SP-1640).

Work in PI12 will be executed as follows:

1. SP-1827: Update implementation of the command in the SKA Base Class as per SP-1640.
2. SP-1984: Update MCCS to adopt SP-1640 design, including the input queue.  MCCS implements a hierarchy of TANGO devices and provides environment for thorough testing.
3. SP-1627 and SP-1628: Update the SKA Base Classes Controller, Subarray and ObsDevice to fully implement SP-1640 design, including the input queue (which is optional, queue length = 0 means device does not use input queue).

If we are successful, by the end of the PI12 we will have:

• a well tested version 0.12 of the TANGO Base Classes which provides support for implementation of asynchronous communications (as per SP-1640).
• a new version of MCCS software which uses TANGO Base Classes v0.12.
• implementation well documented in Solution Intent.
• the document Control System Guidelines updated as required to support this design.

This will enable broad adoption of the new design in PI13.  In PI13, the teams will be able to upgrade to the TANGO Base Classes v0.12 using MCCS as an example.

Initially defined, more broad scope of this capability includes: 

• To update and release the Control System Guidelines with an ECP including results from:
  • ADR-9 ADR-31 ADR-32  
  • How each TANGO command is staged in sequence of events 
  • How to implement asynchronous interactions
  • How attributes keep track of the status and how they're updated 
  • How each subsystem shall implement availability with respect to failures and unavailability of other subsystems
• To implement the related changes as part of the SKA LMC Base Classes
• To implement common behavioural aspects of the control mechanisms in other common areas of code where they can be shared by different components. See https://confluence.skatelescope.org/display/SWSI/Common+Modules+Handling+proposal 
• To refactor existing implementation according to the newly stated patterns. It is expected that this will involve in greater proportion the "caller" side of the controls. 
• To clearly mark SKB bugs that are affected by this refactoring activity so that it is understood if this activity solves some of the current issues.