Command attribute/binding

[MerrionComputing]

Need to have a Command class which can be bound to a parameter on an Azure function with autoresolve properties for command name and unique identifier.

If the unique identifier is not set, use a GUID

This will create an event stream to use to orchestrate execution of the step(s) required to process the command.

[MerrionComputing]

Needs to be on a per Domain basis so command handlers can be set up to watch a single domain.

[MerrionComputing]

Each command is backed by an event stream

[MerrionComputing]

The life cycle for a command should be something along the lines of:-

• Creation

• Parameter(s) set

• Validations performed

• Action step(s) performed

At any stage the current parameter(s), and the current progress of the command can be attained by running a projection over the command event stream.

[MerrionComputing]

Projections required:-

1. Command parameters - because parameters can be added or changed while the command is in flight (by the command handler itself usually) it is handy to be able to get the set of parameters as at a given point in time.

2. Command state - is the command complete, in error, running etc.

[MerrionComputing]

Question: should there be an explicit "Command Complete" event?

[MerrionComputing]

Added a Command.GetExecutionState() method to get the current state of the command orchestration

[MerrionComputing]

Needs a way to get the current state of a command from HTTP request

[MerrionComputing]

Command functions

• GetCommandState - Get the state of the given command instance
• CancelCommand - cancel a command in progress (and issue any compensating actions)
• ReissueCommand - re run a previously completed or cancelled command