Dynamic definition and evaluation of states machine

[daya]

Using something like States Language editor and resulting json output, is it possible to dynamically (at runtime) define state machines and have the state machine executed/evaluated?

[entone]

Yes, it is. I would need a bit more details on your use-case to provide an ideal path forward. My use-case in the past was that the state machines were pre-defined, but you could update the JSON itself backing the state machine and use hot code reloading to update the gen_statem module.

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On Sat, Jan 9, 2021 at 3:39 PM Daya Sharma ***@***.***> wrote: Using something like States Language editor and resulting json output, is it possible to dynamically (at runtime) define state machines and have the state machine executed/evaluated? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#9>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABGNLKZQ2QHXTXR5QH5KGDSZDEKLANCNFSM4V34MUIA> .

[daya]

Thanks for the reply @entone my use case is a logged in User using some Editor (like states-language editor) is able to define a State machine with all the steps, branching logic and callouts (webhooks). The system/application will then run one or more executions of this user defined state machine and generate report on them.

Obviously as you can make out there will be a Schema based on the business domain which will control the possible state machines that can be generated.

Do you think this kind of runtime creation and execution of state machines is easy enough to implement states_language? or will it require too much arm twisting?

[entone]

Not at all, I think it is quite doable. My approach has been to create a Macro that will define the StatesLanguage implementation, the macro should accept the JSON file or Map structure and generate a module at runtime, you can then start a process based on the compiled module. I have implemented something very similar for an IVR system, the original inspiration for the project, however I'm not able to share that code. It will come down to using something along the lines of https://hexdocs.pm/elixir/Code.html#compile_string/2 to compile the module, and starting that as a Task or under a supervision tree.

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On Mon, Jan 11, 2021 at 1:57 PM Daya Sharma ***@***.***> wrote: Thanks for the reply @entone <https://github.com/entone> my use case is a logged in User using some Editor (like states-language editor) is able to define a State machine with all the steps, branching logic and callouts (webhooks). The system/application will then run one or more executions of this user defined state machine and generate report on them. Obviously as you can make out there will be a Schema based on the business domain which will control the possible state machines that can be generated. Do you think this kind of runtime creation and execution of state machines is easy enough to implement states_language? or will it require too much arm twisting? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#9 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABGNLMO2Y3BLUZJXXO56FDSZNJ4JANCNFSM4V34MUIA> .

[daya]

the macro should accept the JSON file or Map structure and generate a module at runtime, you
can then start a process based on the compiled module.

Right that's one high level interface to the internals, and I hope you meant something along these lines, right?

defmodule MyModule do

use StatesLanguage, data: %{state1: %{}, state2: %{}} 

end

but as that is compile time still, I am looking for some place in code base where that compile time configuration is executed to interpret the graph into a gen_statem process. Could you please help me with a pointer to that module/line?

[entone]

You will need to use Code.compile_string in order to do it at runtime, or another one of the functions that will compile a module, and pass in the data by either writing the JSON to a file, or using something like Code.compile_quoted to pass in a map to your macro.

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On Mon, Jan 11, 2021 at 4:48 PM Daya Sharma ***@***.***> wrote: the macro should accept the JSON file or Map structure and generate a module at runtime, you can then start a process based on the compiled module. Right that's one high level interface to the internals, and I hope you meant something along these lines, right? defmodule MyModule do use StatesLanguage, data: %{state1: %{}, state2: %{}} end but as that is compile time still, I am looking for some place in code base where that compile time configuration is executed to interpret the graph into a gen_statem process. Could you please help me with a pointer to that module/line? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#9 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABGNLOOUNIRT46S2FVGCQ3SZN53BANCNFSM4V34MUIA> .

[entone]

@daya not sure if you ever figured this out, but I put together an example, https://github.com/entropealabs/states_language_runtime