Module registrations / start up sequence

[FabiolaDelaCueva]

Excellent reply Joerg!

One word of caution for everyone: Understand that anything that happens on the left of the main case structure that houses the MHL and EHL has the potential to delay the module's start. Most of the time, your modules get to the init case fast enough to execute the synchronization. 

The HSE team got bitten once by an error a customer had where they (they = the customer) didn't understand why they were getting an error due to things taking too long before the Init case synchronization. The HSE team found out the issue withing a second of looking at the code.

I have worked with plenty of teams that have no problem executing code on the left of the main case structure.

That said, error wiring to the Start Modules is important, especially from the Start Module to the Register for events and from the Register for Events to the Synchronize Module Events is very important (as the OP already confirmed 😉 ).

Happy wiring!

Fab

EDITED-->> edited to clarify that the they in the comment above referred to the customer not to the HSE team 🙂

[joerg.hampel]

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@FabiolaDelaCueva wrote:

The HSE team got bitten once by an error a customer had where they didn't understand why they were getting an error due to things taking too long before the Init case synchronization. 

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Our customer had spent a week or more, going in circles, even reinstalling systems, and slowly succumbing to insanity… but it only took me one glance to identify the issue in an instance. 

Because I’m so clever? No!!! Because I am aware of the mechanisms behind the scenes of starting a module. 

What I’m trying to create with my slightly dogmatic stance on how to start modules, and with my never-ending sermons on it,  is merely a better understanding in the community of what’s happening and where problems might arise in the future 🤷‍♂️😇

[shuttlefan]

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@joerg.hampel wrote:

Personally, I prefer a more "controlled" way of starting modules - meaning I like to place the Start/Sync VIs into a MHL or EHL (or Helper Loop) case.

Spoiler

Our HSE Way of Working goes one step further than many others and explicitly forbids any code from being executed outside MHL, EHL or Helper Loops - see https://dokuwiki.hampel-soft.com/kb/bestpractices/codingconventions/dqmh#starting_sub_modules

Ideally, you use the new VI Null Broadcast Events–constant.vi for preparing the event data type when creating the event registration reference. Then use either the Start Module.vi or the Obtain Broadcast References for Registration.vi for actually registering the real references at runtime:

Ok, so I created a private request and placed the code as you have it in the EHL.  Where should this request be called in the INITIALIZE case?  is there a certain timing it has to be done at?
I've put it after Synch Caller Events and before Module Did Init and appears to be working correctly.

[Ludwig72]

I think it makes no sense if you just move all registrations from outside into one event. I normally start each module with its own request inside the main DQML module and I do the same with stopping modules. At one hand you can order the modules startup this way and at the other hand debugging is easy.

[shuttlefan]

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@Ludwig72 wrote:

I think it makes no sense if you just move all registrations from outside into one event. I normally start each module with its own request inside the main DQML module and I do the same with stopping modules. At one hand you can order the modules startup this way and at the other hand debugging is easy.

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where are you starting the modules? inside the initialize MHL case?

[Ludwig72]

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@shuttlefan wrote:

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@Ludwig72 wrote:

I think it makes no sense if you just move all registrations from outside into one event. I normally start each module with its own request inside the main DQML module and I do the same with stopping modules. At one hand you can order the modules startup this way and at the other hand debugging is easy.

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where are you starting the modules? inside the initialize MHL case?

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yes, inside the MHL case

[FabiolaDelaCueva]

The VI surrounded by the blue circle is floating arround with nothing to enforce when it is supposed to execute.

If you want it to execute after the Synchronize Events and the Module Did Init, then you could wire some error wires in between the Synchronize Events, your Private Request VI to Register for Events, and the Module Did Init Broadcast.

[shuttlefan]

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@FabiolaDelaCueva wrote:

The VI surrounded by the blue circle is floating arround with nothing to enforce when it is supposed to execute.

If you want it to execute after the Synchronize Events and the Module Did Init, then you could wire some error wires in between the Synchronize Events, your Private Request VI to Register for Events, and the Module Did Init Broadcast.

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Yes, sorry, used the wrong screenshot.  I did wire it in 

I suppose the question is should that be after the Synch caller events or before?  is it in the right place?

[FabiolaDelaCueva]

Nothing should be wired before the Sync events. So it is in the right place now.