Communicating to actors from TestStand

[justACS]

Brian_Powell wrote:

And then there was the day that a customer asked me how to call an actor as a step in TestStand.  Sigh.  No, dear customer, the AF is not the best solution for everything.

I've done it.  That particular solution proved not to be viable for unrelated reasons, but the process is straightforward.  You can send a message easily enough, and inject replies into your sequence via a queue.  If you need round-trip service in a single step, then you can use a Reply Message.

I could actually imagine needing to combine TestStand with a set of actors.  But the question to ask is how to architect TestStand the best way to have steps interact with other processes running in parallel.  E.g., how does one build a producer/consumer interaction between TestStand and something else?  I would try to avoid bubbling up inter-actor communications into the TestStand layer.  It can be done, but I'm pretty sure I would never stop telling myself that it was an abuse of TestStand.

Agreed.  TestStand should be talking to top level actors that need minmimal interoperabilty.  The environmental controls on a test cell, for example.

If we flip that around, one of the things that Nancy and I keep asking ourselves is how to incrementally convert an existing architecture to use the AF.  How do you use the AF as a small component within a larger framework that's not actor-oriented?  Is that worth thinking about?  From our perspective, it looks like if you want to use AF, you are biting off a rearchitecture, and that scares people away.

I've thought about this problem a lot, and I don't think that's true, necessarily.  Any piece of code can send a message to an actor.  The caller needs a receive loop to handle messages from the actor, but those messages could be abstract messages with data accessors.  That's enough to manage interactions with queued message handler/producer-consumer applications.  If you need synchronous messaging (as in web services, which are inherently command-response), you do have Reply Messages.  You may need an adapter layer, but it should be straightforward.

[mthimm1]

I would like to call an actor from Teststand:

I have an dedicated sequencer actor. It starts Teststand and is able to  start sequences. I want to pass the results of the steps to the actor. The best way seems to me to send a result message to my sequencer actor which is able to process it further.

There are other sequencer, a customer solution and a very simple LabView Sequencer which were easy to integrate because the are already available as LabVIEW VIs.

But I have heavy problems to integrate Teststand the same way (which would be nice since I could use the messages which are already available). How and where did you store the enqueuer of the actor and how do you send a message?

I tried to set it as parameter of the sequence and used the setValVariant method of the parameter subproperty object. This throws error 1 in Labview.

[Oli_Wachno]

I have stored the Actors Enqueuer as a Object Reference. To communicate, I call (encapsulations of) the Send Message VIs.

Works fine.

[mthimm1]

Thanks, but exactly this did not work for me: Which method did you use to store the enqueuer in teststand? It seems that you both, niACS and you are using the same straight forward approach I try to use, but mine does not work.

I am reading the self enqueuer of my actor, transform it to variant and set this as the "newValue" Parameter of the "SetValVariant" method which is applied to the "AFEnqueuer"-Subproperty of the sequence parameters. This method throws "error 1". I am quite new to Teststand but I was able to execute the sequence by my older TestStand Actors which were polling the results and which were using callbacks respectively.

It seems strange to me that I have to use variant to pass the object reference to Teststand. Is this the right way or am I on the wrong steamboat (german saying, SCNR,). Is there a way to delegate type control to the API?

[Oli_Wachno]

Ok...

I don't see a need to convert this value to variant... I am calling the "Actor Vis" from TestStand and just assign the outputs of those VIs to the corresponding object in TestStand....

As long as you don't understand nothing but train station

[mthimm1]

Ah okay now it seems that I understand a bit more than train station, probably I am somehow still standing on the hosepipe:

I do not start the AF (the root actor) from Teststand. Due to this I seem to need to transfer some communication information from LabVIEW to Teststand. If I transfer an actor (-reference), I can extract the corresponding enqueuers by using the AF vis. And if I transfer an enqueuer, I can use itself for communication. Either way I need to set a property in Teststand which is provided by a calling actor which has been started _not_ by calling a vi from Teststand.

Unfortunately I cannot start the root actor from Teststand, since I do not have Testand in most applications my project is build for.

Oli_Wachno wrote:

I have stored the Actors Enqueuer as a Object Reference.

Is this enqueuer the output of some vi you previously called from Teststand? If yes: What are the input parameter of this vi?

I am somehow not able to transfer an object reference to Teststand. I am sorry if I occupy your mind for an inappropriate amount of time.

[Oli_Wachno]

mthimm1 schrieb:

I am somehow not able to transfer an object reference to Teststand. I am sorry if I occupy your mind for an inappropriate amount of time.

No worries But we better stop this German-English nonsense befor being excluded from the group 😉

How about this:

1.) Create an Object in TestStand for the Enqueuer (e.g. "StationGlobals.MyEnqueuer")

2.) In your LabVIEW VI, call the Set Property.vi from the TestStand Palette (Object Instance) with the enqueuer and correct name

But maybe I'm missing an important part.... don't know

[Oli_Wachno]

Just found that important part....

the VI expects a reference for identifying an object....

[mthimm1]

According to one of the gods of AF it seems not to be possible at all:

click!

The problem seems to me that the data segment of the two applications is different, so it is not meant to work at all.

I am leaving this path. Very likely a and "more" straightforward approach is to create message objects and send them by value through a TS queue from TS to my sequencer actor. Message sending is something that should not be done by another program and TS itself should not act like an actor. I already have an constructor for each message because I enqueue them always manually.

Since test results are also LabVIEW objects (to take advantage of heritage) in my application I could even send the test result instead of the message object. Probably I misunderstood niACS (the other AF god) in his OP.

What a tremendous waste of gummi bears!

[A.Rohde]

mthimm1 --> Is there a reason why you can't start your root actor from TestStand? Then it should work.

You will have the communication problem no matter what framework you work in if you want to start both applications as seperate instances then references won't work between them. If you follow that approach I see no other way than using TCP/IP to communicate. Maybe using the Linked Network Actor but I never tried that in TestStand.