Elsa Workflows Community, 31 May 2022

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From YouTube: Elsa Workflows Community Meeting 11 ( 2022-05-31 )

Description

Meeting 11
Topics

- Elsa 2.8 release
- Elsa 3 updates
○ Service registration cleanup
○ Resizable panels
○ Workflow instance viewer
- Demos
○ SQL syntax + intellisense
○ Cascading dropdowns
- Plugins
○ https://docs.microsoft.com/en-us/dotnet/core/tutorials/creating-app-with-plugin-support

A

All right I'll just get started with the topics for today. So first off elsa 2.8 has been released about 30 minutes ago, so let's go for their release notes. So the first change of note was some fixes for the identity accessor made by tomi. So this improves the multi-tenancy support. There was a build issue fixed by p davis. So that's a this has something through with case and since the file systems or case sensitive file systems, some improvement on the workflow into the summary model.

A

This is useful when you query using the api endpoints and you want the wanted list of workflow summaries. So now it includes metadata. This is a new feature that I demoed last week, so this is about being able to list workflow versions through the designer and the ability to revert to all the versions of the workflow definition. So that's now part of the 2.8 release, some library, reference system, component, metal, annotations or a preview package thereof that has been fixed. That was causing issues for some users.

A

There's a new sql editor created by muhammad he's, hopefully going to demo. This later today, it includes intellisense, which is pretty cool some mapping for a sql for the trigger entity that was introduced, I think with elsa 2.7 or even 2.6. I am not sure, but we missed something in the yes sql provider, so that's been fixed by matt and jay added a nice little feature that purchased azure subscriptions on startup.

A

Now this is only an issue if you actually use the azure service bus integration and when you use that what happens is that as your service bus creates topics, but if you are in a multi-node environment and multiple queues get or subscriptions get created for those topics, those subscriptions do not get cleaned or removed when those nodes in your cluster go out of commission leaving behind phantom or orphaned subscriptions, and the issue with that is as long as the application generates messages.

A

Those subscriptions keep receiving those messages, but they are not being consumed because the consumer is no longer there and that causes ultimately the subscription count to reach its its maximum number of items, and that will cause exceptions in the application and we'll. I see this happening in a production instance. It will cause that production instance to fail. So this is a pretty important improvement. Without this, you would have to manually check your topics in azure service, bus and manually delete them, so that's less than ideal.

A

So this is great and finally there's a there was an issue with the retention module or the cleanup job in that module which takes care of cleaning out old, completed workflow instances, and then there was a recent improvement that allows the application to implement custom logic to determine what workflow instances would be deleted, but that also introduced a bug and that block has been fixed with this chains and what's nice about these release notes they were entirely generated by github that I just discovered today.

A

So it includes things like new contributors, a full chain slot here and a list of contributors of this vr. So I think that's really nice, so work has been done on lsat3 and mainly so. This was mainly cleanup work, but it's interesting all the same, so I'll briefly go over it. First and foremost, structure has been restructured, so everything almost everything lives inside a folder called modules, and this more or less embraces the the onion architecture.

A

I think that's name, I'm not entirely sure. Let me look up what the correct name is. I think I had it exactly right. So what does this mean? Every module adds its own set of features uh to the system, so that means workflows itself is a feature with other features that consume core features. So, for example, this workflow score module introduces a workflow runner, so it contains the logic to execute workflows, then there's another module that exposes functionality to http clients, just as an example.

A

Similarly, we have a management module that introduces functionality to manage workflow definitions, another one that adds persistence and then there's the runtime one where this one introduces some primitives to host workflows, and it also offers a bunch of abstractions that can then be used by other modules, in this case the protoactor module. So the these. These are just examples for workflow related functionality.

A

As a as a developer, you can extend the system by creating your own modules, which, at the end of the day, are just.net packages, so to just give another example, there's a javascript module that adds scripting features using the javascript syntax using the tnt packets, but it also adds activities to the system. So this is a big restructuring and then, let's take a look at how to configure these modules in your application.

A

So here's a new folder called bundles and my idea with these bundles is that it contains packages that reference a bunch of other module packages with common configurations. So, for example, a typical workflow server wall reference. This elsa bundle which itself in turn references most commonly used packages like the mediator and, of course, workflow related modules and then there's a all-in-one web application and that hosts both the elsa designer, as well as a workflow server.

A

So this is what we call an lsat to the monolith setup and this one is the workflow server and that's a common configuration for just having a workflow server that does not serve the designer, so that would require the user to create their own dashboard application into which they can, of course, host the reusable elsa designer components. So the syntax to configure elsa looks like this. So it's the same as.

B

A

So there's the ad elsa extension method on the iservice collection object, but the elsa lambda parameter as you can see, it's an I module and that basically is consumed by the module, other modules to add their own services to the system and it's convenient mechanism to register other services, because it also allows you to define dependencies between modules and this all to make it easier for the user to configure elsa so that they can ultimately can just do something like this at elsa and then this should enable a default most commonly used configuration of elsa.

A

But if you want, you can then drill into the details and tweak the configuration as you see fit. In this way you can add features, remove features and change default settings, so that was a lot of refactoring took up quite some time, but I think it's pretty clean, I'm pretty happy with it. So that is everything about the surface tracing cleanup.

A

A new contribution came in today that adds resizable panels to the lz3 designer, which is pretty cool, I'll, show you what that looks like so, for example, let's go to the workflow definitions and open a warfare definition here, and these two panels now are resizable, and this is very convenient because for certain activities you may need some more screen real estate to conveniently change the properties of a given activity. So that's cool. I've been working on the workflow instance viewer.

A

So what we see here is a workflow definition editor, but when you execute workflows, workflow instances will be created and, of course, you will want to look at those workflow instances. So there's a workflow instances model.

B

A

And here I just have one workflow instance:.

B

A

I will now open it opens that workflow of this version in the designer here it's in read-only mode, so you shouldn't be able to drag and drop, but I think I I just broke it or forgot to implement this work in progress, as you can see, and the panel on the right-hand side is different compared to the workflow definition editor here. It shows workflow instance related information like the instance id definition, id diversion, etc the status and some timestamps.

A

So the next feature for me to work on is the workflow journal, and that will I'm thinking of adding it to the left-hand side so that you always have the journal in view, while looking at a workflow instance, and you have the ability to inspect individual activity properties on the right-hand side, all right. So that's my brief update in a nutshell for elsa 2 and elsa 3. mohammed. If you are prepared, if you like, you can demo the sequel, syntax work that you've done.

B

Yeah yeah, yes, okay, so let me share my screen quickly. Are you able to see my screen.

A

B

So in here I'm going to present the new sql syntax and basically because we are using the monaco editor, I was looking for some time how we can implement sql syntax supports and now, especially that we have sql activities. So that part is now added and you can see. For example, here we have the javascript liquid and the sequence in text now is an added option.

B

So, if you'd like to use that one you'll get the syntax highlighting for uh sql in your code and activity, and so that is already there and the other thing that I wanted is that uh for the variables like the string and the number variables the simple ones.

B

If I want to use that as part of my sql query, so auto completion is also available and it will pick from the type definitions, strings and numbers so workflow and stands for definition, and also, if I have defined some variables in my workflow, it will also be able to pull these ones here. So that is also possible and, for example, I can demonstrate here.

B

I will must run this workflow and what it's going to do is that it will pull the correlation id and insert it as our recording database, and one more thing here is that to handle the null values, because I think sql has some special treatment for none. So in this activity. I am setting this just a test variable I'm setting the value as num and then, if I use that variable instead here, so it will also be able to handle that now. If I test this activity, it is also able to handle the null values.

B

So this kind of support. I think it is quite handy, especially if you have a very complex sequel series and you want to get the code highlighting and also, if you want to integrate some variables into your query without breaking the syntax of the sql, which I think it will be really useful. uh Moving forward. Yeah.

A

I agree this looks great awesome, so you also had to update the execute sql command activity. To add support for the no value is that right.

B

uh I've done it in the handler, so the handler will check the value for the variable. Oh.

A

B

If it is a null, it will just replace it with other.

A

Yeah make sense cool. Thank you.

C

A quick question: do you think it could be uh possible to make a command like a select into a variable? It's not related to your work, but maybe uh it could be a useful.

A

C

You mean a sql.

A

Query that selects some value into a workflow variable yeah.

C

I know we can. We can write this kind of command in sql directly, but I don't know if there is a if it is useful to do this directly uh with a viable workflow variable.

B

Yeah, so currently the variable handling is a very just as a replacement, so I'm just checking the value and then replacing it in into the query. So if it's a number or if it's a string, I'm just replacing this variable with the value, but what you mentioned is, I think, is really helpful and uh that is more about parameter handling. I think yeah yeah. So that could be the next step. Maybe in this actually currently we are doing some custom activities using oracle and oracle has the concept of input and output parameters.

B

So we have built some custom activity there to map these parameters, because we also found there's some challenge in that case, but yeah. This could be maybe some advanced way to to handle the variables. If I can really select the statement and then insert it directly to the variable, that would be awesome.

A

Yeah, this might be related to what tommy suggested on github, where currently, if you want to capture output of activities, you need to add a set variable activity to the workflow. But if you need to do this often, then it kind of pollutes the workflow with a lot of set variable activities. So this would be one nice way to work around that so that you can directly from your command, insert a sql value or a value from the database directly into a workflow variable. Yeah.

C

I think this kind of thing has to be done more globally or not just for a sequel, commander activity. That's.

A

Right and, of course, this this suggestion is specific for the sql query activity, but you're right to make it more convenient holistically. That requires a different solution. This.

C

Is this, this feature is very cool yeah.

A

This is, this is awesome. Thank you so much mohammed. Thank you all right, jay. I know you have a pr open. Should we spend a couple of minutes talking about that? One yeah sure. Do you want to walk us through? What's been done and what is the status and do you need anything from me? Yes,.

C

Try to get them to commit and launch everything. So the idea, if we take a look at the pr, so I have some I think race condition is you is a ui event? Does the id? Do you see my screen? One? Second yeah. I see it okay, so the idea is to be able to create more than two drop-down lists in cascade, and so here I have a brand with a different car.

C

Then for each car I will have some model and with a combination of rand and model I can have different color so and everything in the data is configured on the back end in c-sharp, using the iron time select list item, and so we could. We can then plug this to a database, for example, and one issue I have is when I select, for example, here tesla, I should have a problem with the event, because some elements are repeat in my list. I.

A

See yeah, okay,.

C

So this is here we are, I have the the color, for example, and the model, so I think it's a ui issue and if we take a look at the the c sharp, the idea is to create to use the drop down. Okay, I use an option provider like widow like we do with a natural drop down, and here I have just had some option and this option I use in the ui. So it's a little trick for now, but as explained in the pier, we could add some property.

C

The activity input which could be depends on depends on property and depends on value, because here I want to, for example, for the model. I need to update the model when the user change the brand list, so I need to depends on the event change on brand, but I want to get the value of the model and brand to show different color. That is why that is how I implement this in the get select list. For example, if my property change is brand, I will do the the different return, the different element.

C

If the name is modal, I will check what values are sent to the api, to choose a good as a good model regarding the brand and for color. I need the brand and the model and because I choose in the option model and brand the ui send me the two values. So I see element configure here. I use buy the ui but generically to send the value and to react to specific events. This one.

C

This line is just a trick for the event to be sure to use the event or model, but it will disappear if we add the two properties yeah.

A

You mean that depends on property, it depends on events. Yes,.

C

Right so this, uh so the this line is depend on event, then in 64 and then 65 is depend on a value card and then in the get select list. I think we could change this code to use a database and to use a lazy lazy select on the database, for example, and this could be a really early april for this kind of choice. This.

A

Will be great because this way users can implement cascading drop-downs selections without having to write custom plugins for the for the designer yeah.

C

A

All right, so it looks like you only need to do a little bit of cleanup, introduce that depends on event and property. Yes, and.

C

And we need to.

A

Fix the uh the race condition in the ui that you mentioned. Yes,.

C

I don't find I do a lot of tests. I don't succeed to find the issue on the ui so uh for this I need your help and I can clean up the code before and add the depends on event and depends on value yeah.

A

Perfect, so if you work on that- and let me know when that's part of the pr, then I will take a crack at fixing the ui issue. Okay,.

C

That's good and I think I have only two change file, so uh everything should be in the dropdown property yeah.

A

These are my favorite pr's, just two changed files.

C

Very cool thanks, jay you're welcome, and I just have a one question about the the loading what you show uh at the beginning for azer3. I don't know if you can just uh show you your notes.

A

Oh, am I sharing no yeah.

C

Are you sharing? um I.

A

C

Okay for the service registration- uh I'm just wondering if um rls are three, we could register some activity like a plugin, so uh once the the server is started in the lifecycle of the application, we can using an api load with a package, send a package to an api and load new activity by using a plugin architecture right so.

A

The answer is yes, but what it would require, I think, is being able to load a packets or an assembly of from a package into the current app domain and with asp.net core or net core. The way to do this has changed done it myself, but there is. There is good support.

A

I believe these days to to do so, so that would be possible, but of course the activities are registered at startup time, but I think, if we take a look at the implementation, you should be able to add it at runtime as well yeah, because here there is a api options. Object that's been configured during startup, but you could inject this high options of api options and then add more activity types at runtime, so that is certainly possible.

A

Maybe we need to create a nice api to to make it easy for users to uh to do so, but uh it should definitely be possible. Okay,.

C

I think when I will start to work on the three I will, uh I will try this cool.

B

Yeah, I think I was checking the same thing. The other day in the microsoft docs itself. There is page for the net core plugins how to load the assemblies at runtime and also how to make it work with dependency injection the container. So I think from from that angle, it is possible, but then it would be uh how to do that with elsa. Yes,.

C

The idea is, uh if, if everything is uh well decoupled with uh using interface, we could load a different thing and uh there is no abdomen and the the unloading of asmry is a little bit different, but there is a very good sample on the msdn. That's.

A

Cool yeah, then, let's give that a try. I know it's been asked multiple times in ls2 to add support for loading assemblies at runtime. So, let's see what, if there's any changes we need to make in the in the elsa library itself, do you have a link to that msdn article by any chance? Yes,.

C

The use of assembly load context and it's uh it's uh it's easy to use, and we just have to to be sure that we can unload the assembly after to be uh to be very powerful. Indeed,.

A

This is very cool yeah. We should definitely add support for this yeah.

B

I think, even if you consider, for example, the sequel activity, so you can have an adapters of different database drivers in that case. So if I want to load for oracle for sql server to become really powerful, yeah.

A

Especially, if you, um if you have an elsa, workflow server, hosted somewhere, and you want to be able to add plugins at runtime dynamically, then this is what allows you to do this.

C

But in fact, this kind of feature is also um linked to the kappa, the capability to execute some activity in specific environment, because uh if we can, for example, uh start one container uh to execute a specific activity, we can load a specific container with some external dependencies to execute this activity. It's it could be a good also, and it's not another kind of using plugin.

C

You mentioned this topic a couple of meetings ago, yeah, yeah yeah, that's that's a that is. This is my two points on the edge that three plugin and uh context execution. What I call context execution, yeah.

A

I remember that's great. I look forward to to those pr's okay, do we have anything else.

C

Not for me, that's good, alright,.

A

In that case, I'm gonna stop the recording.