I have a Camunda flow with a Call Activity (sequential), the call Activity calls several subflows based on a list of process keys (ids) in a certain order.
For instance I get a list of ["flow-1", "flow-2"], then flow-1.bpmn and flow-2.bpmn are executed.
But, also in the scope is flow specific data, added to the scope in "Read LOT Configuration". For instance [{"name", "flow-1", "identifier" : "some-data"}, {name: "flow-2", "identifier" : "some other data"}].
I would like the call activity to determine that for flow-1, I need to send the flow-1 related object along.
I do not want to send the entire collection, but only the flow specific data.
How can I achieve this?
Some ideas:
a) use the element variable from the call activity settings as key to extract the correct data element in a data mapping
b) surround the call activity with a multi-instance embedded sub process. In this scope you will have the element variable (processId), which can then be used to perform delegate variable mapping (https://docs.camunda.org/manual/7.16/reference/bpmn20/subprocesses/call-activity/#delegation-of-variable-mapping)
c) pass the processID as data and fetch the configuration for the particular process inside its sub process implementation only
Related
Say I have 3 states, A -> B -> C. Let's assume inputs to A include a field called names which is of type List and each element contains two fields firstName and lastName. State B will process the inputs to A and and return a response called newLastName. If I want to override every element in names such that names[i].lastName = newLastName before passing this input to state C, is there an built-in syntax to achieve that? Thanks.
You control the events passed to the next task in a Step Function with three defintion attributes: ResultPath and OutputPath on leaving one task and InputPath on entering the next one.
You have to first understand how the event to the next task is crafted by a State Machine, and each of the 3 above parameters changes it.
You have to at least have Result Path. This is the key in the event that the output of your lambda will be placed under. so ResultPath="$.my_path" would result in a json object that has a top level key of my_path with the value equal to whatever is outputted from the lambda.
If this is the only attribute, it is tacked onto whatever the input was. So if your Input event was a json object with keys original_key1 and some_other_key your output with just the above result path would be:
{
"original_key_1": some value,
"some_other_key": some other value,
"my_path": the output of your lambda
}
Now if you add OutputPath, this cuts off everything OTHER than the path (AFTER adding the result path!) in the next output.
If you added OutputPath="$.my_path" you would end up with a json of:
{ output of your lambda }
(your output better be a json comparable object, like a python dict!)
InputPath does the same thing ... but for the Input. It cuts off everything other than the path described, and that is the only thing sent into the lambda. But it does not stop the input from being appeneded - so InputPath + ResultPath results in less being sent into the lambda, but everything all together on the exit
There isn't really a loop logic like the one you describe however - Task and State Machine definitions are static directions, not dynamic logic.
You can simply handle it inside the lambda. This is kinda the preferred method. HOWEVER if you do this, then you should use a combination of OutputPath and ResultPath to 'cut off' the input, having replaced the various fields of the incoming event with whatever you want before returning it at the end.
I am using a ServiceBusTrigger to execute code when receiving a message. I would like to use the Singleton attribute to limit which messages can be executed in parallel. This attribute allows specifying a scope bound to properties on the incoming message, such that messages with different values can be executed in parallel but ones with the same value must be done serially.
This works when using top level properties on the incoming message object like CorrelationId.
Example
[Singleton("{CorrelationId}", SingletonScope.Function, Mode = SingletonMode.Function)]
public async Task HandleMessage(
[ServiceBusTrigger("my-topic-name", "my-subscription-name"), ServiceBusAccount("my-account-name")]
Message message,
CancellationToken cancellationToken
)
{
await Task.Yield();
}
What I am struggling to figure out is how to achieve the same behavior with user properties on the message. These are stored in the UserProperties dictionary on the Message object. I'm not seeing a way to refer to these with the binding statement in the Singleton attribute, but it seems like this would be a very common use case when combining Singleton with ServiceBusTrigger
The Service Bus Bindings exposes Message Metadata in binding expressions. So, userProperties.<key> should do the trick.
I need to do a callout to webservice from my ApexController class. To do this, I have an asycn method with attribute #future (callout=true). The webservice call needs to refeence an object that gets populated in save call from VF page.
Since, static (future) calls does not all objects to be passed in as method argument, I was planning to add the data in a static Map and access that in my static method to do a webservice call out. However, the static Map object is getting re-initalized and is null in the static method.
I will really appreciate if anyone can give me some pointeres on how to address this issue.
Thanks!
Here is the code snipped:
private static Map<String, WidgetModels.LeadInformation> leadsMap;
....
......
public PageReference save() {
if(leadsMap == null){
leadsMap = new Map<String, WidgetModels.LeadInformation>();
}
leadsMap.put(guid,widgetLead);
}
//make async call to Widegt Webservice
saveWidgetCallInformation(guid)
//async call to widge webserivce
#future (callout=true)
public static void saveWidgetCallInformation(String guid) {
WidgetModels.LeadInformation cachedLeadInfo =
(WidgetModels.LeadInformation)leadsMap.get(guid);
.....
//call websevice
}
#future is totally separate execution context. It won't have access to any history of how it was called (meaning all static variables are reset, you start with fresh governor limits etc. Like a new action initiated by the user).
The only thing it will "know" is the method parameters that were passed to it. And you can't pass whole objects, you need to pass primitives (Integer, String, DateTime etc) or collections of primitives (List, Set, Map).
If you can access all the info you need from the database - just pass a List<Id> for example and query it.
If you can't - you can cheat by serializing your objects and passing them as List<String>. Check the documentation around JSON class or these 2 handy posts:
https://developer.salesforce.com/blogs/developer-relations/2013/06/passing-objects-to-future-annotated-methods.html
https://gist.github.com/kevinohara80/1790817
Side note - can you rethink your flow? If the starting point is Visualforce you can skip the #future step. Do the callout first and then the DML (if needed). That way the usual "you have uncommitted work pending" error won't be triggered. This thing is there not only to annoy developers ;) It's there to make you rethink your design. You're asking the application to have open transaction & lock on the table(s) for up to 2 minutes. And you're giving yourself extra work - will you rollback your changes correctly when the insert went OK but callout failed?
By reversing the order of operations (callout first, then the DML) you're making it simpler - there was no save attempt to DB so there's nothing to roll back if the save fails.
I'm writing a little clojure pub/sub interface. It's very barebones, only two methods that will actually be used: do-pub and sub-listen. sub-listen takes a string (a sub name) and do-pub takes two strings (a sub name and a value).
I'm still fairly new at clojure and am having some trouble coming up with a workable way to do this. My first thought (and indeed my first implementation) uses a single agent which holds a hash:
{ subname (promise1 promise2 etc) }
When a thread wants to sub it conj's a promise object to the list associated with the sub it wants, then immediately tries to de-reference that promise (therefore blocking).
When a pub happens it goes through every item in the list for the sub and delivers the value to that item (the promise). It then dissoc's that subname from the map and returns it to the agent.
In this way I got a simple pub sub implementation working. However, the problem comes when someone subs, doesn't receive a pub for a certain amount of time, then gets killed due to timeout. In this scenario there will be a worthless promise in the agent that doesn't need to be, and moreover this will be a source of a memory leak if that sub never gets pub'd.
Does anyone have any thoughts on how to solve this? Or if there is a better way to do what I'm trying to do overall (I'm trying to avoid using any external pre-cooked pubsub libraries, this is a pet project not a work one)?
You can do something like this:
Create an atom
publish function will update the atom value by the passed in value to the function
Subscribers can use add-watch on the atom to be notified of when the atom value changes i.e due to call to publish function
Use remove-watch to remove the subscription.
This way you will have a very basic pub-sub system.
I have marked Ankur's answer as the solution but I wanted to expand on it a bit. What I ended up doing is having a central atom that all client threads do an add-watch on. When a pub is done the atom's value is changed to a vector containing the name of the sub and the value being pub'd.
The function the clients pass to add-watch is a partial function which looks like
(partial (fn [prom sub key ref _old new] ...) sub prom)
where prom is a promise previously generated. The client then blocks while waiting on that promise. The partial function checks if the sub in new is the same as sub, if so it removes the watch and delivers on the promise with the value from new.
I made a class that has an asynchronous OpenWebPage() function. Once you call OpenWebPage(someUrl), a handler gets called - OnPageLoad(reply). I have been using a global variable called lastAction to take care of stuff once a page is loaded - handler checks what is the lastAction and calls an appropriate function. For example:
this->lastAction == "homepage";
this->OpenWebPage("http://www.hardwarebase.net");
void OnPageLoad(reply)
{
if(this->lastAction == "homepage")
{
this->lastAction = "login";
this->Login(); // POSTs a form and OnPageLoad gets called again
}
else if(this->lastAction == "login")
{
this->PostLogin(); // Checks did we log in properly, sets lastAction as new topic and goes to new topic URL
}
else if(this->lastAction == "new topic")
{
this->WriteTopic(); // Does some more stuff ... you get the point
}
}
Now, this is rather hard to write and keep track of when we have a large number of "actions". When I was doing stuff in Python (synchronously) it was much easier, like:
OpenWebPage("http://hardwarebase.net") // Stores the loaded page HTML in self.page
OpenWebpage("http://hardwarebase.net/login", {"user": username, "pw": password}) // POSTs a form
if(self.page == ...): // now do some more checks etc.
// do something more
Imagine now that I have a queue class which holds the actions: homepage, login, new topic. How am I supposed to execute all those actions (in proper order, one after one!) via the asynchronous callback? The first example is totally hard-coded obviously.
I hope you understand my question, because frankly I fear this is the worst question ever written :x
P.S. All this is done in Qt.
You are inviting all manner of bugs if you try and use a single member variable to maintain state for an arbitrary number of asynchronous operations, which is what you describe above. There is no way for you to determine the order that the OpenWebPage calls complete, so there's also no way to associate the value of lastAction at any given time with any specific operation.
There are a number of ways to solve this, e.g.:
Encapsulate web page loading in an immutable class that processes one page per instance
Return an object from OpenWebPage which tracks progress and stores the operation's state
Fire a signal when an operation completes and attach the operation's context to the signal
You need to add "return" statement in the end of every "if" branch: in your code, all "if" branches are executed in the first OnPageLoad call.
Generally, asynchronous state mamangment is always more complicated that synchronous. Consider replacing lastAction type with enumeration. Also, if OnPageLoad thread context is arbitrary, you need to synchronize access to global variables.