An external service can receive a message from Camunda process engine using below piece of code. Does client polling Camunda process engine periodically to get messages ?
ExternalTaskClient client = ExternalTaskClient.create().baseUrl(“http://localhost:8080/engine-rest”)
.asyncResponseTimeout(10000)
.build();
client.subscribe(“AdlDMNOtherClient”).lockDuration(1000)…
It uses "long polling", so it does not open new requests but tries to keep a single connection as long as possible, see https://github.com/camunda/camunda-external-task-client-java/blob/master/examples/order-handling/src/main/java/org/camunda/bpm/App.java
So if your question is: "will my code get notified automatically when a new task is created", the answer is YES.
If your question is: Will I have many HTTP request, the answer is NO, normally not.
Yes. The architecture, interaction patter (incl. long polling) and ways to communicate errors or results back to the process engine are described with a few diagrams here:
https://docs.camunda.org/manual/latest/user-guide/process-engine/external-tasks/
and here:
https://docs.camunda.org/manual/latest/user-guide/ext-client/
Related
I am using Camunda workflows to automate various processes. I have come across a scenario where the process is not moving from a service task. Usually, we call the task/{taskid}/complete to complete the task, but since the process is stuck on a service task, I am not able to complete that task. Can anybody help me find a way to complete the service task?
You are using a service task. That basically means "a machine should do something". The "normal" implementation is to provide code (a java Delegate or a connector endpoint) that is called by the process engine to execute this task.
The alternativ is to use the "external task" pattern. Think of external tasks as "user tasks for computers". So the process waits, tells subscribed clients that a job is to be done and waits for their completion.
I suppose your process uses the second option? (you can check in the modeler under "Implementation"). So completion can be done through the external task API, see docs.
/external-task/{id}/complete
If it is a connector then you likely will see when checking the log that retries have occurred and that the transaction rolled back. After addressing the underlying issue the service task (email) should be sent without explicitly triggering the service task and the following user task (Approval) should be created.
My application creates a new EventHubClientBuilder() every time it sends an event to EventHub.
EventHubProducerClient producer = new EventHubClientBuilder()
.connectionString(connectionString, eventHubName)
.buildProducerClient();
I followed this quick start guide when building this application. I don't think it is best practice to create a new client if the application is expected to be publishing an event regularly (every 2-3 min) however, I cannot find any documentation that explains how to keep the client connection open aside from this .NET guide but my application is using Java.
Can someone explain how I could use a single producer client for the duration of the application? The application is consuming messages from another application and needs to published each message to EventHub.
We have a BizTalk application which sends XML files to external applications by using a web-service.
BizTalk calls the web-services method by passing XML file and destination application URL as parameters.
If the external applications are not able to receive the XML, or if there is no response received from the web-service back to BizTalk the message gets suspended in BizTalk.
Presently for this situation we manually go to BizTalk admin and resume each suspended message.
Our clients want this process to be automated all, they want an dashboard which shows list of message details and a button, on its click all the suspended messages have to be resumed.
If you are doing this within an orchestration and catching the connection error, just add a delay shape configured to 5 hours. Or set a retry interval to 300 minutes and multiple retries on the send port if that makes sense. You can do this using the rule engine as well.
Why not implement an asynchronous pattern?
You make it so, so that the orchestration sends the file out via a send shape while initializing a certain correlation set.
You then put a listen shape with at one end:
- the receive (following the initialized correlation set)
- a delay shape set to 5 hours.
When you receive the message, your orchestration can handle it gracefully.
When you don't, the delay shape will kick in and you handle accordingly.
Benefit to this solution in comparison to the solution of 40Alpha will be that your orchestration will only 'wake up' from a dehydrated state if the timeout kicks in OR when the response is received. In the example of 40Alpha, the orchestration would wake up a lot of times, consuming extra resources.
You may want to look a product like BizTalk 360. It has those sort of monitoring and command built into it. I'm not sure it works with BizTalk 2006R2 though, but you should be thinking about moving off that platform anyway as it is going out of Microsoft support.
I'm quite a newbie in WSO2 so sorry for the mistakes (and for my english too ... )
I need to implement a proxy with delivery-garantee pattern and here you are my solution (I'm started from this post http://charith.wickramaarachchi.org/2012/05/another-message-redelivery-pattern-with.html):
a proxy invoke an external service giving, as input, the initial
client message
if the external service is running all works fine and
the reply is given to the client
if the external service is down or generate a SOAP fault, I'll
put the message in a store (retry store), and then, using a sampling
processor (after a time "t"), I'll try again for "n" max attempts:
at any attempt, if the external service is down or generate a SOAP
fault, I'll put the message again in the retry store, and the
process is repeated
after "n" attempts, if the external service is still out of
service, the message is stored in another store (garbage store)
All works fine when I try to test with one message, but when I try to test with more messages (> 20 but this number is variable ... ), the sampling processor hangs completely, nothing is shown in the logs. Looking in the console, sometimes (but not always ...), the processor is off, deactivate and in this case, to restore, I need to undeploy, stop and restart, and then deploy again my .car.
NOTE: I've to use the sampling processor and not the forwarding processor because this processor, after "n" attempts deactive itself and I can't use it for my goals.
I can't put here the complete code because is too long, but I can give you a sample .car that you can deploy and execute on your WSO2 installation (to simulate the external service I've used the echo service ...).
Here you are the sample car that you can download
Thank you very much in advance: all suggestions are appreciated!!!
Cesare
Message Forwarding Processor
Retrieves the messages stored in a message store and reliably forwards them to a specified endpoint. This processor attempts to send one message at a time and it does not dequeue a message from the store until it receives a response from the target endpoint. Therefore this processor is ideal for implementing in-order delivery scenarios and guaranteed delivery scenarios.
Sampling Processor
Retrieves the messages stored in a message store and injects them to a given sequence at specified intervals. This processor utilizes the Quartz scheduler framework for periodically processing messages. This can be used to implement message rate throttling scenarios.
--> You can use the forwarding processor and configure it so that it will never be deactivated, just add this parameter : <parameter name="max.delivery.attempts">-1</parameter>
Is there a way that I can retrieve the timestamp of a web service call? I'm trying to get the time of the server hosting the web service.
Easiest thing to do is to just log them in the server implementation of your service contract, you can use PostSharp to make some attributes to take of this aspect.
For instance, you can write a Trace attribute which simply logs a debug message when a method is invoke. Here's one I wrote a while back which tracks how long a method takes and log a warning message if it takes longer than a set threshold:
http://theburningmonk.com/2010/03/aop-method-execution-time-watcher-with-postsharp/
I came across some 'trace' attribute example before, if you want I can look for it for ya.