How to check if a Process Instance is running and take action upon it

Question

Hi All, 
 I have an Asynchronous Process Model, Which is starting from an interface Button Action. 
 I need to check if an instance of the process is running already, based on that and some other values, take decision whether to trigger another instance. 
 Basically i want to check if a Process Instance is running or not, even if its a Sync. or Async Process Model, either triggered from a Process Model or an interface or a WebAPI. 
 
 Please let me know

seanw583 · Accepted Answer

I think the exact approach would depend on your use case. You could implement a queue manager process, where all new instances would write to a database table (the queue) and the manager process would initiate new instances one at a time off the queue. 
Alternatively, a simple loop with a timer node can periodically re-check for running instances, and proceed with the new instance once there aren't any others running.

seanw583 · Answer

I believe this can be handled via a process report, along with the queryProcessAnalytics function( docs.appian.com/.../fnc_system_a_queryprocessanalytics.html) . I recommend you include the process instance Id as part of your query criteria, as I have seen this type of implementation find the new instance when checking for existing instances.