ExternalActivityExtension

Berend Veldkamp

22. August 2013 15:33

When running a certain Geoprocessor activity, I get this errormessage: "This activity requires an ExternalActivityExtension" . Does anyone have a clue what this is about?

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  Ryan Cooney

  22. August 2013 23:23

  Hi Berend,

  You will see this error when using the "Invoke Workflow" and "Invoke Workflow Async" activities if you attempt to use an external activity (anything from the Common Client and Common Viewer categories) in the child workflow that you are attempting to invoke.

  --Ryan

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  Berend Veldkamp

  23. August 2013 18:18

  Hi Ryan,

   

  Well, I am using InvokeWorkflowAsync, but the workflow being called only contains Log, GenerateToken and Geoprocessor activities. I wrapped the Geoprocessor in a try..catch, and it appears that the error is actually triggered by that activity.

  I can use a Geoprocessor in an async workflow, right?

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  Ryan Cooney

  27. August 2013 01:09

  Hi Berend,

  Short answer: Try checking the "Wait On Server" checkbox of the Geoprocessor activity.

  Long answer: Geoprocessor is a hybrid activity. In some cases it can act as an external activity. ArcGIS Server GP Tasks themselves can be synchronous or asynchronous. If the GP task is synchronous the activity will just run as a normal server activity. If the GP task is async then the default behavior of the activity is to create a child External Delay activity (which you can't see) so that the workflow will return to the client application for a moment (the duration is controlled by the Update Delay argument) and then come back to the server to see if the GP task is complete and capture the result. It will do this in a loop so that we are effectively using the client application to establish a delay for polling the GP task. Since External Delay is an external activity this is not supported in the the InvokeWorkflow and InvokeWorkflowAsync activities. The good news is that you can opt out of this client polling behavior by checking the "Wait On Server" checkbox of the Geoprocessor activity. In this case the activity manages its own polling delay and it behaves like a regular server activity and should work fine for you.

  --Ryan

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  Berend Veldkamp

  29. August 2013 13:36

  Thanks Ryan, that fixed it.

   

  Berend

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