Geoprocessing widget. Code runs in ArcGIS Pro, but doesn't do anything in Web App Builder. output clears on completion

Question

I have a layer of polygons representing land parcels, each of these has a number that identifies it as part of an application, I want the user to be able to select one of these polygons, submit it to a tool and have it return all of the other polygons with a matching application number. It currently runs fine in ArcGIS Pro, but not in web app builder.

This is a snippet of the code that runs in ArcGIS Pro, but I can't get to work as a geoprocessing service within Web App Builder

It basically takes a layer with a selection, determines a value with a search cursor and then uses that value to make a selection based on it to capture all polygons that had that value. This is meant to be used for a data validation sequence, so users aren't manually entering the polygon ID number.

import arcpy

# Get parameters for input
# Existing DID Layer
inputpolygons = arcpy.GetParameterAsText(0)

#tableview="didofinterest"
arcpy.AddMessage("Executing...")

# Determine if a selection has been made.  If not, report error.
desc=arcpy.GetCount_management(inputpolygons)
if int(desc[0])>0:
    arcpy.AddMessage("Selection found.")
    arcpy.AddMessage(f"Found {str(desc[0])} Selections, choosing first")

    # Get the first DISP Num of the input table (first of the selection)
    with arcpy.da.SearchCursor(inputpolygons,["DISP_NUM"]) as cursor:
        for row in cursor:
            polynum=row[0]
            arcpy.AddMessage(f"Getting {polynum} from {inputpolygons}")
            break

    # Build where clause
    whereclause = """ DISP_NUM = '%s' """ % polynum

    # Make a selection.
    selected_polygons=arcpy.management.SelectLayerByAttribute(inputpolygons,"NEW_SELECTION",whereclause)

As a script tool it has a single input parameter which is currently set as a Feature Layer type.

When I publish to Portal, the tool has upload capabilities, Asynchronous execution and the message level is set to Info. The input parameter is set as user defined.

When I add the widget into web app builder the single input layer is set to Choose from map.

Running it as a widget causes the app to execute and its output to post to the output screen for a split second and then it clears it, making it nearly impossible to see what is happening. I have managed to determine the geoprocessing widget is not honoring the selection in the web app layer.

Answer 1

There is a very loose coupling between a GP Service and the layers found within a Webmap. Inside ArcGIS Pro, the coupling is very tight. This is a very high-level way of saying it doesn't work in the same way: The GP Service isn't going to put a selection on the layers in your webmap.

In a webapp, or in your case of WebApp Builder, you have 2 services. These services are not using the same data. They may appear to be, but they aren't. Or at least they aren't in the sense that what one service does will be available to the other service. When your GP Service puts a selection on a layer (and yes, the GP Service can be making use of layers internal to itself), that selection is not applied to the data in the map service. It's a selection unique to the single job execution of the GP Service. You'd need to return the output, either as a MapImage Layer, or the actual selected features and have the web app draw them. As you only mention you make use of a single input parameter, it sounds as if your tool has no outputs. In that case, the GP Service is never "returning" anything, thus the web app has nothing to draw.

I wrote this blog a few years ago and it covers some of the same concepts. While it doesn't get into the same details here as the difference in layer sources, it may further your understanding of this task.