How to increment a parameter in an Azure Data Factory Until Activity? - azure-data-factory

Question

I am accessing a RESTful API that pages results in groups of 50 using the HTTP connector. The REST connector doesn't seem to support Client Certificates so I can't use the pagination in that.
I have a Pipeline Variable called SkipIndex that defaults to 0. Inside the Until loop I have a Copy Data Activity that works (HTTP source to BLOB sink), then a Set Variable Activity that I am trying to get to increment this Variable.
{
"name": "Add 50 to SkipIndex",
"type": "SetVariable",
"dependsOn": [
{
"activity": "Copy next to temp",
"dependencyConditions": [
"Succeeded"
]
}
],
"userProperties": [],
"typeProperties": {
"variableName": "SkipIndex",
"value": {
"value": "50++",
"type": "Expression"
}
}
}
Everything I have tried results in errors such as "The expression contains self referencing variable. A variable cannot reference itself in the expression." and the one above with 50++ causes a sink error during debug.
How can I get the Until loop to increment this variable after it retrieves data?

Answer 1

Agree that REST Connector does supports pagination but does not for Client Certificates Authentication type.
For the idea of your Until activity scenario,i am tripped by the can't self-reference a variable in an expression limitation also. Maybe you could make a little trick on that: Add one more variable to persist the index number.
For example,i got 2 variables: count and indexValue
Until Activity:
Inside Until Activity:
V1:
V2:
BTW, no usage of 50++ in ADF.