I have application insights configured. In the Request Telemetry data I see the Source column is not set for most of the api request. There are some apis for which it is set. I am not able to understand logic used to set the Source column in Request Telemetry.
I have gone through the documentation, no help.
It is explained in the documentation.
When the number of storage items is large, you'll need a hint about where to look next. The Application Insights data model defines two fields to solve this problem: request.source and dependency.target. The first field identifies the component that initiated the dependency request. The second field identifies which component returned the response of the dependency call. (source)
and
[...] Application Insights also defines the extension for the correlation HTTP protocol. It uses Request-Context name-value pairs to propagate the collection of properties used by the immediate caller or callee. The Application Insights SDK uses this header to set the dependency.target and request.source fields. (source)
The reason not all request telemetry have the source property set is probably because the are the entry point for an operation and as such do not have an origin. Http request made during the operation initiated by the root request will have their source property set.
