Distinguish applications emitting events to AI using Microsoft.Diagnostics.EventFlow - azure-application-insights

Question

I have two services running in Azure Service Fabric. Now, i want to capture some events from both and redirect them to the same instance of AI.
My eventFlowConfig.json looks like this:
{
"inputs": [
{
"type": "EventSource",
"sources": [
{
"providerName": "My-Provider-Name"
}
]
}
],
"outputs": [
{
"type": "ApplicationInsights",
"instrumentationKey": "AI_INSTRUMENTATION_KEY"
}
],
"schemaVersion": "2016-08-11"
}
This works just fine. One problem though: in AI I cannot tell if a particular trace item came from service A or service B. So, i need a way to add some custom property to AI items coming from a particular app (service). Like, "Service A" or "Service B". Ideally, i should also be able to add PartiotionId & ReplicaOrInstanceId of that service instance, but that is a bonus without which i can live.
UPDATE:
As #cijothomas suggested, we can use an ITelemetryInitializer. This works because EventFlow uses TelemetryConfiguration.Active. We can do this in the constructor of our service:
TelemetryConfiguration.Active.TelemetryInitializers.Add(new TelemetryInitializer("Service A", context.TraceId));
And here is the definition for the TelemetryInitializer class:
class TelemetryInitializer : ITelemetryInitializer
{
private readonly string _roleName;
private readonly string _roleInstance;
public TelemetryInitializer(string roleName, string roleInstance)
{
_roleName = roleName;
_roleInstance = roleInstance;
}
public void Initialize(ITelemetry telemetry)
{
telemetry.Context.Cloud.RoleName = _roleName;
telemetry.Context.Cloud.RoleInstance = _roleInstance;
}
}

Answer 1

If same ikey is used for multiple apps, they can be distinguished using their cloudRoleInstance. If its not auto-populated, then you can write own telemetry initializer to populate it correctly.
https://learn.microsoft.com/en-us/azure/azure-monitor/app/api-filtering-sampling#add-properties-itelemetryinitializer
item.Context.Cloud.RoleInstance = "service A or B"