Passing service instance ID into guest executable at runtime - azure-service-fabric

Question

Is it possible to pass service instance ID (int value) into guest executable at runtime? I have looked at <ExeHost><Arguments>, but it's only good for static data that has to be provided up front.

Answer 1

The environment variable provides the service package instance ID which is not the same as the instance/replica ID. Generally speaking, SF's environment variables can provide the same information available using FabricRuntime, i.e. the node context and the code package activation context. In native SF services, the instance ID is provided at run-time by the Fabric (in the ServiceContext class), as a single process can host multiple partitions and instances/replicas.
In a guest executable, which does not use SF APIs, the only option AFAIK is to query the Fabric for this information in a separate executable, run it as the SetupEntryPoint (which runs every time before the guest executable) and write the information to a file.
For example (compile the code into GetFabricData.exe and add it to the code package):
private static async Task MainAsync(string[] args)
{
var serviceTypeName = args.FirstOrDefault();
if (string.IsNullOrEmpty(serviceTypeName)) throw new ArgumentNullException(nameof(serviceTypeName));
using (var client = new FabricClient())
{
var activationContext = FabricRuntime.GetActivationContext();
var nodeContext = FabricRuntime.GetNodeContext();
var nodeName = nodeContext.NodeName;
var applicationName = new Uri(activationContext.ApplicationName);
var replicas = await client.QueryManager.GetDeployedReplicaListAsync(nodeName, applicationName);
// usually taking the first may not be correct
// but in a guest executable it's unlikely there would be multiple partitions/instances
var instance = replicas.OfType<DeployedStatelessServiceInstance>()
.FirstOrDefault(c => c.ServiceTypeName == serviceTypeName);
if (instance == null)
{
throw new InvalidOperationException($"Unable to find a service instance for {serviceTypeName}");
}
File.WriteAllText("FabricData", instance.InstanceId.ToString());
}
}
And in the service manifest:
<SetupEntryPoint>
<ExeHost>
<Program>GetFabricData.exe</Program>
<Arguments>Guest1Type</Arguments>
</ExeHost>
</SetupEntryPoint>
Then, the guest executable can simply read the FabricData file.

Answer 2

It's available in an environment variable. See here for a complete list of environment variables available to services: https://learn.microsoft.com/en-us/azure/service-fabric/service-fabric-manage-multiple-environment-app-configuration
Note that the one you're asking for, Fabric_ServicePackageInstanceId is generally only meant for internal consumption, and it identifies the entire service package. That means if you have multiple code packages (executables) in your service package, they will all get the same ID.