Azure Durable Function - read users from Graph in a quicker way - microsoft-graph-api

Question

I have an Azure Function with Premium Plan where users from multiple AzureAD groups are read and put to a queue. Currently, I'm looking into converting this function to Durable Function and use consumption plan. Here is my code:
Orchestrator:
public async Task RunOrchestrator([OrchestrationTrigger] IDurableOrchestrationContext context)
{
var groups = await context.CallActivityAsync<List<AzureADGroup>>("GroupsReaderFunction"), null);
if (groups != null && groups.Count > 0)
{
var processingTasks = new List<Task>();
foreach (var group in groups)
{
var processTask = context.CallSubOrchestratorAsync("SubOrchestratorFunction", group);
processingTasks.Add(processTask);
}
await Task.WhenAll(processingTasks);
}
}
SubOrchestrator:
public async Task RunSubOrchestrator([OrchestrationTrigger] IDurableOrchestrationContext context)
{
var request = context.GetInput<Group>();
var users = await context.CallActivityAsync<List<AzureADUser>>("UsersReaderFunction", request.objectId);
return users;
}
Here is the function that gets users from AzureAD group:
public async Task<List<AzureADUser>> GetUsersInGroup(Guid objectId)
{
IGroupTransitiveMembersCollectionWithReferencesPage members;
members = await GraphServiceClient.Groups[objectId.ToString()].TransitiveMembers.Request().Select("id").GetAsync();
var toReturn = new List<AzureADUser>(ToUsers(members.CurrentPage));
while (members.NextPageRequest != null)
{
members = await members.NextPageRequest.GetAsync();
toReturn.AddRange(ToUsers(members.CurrentPage));
}
return toReturn;
}
private IEnumerable<AzureADUser> ToUsers(IEnumerable<DirectoryObject> fromGraph)
{
foreach (var users in fromGraph)
{
return new AzureADUser { ObjectId = Guid.Parse(user.Id) };
}
}
Number of users in groups vary - one group contains 10 users and another group contains ~500k users. Timeout occurs when reading users from larger groups (> 10 minutes). Is there a faster way to get users from AzureAD group (for example, get users in batches) so that I should be able to use Consumption Plan? Or is there a different way to use Durable Functions (fan in - fan out pattern or some other patterns) for a faster performance?
UPDATE:
var users = new List<AzureADUser>();
public async Task RunSubOrchestrator([OrchestrationTrigger] IDurableOrchestrationContext context)
{
var request = context.GetInput<Group>();
var response = await context.CallActivityAsync<(List<AzureADUser> users, nextPageLink link)>("UsersReaderFunction", request.objectId);
users.AddRange(response.users);
return users;
}
Here response contains 2 values - users from current page and link to next page. I need to keep calling "UsersReaderFunction" activity function until link to next page is null.
var users = new List<AzureADUser>();
public async Task RunSubOrchestrator([OrchestrationTrigger] IDurableOrchestrationContext context)
{
var request = context.GetInput<Group>();
var response = await context.CallActivityAsync<(List<AzureADUser> users, nextPageLink link)>("UsersReaderFunction", request.objectId);
users.AddRange(response.users);
while (response.link != null) {
var response = await context.CallActivityAsync<(List<AzureADUser> users, nextPageLink link)>("UsersReaderFunction", request.objectId);
users.AddRange(response.users);
}
return users;
}
But this is not working. What am I missing?