Blazor Multitenant Configuration with Azure App Configuration Service

Tom McCartan 25

I have read the following article, but no where in this document does it talk about how this can be instantiated within your program.cs or startup using builder.Configuration.AddAzureAppConfiguration

https://learn.microsoft.com/en-us/azure/architecture/guide/multitenant/service/app-configuration

In a typical Multi-Tenant app, we are using Azure Front Door and injecting a Header specifying the Customer ID. We also have a custom route.

Using this in the program.cs we can get all the Azure App Settings for a section. This is assming the GUID there is the customer ID.

// Retrieve the connection string

//string connectionString = builder.Configuration.GetConnectionString("AppConfiguration");

//// Load configuration from Azure App Configuration

//builder.Configuration.AddAzureAppConfiguration(connectionString);

// Bind configuration "TNof1:0bc2b8a2-2500-44e5-858b-9259fc1a6d50" section to the Settings object

//builder.Services.Configure<AppConfigSettings>(builder.Configuration.GetSection("Nof1:0bc2b8a2-2500-44e5-858b-9259fc1a6d50"));

The issue is that the GUID is in the HTTP Header and that needs to be dynamic to get the Azure App Configurations specific for that customer.

So you can follow the recommendations in the article, use a Single Azure App Config, and then identify your settings using Labels, or this hierarchy. But there is no way to dynamically retrieve it in your host startup?

So can this feature be used for multi-tenant in a Blazor Server Side App, hosted in an Azure App Service, using Azure Front Door and using Azure SignalR?

For now, I have resorted to using the Azure App Service Config API Client and retrieving them in my Master Page where I have a persisted state and the HttpContext, which does not seem like the right way to do this, as it does not allow you to use the services in the startup, to use default dependency injection using the IOptionsSnapshot, etc.

Any thoughts on this? It looks like it may have been asked a few times over the past couple years with no solution to this?

Thanks,

Tom

1 answer

Bruce (SqlWork.com) 66,056 Reputation points

2024-05-01T21:11:00.2966667+00:00
to get the tenant id you need access to the HttpContext to get the header value. this means the constructor of the service will need to read the settings, rather than passed.

I probably create a new configuration service that fetched the tenantid from the context, and exposed setting for that context. trival implementation using:

public class TenantSettings { private IHttpContextAccessor httpContextAccessor; private IConfiguration config; private string tentantHeaderName; private string TenantId => httpContextAccessor.HttpContext?.Request.Headers[tenantHeaderName] ?? ""; public TentantSettings(IHttpContextAccessor httpContextAccessor, IConfiguration config) { this.httpContextAccessor = httpContextAccessor; this.config = config; tenantHeaderName = config.GetValue<string>("tenantHeaderName") ?? "defaultname"; } public string GetStringValue(string key) { return config.GetValue<string>($"{TenantId}:{key}"); } public string GetConnectionValue(string key) { return config.GetValue<string>($"ConnectionStrings:{TenantId}:{key}"); } }

just inject into services to access the settings. you could use different settings stores, prefix, postfix, whatever you want.
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Tom McCartan 25 Reputation points

2024-05-02T15:06:15.65+00:00

Thanks for the response. To follow up, is this creating your own Configuration Managment?

So we can't use the existing "AddAzureAppConfiguration", along with its exiting options, like "ConfigureRefresh", etc.? The benefit of this, is it allows all the settings to be queried from Azure App Configuration, Scoped to the Session and available. As well as having a refresh key to let it know when it changes, so it can re-request the app configuration used for Feature Toggle, and Feature Settings.

How would the above be used in Program.cs to load all keys based on the TenantID and then made available in the Blarzor Pages?

I can see from the code, I could inject the existing Azrue App Configuration API ("ConfigurationClient") to Get a Value based on the Key, but I would need to create a custom class for each Key/Value.

So I guess the question is still there:

Can you use the existing Azure App Configuration ("AddAzureAppConfiguration") to load keys for a Specific Tenant during host app start, and scope it to the given session for the user to be available in Blazor Pages?

It seems like the answer is No, you have to create your own custom IConfiguration Module?

Thanks,

Tom

Bruce (SqlWork.com) 66,056 Reputation points

2024-05-02T15:28:05.01+00:00

of course you can use Azure App Config (my sample code would). you just need to know the tenant id when you lookup the key value. you could just inject a service that returned the id:

public class TenantAccessor { private IHttpContextAccessor httpContextAccessor; private string tentantHeaderName; public TenantAccessor(IHttpContextAccessor httpContextAccessor, IConfiguration config) { this.httpContextAccessor = httpContextAccessor; tenantHeaderName = config.GetValue<string>("tenantHeaderName") ?? "defaultname"; } public string TenantId => httpContextAccessor.HttpContext?.Request.Headers[tenantHeaderName] ?? ""; }

Tom McCartan 25 Reputation points

2024-05-02T18:34:25.2+00:00

So this is something that can't be used in the Startup, correct? As when configuration builder.Configuratio and Builder.Services HttpContext is not available. It is available at time of Middleware, when using services, but at that time its to late for scoped services.

So where are you suggesting to use TenantAccessor/TenantSettings? Say I have 50 settings for each Tenenat in Azure App Configuration. You can't call this during the app.razor, it seems that you need to do this during PreRender, use PersistentComponentState and [Inject] HttpContext into a component (MasterLayout.razor.cs), read all the settings there, store them in PersistentComponentState.

Is this how you see it?

Also, using it in program.cs, you could set the refresh time to, to automatically get any new settings automatically. But once again, you can't set the [TENANTID] as HttpContext is not available at the time of builder.Configuration.

// Load configuration from Azure App Configuration

builder.Configuration.AddAzureAppConfiguration(options =>

{

options.Connect(connectionString) // Load all keys that start with `TestApp:` and have no label .Select("Nof1:[TENANTID]:*", LabelFilter.Null) // Configure to reload configuration if the registered sentinel key is modified .ConfigureRefresh(refreshOptions => refreshOptions.Register("Nof1:[TENANTID]:Sentinal", refreshAll: true).SetCacheExpiration(TimeSpan.FromSeconds(30)) );

});

So where do you use your code TenantAccessor?

Thanks and sorry for troubling you.

Tom

Bruce (SqlWork.com) 66,056 Reputation points

2024-05-02T21:14:47.6633333+00:00

no you cannot access the http context in startup.

that is why you use middleware and httpcontext accessor. if a component or other middleware needs configuration, you get the injected tenantid, and config and fetch settings.

You would add TenantAccessor as a service, and inject. you dbcontext, etc would add it to its DI list and use it to get the tenantid.

again I'd probably use an injected config that filtered by tenant. though I tend to inject POCO options, so the services do not need to know about config.

note: as the azure config refresh refresh is triggered by a request, and with blazor apps, there is only one request (2 counting pre-render) the refresh is not triggered. your middleware will have to do the refresh.

Tom McCartan 25 Reputation points

2024-05-03T17:10:13.71+00:00

So It turns out that I can use the default App Config, along with the refresh for both settings and features. Then use Middleware to Filter out based on the TenantID in the Header, as shown below. This works, but the only way this works is that the select query needs to pull in all settings and features. I am not sure how this will affect performance the more tenants get added and settings/features are added. But this does work. And yes, in Blazor, I needed to use PersistedState and Pre-Render to retrieve/store config settings.

Is this an acceptable solution for doing this? Not sure? It works but doesn't seem like it would scale very well?

In Program.cs

// Add the N of 1 Customer Configuration Service as a Scoped Service

builder.Services.AddScoped<CustomerConfigData>();

// Load configuration from Azure App Configuration

builder.Configuration.AddAzureAppConfiguration(options =>

options.Connect(

builder.Configuration["ConnectionStrings:AppConfiguration"])

.Select("*", "\0")

.ConfigureRefresh(refreshOptions =>

refreshOptions.Register("Nof1:Sentinal", refreshAll: true)

)

.UseFeatureFlags(featureFlagOptions =>

{

featureFlagOptions.CacheExpirationInterval = TimeSpan.FromSeconds(30);

}));

// Add feature management to the container of services.

builder.Services.AddFeatureManagement();

builder.Services.AddAzureAppConfiguration();

Then after the services are added, run the middleware

// Use Azure App Configuration middleware for dynamic configuration refresh.

app.UseAzureAppConfiguration();

// Add the Custom Nof1 Middleware to the pipeline

app.UseMiddleware<Nof1CustomerConfigurationMiddleware>();

Middleware class looks like this

`public class Nof1CustomerConfigurationMiddleware`

{

private readonly RequestDelegate _next;

private readonly IConfiguration _configuration;

public Nof1CustomerConfigurationMiddleware(RequestDelegate next, IConfiguration configuration)

{

_next = next;

_configuration = configuration;

}

public async Task Invoke(HttpContext httpContext, CustomerConfigData customerConfigData)

{

string CustomerID = string.Empty;

// Try to get the Customer ID from the request headers

httpContext.Request.Headers.TryGetValue("nof1-customer-id", out var customerId);

if (customerId.Count == 0)

{

// If in DEV mode, there won't be a nof1-customer-id header, so default to DEV settings

httpContext.Request.Headers.Add("nof1-customer-id", "00000000-0000-0000-0000-000000000000");

CustomerID = "00000000-0000-0000-0000-000000000000";

}

else

{

CustomerID = customerId.FirstOrDefault();

}

// Filter the Config Settings to the customer

var customerConfigSettings = _configuration.GetSection("NOF1:" + CustomerID).GetChildren();

// Add the configurations to the scoped customerConfigData class

customerConfigData.id = CustomerID;

customerConfigData.Name = customerConfigSettings.FirstOrDefault(x => x.Key == "Name").Value;

customerConfigData.PrimaryDarkColor = customerConfigSettings.FirstOrDefault(x => x.Key == "PrimaryDarkColor").Value;

customerConfigData.PrimaryLightColor = customerConfigSettings.FirstOrDefault(x => x.Key == "PrimaryLightColor").Value;

customerConfigData.SecondaryDarkColor = customerConfigSettings.FirstOrDefault(x => x.Key == "SecondaryDarkColor").Value;

customerConfigData.SecondaryLightColor = customerConfigSettings.FirstOrDefault(x => x.Key == "SecondaryLightColor").Value;

customerConfigData.TertiaryDarkColor = customerConfigSettings.FirstOrDefault(x => x.Key == "TertiaryDarkColor").Value;

customerConfigData.TertiaryLightColor = customerConfigSettings.FirstOrDefault(x => x.Key == "TertiaryLightColor").Value;

customerConfigData.AppbarBackgroundDarkColor = customerConfigSettings.FirstOrDefault(x => x.Key == "AppbarBackgroundDarkColor").Value;

customerConfigData.AppbarBackgroundLightColor = customerConfigSettings.FirstOrDefault(x => x.Key == "AppbarBackgroundLightColor").Value;

// Future we should also store Features Flags in the CustomerConfigData Class as well.

await _next(httpContext);

}

}

}

Then you can access it in the MainLayout.razor.cs OnInitialize

[Inject] public CustomerConfigData _CustomerConfigData { get; set; }

protected override async Task OnInitializedAsync()

{

// Register the internal State Persister

_PersistingSubscription = _ApplicationState.RegisterOnPersisting(PersistData);

// Try to restore the state from the memory

// This is done due to Pre-Render, as the OnInitializedAsync is called 2 times. Once on Pre-Render and the other on Render. During Render the Scoped Client Side Objects will be null.

if (_ApplicationState.TryTakeFromJson<CustomerConfigData>(nameof(_CustomerConfigData), out var restored))

{

_CustomerConfigData = restored!;

}

TenantName = _CustomerConfigData.Name;

}

Bruce (SqlWork.com) 66,056 Reputation points

2024-05-06T18:01:36.8333333+00:00

you solution looks responsible. your middleware will only fire once per Blazor session. the pre-render session will be disposed. Your middleware is only updating the setting for the current tenant.

As Blazor server keeps a connection, and dedicated application state for each session, it uses a lot of resources to begin with. You will need pretty beefy hardware if you have a lot of tenants. also it pretty chatty because every subscribed browser event must be sent to the server.

note: your config refresh will only happen on new Blazor sessions, not on existing connections.
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Blazor Multitenant Configuration with Azure App Configuration Service

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