multiple configuration databases for IdentityServer4 - identityserver4

Question

Iam using an identityServer4 with multiple Databases. I could so far use muliple databases with the user-store. I solve it as the follwoing code of a middleware:
public async Task Invoke(HttpContext context)
{
var req = context.Request;
if (req.Path == "/Account/Login" && req.Method.Equals("POST"))
{
if (req.Form.Keys.Contains("Input.Database") == false)
{
throw new InvalidOperationException("No database key was sent with this request: " + req.Path);
}
var lDatabasKey = req.Form["Input.Database"];
_configuration["ConnectionStrings:default"] = _configuration[$"ConnectionStrings:{lDatabasKey}"];
}
the configuration Object get updated, so the value ConnectionString:default get updated with the connectionstring i need to use.
This concept unfortunatley not working the the configuration database, which inistalised in the ConfigureServices in Startup.cs:
string connectionString = Configuration.GetConnectionString("default");
services.AddIdentity<ApplicationUser, IdentityRole>(options =>
{
options.SignIn.RequireConfirmedEmail = false;
})
.AddEntityFrameworkStores<IdentityUserDbContext>()
.AddDefaultTokenProviders().AddClaimsPrincipalFactory<CentralHubClaimsPrincipalFactory>();
var builder = services.AddIdentityServer(options =>
{
options.Events.RaiseErrorEvents = true;
options.Events.RaiseInformationEvents = true;
options.Events.RaiseFailureEvents = true;
options.Events.RaiseSuccessEvents = true;
options.UserInteraction.LoginUrl = "/Account/Login";
options.UserInteraction.LogoutUrl = "/Account/Logout";
options.Authentication = new AuthenticationOptions()
{
CookieLifetime = TimeSpan.FromHours(10), // ID server cookie timeout set to 10 hours
CookieSlidingExpiration = true
};
})
.AddConfigurationStore(options =>
{
options.ConfigureDbContext = b => b.UseSqlServer(connectionString, sql => sql.MigrationsAssembly(migrationsAssembly));
})
.AddOperationalStore(options =>
{
options.ConfigureDbContext = b => b.UseSqlServer(connectionString, sql => sql.MigrationsAssembly(migrationsAssembly));
}).AddAspNetIdentity<ApplicationUser>()
.AddProfileService<AspNetIdentityProfileService>();
using breaking point i can see that the connectionString:default in the middleware has correct value of the database i want to use. but it still uses the default connectionString which has been saved in the previous method in startup.cs.
So is it possible to use multiple configuration databases for the identityServer?

Answer 1

One option is to create your own EntityFramework configuration backend for IdentityServer by taking the existing source code and hack the queries made.
Then use a clientID prefix as the "database" identifier/selector, like
A0000-A9999 -> goes to Database A
B0000-B9999 -> goes to Database B
C0000-C9999 -> goes to Database C
or use a clientID like:
AAA:XXX where AAA is the client/DB identifier and XXX is the client within that database.
To select the database/connection string to use. To "fool" IdentityServer to believe that there is only one "database".
Having a structured clientID also makes it easier to debug and reason about the system.