ASP.Net Core 2.1 Serilog SQL Server Sink using Azure SQL is working locally but not from Azure app service - azure

Question

I have an ASP.Net Core 2.1 Website that uses Azure SQL Database for the Microsoft Identity component.
I added a Logs table to that database and added Serilog to my website with the SQL Server Sink.
When I run the website locally, while still connected to the Azure SQL database, I can see my log entries in the Logs table just fine. However, when I deploy the website to my Azure App Service, I no longer get any log entries in the Logs table of the database.
Mind you, in the deployed version, I am connecting to and using the Azure SQL database for my MS Identity stuff just fine and I can create new users and edit existing users just fine. So I know the Connection String in my App Service Application Settings is correct.
I have reviewed the Serilog MSSQL Github to compare their configuration recommendations to my own and could not find anything that stood out.
I have this setup working correctly on an ASP.Net Core API that I deploy to another Azure App Service. That service uses a different database but it is on the same SQL Server resource.
I have reviewed the list of SO posts recommended when I started this question with no luck.
I ran the following SQL on the database when I first set up the user account;
EXEC sp_addrolemember N'db_datareader', N'myuser'
EXEC sp_addrolemember N'db_datawriter', N'myuser'
EXEC sp_addrolemember N'db_ddladmin', N'myuser'
And, as I stated, the user account can update and add user data in the AspNetUsers table just fine. So, it doesn't seem like a user account issue.
I have verified that the connection string in my Azure app service DEV deployment slot (the one I am testing), Application Settings, Connection Strings is the exact same as what I have in my local DEV UserSecrets. Plus, again, I can read/write to the AspNet* tables in that same database when deployed to Azure.
Here is my Program.cs class where I set up Serilog;
public class Program
{
public static IConfiguration Configuration { get; } = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
.AddJsonFile($"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Production"}.json", optional: true)
.AddUserSecrets<Startup>()
.AddEnvironmentVariables()
.Build();
public static void Main(string[] args)
{
var connectionString = Configuration.GetConnectionString("MyConnectionString");
const string tableName = "Logs";
Log.Logger = new LoggerConfiguration()
.MinimumLevel.Information()
.MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
.Enrich.FromLogContext()
.Enrich.WithMachineName()
.Enrich.WithThreadId()
.WriteTo.MSSqlServer(connectionString, tableName)
.CreateLogger();
// TODO Enable to debug any startup Serilog issues. Make sure to comment out for PROD
//Serilog.Debugging.SelfLog.Enable(msg =>
//{
// Debug.Print(msg);
// Debugger.Break();
//});
try
{
Log.Information("Starting Application");
CreateWebHostBuilder(args).Build().Run();
}
catch (Exception ex)
{
Log.Fatal(ex, "Host terminated unexpectedly");
}
finally
{
Log.CloseAndFlush();
}
}
public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseStartup<Startup>()
.UseSerilog();
}
}
The only difference between the API that I have deployed in Azure that is writing logs to Azure SQL and this website is that in the API, which is older, I have
public static IWebHost BuildWebHost(string[] args)
in program.cs whereas the newer website has
public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
So... any ideas would be greatly appreciated.
[UPDATE 1/23/19]
I added the connection string directly to the
var connectionString
in Program.cs rather than getting it from
Configuration.GetConnectionString("MyConnectionString")
and it started logging to the database.
So it seems the issue is with Program.cs being able to read the connection string from Azure App Service deployment slot, Application Settings, Connection Strings section.
This connection string is being correctly read from Startup.cs and has worked since I first created the website.
So, is there some known issue with Azure not being able to read values from deployment slot Application Settings / Connection Strings from Program.cs?

Answer 1

Since there seems to be an issue with Azure, that it doesn't provide the application settings to the web app until CreateWebHostBuilder is invoked, a straightforward workaround (assuming that hardcoding the connection string in the source code isn't a viable option) would be to configure Serilog to use SqlServer in Startup.cs instead of Program.cs.
If it's important to log the initial events that occur during the app's starting up, Serilog can temporarily be configured in Program.cs to write to a file.
Program.cs:
public class Program
{
public static void Main(string[] args)
{
var AzureLogFilePath = #"D:\home\LogFiles\Application\log.txt";
Log.Logger = new LoggerConfiguration()
.MinimumLevel.Information()
.Enrich.FromLogContext()
.WriteTo.File(path: AzureLogFilePath, fileSizeLimitBytes: 1_000_000, rollOnFileSizeLimit: true, shared: true);
.CreateLogger();
try
{
Log.Information("Starting Application");
CreateWebHostBuilder(args).Build().Run();
}
catch (Exception ex)
{
Log.Fatal(ex, "Host terminated unexpectedly");
}
finally
{
Log.CloseAndFlush();
}
}
public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseStartup<Startup>()
.UseSerilog();
}
Startup.cs:
public class Startup
{
public Startup(IHostingEnvironment env)
{
var builder = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
.AddJsonFile($"appsettings.{env.EnvironmentName ?? "Production"}.json", optional: true)
.AddEnvironmentVariables();
if (env.IsDevelopment()) builder.AddUserSecrets<Startup>(); // according to the docs, AddUserSecrets should be used only in development
Configuration = builder.Build();
}
public IConfiguration Configuration { get; }
public void ConfigureServices(IServiceCollection services)
{
var connectionString = Configuration.GetConnectionString("MyConnectionString");
const string tableName = "Logs";
Log.Logger = new LoggerConfiguration()
.MinimumLevel.Information()
.MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
.Enrich.FromLogContext()
.Enrich.WithMachineName()
.Enrich.WithThreadId()
.WriteTo.MSSqlServer(connectionString, tableName)
.CreateLogger();
//...
}
}