WebHostExtensions.cs

using System.Data.SqlClient;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Polly;

namespace Microsoft.AspNetCore.Hosting;

public static class IWebHostExtensions
{
    public static bool IsInKubernetes(this IServiceProvider services)
    {
        var cfg = services.GetService<IConfiguration>();
        var orchestratorType = cfg.GetValue<string>("OrchestratorType");
        return orchestratorType?.ToUpper() == "K8S";
    }

    public static IServiceProvider MigrateDbContext<TContext>(this IServiceProvider services, Action<TContext, IServiceProvider> seeder) where TContext : DbContext
    {
        var underK8s = services.IsInKubernetes();

        using var scope = services.CreateScope();
        var scopeServices = scope.ServiceProvider;
        var logger = scopeServices.GetRequiredService<ILogger<TContext>>();
        var context = scopeServices.GetService<TContext>();

        try
        {
            logger.LogInformation("Migrating database associated with context {DbContextName}", typeof(TContext).Name);

            if (underK8s)
            {
                InvokeSeeder(seeder, context, scopeServices);
            }
            else
            {
                var retries = 10;
                var retry = Policy.Handle<SqlException>()
                    .WaitAndRetry(
                        retryCount: retries,
                        sleepDurationProvider: retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)),
                        onRetry: (exception, timeSpan, retry, ctx) =>
                        {
                            logger.LogWarning(exception, "[{prefix}] Error migrating database (attempt {retry} of {retries})", nameof(TContext), retry, retries);
                        });

                //if the sql server container is not created on run docker compose this
                //migration can't fail for network related exception. The retry options for DbContext only 
                //apply to transient exceptions
                // Note that this is NOT applied when running some orchestrators (let the orchestrator to recreate the failing service)
                retry.Execute(() => InvokeSeeder(seeder, context, scopeServices));
            }

            logger.LogInformation("Migrated database associated with context {DbContextName}", typeof(TContext).Name);
        }
        catch (Exception ex)
        {
            logger.LogError(ex, "An error occurred while migrating the database used on context {DbContextName}", typeof(TContext).Name);
            if (underK8s)
            {
                throw;          // Rethrow under k8s because we rely on k8s to re-run the pod
            }
        }

        return services;
    }

    private static void InvokeSeeder<TContext>(Action<TContext, IServiceProvider> seeder, TContext context, IServiceProvider services)
        where TContext : DbContext
    {
        context.Database.Migrate();
        seeder(context, services);
    }
}