Program.cs

/*
 * Copyright (c) 2019 Google LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

using CloudSql.Settings;
using Google.Cloud.Diagnostics.AspNetCore3;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using System;
using System.IO;

namespace CloudSql
{
    public class Program
    {
        public static AppSettings AppSettings { get; private set; }

        public static void Main(string[] args)
        {
            // Create Database table if it does not exist.
            StartupExtensions.InitializeDatabase();
            BuildWebHost(args).Build().Run();
        }

        public static IWebHostBuilder BuildWebHost(string[] args)
        {
            ReadAppSettings();

            return WebHost.CreateDefaultBuilder(args)
                .ConfigureServices(services =>
                    services.AddGoogleDiagnosticsForAspNetCore(
                        AppSettings.GoogleCloudSettings.ProjectId,
                        AppSettings.GoogleCloudSettings.ServiceName,
                        AppSettings.GoogleCloudSettings.Version))
                .UseStartup<Startup>()
                .UsePortEnvironmentVariable();
        }

        /// <summary>
        /// Read application settings from appsettings.json. 
        /// </summary>
        private static void ReadAppSettings()
        {
            var config = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("appsettings.json", optional: false)
                .Build();

            // Read json config into AppSettings.
            AppSettings = new AppSettings();
            config.Bind(AppSettings);
        }
    }

    static class ProgramExtensions
    {
        // Google Cloud Run sets the PORT environment variable to tell this
        // process which port to listen to.
        public static IWebHostBuilder UsePortEnvironmentVariable(
            this IWebHostBuilder builder)
        {
            string port = Environment.GetEnvironmentVariable("PORT");
            if (!string.IsNullOrEmpty(port))
            {
                builder.UseUrls($"http://0.0.0.0:{port}");
            }
            return builder;
        }
    }
}