【Azure 應用服務】App Service .NET Core項目在Program.cs中自定義添加的logger.LogInformation,部署到App Service上后日志不顯示Log Stream中的問題

問題描述

在.Net Core 5.0 項目中，添加 Microsoft.Extensions.Logging.AzureAppServices 和 Microsoft.Extensions.Logging.Abstractions插件后，需要在構建Host的代碼中添加  logging.AddAzureWebAppDiagnostics() 。

    return Host.CreateDefaultBuilder(args)
                .ConfigureLogging(logging =>
                {
                    //logging.AddConsole();
                    logging.AddAzureWebAppDiagnostics();
                })

然后 初始化Logger對象，添加 Console方式輸出日志（ var _logger = LoggerFactory.Create(builder => builder.AddConsole()).CreateLogger<Program>(); ）

 

全部代碼為：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace hellodotnetcore
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }


        public static IHostBuilder CreateHostBuilder(string[] args)
        {
             var _logger = LoggerFactory.Create(builder => builder.AddConsole()).CreateLogger<Program>(); //初始化當前Host實例時候隨機生成一個GUID，用於在此后的請求中判斷當前時候是否被標記為健康，非健康，回收。
            var instance = Guid.NewGuid();
            //firstFailure來記錄第一個失敗請求所進入當前實例的時間，firstFailure保存在內存中
            DateTime? firstFailure = null;
            //ILogger _logger = null;

            return Host.CreateDefaultBuilder(args)
               .ConfigureLogging(logging => { //logging.AddConsole();
 logging.AddAzureWebAppDiagnostics(); })
                .ConfigureWebHostDefaults(webBuilder =>
                webBuilder.Configure(configureApp =>
                configureApp.Run(async context =>
                {
         _logger.LogInformation("TEST THE SELF LOG INFORMATION..."); _logger.LogError("TEST THE SELF LOG ERROR..."); _logger.LogDebug("TEST THE SELF LOG Debug..."); _logger.LogTrace("TEST THE SELF LOG Trace..."); _logger.LogWarning("TEST THE SELF LOG Warning...");//當請求URL為fail時候，認為設置返回狀態為500，告訴App Service的Health Check功能，當前實例出現故障。
                    if (firstFailure == null && context.Request.Path.Value.ToLower().Contains("fail"))
                    {
                        firstFailure = DateTime.UtcNow;
                    }

                    if (context.Request.Path.Value.ToLower().Contains("exception"))
                    {
                        throw new Exception("this is custom exception for logging ...");

                    }

                    if (firstFailure != null)
                    {
                        context.Response.StatusCode = 500;
                        context.Response.ContentType = "text/html; charset=utf-8";
                        await context.Response.WriteAsync(
                           $"當前實例的GUID為 {instance}.\n<br>" +
                            $"這個實例最早出現錯誤的時間是 {firstFailure.Value}. 當前時間為是{DateTime.UtcNow}\n\n<br><br>" +
                            $"根據文檔的描述 https://docs.microsoft.com/en-us/azure/app-service/monitor-instances-health-check, 如果一個實例在一直保持unhealthy狀態一小時，它將會被一個新實例所取代\n\n<br>" +
                            $"According to https://docs.microsoft.com/en-us/azure/app-service/monitor-instances-health-check, If an instance remains unhealthy for one hour, it will be replaced with new instance.<br>");
                    }
                    else
                    {
                        context.Response.StatusCode = 200;
                        context.Response.ContentType = "text/html; charset=utf-8";
                        await context.Response.WriteAsync($"當前實例的GUID為 {instance}.\n<br>" +
                            $"此實例報告顯示一切工作正常.");
                    }
                })));
        }
    }
}

 

在本地通過dotnet run測試發現，訪問 http://localhost:5000/ 和 http://localhost:5000/exception 就可以看見在代碼中的加入的日志信息，達到期望。

 

但是把代碼發布到Azure App Service后，通過Log Stream發現，卻沒有觀察到 _logger 日志：

_logger.LogInformation("TEST THE SELF LOG INFORMATION...");

_logger.LogError("TEST THE SELF LOG ERROR...");

_logger.LogDebug("TEST THE SELF LOG Debug...");

_logger.LogTrace("TEST THE SELF LOG Trace...");

_logger.LogWarning("TEST THE SELF LOG Warning...");

App Service 中查看Docker中運行應用的日志：

 

 

問題解決

這是因為App Service沒有啟用App Service Logs. 當在門戶上啟用后，在此查看Log Stream文件信息，就可以看見和本地同樣的日志信息：

 

 

 

 

參考資料

為 Azure 應用服務配置 ASP.NET 應用: https://docs.azure.cn/zh-cn/app-service/configure-language-dotnet-framework#access-diagnostic-logs

'ILoggerFactory' does not contain a definition for 'AddConsole': https://stackoverflow.com/questions/58259520/iloggerfactory-does-not-contain-a-definition-for-addconsole

There is a seperate issue at play, previously the signature for AddConsole() expected an ILoggerFactory, that has since changed to an ILoggerBuilder, as hinted at in the error message.

The following it seems is the new way to stand up a new Console logger:

var loggerFactory = LoggerFactory.Create(builder => builder.AddConsole());