问题描述
App Service开启多实例后，如何在代码中获取当前请求所真实到达的实例ID(Instance ID)呢？
问题答案
App Service 通过 环境变量的方式 显示的输出实例ID等信息，如：
Website Environment Variables
WEBSITE_SITE_NAME- The name of the site.WEBSITE_SKU- The sku of the site (Possible values:Free,Shared,Basic,Standard).WEBSITE_COMPUTE_MODE- Specifies whether website is on a dedicated or shared VM/s (Possible values:Shared,Dedicated).WEBSITE_HOSTNAME- The Azure Website's primary host name for the site (For example:site.azurewebsites.net). Note that custom hostnames are not accounted for here.WEBSITE_INSTANCE_ID- The id representing the VM that the site is running on (If site runs on multiple instances, each instance will have a different id).WEBSITE_NODE_DEFAULT_VERSION- The default node version this website is using.WEBSOCKET_CONCURRENT_REQUEST_LIMIT- The limit for websocket's concurrent requests.WEBSITE_COUNTERS_ALL- (Windows only) all perf counters (ASPNET, APP and CLR) in JSON format. You can access specific one such as ASPNET byWEBSITE_COUNTERS_ASPNET.
可以通过App Service的高级管理工具(Kudu站点）来查看这些信息：
所以如果要在代码中获取Instance ID信息，可以直接通过 var instanceID = Configuration["WEBSITE_INSTANCE_ID"] 获取。全部示例代码为：
Index.cshtml.cs :
using Microsoft.AspNetCore.Mvc; using Microsoft.AspNetCore.Mvc.RazorPages; namespace MyFirstAzureWebApp.Pages; public class IndexModel : PageModel { private readonly IConfiguration Configuration; private readonly ILogger<IndexModel> _logger; public IndexModel(ILogger<IndexModel> logger, IConfiguration configuration) { _logger = logger; Configuration = configuration; } public void OnGet() { var instanceID = Configuration["WEBSITE_INSTANCE_ID"]; ViewData["InstanceID"] = instanceID; //return Content($"Instance ID value: {instanceID} \n"); } }
如要快速创建一个ASP.NET应用来验证Instance ID，可以参考文档：https://docs.azure.cn/zh-cn/app-service/quickstart-dotnetcore?tabs=net60#create-an-aspnet-web-app
Index.cshtml 文件内容为：
@page @model IndexModel @{ ViewData["Title"] = "Home page"; } <div class="text-center"> <h1 class="display-4">Welcome</h1> <div> The current Instance ID is:@ViewData["InstanceID"]; </div> <hr /> <p>Learn about <a href="https://docs.microsoft.com/aspnet/core">building Web apps with ASP.NET Core</a>.</p> </div>
发布到App Service后，就可以检验效果：
此外，如果App Service开启了ARR Affinity(请求粘连性)功能后，在客户端的Cookie值ARRAffinity和ARRAffinitySameSite中，也是可以找到Instance ID信息。如:
附录一：在Function App中可以通过 Environment.GetEnvironmentVariable("WEBSITE_INSTANCE_ID"); 来获取实例ID， App Service中也一样
using System; using System.Configuration; using System.Threading; using Microsoft.Azure.WebJobs; using Microsoft.Azure.WebJobs.Host; using Microsoft.Extensions.Logging; namespace FunctionAppforTime { public class Function5 { [FunctionName("Function5")] public void Run([TimerTrigger("0 */1 * * * *")]TimerInfo myTimer, ILogger log) { var instanceid = Environment.GetEnvironmentVariable("WEBSITE_INSTANCE_ID"); log.LogInformation($"function host in: {instanceid}"); log.LogInformation($"function host in: {instanceid} and sleep 100s"); Thread.Sleep(100000); log.LogInformation($"C# Timer trigger function executed at: {DateTime.Now}"); } } }
参考资料
Azure runtime environment：https://github.com/projectkudu/kudu/wiki/Azure-runtime-environment#website-environment-variables
快速入门：部署 ASP.NET Web 应用：https://docs.azure.cn/zh-cn/app-service/quickstart-dotnetcore?tabs=net60#create-an-aspnet-web-app
