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 = Configuration = configuration;public void OnGet()
{
var instanceID = Configuration["WEBSITE_INSTANCE_ID"];"InstanceID"] = instanceID;
//return Content($"Instance ID value: {instanceID} \n");
}
}
如要快速创建一个ASP.NET应用来验证Instance ID，可以参考文档：https://docs.azure.cn/zh-cn/app-service/quickstart-dotnetcore?tabs=net60#create-an-aspnet-web-app
Index.cshtml 文件内容为：
@page
@model IndexModel
@{
ViewData["Title"] = "Home page";
}
<div class="text-center">
<h1 class="display-4">Welcome</h1>
<div>
The current Instance ID is:@ViewData["InstanceID"];
</div>
<hr />
<p>Learn about <a href="https://docs.microsoft.com/aspnet/core">building Web apps with ASP.NET Core</a>.</p>
</div>
发布到App Service后，就可以检验效果：
此外，如果App Service开启了ARR Affinity(请求粘连性)功能后，在客户端的Cookie值ARRAffinity和ARRAffinitySameSite中，也是可以找到Instance ID信息。如:
附录一：在Function App中可以通过 Environment.GetEnvironmentVariable("WEBSITE_INSTANCE_ID"); 来获取实例ID， App Service中也一样
using System;
using System.Configuration;
using System.Threading;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Host;
using Microsoft.Extensions.Logging;
namespace FunctionAppforTime
{
public class Function5
{
[FunctionName("Function5")]
public void Run([TimerTrigger("0 */1 * * * *")]TimerInfo myTimer, ILogger log)
{
var instanceid = Environment.GetEnvironmentVariable("WEBSITE_INSTANCE_ID");"function host in: {instanceid}");
log.LogInformation($"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
当在复杂的环境中面临问题，格物之道需：浊而静之徐清，安以动之徐生。 云中，恰是如此!
