asp.netcore 实现健康检测

建议大家使用VS2019开发时把自带的反编译功能打开：

进入正题，首先上一个本节最终能实现的健康检测UI界面：

本节实现的健康检测是通过引用以下系列nuget进行的实现：

github上有该包的实现方式，使用过程中可以参考源码来编写相关参数，github地址：https://github.com/Xabaril/AspNetCore.Diagnostics.HealthChecks

在此也列一下清单吧，总共实现了对以下功能点的健康检测功能：

以上主要是些通用的检测点，如api是否正常，数据库、redis等存储库是否正常，rabbitmq是否正常等，除此之后我们还可以自己扩展，比如与我们系统业务相关的功能数据检测等，简单的实现估计也就几行代码，主要看需求。

如何实现web或api、数据库、redis等的状态检测呢？下面开始各种配置。

• 首先还是引用nuget包，我是引用了以下一堆，用哪个还是看需求：

• 配置Startup.cs文件：

    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }
        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddCustomHealthCheck(this.Configuration);

            services.AddHealthChecksUI(setupSettings =>
            {
                //检测站点，可以添加多条，UI中会把站点内的检测点分组显示（也可通过配置文件实现）
                setupSettings.AddHealthCheckEndpoint(name: "localhost-5000", uri: "http://localhost:5000/health");
                //当检测出异常结果时发送消息给api
                setupSettings.AddWebhookNotification("webhook1",
                    uri: "http://localhost:5008/WeatherForecast/message",
                    payload: "{ "message": "Webhook report for [[LIVENESS]]: [[FAILURE]] - Description: [[DESCRIPTIONS]]"}",
                    restorePayload: "{ "message": "[[LIVENESS]] is back to life"}");
                setupSettings.SetMinimumSecondsBetweenFailureNotifications(60);
                setupSettings.SetEvaluationTimeInSeconds(10);
            }).AddSqlServerStorage(Configuration["HealthStorageConnectionString"]);//数据库持久化
            //.AddInMemoryStorage();//内存持久化
        }

        public void ConfigureContainer(ContainerBuilder builder)
        {
            //autofac
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapHealthChecks("/health", new HealthCheckOptions()
                {
                    Predicate = _ => true,
                    ResponseWriter = UIResponseWriter.WriteHealthCheckUIResponse
                });
                endpoints.MapHealthChecksUI();
            });
        }
    }

其中AddCustomHealthCheck的实现如下，实现的检测实例：

        public static IServiceCollection AddCustomHealthCheck(this IServiceCollection services, IConfiguration configuration)
        {
            var hcBuilder = services.AddHealthChecks();

            hcBuilder.AddCheck("Jobs.MicrosoftBackgroundService-apiself", () => HealthCheckResult.Healthy());
            hcBuilder.AddSqlServer(
                    configuration["ConnectionString"],
                    name: "Jobs.MicrosoftBackgroundService-sqlserver-check",
                    tags: new string[] { "sqlserverdb" });
            hcBuilder.AddRabbitMQ(
                    $"amqp://{configuration["EventBusConnection"]}",
                    name: "Jobs.MicrosoftBackgroundService-rabbitmqbus-check",
                    tags: new string[] { "rabbitmqbus" });
            hcBuilder.AddRedis(
                configuration["RedisConnectionString"],
                name: "Jobs.MicrosoftBackgroundService-redis-check",
                tags: new string[] { "redisdb" });
            hcBuilder.AddUrlGroup(new Uri(configuration["testApiUrl"]), name: "testApiUrl-check", tags: new string[] { "testApiUrl" });

            return services;
        }

可以看到这里实现了对sqlserver数据库、rebbitmq、redis、webapi的健康检测，参数中最重要的是名称及配置如连接字符串的信息，如redis的连接字符串格式如何写，我们可以通过查看源码来了解，此处实现redis的健康检测源码如下：

using Microsoft.Extensions.Diagnostics.HealthChecks;
using StackExchange.Redis;
using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;

namespace HealthChecks.Redis
{
    public class RedisHealthCheck : IHealthCheck
    {
        private static readonly ConcurrentDictionary<string, ConnectionMultiplexer> _connections = new ConcurrentDictionary<string, ConnectionMultiplexer>();

        private readonly string _redisConnectionString;

        public RedisHealthCheck(string redisConnectionString)
        {
            _redisConnectionString = (redisConnectionString ?? throw new ArgumentNullException("redisConnectionString"));
        }

        public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default(CancellationToken))
        {
            _ = 1;
            try
            {
                if (!_connections.TryGetValue(_redisConnectionString, out ConnectionMultiplexer value))
                {
                    value = await ConnectionMultiplexer.ConnectAsync(_redisConnectionString);
                    if (!_connections.TryAdd(_redisConnectionString, value))
                    {
                        value.Dispose();
                        value = _connections[_redisConnectionString];
                    }
                }

                await value.GetDatabase().PingAsync();
                return HealthCheckResult.Healthy();
            }
            catch (Exception exception)
            {
                return new HealthCheckResult(context.Registration.FailureStatus, null, exception);
            }
        }
    }
}

实现就几行的代码，同时我们看到这里是通过StackExchange.Redis实现的redis连接，我们传递的连接字符串就很明显了，如下：

"RedisConnectionString": "192.168.217.128:6379,defaultDatabase=1,password=123!@#..."

其他的相关参数也可以通过查看源码的方式来进行操作。。。

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设置数据持久化，可以通过查看源码得知此处是使用的EFCore，支持以下种类的持久化：

services中添加配置（记得引用需要的持久化nuget包）：

services.AddSqlServerStorage(Configuration["HealthStorageConnectionString"]);

程序启动后会自动根据配置的数据库连接信息创建数据表，大概就是配置信息、当前状态信息、历史记录信息。

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如果健康检测异常需要发送消息至api，可以添加以下配置：

具体参数格式也可通过源码查看，此处是post方式数据传输，关键源码如下：

                foreach (var webHook in _settings.Webhooks)
                {
                    bool shouldNotify = webHook.ShouldNotifyFunc?.Invoke(report) ?? true;

                    if (!shouldNotify)
                    {
                        _logger.LogInformation("Webhook notification will not be sent because of user configuration");
                        continue;
                    };

                    if (!isHealthy)
                    {
                        failure = webHook.CustomMessageFunc?.Invoke(report) ?? GetFailedMessageFromContent(report);
                        description = webHook.CustomDescriptionFunc?.Invoke(report) ?? GetFailedDescriptionsFromContent(report);
                    }

                    var payload = isHealthy ? webHook.RestoredPayload : webHook.Payload;
                    payload = payload.Replace(Keys.LIVENESS_BOOKMARK, name)
                        .Replace(Keys.FAILURE_BOOKMARK, failure)
                        .Replace(Keys.DESCRIPTIONS_BOOKMARK, description);


                    Uri.TryCreate(webHook.Uri, UriKind.Absolute, out var absoluteUri);

                    if (absoluteUri == null || !absoluteUri.IsValidHealthCheckEndpoint())
                    {
                        Uri.TryCreate(_serverAddressesService.AbsoluteUriFromRelative(webHook.Uri), UriKind.Absolute, out absoluteUri);
                    }

                    await SendRequest(absoluteUri, webHook.Name, payload);
                }

可以看到此处的Webhooks可以配置多个

        private async Task SendRequest(Uri uri, string name, string payloadContent)
        {
            try
            {
                var payload = new StringContent(payloadContent, Encoding.UTF8, Keys.DEFAULT_RESPONSE_CONTENT_TYPE);
                var response = await _httpClient.PostAsync(uri, payload);
                if (!response.IsSuccessStatusCode)
                {
                    _logger.LogError("The webhook notification has not executed successfully for {name} webhook. The error code is {statuscode}.", name, response.StatusCode);
                }

            }
            catch (Exception exception)
            {
                _logger.LogError($"The failure notification for {name} has not executed successfully.", exception);
            }
        }

我们可以通过api接收异常消息后添加日志或进行发送邮件等提醒信息。

 最后如果要配置UI界面，只需在endpoint中添加配置：

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapHealthChecks("/health", new HealthCheckOptions()
                {
                    Predicate = _ => true,
                    ResponseWriter = UIResponseWriter.WriteHealthCheckUIResponse
                });//要进行该站点检测应添加此代码
                endpoints.MapHealthChecksUI();//添加UI界面支持
            });

写的比较散，希望对大家学习有一丝丝帮助~~