HttpClientFactory 日志不好用，自己扩展一个？
nodotnet 人气:0前言
.NetCore2.1新推出HttpClientFactory工厂类， 替代了早期的HttpClient， 并新增了弹性Http调用机制 (集成Policy组件)。
替换的初衷还是简单说下：
① using(var client= new HttpClient()) 调用Dispose()方法，并不会很快释放底层Socket连接， 同时新建Socket需要时间，这在高并发场景下Socket耗尽。 传送门
② 由于①很多人会想到用单例或静态类构建HttpClient实例，但是这里还有一个坑，HttpClient 会忽略DNS的变化。 传送门
HttpClientFactory 以一种模块化、可命名、弹性可预期的方式重建了HttpClient的使用方式。
现在的HttpClientFactory以依赖注入的方式集成到.NETCore 框架：
// 截取自Startup.cs文件服务配置部分
public void ConfigureServices(IServiceCollection services)
{
services.AddHttpClient("bce-request", x =>
x.BaseAddress = new Uri(Configuration.GetSection("BCE").GetValue<string>("BaseUrl")))
.ConfigurePrimaryHttpMessageHandler(_ => new BceAuthClientHandler()
{
AccessKey = Configuration.GetSection("BCE").GetValue<string>("AccessKey"),
SerectAccessKey = Configuration.GetSection("BCE").GetValue<string>("SecretAccessKey"),
AllowAutoRedirect = true,
UseDefaultCredentials = true
})
.SetHandlerLifetime(TimeSpan.FromHours(12))
.AddPolicyHandler(GetRetryPolicy(3));
}
static IAsyncPolicy<HttpResponseMessage> GetRetryPolicy(int retry)
{
var retryPolicy = HttpPolicyExtensions
.HandleTransientHttpError()
.OrResult(msg => msg.StatusCode == System.Net.HttpStatusCode.NotFound)
.WaitAndRetryAsync(retry, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)));
return retryPolicy;
}
使用时从 IHttpClientFactory工厂创建所需HttpClient实例，发起业务端请求。
观察Info级别日志：
19/12/04 11:06:46 [Info].[System.Net.Http.HttpClient.bce-request.LogicalHandler].[18}].[] Start processing HTTP request GET http://localhost:5000/v1/eqid/b827a9400004132a000000065dc26470 19/12/04 11:06:46 [Info].[System.Net.Http.HttpClient.bce-request.ClientHandler].[18}].[] Sending HTTP request GET http://localhost:5000/v1/eqid/b827a9400004132a000000065dc26470 19/12/04 11:06:46 [Info].[System.Net.Http.HttpClient.bce-request.ClientHandler].[34}].[] Received HTTP response after 174.5088ms - OK 19/12/04 11:06:46 [Info].[System.Net.Http.HttpClient.bce-request.LogicalHandler].[34}].[] End processing HTTP request after 211.1478ms - OK
一切都是那么自然，优雅。
头脑风暴
观察上面单次请求的日志，由外层LogicHandler和内层ClientHandler 日志头组成。 这样的日志可以想象到有2个问题：
① 在高并发使用HttpClient，日志条数众多，没有类似TraceId 这样的机制定位 某次HttpClient调用的完整日志。
② 若是微服务/ 分布式调用，可能还有 将本次HttpClient调用日志与后置api日志 结合分析的需求， 这个日志也支持不了。
因此本文打算重新构建 HttpClientFactory日志： 给某次请求的全部日志设置 TraceId
结合我给出的典型用法来看IHttpClientFactory组件原理：
示例中System.Net.Http.HttpClient.bce-request.LogicalHandler，System.Net.Http.HttpClient.bce-request.ClientHandler 日志头即是来自LoggingScopeHttpMessageHandler ，LoggingHttpMessageHandler 两个处理器，
给出手绘的UML类图：
本次要扩展的入口便是 IHttpMessageHandlerFilter接口， 核心是自定义DelegatingHandler日志处理器
+ https://github.com/aspnet/HttpClientFactory/blob/master/src/Microsoft.Extensions.Http/Logging/LoggingHttpMessageHandlerBuilderFilter.cs
编程实践
如以上分析，
P1 实现 IHttpMessageHandlerFilter接口，在接口中移除默认的两个日志处理器；
public class TraceIdLoggingMessageHandlerFilter : IHttpMessageHandlerBuilderFilter
{
private readonly ILoggerFactory _loggerFactory;
public TraceIdLoggingMessageHandlerFilter(ILoggerFactory loggerFactory)
{
_loggerFactory = loggerFactory ?? throw new ArgumentNullException(nameof(loggerFactory));
}
public Action<HttpMessageHandlerBuilder> Configure(Action<HttpMessageHandlerBuilder> next)
{
if (next == null)
{
throw new ArgumentNullException(nameof(next));
}
return (builder) =>
{
// Run other configuration first, we want to decorate.
next(builder);
var outerLogger =_loggerFactory.CreateLogger($"System.Net.Http.HttpClient.{builder.Name}.LogicalHandler");
builder.AdditionalHandlers.Clear();
builder.AdditionalHandlers.Insert(0,new CustomLoggingScopeHttpMessageHandler(outerLogger));
};
}
}
P2 实现带有TraceId能力的HttpClient 日志处理器， 并加入到 IHttpMessageHandlerFilter接口实现类；
public class CustomLoggingScopeHttpMessageHandler : DelegatingHandler
{
private readonly ILogger _logger;
public CustomLoggingScopeHttpMessageHandler(ILogger logger)
{
_logger = logger ?? throw new ArgumentNullException(nameof(logger));
}
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request,
CancellationToken cancellationToken)
{
if (request == null)
{
throw new ArgumentNullException(nameof(request));
}
using (Log.BeginRequestPipelineScope(_logger, request))
{
Log.RequestPipelineStart(_logger, request);
var response = await base.SendAsync(request, cancellationToken);
Log.RequestPipelineEnd(_logger, response);
return response;
}
}
private static class Log
{
private static class EventIds
{
public static readonly EventId PipelineStart = new EventId(100, "RequestPipelineStart");
public static readonly EventId PipelineEnd = new EventId(101, "RequestPipelineEnd");
}
private static readonly Func<ILogger, HttpMethod, Uri, string, IDisposable> _beginRequestPipelineScope =
LoggerMessage.DefineScope<HttpMethod, Uri, string>(
"HTTP {HttpMethod} {Uri} {CorrelationId}");
private static readonly Action<ILogger, HttpMethod, Uri, string, Exception> _requestPipelineStart =
LoggerMessage.Define<HttpMethod, Uri, string>(
LogLevel.Information,
EventIds.PipelineStart,
"Start processing HTTP request {HttpMethod} {Uri} [Correlation: {CorrelationId}]");
private static readonly Action<ILogger, HttpStatusCode,string,Exception> _requestPipelineEnd =
LoggerMessage.Define<HttpStatusCode,string>(
LogLevel.Information,
EventIds.PipelineEnd,
"End processing HTTP request - {StatusCode}, [Correlation: {CorrelationId}]");
public static IDisposable BeginRequestPipelineScope(ILogger logger, HttpRequestMessage request)
{
var correlationId = GetCorrelationIdFromRequest(request);
return _beginRequestPipelineScope(logger, request.Method, request.RequestUri, correlationId);
}
public static void RequestPipelineStart(ILogger logger, HttpRequestMessage request)
{
var correlationId = GetCorrelationIdFromRequest(request);
_requestPipelineStart(logger, request.Method, request.RequestUri, correlationId, null);
}
public static void RequestPipelineEnd(ILogger logger, HttpResponseMessage response)
{
var correlationId = GetCorrelationIdFromRequest(response.RequestMessage);
_requestPipelineEnd(logger, response.StatusCode, correlationId, null);
}
private static string GetCorrelationIdFromRequest(HttpRequestMessage request)
{
string correlationId = Guid.NewGuid().ToString();
if (request.Headers.TryGetValues("X-Correlation-ID", out var values))
correlationId = values.First();
else
request.Headers.Add("X-Correlation-ID",correlationId);
return correlationId;
}
}
}
以上TraceId的实现思路，参考了我前一篇博文《被忽略的TraceId，可以用起来了》的思路，为每次HttpClient调用过程设定 全局唯一的GUID标记， 后置api服务可酌情修改以上代码处理。
其中写入日志的代码Copy自HttpClientFactory源代码。
P3 在DI框架中替换原有的 IHttpMessageHandlerFilter 实现:
services.Replace(ServiceDescriptor.Singleton<IHttpMessageHandlerBuilderFilter, TraceIdLoggingMessageHandlerFilter>());
发起两次HttpClient请求， 输出的日志如下:
19/12/04 12:59:22 [Info].[System.Net.Http.HttpClient.bce-request.LogicalHandler].[17}].[] Start processing HTTP request GET http://localhost:5000/v1/eqid/ad78deef00444ed7000000035de704e8 [Correlation: 03de676d-680e-4a92-aef5-749bcc3ba499] 19/12/04 12:59:22 [Info].[System.Net.Http.HttpClient.bce-request.LogicalHandler].[4}].[] End processing HTTP request - OK, [Correlation: 03de676d-680e-4a92-aef5-749bcc3ba499] 19/12/04 12:59:48 [Info].[System.Net.Http.HttpClient.bce-request.LogicalHandler].[17}].[] Start processing HTTP request GET http://localhost:5000/v1/eqid/8ea0c3b66b60f0ff100000005de704fb [Correlation: 6f14393a-3a2b-45c4-a9b4-0b4ab874ef1d] 19/12/04 12:59:48 [Info].[System.Net.Http.HttpClient.bce-request.LogicalHandler].[42}].[] End processing HTTP request - OK, [Correlation: 6f14393a-3a2b-45c4-a9b4-0b4ab874ef1d]
可以看到每次请求的开始和结束都带上了设定的GUID TraceId。
值得提醒的是：
① 这个TraceId 可以使用你业务上独具一格的标记，这样在排查时， 能根据上游业务更好的追踪日志。
② 现在这个TraceId位于LogMessage，实际上可以为nlog自定义LogoutRenderer，将该TraceId放在显著位置，便于ETL等日志集成框架过滤。
That's All， 这是本次解决 HttpClient 日志无法追踪的思路和方案， 思考 + 实践 + UML制图，希望能被大家一些启发。
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