ASP.NET Core中使用Graylog记录日志

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以下基于.NET Core 2.1

定义GrayLog日志记录中间件：

中间件代码：

public class GrayLogMiddleware
{
private readonly RequestDelegate _next;
private readonly ILogger _logger;

//在应用程序的生命周期中，中间件的构造函数只会被调用一次
public GrayLogMiddleware(RequestDelegate next, ILoggerFactory loggerFactory)
{
_next = next;
_logger = loggerFactory.CreateLogger("GrayLog");
}

public async Task InvokeAsync(HttpContext context)
{
var additionalFields = new Dictionary<string, object>()
{
["LogId"] = Guid.NewGuid()
};

// 若将该中间件做为第一个请求管道中的第一个中间件进行注册
// 那么在此处就可以进行全局异常处理
try
{
var startTime = DateTime.Now;
await _next(context);
var endTime = DateTime.Now;
additionalFields["Elapsed"] = (endTime - startTime).Milliseconds;
_logger.LogInfo(context, additionalFields);
}
catch (Exception ex)
{
if (context.Response.HasStarted == false)
{
await WriteExceptionInfoIntoResponseAsync(context, ex);
}
_logger.LogException(context, ex, additionalFields);
#if DEBUG
throw;
#endif
}
}

private async Task WriteExceptionInfoIntoResponseAsync(HttpContext context, Exception ex)
{
try
{
var resp = new ApiResponse();
resp = resp.Exception(ex);
var respStr = JsonConvert.SerializeObject(resp);
await context.Response.WriteAsync(respStr, Encoding.UTF8);
}
catch
{
// ignore
}
}

}

日志记录代码：

public static class LogExtension
{
public static void LogInfo(this ILogger logger, HttpContext context, IDictionary<string, object> addtionalFields = null)
{
logger.LogCore(context, LogLevel.Information, addtionalFields: addtionalFields);
}

public static void LogException(this ILogger logger, HttpContext context, Exception ex, IDictionary<string, object> addtionalFields = null)
{
logger.LogCore(context, LogLevel.Error, ex, addtionalFields);
}

private static void LogCore(this ILogger logger, HttpContext context, LogLevel logLevel, Exception ex = null, IDictionary<string, object> addtionalFields = null)
{
try
{
var shortMessage = GetShortMessage(context);
if (addtionalFields == null)
{
addtionalFields = GetAddtionalFields(context);
}
else
{
var temp = GetAddtionalFields(context);
addtionalFields = addtionalFields.Union(temp).ToDictionary(d => d.Key, d => d.Value);
}

// 需要使用Scope才能将additionalFields记录到GrayLog中
using (logger.BeginScope(addtionalFields))
{
logger.Log(logLevel, exception: ex, message: shortMessage);
}
}
catch
{
#if DEBUG
throw;
#endif
// ignore
}
}

/// <summary>
/// 获取请求的短消息
/// <para>
/// 消息格式：HttpMethod RequestUrl HttpStatusCode
/// </para>
/// </summary>
/// <example> GET http://localhost:5000 200</example>
private static string GetShortMessage(HttpContext context)
{
var request = context.Request;

var method = request.Method;
var url = request.GetEncodedUrl();
var statusCode = context.Response.StatusCode;

return $"{method} {url} {statusCode}";
}

/// <summary>
/// 需要写入到日志中的额外字段：请求来源，请求参数
/// </summary>
private static IDictionary<string, object> GetAddtionalFields(HttpContext context)
{
var referer = context.Connection.RemoteIpAddress;
var requestData = GetRequestParameters(context);

return new Dictionary<string, object>()
{
["Referer"] = referer,
["RequestData"] = requestData
};
}

private static string GetRequestParameters(HttpContext context)
{
if (context.Request.ContentLength > )
{
var stream = context.Request.Body;
if (stream.CanRead == false)
{
return null;
}
if (stream.CanSeek == false)
{
// 将HttpRequestStream转换为FileBufferingReadStream
context.Request.EnableBuffering();
stream = context.Request.Body;
}
stream.Position = ;

using (var reader = new StreamReader(stream))
{
var data = reader.ReadToEnd();
return data;
}
}

return null;
}

}

Graylog日志配置：

public class Program
{
public static void Main(string[] args) => CreateWebHost().Run();

private static IWebHost CreateWebHost() => CreateWebHostBuilder().Build();

// 这里未使用.NET Core封装的CreateDefaultBuilder方法，因为它封装了过多不需要的东西
private static IWebHostBuilder CreateWebHostBuilder() =>
new WebHostBuilder()
.UseContentRoot(Directory.GetCurrentDirectory())
#if RELEASE
.UseIISIntegration()
#endif
.UseKestrel()
.ConfigureLogging((context, builder) =>
{
ConfigLogger(context, builder);
})
.UseStartup<Startup>();

private static void ConfigLogger(WebHostBuilderContext context, ILoggingBuilder builder)
{
// 使用日志过滤器(log filtering)，禁止Kestrel记录访问日志
builder.ClearProviders();
builder.AddFilter("Microsoft", LogLevel.None);
builder.AddFilter("System", LogLevel.Error);

if (context.HostingEnvironment.IsDevelopment())
{
builder.AddDebug();
}

// GrayLog配置（这里使用App.config作为配置文件
builder.AddGelf(option =>
{
option.Host = ConfigurationManager.AppSettings["grayLogHost"];
option.Port = Convert.ToInt32(ConfigurationManager.AppSettings["grayLogPort"]);
option.LogSource = ConfigurationManager.AppSettings["grayLogSource"];
option.Protocol = GelfProtocol.Udp;
});
}
}

注册中间件到请求处理管道：

public static class GrayLogMiddlewareExtension
{
/// <summary>
/// 向请求管道中添加GrayLog记录功能及全局异常处理
/// </summary>
public static IApplicationBuilder UseGrayLog(this IApplicationBuilder builder) =>
builder.UseMiddleware<GrayLogMiddleware>();
}

public class Startup
{
public void Configure(IApplicationBuilder app)
{
app.UseGrayLog()
.UseMvc();
}
}

以上日志记录了如下几个方面：

日志信息Id
请求来源
请求基础信息
采用类似HTTP请求行格式，即：HttpMethod RequestUrl ResponseStatusCode，如：GET http://localhost 200
入参
接口耗时
若发生异常，则记录异常信息

HttpRequestStream vs FileBufferingReadStream

GET请求参数都体现在Url中了，这里讲述如何获取POST请求的参数。

通常POST请求数据都在请求体中，ASP.NET Core中HttpRequest类型的Body属性是HttpRequestStream类型，该类型源码在Github上可以看到，但在Google和微软关方文档中都没搜索到。反编译Microsoft.AspNetCore.Server.Kestrel.Core.dll只找到了同样继承自ReadOnlyStream的FrameRequestStream

HttpRequestStream类的CanSeek属性返回值为false，不支持多次读取，所以需要先转换为FileBufferingReadStream。转换过程可参考：BufferingHelper及HttpRequestRewindExtensions。实现代码如下：

public static class HttpRequestRewindExtensions
{
public static void EnableBuffering(this HttpRequest request, int bufferThreshold, long bufferLimit)
{
BufferingHelper.EnableRewind(request, bufferThreshold, bufferLimit);
}
}

public static class BufferingHelper
{
public static HttpRequest EnableRewind(this HttpRequest request, int bufferThreshold = DefaultBufferThreshold, long? bufferLimit = null)
{
if (request == null)
{
throw new ArgumentNullException(nameof(request));
}

var body = request.Body;
if (!body.CanSeek)
{
var fileStream = new FileBufferingReadStream(body, bufferThreshold, bufferLimit, _getTempDirectory);
request.Body = fileStream;
request.HttpContext.Response.RegisterForDispose(fileStream);
}
return request;
}
}