c# HttpClient超时重试
当使用c# HttpClient 发送请求时，由于网络等原因可能会出现超时的情况。为了提高请求的成功率，我们可以使用超时重试的机制。
超时重试的实现方式可以使用循环结构，在请求发起后等待一定时间，若超时未收到响应，则再次发起请求。循环次数可以根据实际情况进行设置，一般建议不超过三次。
百度搜索的关于c#HttpClient 的比较少，简单整理了下，代码如下
//调用方式 3秒后超时 重试2次 .net framework 4.5
HttpMessageHandler handler = new TimeoutHandler(2,3000);
using (var client = new HttpClient(handler))
{
using (var content = new StringContent(""), null, "application/json"))
{
var response = client.PostAsync("url", content).Result;
string result = response.Content.ReadAsStringAsync().Result;
JObject jobj = JObject.Parse(result);
if (jobj.Value<int>("code") == 1)
{
}
}
}
public class TimeoutHandler : DelegatingHandler
{
private int _timeout;
private int _max_count;
///
/// 超时重试
///
///重试次数
///超时时间
public TimeoutHandler( int max_count = 3, int timeout = 5000)
{
base .InnerHandler = new HttpClientHandler();
_timeout = timeout;
_max_count = max_count;
}
protected async override Task SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
HttpResponseMessage response = null ;
for ( int i = 1; i <= _max_count + 1; i++)
{
var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
cts.CancelAfter(_timeout);
try
{
response = await base .SendAsync(request, cts.Token);
if (response.IsSuccessStatusCode)
{
return response;
}
}
catch (Exception ex)
{
//请求超时
if (ex is TaskCanceledException)
{
MyLogService.Print( "接口请求超时：" + ex.ToString());
if (i > _max_count)
{
return new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new StringContent( "{\"code\":-1,\"data\":\"\",\"msg\":\"接口请求超时\"}" , Encoding.UTF8, "text/json" )
};
}
MyLogService.Print($ "接口第{i}次重新请求" );
}
else
{
MyLogService.Error( "接口请求出错：" + ex.ToString());
return new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new StringContent( "{\"code\":-1,\"data\":\"\",\"msg\":\"接口请求出错\"}" , Encoding.UTF8, "text/json" )
};
}
}
}
return response;
}
}
