为代码加上重试机制
1.前言:对于经常跟网络编程打交道的你来说,并不是你的每次Request,Server都会给你想要的Response。重试机制虽然并不能解决这种情况,但是却可以大大减少这种情况的发生。
2.介绍下重试机制类:RetryUtil.cs
使用了委托,代码很短,也不难理解。
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1 public class RetryUtil 2 { 3 public delegate void NoArgumentHandler(); 4 /// <summary> 5 /// retry mechanism without argument 6 /// </summary> 7 /// <param name="retryTimes">try times</param> 8 /// <param name="interval">time span</param> 9 /// <param name="throwIfFail">throw exception</param> 10 /// <param name="function">function name</param> 11 public static void Retry(int retryTimes, TimeSpan interval, bool throwIfFail, NoArgumentHandler function) 12 { 13 if (function == null) 14 return; 15 16 for (int i = 0; i < retryTimes; ++i) 17 { 18 try 19 { 20 function(); 21 break; 22 } 23 catch (Exception) 24 { 25 if (i == retryTimes - 1) 26 { 27 if (throwIfFail) 28 throw; 29 else 30 break; 31 } 32 else 33 { 34 if (interval != null) 35 Thread.Sleep(interval); 36 } 37 } 38 } 39 } 40 }
3.举例使用:Demon
3.1 下载文件,如果出错重复尝试五次,每次间隔2秒,全部失败抛出异常。
1 RetryUtil.Retry(5, TimeSpan.FromSeconds(2), true, delegate 2 { 3 WebClientUtil.DownloadFile(string.Format("{0}{1}", baseUrl, tdNewSeries), 30000, dexsrp); 4 });
3.2 搜索Outlook邮件,如果出错重复尝试五次,每次间隔2秒,全部失败抛出异常。
1 public List<EmailMessage> GetSearchQueryEmailMessage(string mailbox, string subjectKeyword, DateTime startDate, DateTime endDate, string sendAddress = "", string mailFolderPath = @"Inbox", string bodyKeyword = "") 2 { 3 List<EmailMessage> emails = null; 4 this.query = new EWSMailSearchQuery(sendAddress, mailbox, mailFolderPath, subjectKeyword, bodyKeyword, startDate, endDate); 5 6 RetryUtil.Retry(5, TimeSpan.FromSeconds(2), true, delegate 7 { 8 emails = EWSMailSearchQuery.SearchMail(service, query); 9 }); 10 11 return emails; 12 }
3.3 访问网页,如果出错重复尝试五次,每次间隔2秒,全部失败抛出异常。
1 RetryUtil.Retry(5, TimeSpan.FromSeconds(2), true, delegate 2 { 3 htc = WebClientUtil.GetHtmlDocument(sourceUrl, 3000); 4 });