当与Google API交互时，作为批处理请求一部分的请求失败时，如何执行重试。他们在他们的documentation中建议添加“指数补偿”算法。我在他们的文档中使用了以下code片段：
UserCredential credential;
using (var stream = new FileStream("client_secrets.json", FileMode.Open, FileAccess.Read))
{
credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
GoogleClientSecrets.Load(stream).Secrets,
new[] { CalendarService.Scope.Calendar },
"user", CancellationToken.None, new FileDataStore("Calendar.Sample.Store"));
}
// Create the service.
var service = new CalendarService(new BaseClientService.Initializer()
{
HttpClientInitializer = credential,
ApplicationName = "Google Calendar API Sample",
});
// Create a batch request.
var request = new BatchRequest(service);
request.Queue<CalendarList>(service.CalendarList.List(),
(content, error, i, message) =>
{
// Put your callback code here.
});
request.Queue<Event>(service.Events.Insert(
new Event
{
Summary = "Learn how to execute a batch request",
Start = new EventDateTime() { DateTime = new DateTime(2014, 1, 1, 10, 0, 0) },
End = new EventDateTime() { DateTime = new DateTime(2014, 1, 1, 12, 0, 0) }
}, "YOUR_CALENDAR_ID_HERE"),
(content, error, i, message) =>
{
// Put your callback code here.
});
// You can add more Queue calls here.
// Execute the batch request, which includes the 2 requests above.
await request.ExecuteAsync();
答案 0 :(得分：0)
这是一个简单的帮助器类，可简化Google在其API错误页面上谈到的许多情况下实现指数补偿的方法：https://developers.google.com/calendar/v3/errors
使用方法：
GCalAPIHelper.Instance.Auth(); GCalAPIHelper.Instance.CreateEvent(event, calendarId);（您可能需要根据需要将此类扩展到其他API端点）using Google;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Calendar.v3;
using Google.Apis.Calendar.v3.Data;
using Google.Apis.Services;
using Google.Apis.Util.Store;
using System;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading;
using static Google.Apis.Calendar.v3.CalendarListResource.ListRequest;
/*======================================================================================
* This file is to implement Google Calendar .NET API endpoints WITH exponential backoff.
*
* How to use:
* - Install the Google Calendar .NET API (nuget.org/packages/Google.Apis.Calendar.v3)
* - Edit the class below to include your client secret and application name as you
* set up on https://console.developers.google.com
* - In the startup of your application (or when you ask the user to authorize), call
* GCalAPIHelper.Instance.Auth();
* - Anywhere you would call the Google Calendar API (eg Get, Insert, Delete, etc),
* instead use this class by doing:
* GCalAPIHelper.Instance.CreateEvent(event, calendarId); (you may need to expand
* this class to other API endpoints as your needs require)
*======================================================================================
*/
namespace APIHelper
{
public class GCalAPIHelper
{
#region Singleton
private static GCalAPIHelper instance;
public static GCalAPIHelper Instance
{
get
{
if (instance == null)
instance = new GCalAPIHelper();
return instance;
}
}
#endregion Singleton
#region Private Properties
private CalendarService service { get; set; }
private string[] scopes = { CalendarService.Scope.Calendar };
private const string CLIENTSECRETSTRING = "YOUR_SECRET"; //Paste in your JSON client secret here. Don't forget to escape special characters!
private const string APPNAME = "YOUR_APPLICATION_NAME"; //Paste in your Application name here
#endregion Private Properties
#region Constructor and Initializations
public GCalAPIHelper()
{
}
public void Auth(string credentialsPath)
{
if (service != null)
return;
UserCredential credential;
byte[] byteArray = Encoding.ASCII.GetBytes(CLIENTSECRETSTRING);
using (var stream = new MemoryStream(byteArray))
{
credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
GoogleClientSecrets.Load(stream).Secrets,
scopes,
Environment.UserName,
CancellationToken.None,
new FileDataStore(credentialsPath, true)).Result;
}
service = new CalendarService(new BaseClientService.Initializer()
{
HttpClientInitializer = credential,
ApplicationName = APPNAME
});
}
#endregion Constructor and Initializations
#region Private Methods
private TResponse DoActionWithExponentialBackoff<TResponse>(CalendarBaseServiceRequest<TResponse> request)
{
return DoActionWithExponentialBackoff(request, new HttpStatusCode[0]);
}
private TResponse DoActionWithExponentialBackoff<TResponse>(CalendarBaseServiceRequest<TResponse> request, HttpStatusCode[] otherBackoffCodes)
{
int delay = 100;
while (delay < 1000) //If the delay gets above 1 second, give up
{
try
{
return request.Execute();
}
catch (GoogleApiException ex)
{
if (ex.HttpStatusCode == HttpStatusCode.Forbidden || //Rate limit exceeded
ex.HttpStatusCode == HttpStatusCode.ServiceUnavailable || //Backend error
ex.HttpStatusCode == HttpStatusCode.NotFound ||
ex.Message.Contains("That’s an error") || //Handles the Google error pages like https://i.imgur.com/lFDKFro.png
otherBackoffCodes.Contains(ex.HttpStatusCode))
{
Common.Log($"Request failed. Waiting {delay} ms before trying again");
Thread.Sleep(delay);
delay += 100;
}
else
throw;
}
}
throw new Exception("Retry attempts failed");
}
#endregion Private Methods
#region Public Properties
public bool IsAuthorized
{
get { return service != null; }
}
#endregion Public Properties
#region Public Methods
public Event CreateEvent(Event eventToCreate, string calendarId)
{
EventsResource.InsertRequest eventCreateRequest = service.Events.Insert(eventToCreate, calendarId);
return DoActionWithExponentialBackoff(eventCreateRequest);
}
public Event InsertEvent(Event eventToInsert, string calendarId)
{
EventsResource.InsertRequest eventCopyRequest = service.Events.Insert(eventToInsert, calendarId);
return DoActionWithExponentialBackoff(eventCopyRequest);
}
public Event UpdateEvent(Event eventToUpdate, string calendarId, bool sendNotifications = false)
{
EventsResource.UpdateRequest eventUpdateRequest = service.Events.Update(eventToUpdate, calendarId, eventToUpdate.Id);
eventUpdateRequest.SendNotifications = sendNotifications;
return DoActionWithExponentialBackoff(eventUpdateRequest);
}
public Event GetEvent(Event eventToGet, string calendarId)
{
return GetEvent(eventToGet.Id, calendarId);
}
public Event GetEvent(string eventIdToGet, string calendarId)
{
EventsResource.GetRequest eventGetRequest = service.Events.Get(calendarId, eventIdToGet);
return DoActionWithExponentialBackoff(eventGetRequest);
}
public CalendarListEntry GetCalendar(string calendarId)
{
CalendarListResource.GetRequest calendarGetRequest = service.CalendarList.Get(calendarId);
return DoActionWithExponentialBackoff(calendarGetRequest);
}
public Events ListEvents(string calendarId, DateTime? startDate = null, DateTime? endDate = null, string q = null, int maxResults = 250)
{
EventsResource.ListRequest eventListRequest = service.Events.List(calendarId);
eventListRequest.ShowDeleted = false;
eventListRequest.SingleEvents = true;
eventListRequest.OrderBy = EventsResource.ListRequest.OrderByEnum.StartTime;
if (startDate != null)
eventListRequest.TimeMin = startDate;
if (endDate != null)
eventListRequest.TimeMax = endDate;
if (!string.IsNullOrEmpty(q))
eventListRequest.Q = q;
eventListRequest.MaxResults = maxResults;
return DoActionWithExponentialBackoff(eventListRequest);
}
public CalendarList ListCalendars(string accessRole)
{
CalendarListResource.ListRequest calendarListRequest = service.CalendarList.List();
calendarListRequest.MinAccessRole = (MinAccessRoleEnum)Enum.Parse(typeof(MinAccessRoleEnum), accessRole);
return DoActionWithExponentialBackoff(calendarListRequest);
}
public void DeleteEvent(Event eventToDelete, string calendarId, bool sendNotifications = false)
{
DeleteEvent(eventToDelete.Id, calendarId, sendNotifications);
}
public void DeleteEvent(string eventIdToDelete, string calendarId, bool sendNotifications = false)
{
EventsResource.DeleteRequest eventDeleteRequest = service.Events.Delete(calendarId, eventIdToDelete);
eventDeleteRequest.SendNotifications = sendNotifications;
DoActionWithExponentialBackoff(eventDeleteRequest, new HttpStatusCode[] { HttpStatusCode.Gone });
}
#endregion Public Methods
}
}
答案 1 :(得分：0)
derekantrican 有一个我基于我的答案。两件事，如果资源“notFound”等待它不会有任何好处。那是他们在未找到对象的情况下响应请求，因此无需退让。我不确定是否还有其他代码需要处理，但我会仔细研究它。根据 Google 的说法：https://cloud.google.com/iot/docs/how-tos/exponential-backoff 应重试所有 5xx 和 429。
此外，谷歌希望这是一个指数回退；不是线性的。所以下面的代码以指数方式处理它。他们还希望您向重试超时添加随机数量的 MS。我不这样做，但这很容易做到。我只是认为这没有那么重要。
我还需要异步请求，因此我将工作方法更新为这种类型。有关如何调用这些方法，请参阅 derekantrican 的示例；这些只是工作方法。除了在 notFound 上返回“default”之外，您还可以重新抛出异常并在上游处理它。
private async Task<TResponse> DoActionWithExponentialBackoff<TResponse>(DirectoryBaseServiceRequest<TResponse> request)
{
return await DoActionWithExponentialBackoff(request, new HttpStatusCode[0]);
}
private async Task<TResponse> DoActionWithExponentialBackoff<TResponse>(DirectoryBaseServiceRequest<TResponse> request, HttpStatusCode[] otherBackoffCodes)
{
int timeDelay = 100;
int retries = 1;
int backoff = 1;
while (retries <= 5)
{
try
{
return await request.ExecuteAsync();
}
catch (GoogleApiException ex)
{
if (ex.HttpStatusCode == HttpStatusCode.NotFound)
return default;
else if (ex.HttpStatusCode == HttpStatusCode.Forbidden || //Rate limit exceeded
ex.HttpStatusCode == HttpStatusCode.ServiceUnavailable || //Backend error
ex.Message.Contains("That’s an error") || //Handles the Google error pages like https://i.imgur.com/lFDKFro.png
otherBackoffCodes.Contains(ex.HttpStatusCode))
{
//Common.Log($"Request failed. Waiting {delay} ms before trying again");
Thread.Sleep(timeDelay);
timeDelay += 100 * backoff;
backoff = backoff * (retries++ + 1);
}
else
throw ex; // rethrow exception
}
}
throw new Exception("Retry attempts failed");
}