问题描述
我正在尝试将TimeoutPolicy
和RetryPolicy
结合在一起以进行Func
中的API调用,但是我没有找到一种方法来实现这一目标。
如果我仅使用RetryPolicy
,就可以正常工作。
我有一个GetRequest
方法,该方法调用HttpClient
并返回数据:
async Task<Data> GetRequest(string api,int id)
{
var httpClient = new HttpClient();
var response = await httpClient.GetAsync($"{api}{id}");
var rawResponse = await response.Content.ReadAsstringAsync();
return JsonConvert.DeserializeObject<Data>(rawResponse);
}
我也有Func
可以将调用嵌入到此方法中:
var func = new Func<Task<Data>>(() => GetRequest(api,i));
我这样称呼服务:
Results.Add(await _networkService.RetryWithoutTimeout<Data>(func,3,OnRetry));
此RetryWithoutTimeout
方法如下:
async Task<T> RetryWithoutTimeout<T>(Func<Task<T>> func,int retryCount = 1,Func<Exception,int,Task> onRetry = null)
{
var onRetryInner = new Func<Exception,Task>((e,i) =>
{
return Task.Factory.StartNew(() => {
#if DEBUG
System.Diagnostics.Debug.WriteLine($"Retry #{i} due to exception '{(e.InnerException ?? e).Message}'");
#endif
});
});
return await Policy.Handle<Exception>()
.RetryAsync(retryCount,onRetry ?? onRetryInner)
.ExecuteAsync<T>(func);
}
我已使用新的TimeoutPolicy
方法将此代码更新为使用RetryWithTimeout
:
async Task<T> RetryWithTimeout<T>(Func<Task<T>> func,Task> onRetry = null,int timeoutDelay = 30)
{
var onRetryInner = new Func<Exception,i) =>
{
return Task.Factory.StartNew(() => {
#if DEBUG
System.Diagnostics.Debug.WriteLine($"Retry #{i} due to exception '{(e.InnerException ?? e).Message}'");
#endif
});
});
var retryPolicy = Policy
.Handle<Exception>()
.RetryAsync(retryCount,onRetry ?? onRetryInner);
var timeoutPolicy = Policy.TimeoutAsync(TimeSpan.FromSeconds(timeoutDelay));
var policyWrap = timeoutPolicy.WrapAsync((IAsyncPolicy)retryPolicy);
return await policyWrap.ExecuteAsync(
async ct => await Task.Run(func),CancellationToken.None
);
}
但是我看不到如何管理GetRequest()
方法:我所有的测试都失败了...
编辑: 我已经基于@Peter Csala评论创建了一个示例。
因此,第一,我刚刚更新了重试次数,以检查retryPolicy
是否正确应用:
private const int TimeoutInMilliseconds = 2500;
private const int MaxRetries = 3;
private static int _times;
static async Task Main(string[] args)
{
try
{
await RetryWithTimeout(TestStrategy,MaxRetries);
}
catch (Exception ex)
{
WriteLine($"{nameof(Main)} - Exception - Failed due to: {ex.Message}");
}
Console.ReadKey();
}
private static async Task<string> TestStrategy(CancellationToken ct)
{
WriteLine($"{nameof(TestStrategy)} has been called for the {_times++}th times.");
await Task.Delay(TimeoutInMilliseconds * 2,ct);
return "Finished";
}
internal static async Task<T> RetryWithTimeout<T>(Func<CancellationToken,Task<T>> func,int timeoutDelay = TimeoutInMilliseconds)
{
WriteLine($"NetworkService - {nameof(RetryWithTimeout)}");
var onRetryInner = new Func<Exception,i) =>
{
WriteLine($"NetworkService - {nameof(RetryWithTimeout)} #{i} due to exception '{(e.InnerException ?? e).Message}'");
return Task.CompletedTask;
});
var retryPolicy = Policy
.Handle<Exception>()
.RetryAsync(retryCount,onRetry ?? onRetryInner);
var timeoutPolicy = Policy.TimeoutAsync(TimeSpan.FromMilliseconds(timeoutDelay));
var policyWrap = Policy.WrapAsync(retryPolicy,timeoutPolicy); //Important part #1
return await policyWrap.ExecuteAsync(
async ct => await func(ct),//Important part #2
CancellationToken.None);
}
关于日志,情况很好:
NetworkService - RetryWithTimeout
TestStrategy has been called for the 0th times.
NetworkService - RetryWithTimeout - Retry #1 due to exception 'A task was canceled.'
TestStrategy has been called for the 1th times.
NetworkService - RetryWithTimeout - Retry #2 due to exception 'A task was canceled.'
TestStrategy has been called for the 2th times.
NetworkService - RetryWithTimeout - Retry #3 due to exception 'A task was canceled.'
TestStrategy has been called for the 3th times.
Main - TimeoutRejectedException - Failed due to: The delegate executed asynchronously through TimeoutPolicy did not complete within the timeout.
然后,由于我需要全局超时,因此我更改了policyWrap
:
private static async Task<string> TestStrategy(CancellationToken ct)
{
WriteLine($"{nameof(TestStrategy)} has been called for the {_times++}th times.");
await Task.Delay(1500,ct);
throw new Exception("simulate Exception");
}
var policyWrap = timeoutPolicy.WrapAsync(retryPolicy);
关于日志,这也是正确的:
TestStrategy has been called for the 0th times.
NetworkService - RetryWithTimeout #1 due to exception 'simulate Exception'
TestStrategy has been called for the 1th times.
NetworkService - RetryWithTimeout #2 due to exception 'A task was canceled.'
Main - TimeoutRejectedException - Failed due to: The delegate executed asynchronously through TimeoutPolicy did not complete within the timeout.
之后,我实现了一种调用API的方法,该方法带有一些Exceptions
,以更贴近我的需求:
static async Task Main(string[] args)
{
try
{
await RetryWithTimeout(GetClientAsync,MaxRetries);
}
catch (TimeoutRejectedException trEx)
{
WriteLine($"{nameof(Main)} - TimeoutRejectedException - Failed due to: {trEx.Message}");
}
catch (WebException wEx)
{
WriteLine($"{nameof(Main)} - WebException - Failed due to: {wEx.Message}");
}
catch (Exception ex)
{
WriteLine($"{nameof(Main)} - Exception - Failed due to: {ex.Message}");
}
Console.ReadKey();
}
private static async Task<CountriesResponse> GetClientAsync(CancellationToken ct)
{
WriteLine($"{nameof(GetClientAsync)} has been called for the {_times++}th times.");
HttpClient _client = new HttpClient();
try
{
var response = await _client.GetAsync(apiUri,ct);
// ! The server response is faked through a Proxy and returns 500 answer !
if (!response.IsSuccessstatusCode)
{
WriteLine($"{nameof(GetClientAsync)} - !response.IsSuccessstatusCode");
throw new WebException($"No success status code {response.StatusCode}");
}
var rawResponse = await response.Content.ReadAsstringAsync();
WriteLine($"{nameof(GetClientAsync)} - Finished");
return JsonConvert.DeserializeObject<CountriesResponse>(rawResponse);
}
catch (TimeoutRejectedException trEx)
{
WriteLine($"{nameof(GetClientAsync)} - TimeoutRejectedException : {trEx.Message}");
throw trEx;
}
catch (WebException wEx)
{
WriteLine($"{nameof(GetClientAsync)} - WebException: {wEx.Message}");
throw wEx;
}
catch (Exception ex)
{
WriteLine($"{nameof(GetClientAsync)} - other exception: {ex.Message}");
throw ex;
}
}
日志仍然正确:
NetworkService - RetryWithTimeout
GetClientAsync has been called for the 0th times.
GetClientAsync - !response.IsSuccessstatusCode
GetClientAsync - WebException: No success status code InternalServerError
NetworkService - RetryWithTimeout #1 due to exception 'No success status code InternalServerError'
GetClientAsync has been called for the 1th times.
GetClientAsync - !response.IsSuccessstatusCode
GetClientAsync - WebException: No success status code InternalServerError
NetworkService - RetryWithTimeout #2 due to exception 'No success status code InternalServerError'
GetClientAsync has been called for the 2th times.
GetClientAsync - !response.IsSuccessstatusCode
GetClientAsync - WebException: No success status code InternalServerError
NetworkService - RetryWithTimeout #3 due to exception 'No success status code InternalServerError'
GetClientAsync has been called for the 3th times.
GetClientAsync - other exception: The operation was canceled.
Main - TimeoutRejectedException - Failed due to: The delegate executed asynchronously through TimeoutPolicy did not complete within the timeout.
最后,我希望能够调用一个“通用”方法,该方法可以在每个API调用中重复使用。此方法将如下所示:
static async Task<T> ProcessGetRequest<T>(Uri uri,CancellationToken ct)
{
WriteLine("ApiService - ProcessGetRequest()");
HttpClient _client = new HttpClient();
var response = await _client.GetAsync(uri);
if (!response.IsSuccessstatusCode)
{
WriteLine("ApiService - ProcessGetRequest() - !response.IsSuccessstatusCode");
throw new WebException($"No success status code {response.StatusCode}");
}
var rawResponse = await response.Content.ReadAsstringAsync();
return JsonConvert.DeserializeObject<T>(rawResponse);
}
但是,为此,我必须同时通过CancellationToken
传递Uri
和Api RetryWithTimeout
,但我不知道如何管理它。
我试图通过以下方式更改RetryWithTimeout
的签名:
internal static async Task<T> RetryWithTimeout<T>(Func<Uri,CancellationToken,int timeoutDelay = TimeoutInMilliseconds)
但是我找不到如何管理Func
...
您有想法或解释吗?
解决方法
您需要将CancellationToken
传递到要取消的(由于超时)功能。
因此,假设您具有以下简化方法:
private const int TimeoutInMilliseconds = 1000;
private static int _times;
private static async Task<string> TestStrategy(CancellationToken ct)
{
Console.WriteLine($"{nameof(TestStrategy)} has been called for the {_times++}th times.");
await Task.Delay(TimeoutInMilliseconds * 2,ct);
return "Finished";
}
因此,您的RetryWithTimeout
可以像这样调整/修改:
static async Task<T> RetryWithTimeout<T>(Func<CancellationToken,Task<T>> func,int retryCount = 1,Func<Exception,int,Task> onRetry = null,int timeoutDelay = TimeoutInMilliseconds)
{
var onRetryInner = new Func<Exception,Task>((e,i) =>
{
Console.WriteLine($"Retry #{i} due to exception '{(e.InnerException ?? e).Message}'");
return Task.CompletedTask;
});
var retryPolicy = Policy
.Handle<Exception>()
.RetryAsync(retryCount,onRetry ?? onRetryInner);
var timeoutPolicy = Policy.TimeoutAsync(TimeSpan.FromMilliseconds(timeoutDelay));
var policyWrap = Policy.WrapAsync(retryPolicy,timeoutPolicy); //Important part #1
return await policyWrap.ExecuteAsync(
async ct => await func(ct),//Important part #2
CancellationToken.None);
}
重要的部分#1-重试是外部的,超时是内部的策略
重要部分#2-由于超时,CancellationToken传递给了要取消的功能
以下用法
static async Task Main(string[] args)
{
try
{
await RetryWithTimeout(TestStrategy);
}
catch (Exception ex)
{
Console.WriteLine($"Failed due to: {ex.Message}");
}
Console.ReadKey();
}
将产生以下输出:
TestStrategy has been called for the 0th times.
Retry #1 due to exception 'A task was canceled.'
TestStrategy has been called for the 1th times.
Failed due to: The delegate executed asynchronously through TimeoutPolicy did not complete within the timeout.
请记住,重试开始之前有0次尝试。
,我终于找到了一个可行的解决方案,该解决方案已由@Peter Csala完成。
[
{
"NODE": "rabbit@server567","EXCLUSIVE": false,"NAME": "test-01","SYNCHRONISED_SLAVE_NODES": [],"SLAVE_NODES": [],"AUTO_DELETE": false,"VHOST": "/","ARGUMENTS": {},"TYPE": "classic","DURABLE": false
},{
"NODE": "rabbit@server567","NAME": "test-02","NAME": "test-03",{
"MESSAGES_UNACKNOWLEDGED_RAM": 0,"RECOVERABLE_SLAVES": null,"CONSUMERS": 0,"REDUCTIONS": 9700519,"MESSAGE_BYTES_PAGED_OUT": 0,"MESSAGE_BYTES_UNACKNOWLEDGED": 0,"REDUCTIONS_DETAILS": {
"RATE": 0.0
},"MESSAGE_BYTES": 0,"MESSAGES_UNACKNOWLEDGED": 0,"CONSUMER_UTILISATION": null,"GARBAGE_COLLECTION": {
"MAX_HEAP_SIZE": 0,"MIN_HEAP_SIZE": 233,"FULLSWEEP_AFTER": 65535,"MINOR_GCS": 15635,"MIN_BIN_VHEAP_SIZE": 46422
},"MESSAGES_DETAILS": {
"RATE": 0.0
},"SLAVE_NODES": [
"rabbit@server567"
],"MESSAGE_BYTES_PERSISTENT": 0,"POLICY": "ha-all","MESSAGES_PAGED_OUT": 0,"NODE": "rabbit@server566","HEAD_MESSAGE_TIMESTAMP": null,"DURABLE": false,"MESSAGES_READY_RAM": 0,"STATE": "running","EFFECTIVE_POLICY_DEFINITION": {
"HA-MODE": "all"
},"MESSAGES_READY": 0,"MESSAGES_RAM": 0,"MESSAGE_BYTES_READY": 0,"SINGLE_ACTIVE_CONSUMER_TAG": null,"NAME": "test-04","MESSAGES_PERSISTENT": 0,"BACKING_QUEUE_STATUS": {
"MIRROR_SENDERS": 0,"Q1": 0,"Q3": 0,"Q2": 0,"Q4": 0,"AVG_ACK_EGRESS_RATE": 0.0,"MIRROR_SEEN": 0,"LEN": 0,"TARGET_RAM_COUNT": "infinity","MODE": "default","NEXT_SEQ_ID": 0,"DELTA": [
"delta","undefined","undefined"
],"AVG_ACK_INGRESS_RATE": 0.0,"AVG_EGRESS_RATE": 0.0,"AVG_INGRESS_RATE": 0.0
},"MESSAGES": 0,"IDLE_SINCE": "2020-10-16 13:50:50","OPERATOR_POLICY": null,"SYNCHRONISED_SLAVE_NODES": [
"rabbit@server567"
],"MEMORY": 10556,"EXCLUSIVE_CONSUMER_TAG": null,"MESSAGES_READY_DETAILS": {
"RATE": 0.0
},"MESSAGES_UNACKNOWLEDGED_DETAILS": {
"RATE": 0.0
},"MESSAGE_BYTES_RAM": 0
}
]
我得到这些结果:
private const int TimeoutInMilliseconds = 2500;
private const int MaxRetries = 3;
private static Uri apiUri = new Uri("https://api/param");
private static int _times;
public static Country[] Countries
{
get;
set;
}
static async Task Main(string[] args)
{
try
{
await LoadCountriesWithRetry(false);
}
catch (Exception ex)
{
WriteLine($"{nameof(Main)} - Exception - Failed due to: {ex.Message}");
}
Console.ReadKey();
}
static async Task LoadCountriesWithRetry(bool shouldWaitAndRetry)
{
WriteLine($"{nameof(LoadCountriesWithRetry)}");
try
{
Countries = await GetCountriesWithRetry();
}
catch (TimeoutRejectedException trE)
{
WriteLine($"{nameof(LoadCountriesWithRetry)} - TimeoutRejectedException : {trE.Message}");
}
catch (WebException wE)
{
WriteLine($"{nameof(LoadCountriesWithRetry)} - WebException : {wE.Message}");
}
catch (Exception e)
{
WriteLine($"{nameof(LoadCountriesWithRetry)} - Exception : {e.Message}");
}
}
public static async Task<Country[]> GetCountriesWithRetry()
{
WriteLine($"{nameof(GetCountriesWithRetry)}");
var response = await GetAndRetry<CountriesResponse>(uri,MaxRetries);
return response?.Countries;
}
static Func<CancellationToken,Task<T>> IssueRequest<T>(Uri uri) => ct => ProcessGetRequest<T>(ct,uri);
public static async Task<T> GetAndRetry<T>(Uri uri,int retryCount,Task> onRetry = null)
where T : class
{
WriteLine($"{nameof(GetAndRetry)}");
return await RetryWithTimeout<T>(IssueRequest<T>(uri),retryCount);
}
static async Task<T> ProcessGetRequest<T>(CancellationToken ct,Uri uri)
{
WriteLine($"{nameof(ProcessGetRequest)}");
HttpClient _client = new HttpClient();
var response = await _client.GetAsync(uri,ct);
if (!response.IsSuccessStatusCode)
{
WriteLine($"{nameof(ProcessGetRequest)} - !response.IsSuccessStatusCode");
throw new WebException($"No success status code {response.StatusCode}");
}
var rawResponse = await response.Content.ReadAsStringAsync();
WriteLine($"{nameof(ProcessGetRequest)} - Success");
return JsonConvert.DeserializeObject<T>(rawResponse);
}
internal static async Task<T> RetryWithTimeout<T>(Func<CancellationToken,Uri uri,int timeoutDelay = TimeoutInMilliseconds)
{
WriteLine($"{nameof(RetryWithTimeout)}");
var onRetryInner = new Func<Exception,i) =>
{
WriteLine($"{nameof(RetryWithTimeout)} - onRetryInner #{i} due to exception '{(e.InnerException ?? e).Message}'");
return Task.CompletedTask;
});
var retryPolicy = Policy
.Handle<Exception>()
.RetryAsync(retryCount,onRetry ?? onRetryInner);
var timeoutPolicy = Policy.TimeoutAsync(TimeSpan.FromMilliseconds(timeoutDelay));
var policyWrap = timeoutPolicy.WrapAsync(retryPolicy);
return await policyWrap.ExecuteAsync(
async (ct) => await func(ct),CancellationToken.None);
}
=>重试API调用,直到出现超时
谢谢@Peter Csala!