问题描述
我正在开发一个代码,每 30 秒轮询一次 Bitstamp 交易代码.这是我的代码:
I'm developing a code to poll a Bitstamp exchange ticker every 30 seconds. This is a code I have:
public IObservable<string> Stream(Uri way, WebClient wc)
{
Func<IObserver<string>, Task> Fun = async Observer =>
{
var res = await wc.DownloadStringTaskAsync(way);
Observer.OnNext(value: res);
};
return Observable.Create<string>(Fun);
}
public IObservable<string> GetDelay(int secs)
{
var exe = TimeSpan.FromSeconds(secs);
return Observable.Empty<string>("x").Delay(exe);
}
Stream(new Uri("https://bitstamp.net/api/ticker"), new WebClient { }).Concat(GetDelay(30))
.Repeat(5).Subscribe(res => Debug.WriteLine("got result: {0}", res));
问题是WebClient
(以及HttpClient
)在第一次调用后都返回缓存的结果,可以通过相同的时间戳看到:
The problem is that WebClient
(and HttpClient
, too) both return cached results after the first call, it can be seen by the same timestamp:
得到结果:{"high": "690.00", "last": "645.10", "timestamp": "1387715532" ... }
得到结果:{"high": "690.00", "last": "645.10", "timestamp": "1387715532" ... }
...
即使在关闭网络后,他们也会正常返回结果,因此很明显他们将其缓存在某处.添加诸如?cache=random"之类的内容不起作用,因为 Bitstamp 上的代码不允许请求参数.为 WebRequest
设置 Headers[HttpRequestHeader.CacheControl] = "no-cache"
也不起作用.
Even after turning the networks off they return the result normally so obviously they cache it somewhere. Adding something like "?cache=random" does not work because request parameters are not allowed for ticker on Bitstamp. Setting Headers[HttpRequestHeader.CacheControl] = "no-cache"
for WebRequest
does not work either.
如何修复这种奇怪的缓存行为?
How can I fix this weird caching behavior?
推荐答案
通过在每次后续调用之前设置 wc.Headers[HttpRequestHeader.IfModifiedSince] = DateTime.UtcNow.ToString();
解决.
Solved by setting wc.Headers[HttpRequestHeader.IfModifiedSince] = DateTime.UtcNow.ToString();
before each subsequent call.
这篇关于WebClient/HttpClient 的缓存问题的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!