HTTP caching in WCF Web API seems inconsistent across browsers
I'm implementing a simple REST service with the WCF Web API and attempt to set HTTP headers in order to cache responses.
For a simple GET like this
http://localhost:49302/my/2
the response headers look like this:
Server: ASP.NET Development Server/10.0.0.0
Date: Tue, 24 Jan 2012 18:18:44 GMT
X-AspNet-Version: 4.0.30319
Content-Length: 233
Cache-Control: max-age=120
Vary: Accept
Expires: Tue, 24 Jan 2012 18:20:44 GMT
Last-Modified: Tue, 24 Jan 2012 18:18:15 GMT
Content-Type: application/xml; charset=utf-8
The intent is that the client should cache the resource for two minutes.
However, using the WCF Web API Test Client, the behavior is inconsistent across various browsers:
Why doesn't Chrome and IE respect the cache headers?
Is it a bug in the WCF Web API Test Client?
Caching is hard to get right. The fact that a browser may ignore cache directives certainly doesn't help.
According to this document IE never cached any request with a Vary header containing anything but Accept-Encoding and User-Agent
If I test this with a 15 seconds cache period and I just set the MaxAge and MustRevalidate it seems to work fine with IE9, FireFox and Chrome.
Web API HttpResponseMessage:
result = new HttpResponseMessage<Book>(book);
result.Headers.CacheControl = new CacheControlHeaderValue();
result.Headers.CacheControl.MaxAge = TimeSpan.FromSeconds(15);
result.Headers.CacheControl.MustRevalidate = true;
return result;
Response headers:
HTTP/1.1 200 OK
Server: ASP.NET Development Server/10.0.0.0
Date: Wed, 25 Jan 2012 09:13:32 GMT
X-AspNet-Version: 4.0.30319
Content-Length: 98
Cache-Control: must-revalidate, max-age=15
Content-Type: application/json; charset=utf-8
Connection: Close
I am not sure the MustRevalidate is really required but it is recommended to use it. See the specs here.
测试用“真正的域”替换本地主机，所以WCF测试客户端或Chrome / IE没有任何本地主机的特殊技巧。
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