AFNetworking caching using ETag

Question

I have problem implementing caching using AFNetworking and ETag values. My server returns Cache-Control and ETag headers values for every request. But if I make a second request for the same resource AFNetworking won't add ETag. Should I manually save etag for each response I got and append it to next requests?

In app delegate I have set cache object:

 NSURLCache *URLCache = [[NSURLCache alloc] initWithMemoryCapacity:20 * 1024 * 1024 diskCapacity:20 * 1024 * 1024 diskPath:nil];
 [NSURLCache setSharedURLCache:URLCache];

Also, I'm using default cache policy of AFHTTPRequestSerializer.

Any ideas what is the problem? Maybe I don't understand the idea of http caching. As far as I know it should be transparent, and all I have to do is to attach ETag and Cache-Control headers for every response.

EDIT:

The headers of response looks like this:

"Cache-Control" = "max-age=3600";
"Content-Encoding" = gzip;
"Content-Type" = "application/json; charset=utf-8";
Date = "Wed, 05 Aug 2015 07:52:33 GMT";
Etag = "W/f6c8a0f47deb7db0eeea3069061de9ab";
Expires = "Wed, 05 Aug 2015 08:52:30 GMT";
"Last-Modified" = "Wed, 05 Aug 2015 08:52:30 GMT";
Server = "cloudflare-nginx";
Vary = "Accept-Encoding";
"cf-ray" = "2110ec564bde0afc-WAW";
"x-cache-id" = "api_3447fddb8680ed5d082ae871e95214dc";
"x-powered-by" = "PHP/5.5.19";
"x-whom" = "www-stage02-b"

It should work by default, are you sure you have all headers properly set on both sides ? Server side need to attach those headers as well. — Grzegorz Krukowski
You can check server reponses using "[[operation response] allHeaderFields]" — Grzegorz Krukowski
What do you mean on both sides? Shouldn't AFNetworking automatically attach If-None-Match header with latest Etag value for corresponding request path? I have attached the responses headers (using edit). Can you see something that could make any problems? — MichalMoskala
It looks ok, let me paste you the code to confirm if request is loaded from cache or not — Grzegorz Krukowski

Grzegorz Krukowski Grzegorz Krukowski · Accepted Answer · 2015-08-05T10:13:11

To check if your AFHTTPRequestOperation is coming from cache or not, you can use this code:

- (AFHTTPRequestOperation *)HTTPRequestOperationWithRequest:(NSURLRequest *)request
                                                    success:(void (^)(AFHTTPRequestOperation *operation, id responseObject))success
                                                    failure:(void (^)(AFHTTPRequestOperation *operation, NSError *error))failure
{
    NSMutableURLRequest* mutableRequest = [request mutableCopy];
    BOOL __block responseFromCache = YES;

    AFHTTPRequestOperation* operation = [super HTTPRequestOperationWithRequest:mutableRequest
    success:^(AFHTTPRequestOperation *operation, id responseObject)
    {
        NSString* source = responseFromCache ? @"CACHE" : @"SERVER";
        NSLog(@"Request from %@", source);
        success(operation, responseObject);
    }
    failure:nil];

    [operation setCacheResponseBlock:
     ^NSCachedURLResponse *(NSURLConnection *connection, NSCachedURLResponse *cachedResponse) {
         responseFromCache = NO;
         return cachedResponse;
     }];

    return operation;
}

Make sure you also enabled NSURLCache when your application starts running.

NSURLCache *URLCache = [[NSURLCache alloc] initWithMemoryCapacity:5 * 1024 * 1024
                                                     diskCapacity:50 * 1024 * 1024
                                                         diskPath:nil];
[NSURLCache setSharedURLCache:URLCache];

AFNetworking caching using ETag

1 Answers