I was observirng some strange behaviour of my app sometime caching responses and sometime not caching them (all the responses have Cache-Control: max-age=600).
The test is simple: I did a test.php script that was just setting the headers and returning a simple JSON:
<?php
header('Content-Type: application/json');
header('Cache-Control: max-age=600');
?>
{
"result": {
"employeeId": "<?php echo $_GET['eId']; ?>",
"dateTime": "<?php echo date('Y-m-d H:i:s'); ?>'" }
}
This is the response I get from the PHP page:
HTTP/1.1 200 OK
Date: Thu, 28 Nov 2013 11:41:55 GMT
Server: Apache
X-Powered-By: PHP/5.3.17
Cache-Control: max-age=600
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: application/json
{
"result": {
"employeeId": "",
"dateTime": "2013-11-28 11:41:55'"
}
}
Then I've created a simple app and added AFNetworking library.
When I call the script with few parameters, the cache works properly:
AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
NSDictionary *params = @{
@"oId": @"4011",
@"eId": self.firstTest ? @"1" : @"0",
@"status": @"2031",
};
[manager GET:@"http://www.mydomain.co.uk/test.php" parameters:params success:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(@"JSON: %@", responseObject);
NSLog(@"Cache current memory usage (after call): %d", [cache currentMemoryUsage]);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(@"Error: %@", error);
}];
But when I increase the number of parameters, like:
NSDictionary *params = @{
@"organizationId": @"4011",
@"organizationId2": @"4012",
@"organizationId3": @"4013",
@"organizationId4": @"4014",
@"organizationId5": @"4015",
@"organizationId6": @"4016",
@"eId": self.firstTest ? @"1" : @"0",
@"status": @"2031",
};
it doesn't work anymore and it execute a new request each time it is called.
I've done many tests and it seems to me that it is related to the length of the URL, because if I includes this set of params:
NSDictionary *params = @{
@"oId": @"4011",
@"oId2": @"4012",
@"oId3": @"4013",
@"oId4": @"4014",
@"oId5": @"4015",
@"oId6": @"4016",
@"eId": self.firstTest ? @"1" : @"0",
@"status": @"2031",
};
It works!!
I've done many tests and that's the only pattern I've found...
To exclude AFNetworking from the equation, I've created another test program that uses NSURLConnection only and I can see the same behaviour so it's not AFNetworking and definitely NSURLCache. This is the other test:
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://www.mydomain.co.uk/test.php?eId=%@&organizationId=4011&organizationId2=4012&organizationId3=4013&organizationId4=4014&organizationId5=4015&organizationId6=4016", self.firstTest ? @"1" : @"0"]]; // doesn't work
//NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://www.mydomain.co.uk/test.php?eId=%@&oId=4011&oId2=4012&oId3=4013&oId4=4014&oId5=4015&oId6=4016", self.firstTest ? @"1" : @"0"]]; // work
//NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://www.mydomain.co.uk/test.php?eId=%@", self.firstTest ? @"1" : @"0"]]; // work
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSURLResponse *response = nil;
NSError *error = nil;
NSData *data = [NSURLConnection sendSynchronousRequest:request
returningResponse:&response
error:&error];
if (error == nil) {
// Parse data here
NSString *responseDataStr = [NSString stringWithUTF8String:[data bytes]];
NSLog(@"Response data: %@", responseDataStr);
}
I've also tried to establish how many characters in the URL will trigger the problem but even in this case I've got strange results:
This one is 112 characters long and it doesn't work:
This one is 111 characters long and it works:
Ive renamed the PHP script to see if the first part of the URL would matter and I've got a strange behaviour again:
This one is 106 characters long and it doesn't work:
This one is 105 characters long and it works:
So I've removed 3 characters from the page name and I've got a working threshold 6 characters lower.
Any suggestion?
Thanks, Dem
