Custom NSURLProtocol slower after switching NSURLConnection to NSURLSession - ios

Question

I have a custom NSURLProtocol ("UrlProtocol") written to intercept requests from a UIWebView when navigating to specific websites, and apply an extra HTTP header before being sent. I followed https://www.raywenderlich.com/59982/nsurlprotocol-tutorial for a working class. My problem comes with switching from the deprecated NSURLConnection to NSURLSession: I tested an extremely simple one-file html page, which loaded successfully. However, slightly more complex sites with resources like js files, images, etc. will timeout, whereas using NSURLConnection the entire site will load within a few seconds.
I'll paste the original UrlProtocol using NSURLConnection, then the new class using NSURLSession. The original:
#import "UrlProtocol.h"
#import "Globals.h"
#implementation UrlProtocol
+ (BOOL)canInitWithRequest:(NSURLRequest *)request {
if (![request.URL.absoluteString hasPrefix:#"http"]) return NO; //No need to intercept non-http requests
if ([NSURLProtocol propertyForKey:#"handled" inRequest:request]) {
return NO;
}
return YES;
}
+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request {
NSString* key = #"custom-auth-header";
Globals* globals = [Globals getInstance];
NSString* token = [globals token];
NSMutableURLRequest *newRequest = [request mutableCopy]; //Create a mutable copy that can be modified
[newRequest setValue:token forHTTPHeaderField:key];
return [newRequest copy]; //return a non-mutable copy
}
+ (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b {
return [super requestIsCacheEquivalent:a toRequest:b];
}
- (void)startLoading {
NSMutableURLRequest *newRequest = [self.request mutableCopy];
[NSURLProtocol setProperty:#YES forKey:#"handled" inRequest:newRequest];
self.connection = [NSURLConnection connectionWithRequest:newRequest delegate:self];
}
- (void)stopLoading {
NSLog(#"stopLoading");
[self.connection cancel];
self.connection = nil;
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
[self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[self.client URLProtocol:self didLoadData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[self.client URLProtocolDidFinishLoading:self];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
[self.client URLProtocol:self didFailWithError:error];
}
#end
The new UrlProtocol using NSURLSessionDataTasks for every request:
#import "UrlProtocol.h"
#import "Globals.h"
#implementation UrlProtocol
+ (BOOL)canInitWithRequest:(NSURLRequest * _Nonnull) request {
if (![request.URL.absoluteString hasPrefix:#"http"]) return NO; //No need to intercept non-http requests
if ([NSURLProtocol propertyForKey:#"handled" inRequest:request]) {
return NO;
}
return YES;
}
+ (NSURLRequest * _Nonnull)canonicalRequestForRequest:(NSURLRequest * _Nonnull)request {
NSString* key = #"custom-auth-header";
Globals* globals = [Globals getInstance];
NSString* token = [globals token];
NSMutableURLRequest *newRequest = [request mutableCopy]; //Create a mutable copy that can be modified
[newRequest setValue:token forHTTPHeaderField:key];
return [newRequest copy]; //return a non-mutable copy
}
+ (BOOL)requestIsCacheEquivalent:(NSURLRequest * _Nonnull)a toRequest:(NSURLRequest * _Nonnull)b {
return [super requestIsCacheEquivalent:a toRequest:b];
}
- (void)startLoading {
NSMutableURLRequest *newRequest = [self.request mutableCopy];
[NSURLProtocol setProperty:#YES forKey:#"handled" inRequest:newRequest];
[Globals setUrlSessionDelegate:self];
Globals* globals = [Globals getInstance];
self.dataTask = [globals.session dataTaskWithRequest:newRequest];
[self.dataTask resume];
}
- (void)URLSession:(NSURLSession * _Nonnull)session dataTask:(NSURLSessionDataTask * _Nullable)dataTask didReceiveData:(NSData * _Nullable)data{
[self.client URLProtocol:self didLoadData:data];
}
- (void)URLSession:(NSURLSession * _Nonnull)session dataTask:(NSURLSessionDataTask * _Nullable)dataTask didReceiveResponse:(NSURLResponse * _Nullable)response
completionHandler:(void (^ _Nullable)(NSURLSessionResponseDisposition))completionHandler{
[self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
completionHandler(NSURLSessionResponseAllow);
}
- (void)URLSession:(NSURLSession * _Nonnull)session task:(NSURLSessionTask * _Nonnull)task didCompleteWithError:(NSError * _Nullable)error{
if (error){
[self.client URLProtocol:self didFailWithError:error];
} else {
[self.client URLProtocolDidFinishLoading:self];
}
}
- (void)URLSession:(NSURLSession * _Nonnull)session task:(NSURLSessionTask * _Nonnull)task willPerformHTTPRedirection:(NSHTTPURLResponse * _Nonnull)response
newRequest:(NSURLRequest * _Nonnull)request completionHandler:(void (^ _Nonnull)(NSURLRequest * _Nullable))completionHandler {
completionHandler(request);
}
- (void)stopLoading {
[self.dataTask cancel];
self.dataTask = nil;
}
#end
"Globals" is a singleton where I have initialized one NSURLSession meant to be used throughout the runtime of the app. It also contains the token I set as a custom HTTP header for all requests:
#import "Globals.h"
#import "UrlProtocol.h"
#implementation Globals
#synthesize token;
#synthesize session;
static Globals *instance = nil;
+(Globals*) getInstance
{
#synchronized(self)
{
if (instance == nil)
{
instance = [Globals new];
}
}
return instance;
}
//UrlProtocol class has no init method, so the NSURLSession delegate is being set on url load. We will ensure only one NSURLSession is created.
+(void) setUrlSessionDelegate:(UrlProtocol*) urlProtocol{
Globals* globals = [Globals getInstance];
if (!globals.session){
globals.session = [NSURLSession sessionWithConfiguration:NSURLSessionConfiguration.defaultSessionConfiguration delegate:urlProtocol delegateQueue:nil];
}
}
#end

Answer 1

Solved my problem by creating a new default NSURLSession for each NSURLSessionDataTask. Something was wrong with the way I was trying to share one NSURLSession for all my tasks. URLProtocol's startLoading method is now as follows:
- (void)startLoading {
NSMutableURLRequest *newRequest = [self.request mutableCopy];
[NSURLProtocol setProperty:#YES forKey:#"handled" inRequest:newRequest];
NSURLSessionConfiguration* config = NSURLSessionConfiguration.defaultSessionConfiguration;
NSURLSession* session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];
self.dataTask = [session dataTaskWithRequest:newRequest];
[self.dataTask resume];
}
The simple HTML page test before must have worked because only one task was needed to load the page