I am trying to figure out a way to find how much data is sent/received by my requests with AFNetworking. What are some of the best practices to solve this problem?
Example:
do a GET to an endpoint fakeapi/downloadlist
I want to know how many bytes were sent to the server and how many bytes were received back.
Thanks for your help!
Let's take the GET:parameters:success:failure: method on the AFHTTPSessionManager for performing a GET request. The declaration for the method is:
- (nullable NSURLSessionDataTask *)GET:(NSString *)URLString parameters:(nullable id)parameters
success:(nullable void (^) (NSURLSessionDataTask *task, id _Nullable responseObject))success
failure:(nullable void (^) (NSURLSessionDataTask *_Nullable task, NSError *error))failure;
There are two blocks of interest here: One for success (named very smartly success) and another for a failure in the request.
Both of the blocks return a parameter of type NSURLSessionDataTask (which is nullable on the failure event, if that's the case then there was no response, most likely to happen when there's no internet connection). According to the Apple Documentation for NSURLSessionDataTask, which inherits from NSURLSessionTask, it is possible to get the response object some other properties (take a look on the symbols section on the documentation):
int bytesReceived = ((int)[task countOfBytesReceived]);
int bytesSent = ((int)[task countOfBytesSent]);
// Do something with the numbers from here...
Further from here, take a look on the Symbols for NSURLSessionTask and take any other thing you need.
Related
The following code that used to create communication session with a remote server and send/receive HTTP requests/responses.
However, when a large file is attached to the response, the callback block never reached.
Only when explicitly invoke the cancel method after some timeout from the NSURLSession task (_dataTask), this callback is being called.
notice that using tcpdump it can easily observed that the response was properly received on the client side.
NSURLSessionConfiguration* config = [NSURLSessionConfiguration defaultSessionConfiguration];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
queue.maxConcurrentOperationCount = 1;
NSURLSession* session = [NSURLSession sessionWithConfiguration:config delegate:nil delegateQueue:queue];
_dataTask = [session dataTaskWithRequest:req completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
if ([error code] == NSURLErrorCancelled) {
writeLog(LOG_ERROR, "NSURLErrorCancelled");
} else {
...
}
}];
[_dataTask resume]
// after timeout, the operation is cancelled.
sleep(100)
[_dataTask cancel];
I'd like to know if using dataTask has response length limit (because it's working for small files on response body) and if there is such a limit, so which other method should I use in order to overcome it.
I saw that there's an alternative method in NSUrlsession dedicated for downloading files called downloadTaskWithRequest but it doesn't have an async completion block.
Thanks !
When fetching large resources, you should use download task. A data task will attempt to load the entire response in a single NSData object. Loading a large asset in memory at the same time is not only inefficient, but if it is extraordinarily large, can cause problems.
A download task is well suited for these tasks, because it will stream the asset to a temporary file for you, reducing the peak memory usage. (Admittedly, you can manually achieve the same with data task with delegate pattern, but download tasks do this for you.)
You said:
I saw that there's an alternative method in NSURLSession dedicated for downloading files called downloadTaskWithRequest but it doesn't have an async completion block.
Two observations:
There is a rendition, dataTaskWithRequest:completionHandler:, that has a completion block:
NSURLSession* session = [NSURLSession sharedSession];
NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:request completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
...
}];
[task resume];
Note, I would advise using sharedSession if you are not setting a delegate, or otherwise customizing your NSURLSession. You do not want to instantiate NSURLSession objects unnecessarily. And if you really must instantiate a NSURLSession, re-use it for subsequent tasks and/or make sure to call finishTasksAndInvalidate after submitting the last task for that session, or else the NSURLSession will leak. And, if you instantiate your own NSURLSession, you do not have to instantiate your own operation queue, as it will, by default, create a serial queue for you if you do not supply an operation queue.
The rendition without a block parameter, downloadTaskWithURL:, works, too. All you need to do is to specify a delegate for your NSURLSession and then and implement URLSession:downloadTask:didFinishDownloadingToURL:.
The reason I suggest this is that, often, when we are downloading very large assets (especially over cellular), we realize that the users may want to leave our app and let the download complete in the background. In those situations, we would use a background NSURLSessionConfiguration. And when using background sessions, you must use this delegate-based approach. So, if you think you might eventually adopt background sessions for long downloads, then adopting a delegate-based approach now is not a bad idea.
For more information, see Downloading Files in the Background.
I init NSURLSessionDataTask with follow method
- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request completionHandler:(nullable void (^)(NSURLResponse *response, id _Nullable responseObject, NSError * _Nullable error))completionHandler;
then call setDataTaskDidReceiveResponseBlock and setDataTaskDidReceiveDataBlock to write data to file.
and then I call suspend but the after the timeoutInterval I get completionHandler with timeout error.
the document about suspend:
/*
* Suspending a task will prevent the NSURLSession from continuing to
* load data. There may still be delegate calls made on behalf of
* this task (for instance, to report data received while suspending)
* but no further transmissions will be made on behalf of the task
* until -resume is sent. The timeout timer associated with the task
* will be disabled while a task is suspended. -suspend and -resume are
* nestable.
*/
I want to know how to suspend the task,and why I call suspend like this it does not work
It also happened to me. I did several tests, it seems that there is nothing with AFN, you can suspend a NSURLSessionDownloadTask, but not NSURLSessionDataTask. I have no idea about the reason.
Update:I found this post: NSURLSessionTask. Suspend does not work
I have been trying to figure out when it's okay to "just type in what I need done" and when I need to be specific about what kind of work I am doing on what kind of thread.
As I understand I should only update the UI on my main thread. Does this mean that it's not okay to do something like this? Should I put this into a GDC call?
[sessionManager dataTaskWithRequest:aRequest completionHandler:^(NSURLResponse * _Nonnull response, id _Nullable responseObject, NSError * _Nullable error) {
someUILabel.text = #"Hello!"; // Updating my UI
[someTableView reloadData]; // Ask a table view to reload data
}];
That's it for the UI part. Now, let's assume I had an NSMutableArray somewhere in in my class. I would be adding or removing objects to this array by for instance tapping a UIButton. Then again I have a NSURLSessionDataTask going to a server somewhere to get some data and load it into my NSMutableArray, like so:
[sessionManager dataTaskWithRequest:aRequest completionHandler:^(NSURLResponse * _Nonnull response, id _Nullable responseObject, NSError * _Nullable error) {
myMutableArray = [[responseObject objectForKey:#"results"] mutableCopy];
}];
This is not a UI operation. Does this need to be wrapped in a GDC call to avoid crashing in a race condition between my button-tap adding an object (i.e. [myMutableArray insertObject:someObj atIndex:4];) while the completion block runs, or are these designed to not clash into each other?
I have left out all error handling to focus on the question at hand.
TLDR: It costs you nothing to call dispatch_async(dispatch_get_main_queue()... inside your completion handler, so just do it.
Long Answer:
Let's look at the documentation, shall we?
completionHandler The completion handler to call when the load request is complete. This handler is executed on the delegate queue.
The delegate queue is the queue you passed in when you created the NSURLSession with sessionWithConfiguration:delegate:delegateQueue:. If that's not how you created this NSURLSession, then I suggest you make no assumptions about what queue the completion handler is called on. If you didn't pass [NSOperationQueue mainQueue] as this parameter, you are on a background queue and you should break out to the main queue before doing anything that is not thread-safe.
So now the question is:
Is it thread-safe to update the UI and talk to the table view? No, you must do those things only on the main queue.
Is it thread-safe to set myMutableArray? No, because you would then be sharing a property, self.myMutableArray, between two threads (the main queue, where you usually talk to this property, and this queue, whatever it is).
I am having a problem with memory leaking in my code, I have a need to GET many URL's in quick succession, each GET is influenced by the result of the previous GET. The purpose is to look for a specific piece of content within the response.
I found the cleanest way to implement this is recursively, as I can use the same method to identify if the desired value is present in the response. Functionally it works very well, but it leaks memory as described below. I have also implemented the same functionality in an iterative fashion, and this also leaks memory.
To my mind it seems that the NSURLSession API is responsible for leaking this memory, and it only occurs when multiple calls are made in very quick succession. However, I would appreciate if anyone can point out any obvious mistakes I am making.
Update 10/09/14:
Updated to add a recursion counter, demonstrating the leak still occurs even if the code isn't executed an infinite number of times. Also tidied up the implementation slightly, re-using the NSURLSession and NSURLSessionConfiguration as properties within the view controller.
Sample Code:
- (void)performURLCallRecursive {
recursionLimiter++;
if (recursionLimiter > 10) {
[self.session finishTasksAndInvalidate];
return;
}
NSURL * checkURL = [NSURL URLWithString:#"http://www.google.com"];
__block NSMutableURLRequest * urlRequest = [[NSMutableURLRequest alloc] initWithURL:checkURL
cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
timeoutInterval:0.0f];
__weak typeof(self) weakSelf = self;
NSURLSessionDataTask * task = [self.session dataTaskWithRequest:urlRequest
completionHandler:^(NSData *data, NSURLResponse *response, NSError
*error) {
NSString * body = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"Body: %#", body);
[weakSelf performURLCallRecursive];
}];
[task resume];
}
#pragma mark - Getters
- (NSURLSessionConfiguration *)sessionConfiguration {
if (!_sessionConfiguration) {
_sessionConfiguration = [NSURLSessionConfiguration ephemeralSessionConfiguration];
[_sessionConfiguration setAllowsCellularAccess:NO];
[_sessionConfiguration setTimeoutIntervalForRequest:10.0f];
[_sessionConfiguration setTimeoutIntervalForResource:10.0f];
[_sessionConfiguration setURLCache:[[NSURLCache alloc] initWithMemoryCapacity:0 diskCapacity:0 diskPath:nil]];
}
return _sessionConfiguration;
}
- (NSURLSession *)session {
if (_session == nil) {
_session = [NSURLSession sessionWithConfiguration:self.sessionConfiguration
delegate:[SPRSessionDelegate new]
delegateQueue:nil];
}
return _session;
}
The memory leaks as reported by instruments. (NB: These vary slightly every time, but for the most part contain the same leaks, just more or less of the same leaks):
Further Update:
So, I actually implemented the same code iteratively, and the memory leak still occurs. For this example I included a loop limiter so it doesn't execute for ever. Can anyone help me figure out what on earth is going on here?
- (void)performURLCallIterative
{
int loopLimiter = 0;
do {
NSURLSessionConfiguration * defaultSession = [NSURLSessionConfiguration defaultSessionConfiguration];
[defaultSession setAllowsCellularAccess:NO];
[defaultSession setTimeoutIntervalForRequest:10.0f];
[defaultSession setTimeoutIntervalForResource:10.0f];
NSURLSession * session = [NSURLSession sessionWithConfiguration:defaultSession
delegate:self
delegateQueue:nil];
NSURL * checkURL = [NSURL URLWithString:#"http://google.com"];
NSMutableURLRequest * urlRequest = [[NSMutableURLRequest alloc] initWithURL:checkURL
cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
timeoutInterval:0.0f];
__weak NSURLSession * weakSession = session;
dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
NSURLSessionDataTask * task = [session dataTaskWithRequest:urlRequest
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
NSString * body = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"Body: %#", body);
dispatch_semaphore_signal(semaphore);
[weakSession invalidateAndCancel];
}];
[task resume];
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
loopLimiter++;
} while (loopLimiter <= 6);
}
Update 10/09/14:
This is still occurring on iOS 8 for any Googlers who may have found their way here. As far as I am concerned this is a bug in iOS.
- Update 9/12/2014
Solution: wait for iOS8.
- Update 9/10/2014
Whoa, this is spiraling into some Nth dimension of complexity :P. I hope one way or another you get a break here quick.
I have a few other things for you to try.
1) Could you make sure NSZombies is turned off. In Xcode, Product->Scheme->Edit Scheme...->Enable Zombie Objects (NOT ticked).
2) Also try cachePolicy:NSURLCacheStorageNotAllowed for your NSMutableURLRequest.
3) Could you see if you are completing with an error? Just put this around your body string assignment...
if (error == nil)
{
//Enter data->string code here
}
4) Could you see if you are not getting status 200?
NSInteger statusCode = [(NSHTTPURLResponse *)response statusCode];
5) It is hard to picture exactly how your project is set up. I would have an NSObject type class that houses the NSURLSession methods, which is separate from the UIViewController class from which it is being called. The timer or whatever recursion method you wish to choose would then call the url session associated methods from the UIViewController.
- Update 9/9/2014
You are correct about my question (2). The data task is resumed before completion and after the data task completes the session is invalidated. I haven't seen it done this way, but it makes sense. Just tested on my end, no leaks with regards to [session invalidateAndCancel]...
Could you check that your completion handler executes? Perhaps it doesn't and the session is never cancelled before a new task is started?
I am noticing that there are a few references to HTTP Headers in the Instruments Leaks report, maybe if you are not specifying either a [urlRequest setHTTPMethod:#"GET"] the request is missing some basic headers?
(I'll edit after we find the solution, so this doesn't look like a discussion).
- Original 9/8/2014
Interesting question! I have troubleshot leaks associated with NSURLSessions. Definitely #autoreleasepool{} and others are good suggestions to try so far... But!
I am afraid the thing you asked us to look past might be the culprit here.
Just a few observations first:
1) It is not clear to me why you would need to __weak the self here. What is the retain cycle you are trying to avoid? Perhaps this is more clear in the code you are actually using aside from your "sample".
2) What is the reason for the call to invalidate the session before the data task associated with that session even has a chance to complete, let alone resume. The data task is in the suspended state until resumed.
3) If you are recursively running a method like this, then I think it is crucial to specify or at least consider what delegate queue, otherwise having it set to nil defaults it to serial operation queue. What happens when the delegate calls before the completion handler finishes, in an infinite loop - most likely a huge pile up.
--
I believe that the main issue here is that you are starting a new or canceling the NSURLSessionDataTask before it has a chance to complete. Look at +sesssionWithConfiguration:
(sorry can't include pictures yet, hopefully after this answer)
https://developer.apple.com/library/ios/documentation/Foundation/Reference/NSURLSession_class/Introduction/Introduction.html#//apple_ref/occ/clm/NSURLSession/sessionWithConfiguration:
The point is here...
Important
The session object keeps a strong reference to the delegate
until your app explicitly invalidates the session. If you do not
invalidate the session by calling the invalidateAndCancel or
resetWithCompletionHandler: method, your app leaks memory.
My suggestion to try is...
//Your code above...
[task resume];
[session finishTasksAndInvalidate];
}
In theory this should prevent any new sessions from starting before completion, according to the description, "...new tasks cannot be created in the session, but existing tasks continue until completion. After the last task finishes and the session makes the last delegate call, references to the delegate and callback objects are broken..."
I am still not sure about invalidating the session before resuming it.
I hope this helps. Good luck.
A developer support request to Apple reveals this to be a bug within iOS 7. There is no fault with the code sample posted above (Either recursively or iteratively) and it has reportedly been fixed in the iOS 8 GM release.
Update:
This is still occurring in iOS 8.1
I had a lot of problems with memory from NSURLSession and I finally fixed it by not using a new session for each request. Sessions are generally defined on Wikipedia as:
a semi-permanent interactive information interchange
As such, Apple's convenience class method [NSURLSession sharedSession] gives us a clue of how NSURLSession objects are intended to be used: as semi-permanent objects, not one-off objects created fresh for each request, like you are doing.
You are making a new session object per request for a ton of requests that, from the server's perspective, are all part of a single session with a single client.
I was doing the same thing until I realized this was the source of my woes. I did not find Apple's documentation on this very clear, but after I realized the error of my ways, it made certain things in the documentation suddenly make more sense, like why there is a sharedSession singleton convenience method of NSURLSession, why the word "tasks" is plural in finishTasksAndInvalidate, why they called it a "session", why it has a cache, etc. (If it was just for one request, why would it be a "session" and what good would a "cache" be?)
It helps to know how a browser like Safari looks at a session. A new session starts the first time you make a connection to a given server. Setting up the session involves creating a cache of SSL certificates, establishing authentication, handshaking, etc. It would be extraordinarily inefficient to do all of that every time some JavaScript on a page makes a new request to the same server, especially since modern web apps constantly make requests with callbacks etc. That is why a single session is established for a whole huge set of requests and responses -- a conversation, if you will, between the client and server. Eventually, a session expires, but usually this happens after several minutes, not after one request!
The point is, how you should be using NSURLSession objects is to make a singleton with a strongly referenced NSURLSession object as a property. Do this if you need to customize the session's configuration, (like turning caching off, etc.). However if you do not need to customize it, just use Apple's sharedSession.
If you use a singleton on a custom class, then, if you never need to set the session property to nil, then you never need to invalidateAndCancel or finishTasksAndInvalidate. Instead, just resetWithCompletionBlock or flushWithCompletionBlock to clear out connection caches periodically.
If you hate singletons you can still use a session as a property, just make sure to invalidateAndCancel or finishTasksAndInvalidate the session before its last owner gets deallocated by the ARC runtime.
Also note that setting your NSURLSession object's URLCache property to nil is the proper way to shut off caching. That's what Apple says they do for backgroundSessionConfiguration.
See my other answers on this topic here and here.
The only suggestions I have are perhaps using an #autoreleasepool{} and converting the __weak id self to __block id self. I don't think the __block vs. __weak will do anything differently, but give it a shot.
I'm not sure what one should expect with ARC when running something asynchronously AND recursively. Looking at other questions with asynchronous recursive calls and ARC, there isn't any consistent solution. Take a look here, for example.
The Issue
I am using AFNetworking, which generates an NSURLConnection object, to upload a photo.
The NSURLConnection is not making any calls to the
- (void)connection:(NSURLConnection __unused *)connection
didSendBodyData:(NSInteger)bytesWritten
totalBytesWritten:(NSInteger)totalBytesWritten
totalBytesExpectedToWrite:(NSInteger)totalBytesExpectedToWrite
method. (It's part of the NSURLConnectionDataDelegate protocol, defined in NSURLConnection.h)
The request is an HTTP POST request with a photo attachment (Content-Disposition "form-data", Mime type "image/jpeg"). This should (I think) result in periodic calls to this method as the upload progresses.
I need the method to display a progress bar to the user. However, the method is not getting called.
Note:
The delegate is set properly; other delegate methods are called
The file upload is successful
AFNetworking Code
I'm pretty sure this is an NSURLConnection issue, not an AFNetworking issue.
But just in case, here is the relevant code from my AFHTTPClient subclass:
NSMutableURLRequest *request = [self multipartFormRequestWithMethod:#"POST" path:path parameters:parameters constructingBodyWithBlock:constructor];
AFHTTPRequestOperation *operation = [self HTTPRequestOperationWithRequest:request success:success failure:failure];
if (constructor) {
[operation setUploadProgressBlock:^(NSUInteger bytesWritten, long long totalBytesWritten, long long totalBytesExpectedToWrite) {
NSLog(#"Sent %lld of %lld bytes", totalBytesWritten, totalBytesExpectedToWrite);
}];
}
[self enqueueHTTPRequestOperation:operation];
My AFHTTPClient subclass does NOT override ANY of the methods I am calling:
multipartFormRequestWithMethod: path: parameters: constructingBodyWithBlock:
HTTPRequestOperationWithRequest: success: failure:
setUploadProgressBlock:
enqueueHTTPRequestOperation:
constructor is a block with type (void (^)(id<AFMultipartFormData>)) and is not nil (verified by stepping through code).
When I type po operation.uploadProgress in the debugger, I see $0 = 0x1301d9f0 <__NSMallocBlock__: 0x1301d9f0> so I think the block is being set correctly.
The file always uploads successfully, but the code in the upload progress block is not run, so my progress bar never updates.
Questions
Why isn't NSURLConnection calling this method?
What are the circumstances in which NSURLConnection is supposed to? (It doesn't appear to be well-documented.)
And most importantly, how can I display the upload progress to the user?
A third-party error reporting library was overriding that delegate method on NSURLConnection. Removing the library resolved the issue. (There was no issue with either AFNetworking or NSURLConnection.)
If you can provide troubleshooting steps that would have isolated this issue faster, I will award the bounty to you. (Keep in mind that the third-party library is compiled, so a source code search wouldn't have worked.)
The library maybe implements a connection:didSendBodyData:totalBytesWritten:totalBytesExpectedToWrite: method in a category on NSObject. That would be very nasty but that could explain why the method of AFURLConnectionOperation is not called.
In order to check this assumption, you can run class-dump on your compiled binary. Search for didSendBodyData: in the output. If there’s a match in a category, the library is clearly responsible. The library could also be messing with the Objective-C runtime, but that would be harder to detect than just running class-dump.