Large size image uploading issue with latest iOS dropbox sdk - ios

Question

I am trying to upload 4 to 5 mb size image on dropbox using latest iOS dropbox sdk. But every time I get Error code =-1001 The operation couldn't be completed.
My internet connection speed is fair enough (2 mbps).
I have also tried by reducing image size to 512kb and it gets uploaded. But if I try to upload 5 or 6 images in sequence than again i get same error after successful upload of 2 or 3 images.
I have tried using below methods.
[self.restClient uploadFile:filename toPath:destDir withParentRev:nil fromPath:localPath]
[self.restClient uploadFileChunk:nil offset:0 fromPath:localPath]

Answer 1

According to the documentation a -1001 error means NSURLErrorTimedOut, meaning that the connection took too long. There are a number of factors that can contribute to this, including the device, the device's network stack and Internet connection, the particular route between your ISP and the destination servers, etc.
When it comes to your Internet connection, you only upload as fast as your Internet service provider (ISP) allows. Consumer ISP's normally provide less upload speed compared to download speed. In addition to this, your speeds may be slower than what your ISP rates it. Sometimes resetting or retrying your connection gets you a different route and better speeds, but that is outside of our control. Some ISPs also throttle sustained connections so if you see an initial high connection speed followed by lower speeds, that could be the reason.
When using uploadFile, you're attempting to upload the entirety of the file in one HTTPS request. If the file is big enough, along with the above considerations, this may make the request take too long and fail. For that reason, chunked uploading can be better.
When using uploadFileChunk, you're only attempting to upload a portion of the file per HTTPS request, meaning each request doesn't need to take as long and is less likely to fail.
In either case, one more thing to be aware of is how many simultaneous requests you're attempting to make. If you have too many running at the same time, they may all slow down, causing these failures. That being the case, you'll want to limit how many you run concurrently. Some developers choose a limit of 4 simultaneous connections, but the right number for your app will depend on the specifics of the scenario, so you may want to try a few different numbers.
Edit, here's some basic sample code for using chunked uploading:
- (void) doTest {
if ([[DBSession sharedSession] isLinked]) {
NSLog(#"Running test...");
// Write a file to the local documents directory
NSString *text = #"Hello world. Usually something much longer here.";
NSString *filename = #"working-draft.txt";
NSString *localDir = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
self.localPath = [localDir stringByAppendingPathComponent:filename];
[text writeToFile:self.localPath atomically:YES encoding:NSUTF8StringEncoding error:nil];
self.dbClient = [[DBRestClient alloc] initWithSession:[DBSession sharedSession]];
self.dbClient.delegate = self;
// Start the upload. No upload ID known yet
[self.dbClient uploadFileChunk:nil offset:0 fromPath:self.localPath];
}
}
- (void)restClient:(DBRestClient *)client uploadedFileChunk:(NSString *)uploadId newOffset:(unsigned long long)offset
fromFile:(NSString *)localPath expires:(NSDate *)expiresDate {
NSLog(#"uploadedFileChunk: %#, newOffset: %llu, fromFile: %#, expires: %#", uploadId, offset, localPath, expiresDate);
NSFileManager *fileManager = [NSFileManager defaultManager];
NSDictionary *attrs = [fileManager attributesOfItemAtPath:self.localPath error: NULL];
// in real use, there's probably a dangerous race condition here in checking the size each time, but this is just for demonstration purposes
if (offset >= [attrs fileSize]) {
// all data has been uploaded
NSLog(#"Finishing upload...");
[self.dbClient uploadFile:#"chunked_uploaded_file.txt" toPath:#"/" withParentRev:nil fromUploadId:uploadId];
} else {
// more data to upload
NSLog(#"Continuing upload...");
[self.dbClient uploadFileChunk:uploadId offset:offset fromPath:localPath];
}
}
- (void)restClient:(DBRestClient *)client uploadFileChunkFailedWithError:(NSError *)error {
NSLog(#"uploadFileChunkFailedWithError: %#", error);
// in real use, the app should probably implement some retrying logic here
}
- (void)restClient:(DBRestClient *)client uploadFileChunkProgress:(CGFloat)progress {
NSLog(#"uploadFileChunkProgress: %f", progress);
}