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Uploading big file using Objective-C API V2 very SLOW...
Hello,
recently our app updates the Dropbox related code from API V1 to API V2. Usually we need to transfer files to Dropbox, it is OK for small files, but for video files of size about 1.5 GB the progress is very slow, and often the upload is stopped due to request timeout....
We use the following API calls:
1. Start the upload
[client.filesRoutes uploadSessionStartData:data];
2. Repeatedly upload new chunk of data
[client.filesRoutes uploadSessionAppendV2Data:cursor inputData:chunk];
3. Finish upload for the last chunk
[client.filesRoutes uploadSessionFinishData:cursor commit:info inputData:chunk];
And the log messages are as follows:
2017-01-20 14:25:11.336692 MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0000
2017-01-20 14:25:11.343177MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0000
2017-01-20 14:25:11.349521MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0001
2017-01-20 14:25:11.353344MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0001
// Skip...
2017-01-20 14:25:55.059215MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0003
2017-01-20 14:25:55.070222MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0003
2017-01-20 14:26:17.700571MyApp[19184:6471639] start: bytesWritten = 65536 progress = 0.0003
2017-01-20 14:26:17.704239MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0003
2017-01-20 14:26:34.987083MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0004
2017-01-20 14:26:34.992280MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0004
2017-01-20 14:26:35.005880MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0004
// No data downloaded for about 23 sec
2017-01-20 14:26:58.848907MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0004
2017-01-20 14:26:58.855699MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0004
2017-01-20 14:26:58.871372MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0005
2017-01-20 14:26:58.873328MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0005
2017-01-20 14:27:15.431969MyApp[19184:6471639] start: bytesWritten = 65536 progress = 0.0005
2017-01-20 14:27:15.436307MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0006
2017-01-20 14:27:44.313052MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0006
2017-01-20 14:27:44.318937MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0006
2017-01-20 14:27:44.323024MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0006
2017-01-20 14:27:44.327415MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0006
2017-01-20 14:28:10.012220MyApp[19184:6471639] start: bytesWritten = 65536 progress = 0.0007
2017-01-20 14:28:10.015194 MyApp[19184:6471639] start: bytesWritten = 32768 progress = 0.0007
// Skip...
2017-01-20 14:59:18.994143 MyApp[19184:6471639] __70-[....]_block_invoke [Line 92] start: requestError = DropboxClientError[{
NSError = "Error Domain=NSURLErrorDomain Code=-1001 \"\U8981\U6c42\U903e\U6642\U3002\" UserInfo={NSUnderlyingError=0x17025bb70 {Error Domain=kCFErrorDomainCFNetwork Code=-1001 \"(null)\" UserInfo={_kCFStreamErrorCodeKey=-2102, _kCFStreamErrorDomainKey=4}}, NSErrorFailingURLStringKey=https://api-content.dropbox.com/2/files/upload_session/start, NSErrorFailingURLKey=https://api-content.dropbox.com/2/files/upload_session/start, _kCFStreamErrorDomainKey=4, _kCFStreamErrorCodeKey=-2102, NSLocalizedDescription=\U8981\U6c42\U903e\U6642\U3002}";
}];
2017-01-20 14:59:18.994833 MyApp[19184:6471639] __74-[...]_block_invoke_2 [Line 428] Failed To Upload /Horrible.Bosses.2011.DVDRip.XVID.AC3.HQ.Hive-CM8.avi
Error = DBRequestErrorClient
2017-01-20 14:59:18.995478 MyApp[19184:6475977] [] __tcp_connection_write_eof_block_invoke Write close callback received error: [89] Operation canceled
It can be seen from the log messages that the time the data arrived is not very smooth, and finally the operation is canceld.
My questions:
Is it pure network traffic problem?(Our network is relatively fast.)
Or is there something in API V2's upload API that causes the upload so slow?
Thanks for your attention.
Best regards,
Logan
- Greg-DB
Dropbox Staff
Hi Logan, are you using a chunk size of 32768 bytes? You should probably use something much larger than that, at least 4 MB, or even significantly larger than that.
The optimal size depends on a variety of factors, so you may want to try a few different ones and see what works best for your app. Using a small chunk size can be useful, as it minimizes how much data you need to re-upload for failed requests, and reduces the chance of any particular request of failing, but it causes more overhead. A larger chunk size can reduce the overhead, which can improve overall transfer speed.
- Hi Greg,
thanks for reply!
1. I have tried to pass the chunk of data with size 5 MB and 100 MB, but the result was the same. It seems that the bytesWritten from the progress block is always 32768 and in few cases also 65536, as shown in the log message. How can I modify the data chunk size for each transfer? Currently I use the following code:
NSData *data = [dropboxObj.fileHandle readDataOfLength:length]; // length = 5 MB or 100 MB or other values
uploadTask = [client.filesRoutes uploadSessionStartData:data];
2. Just a few minutes ago I tried to upload again, but there is no message from the progress block, and after one or two minutes the operation is canceled. My network is normal. So I guess there might be something wrong with the connection to Dropbox, or is there still anything in API V2 that I should know
when doing the upload ?
Thanks for your attention!
Logan- Greg-DB
1. The chunk size should just be the size of the data you supply for any given call, and that's what should get reported back in the progress callback, so it's unexpected that you'd still get 32768. Can you share the rest of the relevant code, including the definition of length, the progresc callback definitifion, etc.?
2. That also doesn't sound like the expected behavior. If you share the rest of the code and the steps to reproduce it we'll be happy to look into it.
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