Set timeout for Background upload task

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Created Dec ’20

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We upload videos form our application, the video upload starts in the foreground but the requirement is to support upload in the background as well. Followed the all steps that I gathered and understood reading in various article to support the upload in background as well.

We have video content as data in the request - create an upload task which is delegate based. Then we write the whole request content into a file and pass to the upload task to upload.
Use background session configuration.

Now, my problem is sometimes I see the progress of upload going upto 100% then re-starting. On debugging further found that the timeout was happening on the server. And based on default timeout 60s it tries to re-start.

How do I change the timeout value, setting the timeout interval on session does not seem to work. It works only it set to less than 60, trying to set to great than 60 doesn’t work.

I tried setting both timeoutIntervalForRequest
And timeoutIntervalForResource

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Answer 1

mutluhan_ OP

Oct ’21

I'm having exact same issue, any update on your situation ?

0

Answer 2

DTS Engineer OP

Apple

Oct ’21

I'm having exact same issue

In a background session? Or a standard session?

And if it’s in a background session, do you see the same problem if you (temporarily, just for debugging purposes) switch to using a standard session?

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

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Answer 3

mutluhan_ OP

Oct ’21

In a background session (default session works as expected).

My background requests just resending every 65-70 ish seconds. I'm trying to upload some files to a server as post request using multipart body.

I've set my timeoutIntervalForRequest = 100 (timeoutIntervalForRequest has no effect, that's correct behavior i believe) in session configuration and 100 in my URLRequest's timeoutInterval property for good measure

But it seems like system is ignoring these values. (setting timeoutIntervalForResource is works as expected, when timeoutIntervalForResource value reached completion handler is called correctly).

I can see upload requests resent after 65 second in proxyman. And system will only listen responses for the last one sent, thus im stuck in a retry loop until timeoutIntervalForResource reached.

note: All requests will eventually returns successfully from server, and other clients can upload large amounts of data for 5 minutes so server-side issue is unlikely.

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Answer 4

DTS Engineer OP

Apple

Oct ’21

I'm trying to upload some files to a server as post request using multipart body.

To be clear, you’ve serialised this multipart body to a file, right? That is, you’re calling -uploadTaskWithRequest:fromFile: or its Swift equivalent?

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

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Answer 5

mutluhan_ OP

Oct ’21

Yes i serialized it to a file

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Answer 6

DTS Engineer OP

Apple

Oct ’21

Yes i serialized it to a file

Thanks for confirming that.

I don’t have a ready explanation for the behaviour you’re seeing. The next step is to look at the device logs to see what’s happening inside that background session. You may be able to make some progress with the new HTTP-level supports in Instruments. For details, see WWDC 2021 Session 10212 Analyze HTTP traffic in Instruments. If not, the next step is to go grovelling through the system log )-:

At this point I think it might be best to open a DTS tech support incident so that either Matt or I can help you one-on-one.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

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Answer 7

mutluhan_ OP

Nov ’21

Hi Quinn,

I enabled CFNETWORK_DIAGNOSTICS and inspected the logs.

At the beggining of the request i can clearly see the timeouts set correctly in the paranthesis.

default	23:00:36.916759+0300	nsurlsessiond	Task <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3> resuming, timeouts(300.0, 300.0) QOS(0x19) Voucher <OS_voucher: 0x7f94a61086e0>

and the request sent without any error logging

default	23:00:37.264507+0300	nsurlsessiond	Task <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3> sent request, body S 104857891

and after 65 second

error	23:01:42.265141+0300	nsurlsessiond	Connection 27: timed out with error(4:-2104)
error	23:01:42.265310+0300	nsurlsessiond	Connection 27: encountered error(4:-2104)
default	23:01:42.265377+0300	nsurlsessiond	Connection 27: cleaning up

so this error(4:-2104) could be usefull but i dont know what it is

and more errors and logs about retry

default	23:01:42.265482+0300	nsurlsessiond	[C27 A6343939-91A0-4B91-9802-215D32D4A003 [REDACTED]:443 tcp, url hash: c6b386c1, traffic class: 200, expected workload: 1000, tls, indefinite] cancel
default	23:01:42.265688+0300	nsurlsessiond	[C27 A6343939-91A0-4B91-9802-215D32D4A003 [REDACTED]:443 tcp, url hash: c6b386c1, traffic class: 200, expected workload: 1000, tls, indefinite] cancelled
	[C27.1 B47D4C9A-ACE2-4C49-96C8-34C455DA4F13 127.0.0.1:54234<->127.0.0.1:9090]
	Connected Path: satisfied (Path is satisfied), viable, interface: lo0
	Duration: 65.346s, TCP @0.007s took 0.000s, TLS 1.3 took 0.013s
	bytes in/out: 1870/105001218, packets in/out: 2/8268, rtt: 0.000s, retransmitted bytes: 0, out-of-order bytes: 0
default	23:01:42.266462+0300	nsurlsessiond	nw_flow_disconnected [C27.1 127.0.0.1:9090 cancelled socket-flow ((null))] Output protocol disconnected
default	23:01:42.266762+0300	nsurlsessiond	nw_connection_report_state_with_handler_on_nw_queue [C27] reporting state cancelled
default	23:01:42.267240+0300	nsurlsessiond	Connection 27: done
default	23:01:42.267585+0300	nsurlsessiond	Task <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3> can retry(N) with reason(2) for error [4:-2104]
default	23:01:42.267621+0300	nsurlsessiond	Task <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3> RELEASING power assertion.
error	23:01:42.267673+0300	nsurlsessiond	Task <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3> HTTP load failed, 104859603/0 bytes (error code: -1001 [4:-2104])
default	23:01:42.268085+0300	nsurlsessiond	Task <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3> summary for task failure {transaction_duration_ms=65350, response_status=0, connection=27, protocol="http/1.1", domain_lookup_duration_ms=0, connect_duration_ms=0, secure_connection_duration_ms=0, request_start_ms=22, request_duration_ms=324, response_start_ms=0, response_duration_ms=0, request_bytes=104859603, response_bytes=0, cache_hit=0}
error	23:01:42.268480+0300	nsurlsessiond	Task <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3> finished with error [-1001] Error Domain=NSURLErrorDomain Code=-1001 "The request timed out." UserInfo={_kCFStreamErrorCodeKey=-2104, NSUnderlyingError=0x7f94a610bda0 {Error Domain=kCFErrorDomainCFNetwork Code=-1001 "(null)" UserInfo={NSErrorPeerAddressKey=<CFData 0x7f94a60267c0 [0x7fff8004b340]>{length = 16, capacity = 16, bytes = 0x100223827f0000010000000000000000}, _kCFStreamErrorCodeKey=-2104, _kCFStreamErrorDomainKey=4}}, _NSURLErrorFailingURLSessionTaskErrorKey=LocalUploadTask <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3>, _NSURLErrorRelatedURLSessionTaskErrorKey=(
    "LocalUploadTask <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3>"
), NSLocalizedDescription=The request timed out., NSErrorFailingURLStringKey=https://[REDACTED]/s3/upload-file, NSErrorFailingURLKey=https://[REDACTED]/s3/upload-file, _kCFStreamErrorDomainKey=4}
default	23:01:42.268615+0300	nsurlsessiond	NDSession <FD814BB3-5B2C-4D3A-9526-F250F73C2029> Task <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3> for client [REDACTED]will be retried after error Error Domain=NSURLErrorDomain Code=-1001 "The request timed out." UserInfo={_kCFStreamErrorCodeKey=-2104, NSUnderlyingError=0x7f94a610bda0 {Error Domain=kCFErrorDomainCFNetwork Code=-1001 "(null)" UserInfo={NSErrorPeerAddressKey=<CFData 0x7f94a60267c0 [0x7fff8004b340]>{length = 16, capacity = 16, bytes = 0x100223827f0000010000000000000000}, _kCFStreamErrorCodeKey=-2104, _kCFStreamErrorDomainKey=4}}, _NSURLErrorFailingURLSessionTaskErrorKey=LocalUploadTask <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3>, _NSURLErrorRelatedURLSessionTaskErrorKey=(
    "LocalUploadTask <5C4414F6-6D5B-46D0-ACBA-E220B2607F14>.<3>"

after that request sent again and timed out again sent again... basically stucks in a loop.

so client thinks the request timed out at 65 seconds altough it has set the timeouts as 300 seconds correctly. And when i inspected http traffic at T+65 seconds server did not send any response or timeout.

PS: some addresses in logs are redacted by me

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Answer 8

DTS Engineer OP

Apple

Nov ’21

so this error(4:-2104) could be usefull but i dont know what it is

Domain 4 is kCFStreamErrorDomainHTTP. See this post (I knew that’d come in handy! :-).

Error -2104 in that domain is not public, but I managed to track it down and it translates to ‘the socket stream watchdog timer fired’.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

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Answer 9

mutluhan_ OP

Nov ’21

Thanks for the information

‘the socket stream watchdog timer fired’.

Now i believe timeouts sets correctly and some watchdog timer blocks the background upload task after 65 seconds. Now it is looking more like an undocumented behavior. Any idea how to circumvent this ?

now i found same error in an old stackoverflow post https://stackoverflow.com/questions/30597905/afnetworking-background-downloads-and-watchdog-timer

nsurlsessiond[6810] <Notice>: SocketStream watchdog timer fired after 65.000000 seconds of inactivity. Timing out the connection.

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Answer 10

DTS Engineer OP

Apple

Nov ’21

Any idea how to circumvent this ?

No, I’m out of ‘obvious’ ideas, which is why I wrote this in my previous post:

At this point I think it might be best to open a DTS tech support incident so that either Matt or I can help you one-on-one.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

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