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[SR-15214] corelibs-foundation URLSession spams slow delegates with more messages than they can handle #3204

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TellowKrinkle opened this issue Sep 19, 2021 · 1 comment
Open

[SR-15214] corelibs-foundation URLSession spams slow delegates with more messages than they can handle #3204

TellowKrinkle opened this issue Sep 19, 2021 · 1 comment
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@TellowKrinkle
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Previous ID SR-15214
Radar rdar://problem/83315554
Original Reporter @TellowKrinkle
Type Bug

Attachment: Download

Additional Detail from JIRA
Votes 0
Component/s Foundation
Labels Bug
Assignee None
Priority Medium

md5: 0c8b298e4a170e8fda01043382b14585

Issue Description:

To reproduce: Run the attached swift file

MacOS Foundation seems to implement some sort of backpressure / coalescing mechanism

Result on macOS 11.5.2（20G95）

Received 8192 bytes, totalling 8192 (queue backlog: 0)...
Received 36864 bytes, totalling 45056 (queue backlog: 0)...
Received 45056 bytes, totalling 90112 (queue backlog: 0)...
Received 53248 bytes, totalling 143360 (queue backlog: 0)...
Received 81920 bytes, totalling 225280 (queue backlog: 0)...
Received 77824 bytes, totalling 303104 (queue backlog: 0)...
Received 110592 bytes, totalling 413696 (queue backlog: 0)...
Received 118784 bytes, totalling 532480 (queue backlog: 0)...
Received 139264 bytes, totalling 671744 (queue backlog: 0)...
Received 196608 bytes, totalling 868352 (queue backlog: 0)...
Received 229376 bytes, totalling 1097728 (queue backlog: 0)...
Cancelling!

Result on Linux + Swift 5.4.3-Release

Received 3072 bytes, totalling 3072 (queue backlog: 4)...
Received 1024 bytes, totalling 4096 (queue backlog: 11)...
Received 3072 bytes, totalling 7168 (queue backlog: 24)...
Received 1024 bytes, totalling 8192 (queue backlog: 44)...
Received 3072 bytes, totalling 11264 (queue backlog: 66)...
Received 1024 bytes, totalling 12288 (queue backlog: 69)...
Received 3072 bytes, totalling 15360 (queue backlog: 104)...
Received 1024 bytes, totalling 16384 (queue backlog: 155)...
Received 3072 bytes, totalling 19456 (queue backlog: 220)...
// Trimmed because very long
Received 3072 bytes, totalling 1190912 (queue backlog: 156994)...
Cancelling!
Received 1024 bytes, totalling 1191936 (queue backlog: 156993)...
Cancelling!
Received 3072 bytes, totalling 1195008 (queue backlog: 156992)...
Cancelling!
Received 1024 bytes, totalling 1196032 (queue backlog: 156991)...
Cancelling!
// I'd expect 156991 more messages but I don't want to wait that long

Obviously this won't happen as badly if you don't sleep in your delegate, but I've still experienced huge amounts of pileup with fast internet and a slow computer
@typesanitizer
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@swift-ci create

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 5, 2022
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@TellowKrinkle @typesanitizer