[Webkit-unassigned] [Bug 185780] forums.swift.org doesn't render in STP 56

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=185780

--- Comment #4 from Jon <jon at jonshier.com> ---
Only plugins are 1Blocker and 1Password. I turned off 1Blocker before reporting the bug, there was no change. I never tried another user.

Investigating this a bit more and I'm pretty sure it's not specific to forums.swift.org (though that's where I see it most often). Sorry about that. 

However, I do have a hypothesis. 

I recently started observing similar behavior for superuser.com. STP would start the load but would just seem to hang. Looking in the inspector it seemed that one of the site resource loads was hanging (in this case, for the primary.css file). On forums.swift.org, this was one or more of the JS files. I thought it was a transitory network issue with forums.swift.org until I saw it again today with superuser.com.

In Console, attempting to load superuser.com creates many logs, but I found the logs for com.apple.WebKit.Networking most interesting. It seems that most of the requests result in some logging like this: 

default 00:36:00.951220 -0400   com.apple.WebKit.Networking     0x10dbbc000 - NetworkResourceLoader::start: Checking cache for resource (pageID = 18, frameID = 1, resourceID = 16, isMainResource = 1, isSynchronous = 0)
default 00:36:00.951297 -0400   com.apple.WebKit.Networking     0x10dbbc000 - NetworkResourceLoader::retrieveCacheEntry: Resource not in cache (pageID = 18, frameID = 1, resourceID = 16, isMainResource = 1, isSynchronous = 0)
default 00:36:00.951321 -0400   com.apple.WebKit.Networking     0x10dbbc000 - NetworkResourceLoader::startNetworkLoad: (pageID = 18, frameID = 1, resourceID = 16, isMainResource = 1, isSynchronous = 0)
default 00:36:00.951466 -0400   com.apple.WebKit.Networking     0x10dbbc000 - NetworkResourceLoader::startNetworkLoad: (pageID = 18, frameID = 1, resourceID = 16, description = <__NSCFLocalDataTask: 0x7fdf3224eb70>{ taskIdentifier: 203 } { running })

I'm not familiar with how this process works, but there did seem to be a correlation between the number of tasks I saw this logging for, and the number of successfully loaded resources. For task 203 I later saw these messages:

default 00:36:00.951812 -0400   com.apple.WebKit.Networking     Task <B8500B17-DF78-4AA0-80E5-7F7AC4CFB030>.<203> now using Connection 72
default 00:36:00.952123 -0400   com.apple.WebKit.Networking     Task <B8500B17-DF78-4AA0-80E5-7F7AC4CFB030>.<203> sent request, body N
default 00:36:01.011952 -0400   com.apple.WebKit.Networking     Task <B8500B17-DF78-4AA0-80E5-7F7AC4CFB030>.<203> received response, status 200 content K
default 00:36:01.037768 -0400   com.apple.WebKit.Networking     Task <B8500B17-DF78-4AA0-80E5-7F7AC4CFB030>.<203> response ended

However, interspersed with these messages were messages for a task 204, which never logged the earlier NetworkResourceLoader messages. Instead, I this for that task:

default 00:36:00.952070 -0400   com.apple.WebKit.Networking     Task <01EF60AF-89A0-40EF-ACDC-63384C33E60E>.<204> now using Connection 1
default 00:36:00.952131 -0400   com.apple.WebKit.Networking     Task <01EF60AF-89A0-40EF-ACDC-63384C33E60E>.<204> sent request, body N

And then nothing more, until a minute later, when this was logged:

error   00:37:01.918511 -0400   com.apple.WebKit.Networking     Task <01EF60AF-89A0-40EF-ACDC-63384C33E60E>.<204> finished with error - code: -1001

It seems suspicious to me that there were no logs for the loader creating this task, and that it tried to use connection 1. But even now, 20 minutes after I start the load of superuser.com, it's still going in the inspector, the load of primary.css having never completed while I wrote this message. I'm also guessing that my load of forums.swift.org from a webarchive allowed the resource loader to properly see some cached resourced or otherwise was able to reset whatever code path was causing the hang.

If none of this is plausible, let me know what else you'd like to see for the hangs I'm observing.

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