PLATFORM AND VERSION
iOS
Development environment: Xcode 16.2, macOS 15.3.2
Run-time configuration: iOS 15-18
This happens in iOS, and leads to to the hybrid home page showing users as wrongly unauthenticated, since the at cookie is missing. For context, we have a JWT token that is stored in the Keychain, and on app launch, before any WKWebViews are created, we synchronize this to the WKWebsiteDataStore as an at cookie.
We have analytics instrumentation on our websitef to show that WKWebView randomly refuses to send out any cookies.
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The following is a snippet from an explanation to the WebKit Slack:
We are having an issue on iOS, in which WKWebView loads pages (and even subsequent reloads) without any cookies, even though we have stored cookies in WKWebsiteDataStore.default() before hand right after application launch and becoming a key window. We reference this object, store it as a singleton, (as well as a process pool), and then all webview configurations are initialized with the same data store, the same process pool, every call on the main thread. From reading the source code, it seems that if the internal IPC logic fails, the APIs for deleting and setting data records and cookies fail without any feedback in completion handlers.
This bug often happens when returning from the background on iOS after a few hours. Sometimes it happens on cold launches of the app. We have mitigated a similar issue (no cookies being sent) by implementing webViewWebContentProcessDidTerminate and reloading the webview ourselves, we found that whatever webview does to reload if that method is not implemented leads to cookies not being used.
There have been multiple reports of WKWebView losing cookies in recent iOS versions, and we have tried to implement all of the workarounds listed. Setting a maximumAge to the cookies we store, and doing a _ = await websiteDataStore.dataRecords(ofTypes: Set([WKWebsiteDataTypeCookies])) before accessing or modifying websiteDataStore.httpCookieStore
Question: is it safe to work with WKWebsiteDataStore before a WKWebView is added as a view, if so are there any timing considerations? Are there any logs that we can take a look at, this issue is very hard to reproduce, about 2% of our users face it at scale? Is there anything that could be happening within our process (runloop issues, timing) that could be causing this issue?
See multiple reports from other companies that have faced the issue: "Now the Thermonuclear Problem with WKWebViewDataStorage"
https://medium.com/axel-springer-tech/synchronization-of-native-and-webview-sessions-with-ios-9fe2199b44c9
STEPS TO REPRODUCE
They don't exist, because the issue only happens at scale. We just know that no cookies are sent for a small percentage of requests. We believe this to be an issue in which Webkit fails to communicate internally with whatever IPC mechanisms it has.
We have not been able to reproduce this issue consistently. The best we can give is that it happens after a few hours that the app is in the background. This happens regardless of whether the WKWebsiteDataStore is persistent or not, but seems to be much worse when it is persistent. Thus we have disabled persistnet data stores and relied on nonPersistent.
The issue is bad enough that we are trying to move away from relying on cookies for iOS and just use request headers which we can only set on the top level request of WKWebView.
DTS Case-ID: 13154329
