Bug 197010

Summary: Safari doesn't preconnect to origin when using rel="preconnect dns-prefetch"
Product: WebKit Reporter: Andy Davies <ad>
Component: Page LoadingAssignee: Nobody <webkit-unassigned>
Status: NEW    
Severity: Normal CC: ad, ap, beidson, cdumez, dmdabbs, koivisto, nicolas, paulirish, rik, webkit-bug-importer, yoav, youennf
Priority: P2 Keywords: InRadar
Version: Safari Technology Preview   
Hardware: Mac   
OS: macOS 10.14   
Attachments:
Description Flags
Test page with preconnect and dns-prefetch
none
Test page with just preconnect resource hint
none
Single link element with rel=preconnect and then rel=dns-prefetch
none
Single link element with rel=dns-prefetch and then rel=preconnect none

Andy Davies
Reported 2019-04-17 07:18:07 PDT
Created attachment 367623 [details] Test page with preconnect and dns-prefetch Safari doesn't preconnect to an origin if both the preconnect and dns-prefetch hints are included in the same rel attribute e.g. <link rel="preconnect dns-prefetch" href="https://www.wikipedia.org/"> I've used this pattern in the past as a graceful degradation for browsers that didn't support preconnect Tests both using WebPageTest and Safari Inspector using the two attached pages - when the preconnect is successfully made a message appears in the Inspector Console Work around is to specify the resource hints separately
Attachments
Test page with preconnect and dns-prefetch (693 bytes, text/html)
2019-04-17 07:18 PDT, Andy Davies 		no flags
Details
Test page with just preconnect resource hint (665 bytes, text/html)
2019-04-17 07:18 PDT, Andy Davies 		no flags
Details
Single link element with rel=preconnect and then rel=dns-prefetch (699 bytes, text/html)
2019-04-18 13:44 PDT, Andy Davies 		no flags
Details
Single link element with rel=dns-prefetch and then rel=preconnect (699 bytes, text/html)
2019-04-18 13:45 PDT, Andy Davies 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
Andy Davies
Comment 1 2019-04-17 07:18:45 PDT
Created attachment 367624 [details] Test page with just preconnect resource hint
Andy Davies
Comment 2 2019-04-17 07:32:46 PDT
Should have also mentioned that this pattern works in Chrome
Alexey Proskuryakov
Comment 3 2019-04-18 09:54:42 PDT
Looking at the code, it looks like we don't support multiple values in "rel" at all. We do seem to support multiple rel attributes though. Andy, can you try 'rel="preconnect" rel="dns-prefetch"'?
Radar WebKit Bug Importer
Comment 4 2019-04-18 09:54:59 PDT
<rdar://problem/50018906>
Andy Davies
Comment 5 2019-04-18 13:44:33 PDT
Created attachment 367746 [details] Single link element with rel=preconnect and then rel=dns-prefetch
Andy Davies
Comment 6 2019-04-18 13:45:15 PDT
Created attachment 367747 [details] Single link element with rel=dns-prefetch and then rel=preconnect
Andy Davies
Comment 7 2019-04-18 13:51:17 PDT
Two new test pages attached where the link element has multiple rel attributes <link rel="dns-prefetch" rel="preconnect" href="https://www.wikipedia.org/"> <link rel="preconnect" rel="dns-prefetch" href="https://www.wikipedia.org/"> In the case where the preconnect rel attribute comes first then Safari preconnects - get message in the console to indicate it, and the WebPageTest waterfall is missing the connection setup (which is normal for Safari when it preconnects) dns-prefetch then preconnect - https://www.webpagetest.org/result/190418_WQ_58c2423b8532c6e12e73677b22a2cffe/ preconnect then dns-prefetch https://www.webpagetest.org/result/190418_15_a09ce74e9616ee5555cc5faaba33cb3c/ For comparison Chrome preconnects in both test cases (preconnect in Firefox appears broken ATM) https://www.webpagetest.org/result/190418_8B_09a0743914357f1ada40740a43065085/ https://www.webpagetest.org/result/190418_XT_62b65003d8ea2a6db70a110aaa84e51f/
dmdabbs
Comment 8 2019-07-26 11:58:20 PDT
Resource Hints can also be signaled by HTTP headers with multiple rel types. Is that properly supported as well?
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