Waterfall not showing "Early Hints" Section in private instance

[Shubham_Singh]

We have a wpt server running in private instance, deployed with master branch. We want the Early hints section from waterfall in our private instance. But it is not showing up there.
We also tried running release branch and cherry-pick early hint code change, but no luck.

We tried running the same site in official WPT and it is showing up there. Want to understand if there is any configuration we have to do to get this feature?

Official WPT log: walmart.com : Chrome...rginia USA - EC2 - WebPageTest Details

Private instance:

[pmeenan]

Are you sure that there are early hints from the server you are connecting to? It’s not uncommon for a private instance to point to a different server than external traffic if it is within your network (maybe not going to the CDN)?

I’m assuming the agent machine has an up-to-date Chrome but that would also be worth checking.

Capturing a netlog as part of the test should show if there are any early hints being sent.

[Shubham_Singh]

1. Verified that early hint is present in the private instance from netlog.
   
   

t=12823 [st= 325]          HTTP_TRANSACTION_READ_EARLY_HINTS_RESPONSE_HEADERS
                           --> HTTP/1.1 103
                               link: <https://i5.walmartimages.com>;rel=preconnect,<https://i5.walmartimages.com/dfw/63fd9f59-397c/135dd224-4517-49f9-9614-fc46d13dee3a/v2/en-US/_next/static/css/0baf6e27c6f86085.css>;rel=preload;as=style,<https://i5.walmartimages.com/dfw/63fd9f59-a78c/fcfae9b6-2f69-4f89-beed-f0eeb4237946/v1/BogleWeb_subset-Regular.woff2>;rel=preload;as=font;type=font/woff2;crossorigin,<https://i5.walmartimages.com/dfw/63fd9f59-a78c/fcfae9b6-2f69-4f89-beed-f0eeb4237946/v1/BogleWeb_subset-Bold.woff2>;rel=preload;as=font;type=font/woff2;crossorigin,<https://i5.walmartimages.com/seo/STGAubron-Gaming-Desktop-PC-Intel-Core-i7-10700KF-5-1G-16G-DDR4-1T-SSD-GeForce-RTX-2060-Super-8G-GDDR6-600M-WiFi-BT-5-0-RGB-Fan-x-7-RGB-Keyboard-Mous_a47694d9-12e3-4378-add6-82a6dca9bd91.9d0a32ca2f4f65d36f990877afb21990.jpeg?odnHeight=612&odnWidth=612&odnBg=FFFFFF>;rel=preload;as=image;fetchpriority=high

2. Chrome is on version: v119.0.6045.200
   
   

[pmeenan]

If you look at the “Raw Details” tab in the request details do you see an entry for “early_hint_headers”?

If the entry is in the json but not in the UI then the issue is on the server/UI side. If the entry is midding from the json then the issue is with the test agent.

[Shubham_Singh]

(I probably should have mentioned it before)
We are using Windows server for wptagent. We tested it with a linux agent and it is working there. Is this feature not for Windows agent servers? We are also facing an issue with filmstrip on windows agent [raised here](which is not in the case of linux agent).

Private instance with linux agent:

[pmeenan]

That’ll do it. The agent code was updated to handle netlog events in a different way a few years back when the trace netlog events broke but only Linux and MacOS were updated so Windows request timings and details won’t be as accurate as the other platforms.

The relevant code is here.

For Windows to work, someone would need to add (and test) the logic to stream the netlog through a pipe (or something similar).

[Shubham_Singh]

only Linux and MacOS were updated so Windows request timings and details won’t be as accurate as the other platforms.

Thanks for the info. This should be mentioned somewhere in the doc, if not already.