WPRGO execrise more of the network stack & more realistic. This is a test change, so this regression is Working as Intended to me.

Can we ignore this "regression" if the metrics are consistent post-migration?

The reason for the increase in loading metrics (e.g. time to first contentful paint) is largely due to the fact that the legacy WPR used only a single cert for all connections. WprGO serves different certs for different connections and Chrome's cert verification takes longer (cert verification cache hit is much less frequent). You can read more in  Issue 756481 .

I have a WIP CL (https://codereview.chromium.org/3003143002/) which will reduce the cert verification time and hopefully the metrics will be closer to what they were before the migration. 

Thanks for the explanation nednguyen@ xunjieli@

I tried to run page_cycler_v2 using the latest Telemetry, with the above-mentioned CL (https://codereview.chromium.org/3003143002/) merged, but failed to load two pages (airbnb.com and flickr.com).

More details are reported in https://bugs.chromium.org/p/chromium/issues/detail?id=762819 

Hi nednguyen@ xunjieli@, recently I found an potential issue in WPR-go server, the 'Date' in response header is the date and time the response was archived in the wprgo file, rather than the date it was generated and sent from the WPR-go server, which may impact the page-loading performance in warm cache case.

I uploaded a CL to address this issue, PTAL.
https://chromium-review.googlesource.com/c/catapult/+/729283

The following revision refers to this bug:
  https://chromium.googlesource.com/catapult/+/b33d83ad5d4f4f59a87d7a68efa50455fc10a76d

commit b33d83ad5d4f4f59a87d7a68efa50455fc10a76d
Author: Lingyun Cai <lingyun.cai@intel.com>
Date: Tue Nov 07 03:33:48 2017

[wpr-go] Ensure 'Date' is updated as current date in response header

In WPR-go server, the 'Date' in response header is the date and time the
response was archived in the wprgo file, rather than the date it was
generated and sent from the WPR-go server. This would make some resources
to be requested again, instead of loading from cache directly in warm
cache case, which may impact user experience and browser performance.

This CL is to make sure 'Date' header is updated as 'current time', and 
add date shift for 'Last-Modified' and 'Expires' headers in WPR-go server.

Bug:  chromium:760422 
Change-Id: I479beff89d67e98c16189847aa9855856130b23c
Reviewed-on: https://chromium-review.googlesource.com/729283
Reviewed-by: Tom Bergan <tombergan@chromium.org>
Commit-Queue: Tom Bergan <tombergan@chromium.org>

[modify] https://crrev.com/b33d83ad5d4f4f59a87d7a68efa50455fc10a76d/web_page_replay_go/src/webpagereplay/proxy_test.go
[modify] https://crrev.com/b33d83ad5d4f4f59a87d7a68efa50455fc10a76d/web_page_replay_go/src/webpagereplay/proxy.go

The following revision refers to this bug:
  https://chromium.googlesource.com/catapult/+/564e33d345ee080be36ad0e6b6107afbcd09df4d

commit 564e33d345ee080be36ad0e6b6107afbcd09df4d
Author: Nghia Nguyen <nednguyen@google.com>
Date: Tue Nov 07 14:06:23 2017

Update wprgo binaries to latest version

This is follows up of the change https://chromium-review.googlesource.com/c/catapult/+/729283
which update header sent out by WPRGO.

This CL is made by executing ./telemetry/bin/update_wpr_go_binary script 

Bug:  chromium:760422 
Change-Id: If880da553b06c685ace34d9c7813292170634d30
Reviewed-on: https://chromium-review.googlesource.com/756793
Commit-Queue: Helen Li <xunjieli@chromium.org>
Reviewed-by: Helen Li <xunjieli@chromium.org>

[modify] https://crrev.com/564e33d345ee080be36ad0e6b6107afbcd09df4d/telemetry/telemetry/internal/binary_dependencies.json

Issue has not been modified or commented on in the last 365 days, please re-open or file a new bug if this is still an issue.

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