1

Issue

Some resources from the CDN take minutes to load because, according to Chrome devtools, are "stalled". This happens only on Chrome and only the first time I open the page in an incognito window. This happened since when we enabled HTTP2 on the CDN. Rolling back to HTTP1.1 solved the issue.

Scenario

These resources are loaded from 3 different domains served from CloudFront. Some resources are loaded as soon as possible, then some others are stalled for more than a minute (in same cases several minutes) while there's nothing else going on in the network tab. Eventually, these other resources are loaded and everything else as well. See screenshots:

Network tab 1 Network tab 2

Only on Chrome, only over HTTP2 and only after some resources from the same domain are loaded successfully. What can be the issue?

  • Could this stalling behavior be related to chrome locking cache whilst re-requesting the resources? What is the result of waterfall with cache-control:no-store? or Cache Disabled? – Max Coates May 24 '17 at 15:37
  • What do the CloudFront logs indicate? – Michael - sqlbot May 25 '17 at 0:27
  • Unfortunately we had the logging off – Alessandro May 25 '17 at 13:40
  • Turn on the logging and test again. :) The timing and durations should help you understand whether the stall is before, during, or after CloudFront processed the request. Importantly, if the origin request fails, CloudFront will send two more attempts at 30 second intervals (default value, they recently made this timimg configurable) and will return the response if it gets one. It seems like what you're seeing could potentially indicate that the third attempt is finally succeeding. You said "several minutes," but I don't see examples of that. – Michael - sqlbot May 25 '17 at 13:47

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