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From "Patrick Lucas (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-5843) Website/docs missing Cache-Control HTTP header, can serve stale data
Date Sun, 19 Feb 2017 21:15:44 GMT
Patrick Lucas created FLINK-5843:

             Summary: Website/docs missing Cache-Control HTTP header, can serve stale data
                 Key: FLINK-5843
                 URL: https://issues.apache.org/jira/browse/FLINK-5843
             Project: Flink
          Issue Type: Bug
          Components: Project Website
            Reporter: Patrick Lucas

When Flink 1.2.0 was released, I found that the [Flink downloads page|https://flink.apache.org/downloads.html]
was out-of-date until I forced my browser to refresh the page. Upon investigation, I found
that the principle pages of the website are served with only the following headers that relate
to caching: Date, Last-Modified, and ETag.

Since there is no Cache-Control header (or the older Expires or Pragma headers), browsers
are left to their own heuristics as to how long to cache this content, which varies browser
to browser. In some browsers, this heuristic is 10% of the difference between Date and Last-Modified
headers. I take this to mean that, if the content were last modified 90 days ago, and I last
accessed it 5 days ago, my browser will serve a cached response for a further 3.5 days (10%
* (90 days - 5 days) = 8.5 days, 5 days have elapsed leaving 3.5 days).

I'm not sure who at the ASF we should talk to about this, but I recommend we add the following
header to any responses served from the Flink project website or official documentation website\[1]:

{code}Cache-Control: max-age=0, must-revalidate{code}

(Note this will only make browser revalidate their caches; if the ETag of the cached content
matches what the server still has, the server will return 304 Not Modified and omit the actual

\[1] Both the website hosted at flink.apache.org and the documentation hosted at ci.apache.org
are affected.

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