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From bugzi...@apache.org
Subject [Bug 50317] Possible error in mod_cache's "Avoiding the Thundering Herd"
Date Wed, 09 Apr 2014 21:55:43 GMT
https://issues.apache.org/bugzilla/show_bug.cgi?id=50317

Jim Riggs <jim@riggs.me> changed:

           What    |Removed                     |Added
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  Attachment #26333|0                           |1
        is obsolete|                            |

--- Comment #6 from Jim Riggs <jim@riggs.me> ---
Created attachment 31503
  --> https://issues.apache.org/bugzilla/attachment.cgi?id=31503&action=edit
2.2 thundering herd fix

The attached patched was discussed and looked at by myself, covener, and mrumph
today at ApacheCon. This fixes the thundering herd problem in 2.2. It also
addresses r572626 (https://issues.apache.org/bugzilla/show_bug.cgi?id=30370)
that created this regression. So, this patch fixes both the original problem in
30370 as well as this issue. It applies only to 2.2; >= 2.3 was fixed in
r1023398.

To summarize: without this patch, 2.2 has NO protection from the thundering
herd, as the stale content is removed before being refreshed. Thus, all
subsequent herd requests have no stale content to serve and flow through to the
backend.

Should the documentation be updated also to alert users to this? That is that
"2.2.x before 2.2.__ is not protected from the thundering herd"?

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