Tilman - done, but apologies for the not very useful link formatting on
that tool tip. I'll file a phab bug to improve that. By the way,
annotations for the pageview data can be collaboratively edited:
(unlocked for
now, we'll limit access if we start having problems).
On Wed, Aug 26, 2015 at 6:22 PM, Tilman Bayer <tbayer(a)wikimedia.org> wrote:
Thanks for the update! And BTW kudos also for marking
these as
annotations in the dashboard at
https://vital-signs.wmflabs.org/
(maybe link the incident reports from there as well?)
On Wed, Aug 26, 2015 at 1:26 PM, Andrew Otto <aotto(a)wikimedia.org> wrote:
Hi all,
Now that we’ve had a little space to analyze the problem, I wanted to
call
out a recent webrequest data loss issue that we
experienced on two
separate
occasions.
We attempted to upgrade to Kafka 0.8.2.1, and it wasn’t until the second
attempt that we actually found the problem. Kafka 0.8.2.1 ships with a
buggy version of Snappy[1] that causes messages to not be compressed
properly. This caused a ~4x increase network and disk I/O around the
cluster all at once.
We’ve documented the incidents and the occasions of significant data loss
here:
https://wikitech.wikimedia.org/wiki/Incident_documentation/20150803-Kafka
https://wikitech.wikimedia.org/wiki/Incident_documentation/20150810-Kafka#C…
https://wikitech.wikimedia.org/wiki/Analytics/Data/Webrequest
This loss will affect the output of pagecount* and pageview datasets, as
well as other webrequest generated statistics. Please consider
statistics
> that are generated from webrequest data using the following UTC hours
> unreliable:
>
> 2015-08-03T18:00 - 2015-08-03T23:00
> 2015-08-10T15:00 - 2015-08-10T21:00
> 2015-08-11T17:00 - 2015-08-11T18:00
>
> Many apologies for any inconvenience this causes. We’ve learned a lot
> during this turmoil, and have a lot of ideas on how to hopefully prevent
> this from happening in the future, and also how to reduce loss and
> complexity if and when it does. The analytics engineering team will be
> doing a post mortem on this soon, in which we will document these ideas.
>
> Thanks,
> -Andrew Otto
>
> [1]
https://issues.apache.org/jira/browse/KAFKA-2189
> _______________________________________________
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>
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>
--
Tilman Bayer
Senior Analyst
Wikimedia Foundation
IRC (Freenode): HaeB
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