[Cloud-announce] Wiki Replicas 2020 Redesign

[Joaquin Oltra Hernandez]

TLDR: Wiki Replicas' architecture is being redesigned for stability and
performance. Cross database JOINs will not be available and a host
connection will only allow querying its associated DB. See [1]
 for
more details.

Hi!

In the interest of making and keeping Wiki Replicas a stable and performant
service, a new backend architecture is needed. There is some impact in the
features and usage patterns.

What should I do? To avoid breaking changes, you can start making the
following changes *now*:
- Update existing tools to ensure queries are executed against the proper
database connection
  - Eg: If you want to query the `eswiki_p` DB, you must connect to the
`eswiki.analytics.db.svc.eqiad.wmflabs` host and `eswiki_p` DB, and not to
enwiki or other hosts
- Check your existing tools and services queries for cross database JOINs,
rewrite the joins in application code
  - Eg: If you are doing a join across databases, for example joining
`enwiki_p` and `eswiki_p`, you will need to query them separately, and
filter the results of the separate queries in the code

Timeline:
- November - December: Early adopter testing
- January 2021: Existing and new systems online, transition period starts
- February 2021: Old hardware is decommissioned

We need your help
- If you would like to beta test the new architecture, please let us know
and we will reach out to you soon
- Sharing examples / descriptions of how a tool or service was updated,
writing a common solution or some example code others can utilize and
reference, helping others on IRC and the mailing lists

If you have questions or need help adapting your code or queries, please
contact us [2]
, or
write on the talk page [3]
.

We will be sending reminders, and more specific examples of the changes via
email and on the wiki page. For more information see [1]
.

[1]: https://wikitech.wikimedia.org/wiki/News/Wiki_Replicas_2020_Redesign
[2]: https://wikitech.wikimedia.org/wiki/Help:Cloud_Services_communication
[3]:
https://wikitech.wikimedia.org/wiki/Talk:News/Wiki_Replicas_2020_Redesign

-- 
Joaquin Oltra Hernandez
Developer Advocate - Wikimedia Foundation
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Re: [Cloud-announce] 2020-11-10 ToolsDB (User databases in Toolforge) read-only downtime

[Brooke Storm]

This will be happening in around 10 minutes. ToolsDB will be read-only until we 
can get a consistent dump to rebuild replication.

Brooke Storm
Staff SRE
Wikimedia Cloud Services
bst...@wikimedia.org 
IRC: bstorm

> On Nov 6, 2020, at 12:12 PM, Brooke Storm  wrote:
> 
> The ToolsDB service suffered a breakage in replication on 2020-10-27. WMCS 
> has tried to restore replication of data, but that has been unsuccessful so 
> far including doing a dump to rebuild replication without downtime.
> At this point, we have a new server waiting to become the replica, but to 
> start the replication process, we need to set the database to read-only for a 
> full dump. This could easily take more than an hour. During that entire time, 
> the database will be read-only.
> 
> We will begin at 1600 UTC and finish when it is done. The database is quite 
> large, but, with it in read-only mode, I hope the backup will not take 
> terribly long.
> 
> Please see https://phabricator.wikimedia.org/T266587 
>  for additional information.
> 
> Brooke Storm
> Staff SRE
> Wikimedia Cloud Services
> bst...@wikimedia.org 
> IRC: bstorm
> 



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