I sometimes get questions about the difference between "web" and "analytics" databases "which one should I use?", I would like to explain in depth the original idea:

Right now there is no difference between them, except they are served by different set of servers; however, if at some point we run out of resources (not happening yet), web databases will be limited in query time (so ok for multiple connections with fast queries) and optimized for no lag, while analytics databases will be limited in the number of simultaneous connections (it is expected that, as queries can take a long time, you only do 1 or 2 long running queries at a time so other can do the same).

Of course, this is the initial idea to try to cover better both kind of usage, feel free to provide feedback on how to use them better.

On Thu, Dec 14, 2017 at 12:58 AM, Bryan Davis <bd808@wikimedia.org> wrote:

The labsdb1003.eqiad.wmnet (aka c3.labsdb) server is no longer serving
*.labsdb requests.

The c3.labsdb service name will continue to point to the
labsdb1003.eqiad.wmnet server for the near future, but replication
will soon stop there and all tables will be made read-only.

User databases on c1.labsdb and c3.labsdb listed at
https://tools.wmflabs.org/tool-db-usage/ will be going away on
2018-01-03. You will need to migrate these to
tools.db.svc.eqiad.wmflabs if you need to save the data.

TL;DR

* Change your tools and scripts to use:
  - "*.web.db.svc.eqiad.wmflabs" (real-time response needed)
  - "*.analytics.db.svc.eqiad.wmflabs" (batch jobs; long queries)
* Replace "*" with either a shard name (e.g. s1) or a wikidb name
  (e.g. enwiki).
* The new servers do not support user created databases/tables because
  replication can't be guaranteed. See T156869 and below for more
  information.
* Migrate your user created tables to tools.db.svc.eqiad.wmflabs
  (also known as tools.labsdb) and JOIN via application space logic
  rather than in-process in the database.

What is changing?

* Wednesday 2017-12-13
** "*.labsdb" service names switched to point at
"*.web.db.svc.eqiad.wmflabs" equivalents.
** User created tables will not be allowed on the new servers.
** "c3.labsdb" still points at labsdb1003.eqiad.wmnet

* Thursday 2017-12-14
** DBAs will stop replication from production hosts to labsdb1003.eqiad.wmnet
** DBAs will make databases on labsdb1003.eqiad.wmnet read-only for all users

* Wednesday 2018-01-03
** labsdb1001.eqiad.wmnet (aka c1.labsdb) will be shutdown permanently
** labsdb1003.eqiad.wmnet (aka c3.labsdb) will be shutdown permanently

Why are we doing this?

See <https://wikitech.wikimedia.org/wiki/Wiki_Replica_c1_and_c3_shutdown>
and <https://phabricator.wikimedia.org/T142807> for a more complete
description of the reasons for these changes.


Bryan (on behalf of the Wikimedia Cloud Services and DBA teams)
--
Bryan Davis              Wikimedia Foundation    <bd808@wikimedia.org>
[[m:User:BDavis_(WMF)]] Manager, Cloud Services          Boise, ID USA
irc: bd808                                        v:415.839.6885 x6855

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