Forwarding in case this is of interest.
---------- Forwarded message ---------
From: Guillaume Lederrey <glederrey(a)wikimedia.org>
Date: Thu, Jun 6, 2019 at 7:33 PM
Subject: [Wikidata] Scaling Wikidata Query Service
To: Discussion list for the Wikidata project. <wikidata(a)lists.wikimedia.org>
There has been a number of concerns raised about the performance and
scaling of Wikdata Query Service. We share those concerns and we are
doing our best to address them. Here is some info about what is going
In an ideal world, WDQS should:
* scale in terms of data size
* scale in terms of number of edits
* have low update latency
* expose a SPARQL endpoint for queries
* allow anyone to run any queries on the public WDQS endpoint
* provide great query performance
* provide a high level of availability
Scaling graph databases is a "known hard problem", and we are reaching
a scale where there are no obvious easy solutions to address all the
above constraints. At this point, just "throwing hardware at the
problem" is not an option anymore. We need to go deeper into the
details and potentially make major changes to the current architecture.
Some scaling considerations are discussed in . This is going to take
Reasonably, addressing all of the above constraints is unlikely to
ever happen. Some of the constraints are non negotiable: if we can't
keep up with Wikidata in term of data size or number of edits, it does
not make sense to address query performance. On some constraints, we
will probably need to compromise.
For example, the update process is asynchronous. It is by nature
expected to lag. In the best case, this lag is measured in minutes,
but can climb to hours occasionally. This is a case of prioritizing
stability and correctness (ingesting all edits) over update latency.
And while we can work to reduce the maximum latency, this will still
be an asynchronous process and needs to be considered as such.
We currently have one Blazegraph expert working with us to address a
number of performance and stability issues. We
are planning to hire an additional engineer to help us support the
service in the long term. You can follow our current work in phabricator
If anyone has experience with scaling large graph databases, please
reach out to us, we're always happy to share ideas!
Thanks all for your patience!
Engineering Manager, Search Platform
UTC+2 / CEST
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