Besides waiting for the new updater, it may be useful to tell us, what
we as users can do too. It is unclear to me what the problem is. For
instance, at one point I was worried that the many parallel requests to
the SPARQL endpoint that we make in Scholia is a problem. As far as I
understand it is not a problem at all. Another issue could be the way
that we use Magnus Manske's Quickstatements and approve bots for high
frequency editing. Perhaps a better overview and constraints on
large-scale editing could be discussed?
Yet another thought is the large discrepancy between Virginia and Texas
data centers as I could see on Grafana [1]. As far as I understand the
hardware (and software) are the same. So why is there this large
difference? Rather than editing or BlazeGraph, could the issue be some
form of network issue?
[1]
https://grafana.wikimedia.org/d/000000489/wikidata-query-service?panelId=8&fullscreen&orgId=1&from=now-7d&to=now
/Finn
On 14/11/2019 10:50, Guillaume Lederrey wrote:
Hello all!
As you've probably noticed, the update lag on the public WDQS endpoint
[1] is not doing well [2], with lag climbing to > 12h for some servers.
We are tracking this on phabricator [3], subscribe to that task if you
want to stay informed.
To be perfectly honest, we don't have a good short term solution. The
graph database that we are using at the moment (Blazegraph [4]) does not
easily support sharding, so even throwing hardware at the problem isn't
really an option.
We are working on a few medium term improvements:
* A dedicated updater service in Blazegraph, which should help increase
the update throughput [5]. Finger crossed, this should be ready for
initial deployment and testing by next week (no promise, we're doing the
best we can).
* Some improvement in the parallelism of the updater [6]. This has just
been identified. While it will probably also provide some improvement in
throughput, we haven't actually started working on that and we don't
have any numbers at this point.
Longer term:
We are hiring a new team member to work on WDQS. It will take some time
to get this person up to speed, but we should have more capacity to
address the deeper issues of WDQS by January.
The 2 main points we want to address are:
* Finding a triple store that scales better than our current solution.
* Better understand what are the use cases on WDQS and see if we can
provide a technical solution that is better suited. Our intuition is
that some of the use cases that require synchronous (or quasi
synchronous) updates would be better implemented outside of a triple
store. Honestly, we have no idea yet if this makes sense and what those
alternate solutions might be.
Thanks a lot for your patience during this tough time!
Guillaume
[1] https://query.wikidata.org/
[2]
https://grafana.wikimedia.org/d/000000489/wikidata-query-service?orgId=1&from=1571131796906&to=1573723796906&var-cluster_name=wdqs&panelId=8&fullscreen
[3] https://phabricator.wikimedia.org/T238229
[4] https://blazegraph.com/
[5] https://phabricator.wikimedia.org/T212826
[6] https://phabricator.wikimedia.org/T238045
--
Guillaume Lederrey
Engineering Manager, Search Platform
Wikimedia Foundation
UTC+1 / CET
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