Gehel created this task.
Gehel added projects: serviceops, Wikidata-Query-Service.
Restricted Application added a subscriber: Aklapper.
Restricted Application added a project: Wikidata.

TASK DESCRIPTION
  As an operator of WDQS, I want to ensure that the Updater isn't overloading 
dependent services by limiting max concurrent requests.
  
  Given the recent incident where the WDQS Flink based streaming updater was 
blocked as it seemed to generate too much traffic, we want to enforce 
appropriate limits on the query parallelism it can generate. The implementation 
is already in place, this is just a matter of finding the appropriate 
configuration. This new updater is a lot more efficient than the current one 
(which is the whole point), so it can potentially generate a lot more load.
  
  As a distributed application, this updater has concurrency limits on each 
node (currently, 12 nodes x 6 thread = 72 concurrent requests max). Note that 
this max number is never reached, each nodes does other things than querying 
Wikidata.
  
  In normal operations, the number of requests is limited by the edit rate on 
Wikidata, and whatever limit we set must be sufficient to support that edit 
rate.
  
  During initial data load, the backlog of edits is consumed as fast as 
possible, limited by whatever concurrency we set. This is where having a 
reasonable limit is necessary.
  
  The current updater duplicates requests to wikidata for each node (18 nodes 
at the moment). The new updater centralises this, so we can expect a 18x 
reduction in queries during normal operation once the new updater is pushed to 
production.
  
  AC:
  
  - parallelism limits are agreed on with Service Ops and configured

TASK DETAIL
  https://phabricator.wikimedia.org/T275133

EMAIL PREFERENCES
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To: Gehel
Cc: Gehel, Aklapper, MPhamWMF, wkandek, JMeybohm, CBogen, Akuckartz, Nandana, 
Namenlos314, jijiki, Lahi, Gq86, Lucas_Werkmeister_WMDE, GoranSMilovanovic, 
QZanden, EBjune, merbst, LawExplorer, _jensen, rosalieper, Scott_WUaS, Jonas, 
Xmlizer, jkroll, Wikidata-bugs, Jdouglas, aude, Tobias1984, Manybubbles, 
Mbch331, Dzahn
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