RKemper added a comment.
Some quick pros/cons of two possible approaches to getting the SLI metrics:
approach #1 is to run a query or set of queries per-dc at a certain frequency,
approach #2 is just to run a query on each host at a certain frequency
* Approach #1: Hit `wdqs.svc.{codfw,eqiad}.wmnet`
-------------------------------------------------
Pros
----
- Routing through pybal so we automatically ignore depooled hosts
- Covers a broader class of failures than just simply running queries on each
host
- Maps a bit better to the actual user experience (ie if 10% of hosts are
down)
Cons
----
- Adds some complexity in terms of understanding how routing works (ex: do we
have to worry about geoDNS [ie that we might end up unintentionally always
routing to the same host] or is that [geoDNS] "higher up" in the stack and
therefore not relevant?)
* Approach #2: Just run a simple query on each host in the fleet
----------------------------------------------------------------
Pros
----
- Easy to reason about
- Constantly testing each host individually, so we have host-level granularity
Cons
----
- For generating the SLI itself, for each host need to filter out time range
in which they're depooled
- Not as pure of a gauge of user experience as compared to hitting
`wdqs.svc.{codfw,eqiad}.wmnet`
---
Personally I lean a bit towards #1 because it intuitively seems to measure
the user experience better, but I do have significant gaps in my understanding
of our network / request routing stack so there's perhaps more unknowns
TASK DETAIL
https://phabricator.wikimedia.org/T313751
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To: RKemper
Cc: MPhamWMF, Aklapper, Astuthiodit_1, AWesterinen, karapayneWMDE, Invadibot,
maantietaja, CBogen, ItamarWMDE, Akuckartz, Nandana, Namenlos314, Lahi, Gq86,
Lucas_Werkmeister_WMDE, GoranSMilovanovic, QZanden, EBjune, merbst,
LawExplorer, _jensen, rosalieper, Scott_WUaS, Jonas, Xmlizer, jkroll,
Wikidata-bugs, Jdouglas, aude, Tobias1984, Manybubbles, Mbch331
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