1280196 - Add stable sampling JEXL filter

Status: RESOLVED FIXED

(Firefox :: Normandy Server, defect, P2)

Description

[Michael Cooper [:mythmon]]

Since we are no longer sampling on the server, we need to port stable sampling to the self-repair shim's driver. This will likely take the form of a JEXL filter, used like this:

    [telemetry.userId, normandy.recipe.revision]|stableSample(0.0001)

This would be a filter `stableSample` that takes input of something to hash (in this case, the user id and the recipe revision). It also takes a parameter of the rate to sample at.

The approach the server takes is to hash the inputs, and compare that to the sample rate times 2^256, since it is using a 256 bit hashing function. The code can be seen here: https://github.com/mozilla/normandy/blob/b99cc7134330aa584d51ecab4fa8615ab0e8d071/normandy/recipes/utils.py#L27

Comment 1

[[github robot]]

Commit pushed to master at https://github.com/mozilla/normandy

https://github.com/mozilla/normandy/commit/d3a7bf080441f680c70ab5d022e5ab190ce0989c
Add stable sampling jexl filter

Fixes bug 1280196

Comment 2

[Osmose [:osmose, :mkelly]]

The sampling filter isn't actually usable in JEXL expressions yet.

Comment 3

[[github robot]]

Commit pushed to master at https://github.com/mozilla/normandy

https://github.com/mozilla/normandy/commit/10e8bcb95194d16c2c302100294346725f480ce5
Standardize usage of jexl across the app

Fixes bug 1280196
Fixes bug 1284597