1778535 - (mozjexl-controlled-rollout) implement controlled rollout code for new versions of mozjexl.js

Status: NEW

(Firefox :: Messaging System, enhancement, P2)

Description

[Dan Mosedale (:dmosedale, :dmose)]

Since mozjexl.jsm is used for targeting in various important critical systems (Nimbus, Firefox Messaging System, Normandy), we can drive the upgrade-risk down lots by making doing a dual deployment and making it observable:

• ship both the new and old interpreters
• set up the main caller of mozjexl.eval() in FilterExpressions.js to call both the old and new interpreters
• if there is a difference, always choose the result from the old interpreter and send telemetry about the mismatch (throw in tests)
• once we stop getting unexpected telemetry, use a nimbus rollout to stop gradually turn off the old interpreter
• once we've hit 100% rollout and things look good, remove the old interpreter from the tree

Comment 1

[Dan Mosedale (:dmosedale, :dmose)]

Attachment: WIP: Bug 1778535 - allow for two JEXL interpreters