Persisted queue for some integrations causes localStorage to fill up to its maximum amount

[rhianvanesch-sc]

Related to #1200, we've noticed that for some users of our site, the localStorage quota is completely filled up due to one or more persisted queue keys getting very large (5MB in some cases).

We use localStorage for some key functionality, so this means that our site does not work properly for these users, because we're unable to save any data there. The only fix from our side is to contact affected users and guide them through clearing localStorage, but it would be great to fix the root issue.

Some examples of how large these queues are getting - these are the localStorage keys of the affected users, and the size is in bytes:

persisted-queue:v1:{id}:dest-Facebook Pixel:items: 4807343
persisted-queue:v1:{id}:dest-Facebook Pixel:seen: 38336
persisted-queue:v1:{id}:dest-Google AdWords New:items: 4448963
persisted-queue:v1:{id}:dest-Google AdWords New:seen: 17303

persisted-queue:v1:{id}:dest-Facebook Pixel:items: 52094
persisted-queue:v1:{id}:dest-Facebook Pixel:lock: 13
persisted-queue:v1:{id}:dest-LinkedIn Insight Tag:items: 5153997
persisted-queue:v1:{id}:dest-LinkedIn Insight Tag:seen: 15417

Without diving into the code I guess these keys relate to the Persistent Queue feature (docs). I wonder if this queue will fill up indefinitely if these users have any of these integrations blocked, e.g. with an adblocker?

As a fix, is it possible to limit the queue to a more reasonable size?

(I'm reporting this as a separate issue since I think the queue not being cleared is a different problem to the one reported in #1200.)