Add the ability to clear cached bids that have expired

[lcorrigall]

Type of issue

Enhancement

Description

If useBidCache is enabled, Prebid.js will cache all bids and never releases them. On SPAs or other long lived pages that refresh ads this can contribute to increased memory usage. Prebid.js should have the ability to remove cached bids that are past their TTL. There are two options:

Function Call

Provide a function like clearExpiredBids that publishers could call in order to remove all bids past their TTL. This would be simpler to implement but require publishers to to call this on their sites.

Automatically

Prebid.js will remove bids past their TTL at some (TBD) periodic time.

Other information

useBidCache documentation
[https://docs.prebid.org/dev-docs/faq.html#does-prebidjs-cache-bids](Prebld.js Bid Caching FAQ)

[patmmccann]

One strategy discussed it a publisher can say at some point 'I dont plan to enableAnalytics'; at which point the event history preserved for this purpose can be released.

[patmmccann]

Another suggestion: flush certain event types, not all analytics events