fix: Release backlog memory when features are blocked by RUM

[cwli24]

Plug a memory leak in Session Trace and other features. When entitlement or enable flag from RUM request returns a 0 for a feature, the agent will now release the reference to the events buffer under that feature so it can be garbage collected.

Overview

The pre-load cycle of the agent sets up listeners and buffers events in a backlog and an internal handlers object to be flushed and processed after the page loads. It was discovered that if the RUM call getting made post-load returns a 0 for an applicable feature, those things are never cleared for such feature. This caused the backlog for instance to indefinitely hold onto events awaiting processing, consuming memory. This fix will flush those events in such cases when the features are not activated via the deregisterDrain call made by each.

Related Issue(s)

https://new-relic.atlassian.net/browse/NR-284960
This issue was also seen in other features and have been addressed together.

Testing

New e2e on -b *:

[github-actions]

Asset Size Report

Merging this pull request will result in the following asset size changes:

Agent	Asset	Previous Size	New Size	Diff
lite	loader	34.16 kB / 11.9 kB (gzip)	34.25 kB / 11.92 kB (gzip)	0.26% / 0.16% (gzip)
lite	async-chunk	50.09 kB / 16.18 kB (gzip)	50.09 kB / 16.18 kB (gzip)	0% / 0% (gzip)
pro	loader	54.83 kB / 18.55 kB (gzip)	54.92 kB / 18.57 kB (gzip)	0.16% / 0.11% (gzip)
pro	async-chunk	96.73 kB / 28.99 kB (gzip)	96.73 kB / 28.99 kB (gzip)	0% / 0% (gzip)
spa	loader	62.77 kB / 20.97 kB (gzip)	62.86 kB / 21 kB (gzip)	0.14% / 0.14% (gzip)
spa	async-chunk	111.84 kB / 33.37 kB (gzip)	111.84 kB / 33.37 kB (gzip)	0% / 0% (gzip)
lite-polyfills	loader	127.79 kB / 41.22 kB (gzip)	127.83 kB / 41.24 kB (gzip)	0.03% / 0.04% (gzip)
lite-polyfills	async-chunk	63.99 kB / 18.45 kB (gzip)	63.99 kB / 18.45 kB (gzip)	0% / 0% (gzip)
pro-polyfills	loader	150.17 kB / 47.51 kB (gzip)	150.21 kB / 47.54 kB (gzip)	0.03% / 0.05% (gzip)
pro-polyfills	async-chunk	116.73 kB / 31.22 kB (gzip)	116.73 kB / 31.22 kB (gzip)	0% / 0% (gzip)
spa-polyfills	loader	158.37 kB / 49.67 kB (gzip)	158.41 kB / 49.69 kB (gzip)	0.03% / 0.04% (gzip)
spa-polyfills	async-chunk	133.71 kB / 35.92 kB (gzip)	133.71 kB / 35.92 kB (gzip)	0% / 0% (gzip)

[github-actions]

Last ran on July 09, 2024 11:59:53 CDT
Checking merge of (d6f1e8d) into main (3d815a3)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.63%. Comparing base (3d815a3) to head (c4d8ba5).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1102   +/-   ##
=======================================
  Coverage   87.62%   87.63%           
=======================================
  Files         162      162           
  Lines        7259     7263    +4     
  Branches     1423     1426    +3     
=======================================
+ Hits         6361     6365    +4     
  Misses        782      782           
  Partials      116      116           

Flag	Coverage Δ
unit-tests	76.44% <100.00%> (+<0.01%)	⬆️

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[patrickhousley]

I did some manual testing locally. Here are my findings.

Looks like the backlog is getting cleared correctly when SR and ST are enabled in the agent config but RUM responds with a 0.