perf(opentelemetry-node): plugin loader search required cache

[blumamir]

Which problem is this PR solving?

• fixes Inefficient looping in PluginLoader "load" function cause new NodeTracerProvider() to take few seconds in serverless framework #1805

Short description of the changes

• in pluginLoader, check if plugins are already required by executing require.resolve once per plugin, and searching for the result in require.cache object in O(1) instead of looping on the entire keys array

[codecov]

Codecov Report

Merging #1807 (58e63d5) into master (5862bc0) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1807      +/-   ##
==========================================
- Coverage   92.46%   92.46%   -0.01%     
==========================================
  Files         173      173              
  Lines        6014     6012       -2     
  Branches     1287     1287              
==========================================
- Hits         5561     5559       -2     
  Misses        453      453              

Impacted Files	Coverage Δ
...trumentation/src/platform/node/old/PluginLoader.ts	93.90% <100.00%> (-0.08%)	⬇️
...telemetry-node/src/instrumentation/PluginLoader.ts	93.75% <100.00%> (-0.08%)	⬇️

[blumamir]

I assume the failing test is due to #1799 (also not passing on master).
Will merge master into the branch once the issue is resolved to fix required checks.

[vmarchaud]

Change need to be made in the instrumentation package too (sorry we are in the process of migrating the loader so there are redundant code)

[blumamir]

Change need to be made in the instrumentation package too (sorry we are in the process of migrating the loader so there are redundant code)

@vmarchaud
thanks for pointing it out.
pushed an update

[obecny]

lgtm, nice finding