[improve][fn] Optimize Function Worker startup by lazy loading and direct zip/bytecode access

[lhotari]

Motivation

Currently the Functions Worker eagerly unpacks and extracts all Pulsar IO connectors when the function worker starts up.
This takes a significant amount of CPU resources and also slows down the startup. On Kubernetes with an empheral filesystem, this will happen every single time the Functions Worker is restarted.
When CPU is limited with k8s resource limits on the Functions Worker, this problem is even worse.

Modifications

Refactor the Functions Worker in a way where it is possible to do minimal work at startup time. This requires avoiding class loading and therefore this PR contains a refactoring where the previous logic that was coupled with classloading is now decoupled. Instead of classloading, Byte Buddy library is used to read the required metadata from the functions and connector packages.
Instead of using the JarFile API, NarClassloader has been modified to use the ZipFile API since the Nar files don't need any features that are specific to Jar file handling.

Additional Context

There was a previous PR #17902 that made the unpacking run in parallel. Those changes aren't needed any more since startup will be fast when no nar files are unpacked on startup time.
This PR doesn't require a PIP since this doesn't change external interfaces. This doesn't introduce new external features and is also a bug fix for the maintained Pulsar releases.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[eolivelli]

Lgtm

This is an amazing improvement

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 59.84733% with 263 lines in your changes missing coverage. Please review.

Project coverage is 73.55%. Comparing base (1b1cfb5) to head (f1ea2d9).
Report is 587 commits behind head on master.

Files with missing lines	Patch %	Lines
.../pulsar/functions/utils/FunctionRuntimeCommon.java	41.02%	43 Missing and 3 partials ⚠️
.../apache/pulsar/functions/utils/ValidatorUtils.java	13.04%	38 Missing and 2 partials ⚠️
...he/pulsar/functions/utils/FunctionFilePackage.java	68.57%	19 Missing and 3 partials ⚠️
...apache/pulsar/functions/utils/SinkConfigUtils.java	53.19%	16 Missing and 6 partials ⚠️
...ache/pulsar/functions/utils/io/ConnectorUtils.java	32.14%	19 Missing ⚠️
...ache/pulsar/functions/utils/SourceConfigUtils.java	51.61%	10 Missing and 5 partials ⚠️
.../apache/pulsar/functions/utils/FunctionCommon.java	64.10%	8 Missing and 6 partials ⚠️
...rg/apache/pulsar/functions/utils/io/Connector.java	56.25%	13 Missing and 1 partial ⚠️
...he/pulsar/functions/worker/rest/api/SinksImpl.java	57.57%	10 Missing and 4 partials ⚠️
...he/pulsar/functions/utils/FunctionConfigUtils.java	69.76%	10 Missing and 3 partials ⚠️
... and 11 more

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #22122       +/-   ##
=============================================
+ Coverage     34.05%   73.55%   +39.49%     
- Complexity    12150    32612    +20462     
=============================================
  Files          1659     1877      +218     
  Lines        129418   139502    +10084     
  Branches      14173    15299     +1126     
=============================================
+ Hits          44079   102610    +58531     
+ Misses        79497    28937    -50560     
- Partials       5842     7955     +2113     

Flag	Coverage Δ
inttests	24.62% <2.13%> (-0.12%)	⬇️
systests	24.24% <29.16%> (?)
unittests	72.83% <57.86%> (+40.96%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...pulsar/functions/runtime/thread/ThreadRuntime.java	72.00% <100.00%> (+16.00%)	⬆️
...g/apache/pulsar/functions/worker/WorkerConfig.java	92.98% <100.00%> (+12.17%)	⬆️
...ache/pulsar/functions/worker/FunctionActioner.java	74.93% <100.00%> (+72.70%)	⬆️
...e/pulsar/functions/worker/PulsarWorkerService.java	70.26% <100.00%> (+17.16%)	⬆️
...ulsar/functions/worker/rest/api/ComponentImpl.java	48.01% <100.00%> (+47.47%)	⬆️
...a/org/apache/pulsar/common/nar/NarClassLoader.java	54.92% <86.66%> (+14.60%)	⬆️
.../pulsar/functions/utils/LoadedFunctionPackage.java	90.90% <90.90%> (ø)
...sar/functions/utils/functions/FunctionArchive.java	88.23% <88.23%> (+28.23%)	⬆️
...java/org/apache/pulsar/common/nar/NarUnpacker.java	78.68% <76.92%> (+0.11%)	⬆️
...ulsar/functions/worker/rest/api/FunctionsImpl.java	56.67% <83.33%> (+55.91%)	⬆️
... and 16 more

... and 1496 files with indirect coverage changes