fix(core): import time latency by lazily loading high level modules

[heitorlessa]

Issue #, if available: #294

Description of changes:

Checklist

• Meet tenets criteria
• Update tests
• Update docs
• PR title follows conventional commit semantics
• Create generic types for Tracer provider
• Create generic types for Tracer subsegments
• Convert EMF JSON Schema into native object to reduce I/O
• Lazily load aws_xray_sdk
• Lazily load aws_xray_sdk.core
• Lazily load fastjsonschema

Changes table

Scenario	Result	Change
Logger import only	0.33s user 0.15s system 82% cpu 0.582 total	No change
Logger import only	0.07s user 0.02s system 97% cpu 0.102 total	Tracer lazily loaded
Tracer imported but not initialized	0.08s user 0.02s system 84% cpu 0.115 total	Tracer lazily loaded
Tracer imported and initialized	0.32s user 0.11s system 92% cpu 0.469 total	Tracer lazily loaded
Logger import only	negligible difference	Metrics EMF JSON Schema as dict

Notes

• LazyLoader adds roughly 10ms due to class instantiation and globals manipulation
• Hard lesson: Type annotations load lazily loaded library ahead of time diminishing its effectiveness
  • Turns out there's an explicit mechanism to do that safely, though we now have a Tracer Provider ABC which can be extended to bring any other Tracer Provider later

Breaking change checklist

RFC issue #:

• Migration process documented
• Implement warnings (if it can live side by side)

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[michaelbrewer]

@heitorlessa nice, definitely handy for lambdas that just want structured logging or want to toggle tracing only for dev and test and disable on production.

[heitorlessa]

BEFORE

AFTER

New flamegraph with these patches - Tracer no longer appears and removes ~400ms for all imports and customers once merged

[heitorlessa]

Done - @nmoutschen, do you have the bandwidth to review?

[nmoutschen]

I have a few questions/remarks before I can approve. We also need to include the proper licensing for the class taken from Terraform (Apache-2.0 license).

[nmoutschen]

LGTM

[codecov-io]

Codecov Report

Merging #301 (01445a3) into develop (fe53a2e) will decrease coverage by 0.05%.
The diff coverage is 96.96%.

@@             Coverage Diff             @@
##           develop     #301      +/-   ##
===========================================
- Coverage    99.71%   99.65%   -0.06%     
===========================================
  Files           87       90       +3     
  Lines         3150     3206      +56     
  Branches       149      150       +1     
===========================================
+ Hits          3141     3195      +54     
- Misses           5        7       +2     
  Partials         4        4              

Impacted Files	Coverage Δ
...mbda_powertools/utilities/parser/envelopes/base.py	100.00% <ø> (ø)
aws_lambda_powertools/shared/lazy_import.py	89.47% <89.47%> (ø)
aws_lambda_powertools/metrics/base.py	100.00% <100.00%> (ø)
aws_lambda_powertools/metrics/schema.py	100.00% <100.00%> (ø)
aws_lambda_powertools/shared/constants.py	100.00% <100.00%> (ø)
aws_lambda_powertools/tracing/base.py	100.00% <100.00%> (ø)
aws_lambda_powertools/tracing/tracer.py	100.00% <100.00%> (ø)
... and 1 more

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