opentelemetry-sdk: cache tracer configs in Tracer

[xrmx]

Description

Instead of creating the TracerConfig at each start_span call, just compute it on change. This changes an internal interface.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[xrmx]

Benchmarks

-------------------------------------------------------------------------------------------------------- benchmark: 6 tests -------------------------------------------------------------------------------------------------------
Name (time in us)                                                 Min                 Max               Mean            StdDev             Median               IQR            Outliers  OPS (Kops/s)            Rounds  Iterations
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
test_simple_start_span_with_tracer_configurator_rules[None]     12.7530 (1.0)      39.7900 (1.53)     14.0253 (1.0)      0.9216 (1.46)     13.8770 (1.0)      0.7010 (1.17)      744;279       71.3000 (1.0)        8740           1
test_simple_start_span_with_tracer_configurator_rules[10]       12.8790 (1.01)     25.9930 (1.0)      14.2303 (1.01)     0.6878 (1.09)     14.1430 (1.02)     0.5973 (1.0)        374;75       70.2724 (0.99)       2909           1
test_simple_start_span_with_tracer_configurator_rules[1]        13.0920 (1.03)     28.6730 (1.10)     14.3815 (1.03)     0.6356 (1.01)     14.3170 (1.03)     0.6070 (1.02)     1181;152       69.5339 (0.98)       7239           1
test_simple_start_span_with_tracer_configurator_rules[0]        13.1550 (1.03)     30.4540 (1.17)     14.3915 (1.03)     0.6302 (1.0)      14.3320 (1.03)     0.6125 (1.03)     2882;316       69.4855 (0.97)      17352           1
test_simple_start_span_with_tracer_configurator_rules[50]       13.2760 (1.04)     27.8670 (1.07)     14.3546 (1.02)     0.8041 (1.28)     14.2400 (1.03)     0.6080 (1.02)        49;18       69.6643 (0.98)        727           1

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

after

-------------------------------------------------------------------------------------------------------- benchmark: 6 tests -------------------------------------------------------------------------------------------------------
Name (time in us)                                                 Min                 Max               Mean            StdDev             Median               IQR            Outliers  OPS (Kops/s)            Rounds  Iterations
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
test_simple_start_span_with_tracer_configurator_rules[0]      12.7130 (1.0)       34.4780 (1.0)      13.9008 (1.0)      0.6829 (1.0)      13.8050 (1.0)      0.5950 (1.14)     1285;287       71.9383 (1.0)        9127           1
test_simple_start_span_with_tracer_configurator_rules[50]     12.8570 (1.01)      85.8870 (2.49)     14.1029 (1.01)     1.0369 (1.52)     13.9990 (1.01)     0.5490 (1.05)      429;429       70.9077 (0.99)      14893           1
test_simple_start_span_with_tracer_configurator_rules[10]     12.8640 (1.01)      57.6480 (1.67)     14.0218 (1.01)     1.1011 (1.61)     13.9040 (1.01)     0.5220 (1.0)       459;583       71.3176 (0.99)      20711           1
test_simple_start_span_with_tracer_configurator_rules[1]      12.9070 (1.02)     186.0220 (5.40)     14.4462 (1.04)     2.6857 (3.93)     14.0930 (1.02)     0.6400 (1.23)     593;1007       69.2222 (0.96)      19222           1
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

[pmcollins]

Looks like a positive change overall, thanks for doing this.

[pmcollins]

If there's already a Tracer with this instrumentation scope registered in _tracers, should it be returned? Looks like we're always creating a new Tracer, and if we overwrite a Tracer that's already registered in _tracers, it gets overwritten, then it won't be iterated over in _set_tracer_configurator, and won't receive config updates, even though it could still be in use.