refactor(tracing): break span-sampling cycle

[P403n1x87]

We break the cycle between the span object and the sampling logic by moving some methods and functions around

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

ddtrace/_trace/processor/__init__.py                                    @DataDog/apm-sdk-api-python
ddtrace/_trace/sampler.py                                               @DataDog/apm-sdk-api-python
ddtrace/_trace/sampling_rule.py                                         @DataDog/apm-sdk-api-python
ddtrace/_trace/span.py                                                  @DataDog/apm-sdk-api-python
ddtrace/appsec/_trace_utils.py                                          @DataDog/asm-python
ddtrace/internal/sampling.py                                            @DataDog/apm-sdk-api-python
ddtrace/propagation/http.py                                             @DataDog/apm-sdk-api-python
tests/integration/test_sampling.py                                      @DataDog/apm-core-python
tests/tracer/test_processors.py                                         @DataDog/apm-sdk-api-python
tests/tracer/test_sampler.py                                            @DataDog/apm-sdk-api-python
tests/tracer/test_single_span_sampling_rules.py                         @DataDog/apm-sdk-api-python

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 238 ± 5 ms.

The average import time from base is: 245 ± 5 ms.

The import time difference between this PR and base is: -6.3 ± 0.2 ms.

Import time breakdown

The following import paths have appeared:

ddtrace.auto 0.616 ms (0.26%)

ddtrace 0.616 ms (0.26%)

ddtrace.trace 0.616 ms (0.26%)

ddtrace._trace.filters 0.616 ms (0.26%)

ddtrace._trace.processor 0.616 ms (0.26%)

ddtrace._trace.sampler 0.616 ms (0.26%)

ddtrace._trace.span 0.616 ms (0.26%)

ddtrace._trace.sampling_rule 0.616 ms (0.26%)

ddtrace.internal.glob_matching 0.267 ms (0.11%)

The following import paths have disappeared:

ddtrace.auto 0.734 ms (0.31%)

ddtrace 0.734 ms (0.31%)

ddtrace.trace 0.734 ms (0.31%)

ddtrace._trace.filters 0.734 ms (0.31%)

ddtrace._trace.processor 0.734 ms (0.31%)

ddtrace._trace.sampler 0.734 ms (0.31%)

ddtrace._trace.span 0.734 ms (0.31%)

ddtrace.internal.sampling 0.734 ms (0.31%)

ddtrace._trace.sampling_rule 0.734 ms (0.31%)

ddtrace.internal.glob_matching 0.365 ms (0.15%)

The following import paths have grown:

ddtrace.auto 1.464 ms (0.61%)

ddtrace.bootstrap.sitecustomize 1.307 ms (0.55%)

ddtrace.bootstrap.preload 1.307 ms (0.55%)

ddtrace.internal.products 1.141 ms (0.48%)

importlib.metadata 0.931 ms (0.39%)

importlib.abc 0.857 ms (0.36%)

importlib.resources 0.857 ms (0.36%)

importlib.resources._legacy 0.857 ms (0.36%)

importlib.metadata._itertools 0.074 ms (0.03%)

multiprocessing 0.075 ms (0.03%)

multiprocessing.context 0.075 ms (0.03%)

ddtrace.internal.symbol_db.remoteconfig 0.071 ms (0.03%)

ddtrace.internal.symbol_db.symbols 0.071 ms (0.03%)

ddtrace.settings.symbol_db 0.071 ms (0.03%)

ddtrace.internal.remoteconfig.worker 0.063 ms (0.03%)

ddtrace.internal.runtime.runtime_metrics 0.096 ms (0.04%)

ddtrace.settings.profiling 0.070 ms (0.03%)

ddtrace.internal.datadog.profiling.stack_v2 0.070 ms (0.03%)

ddtrace.internal.datadog.profiling.stack_v2._stack_v2 0.070 ms (0.03%)

ddtrace 0.156 ms (0.07%)

ddtrace.trace 0.156 ms (0.07%)

ddtrace._trace.filters 0.156 ms (0.07%)

ddtrace._trace.processor 0.156 ms (0.07%)

ddtrace._trace.sampler 0.156 ms (0.07%)

ddtrace._trace.span 0.049 ms (0.02%)

ddtrace.internal.sampling 0.049 ms (0.02%)

The following import paths have shrunk:

ddtrace.auto 4.144 ms (1.74%)

ddtrace.bootstrap.sitecustomize 3.245 ms (1.36%)

ddtrace.bootstrap.preload 3.245 ms (1.36%)

ddtrace.internal.products 2.951 ms (1.24%)

importlib.metadata 1.036 ms (0.43%)

importlib.abc 1.036 ms (0.43%)

importlib.resources 0.070 ms (0.03%)

ddtrace.internal.remoteconfig.client 0.711 ms (0.30%)

ddtrace.internal.symbol_db.remoteconfig 0.202 ms (0.08%)

ddtrace.internal.symbol_db.symbols 0.202 ms (0.08%)

ddtrace.settings.dynamic_instrumentation 0.098 ms (0.04%)

multiprocessing 0.089 ms (0.04%)

multiprocessing.context 0.089 ms (0.04%)

multiprocessing.process 0.089 ms (0.04%)

ddtrace.settings.profiling 0.136 ms (0.06%)

ddtrace.vendor.psutil 0.023 ms (0.01%)

ddtrace.vendor.psutil._pslinux 0.023 ms (0.01%)

glob 0.023 ms (0.01%)

ddtrace.settings.crashtracker 0.115 ms (0.05%)

ddtrace.internal.flare.flare 0.043 ms (0.02%)

ddtrace 0.898 ms (0.38%)

ddtrace._logger 0.114 ms (0.05%)

logging 0.114 ms (0.05%)

traceback 0.114 ms (0.05%)

contextlib 0.114 ms (0.05%)

ddtrace.trace 0.100 ms (0.04%)

ddtrace._trace.filters 0.100 ms (0.04%)

ddtrace._trace.processor 0.100 ms (0.04%)

ddtrace._trace.sampler 0.100 ms (0.04%)

ddtrace._trace.span 0.100 ms (0.04%)