chore: put ddtrace site-packages on the end of the pythonpath [APMS-12275]

[emmettbutler]

This change adjusts single-step instrumentation to put ddtrace's customizations on the end of the pythonpath rather than the beginning. This makes it much less likely that instrumentation will corrupt the app by causing different versions of requirements to be used. Because the injection guardrails are now handling the task of ensuring compatibility between ddtrace and app requirements, which prepending to the pythonpath was a workaround for, this new less destructive approach is available.

Checklist

• Change(s) are motivated and described in the PR description
• Testing strategy is described if automated tests are not included in the PR
• Risks are described (performance impact, potential for breakage, maintainability)
• Change is maintainable (easy to change, telemetry, documentation)
• Library release note guidelines are followed or label changelog/no-changelog is set
• Documentation is included (in-code, generated user docs, public corp docs)
• Backport labels are set (if applicable)
• If this PR changes the public interface, I've notified @DataDog/apm-tees.

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: emmett.butler/end-pypath
Commit report: 14abb42
Test service: dd-trace-py

❌ 16 Failed (0 Known Flaky), 631 Passed, 5340 Skipped, 3m 18.17s Total duration (11m 33.96s time saved)

❌ Failed Tests (16)

This report shows up to 5 failed tests.

• test_and_emit_get_version - test_httpx_patch.py - Details

  Expand for error

   Subprocess Test "python -m unittest tests.contrib.httpx.test_httpx_patch.TestHttpxPatch.test_and_emit_get_version" Failed (exit code 1):
   E
   ======================================================================
   ERROR: test_and_emit_get_version (tests.contrib.httpx.test_httpx_patch.TestHttpxPatch.test_and_emit_get_version)
   Each contrib module should implement a get_version() function. This function is used for
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "/root/project/tests/contrib/patch.py", line 788, in test_and_emit_get_version
       emit_integration_and_version_to_test_agent(
     File "/root/project/tests/contrib/patch.py", line 120, in emit_integration_and_version_to_test_agent
   ...
  

• test_and_emit_get_version - test_httpx_patch.py - Details

  Expand for error

   Subprocess Test "python -m unittest tests.contrib.httpx.test_httpx_patch.TestHttpxPatch.test_and_emit_get_version" Failed (exit code 1):
   E
   ======================================================================
   ERROR: test_and_emit_get_version (tests.contrib.httpx.test_httpx_patch.TestHttpxPatch)
   Each contrib module should implement a get_version() function. This function is used for
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "/root/project/tests/contrib/patch.py", line 789, in test_and_emit_get_version
       self.__integration_name__, version, module_name=self.__module_name__
     File "/root/project/tests/contrib/patch.py", line 120, in emit_integration_and_version_to_test_agent
   ...
  

• test_configured_format - test_loguru_logging.py - Details

  Expand for error

   STDERR: Expected [] got [b'2024-06-07 14:20:53,213 ERROR [ddtrace.internal.writer.writer] [writer.py:399] [dd.service=logging dd.env=global.env dd.version=global.version dd.trace_id=0 dd.span_id=0] - failed to send, dropping 1 traces to intake at http://localhost:9126/v0.5/traces after 3 retries\n']
  

• test_log_DD_TAGS - test_loguru_logging.py - Details

  Expand for error

   STDERR: Expected [] got [b'2024-06-07 14:20:51,134 ERROR [ddtrace.internal.writer.writer] [writer.py:399] [dd.service=ddtagservice dd.env=ddenv dd.version=ddversion dd.trace_id=0 dd.span_id=0] - failed to send, dropping 1 traces to intake at http://localhost:9126/v0.5/traces after 3 retries\n']
  

• test_log_trace_128bit_trace_ids - test_loguru_logging.py - Details

  Expand for error

   STDERR: Expected [] got [b'2024-06-07 14:20:52,136 ERROR [ddtrace.internal.writer.writer] [writer.py:399] [dd.service=logging dd.env=global.env dd.version=global.version dd.trace_id=0 dd.span_id=0] - failed to send, dropping 1 traces to intake at http://localhost:9126/v0.5/traces after 3 retries\n']
  

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-06-11 15:39:30

Comparing candidate commit 4c1871c in PR branch emmett.butler/end-pypath with baseline commit 0c38e09 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 221 metrics, 9 unstable metrics.