chore(rc): avoid expires parsing [backport 2.21] (#13826)

We avoid parsing the expires string into a date-time object. Currently
the value is not used, so we avoid calls to `_strptime`, which make use
of a global lock in its internal implementation.

Refs: [DEBUG-4109](https://datadoghq.atlassian.net/browse/DEBUG-4109)

## Checklist
- [x] 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](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## 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](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
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](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)


[DEBUG-4109]:
https://datadoghq.atlassian.net/browse/DEBUG-4109?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ
[DEBUG-4109]:
https://datadoghq.atlassian.net/browse/DEBUG-4109?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Co-authored-by: Gabriele N. Tornetta <[email protected]>

Author: tylfin

ddtrace/internal/remoteconfig/client.py

@@ -1,6 +1,5 @@
 import base64
 import dataclasses
-from datetime import datetime
 import enum
 import hashlib
 import json
@@ -30,7 +29,6 @@
 from ddtrace.internal.packages import is_distribution_available
 from ddtrace.internal.remoteconfig.constants import REMOTE_CONFIG_AGENT_ENDPOINT
 from ddtrace.internal.service import ServiceStatus
-from ddtrace.internal.utils.time import parse_isoformat
 
 from ..utils.formats import parse_tags_str
 from ..utils.version import _pep440_to_semver
@@ -121,16 +119,14 @@ class Root:
     _type: str
     spec_version: str
     consistent_snapshot: bool
-    expires: datetime
+    expires: str
     keys: Mapping[str, Key]
     roles: Mapping[str, Role]
     version: int
 
     def __post_init__(self):
         if self._type != "root":
             raise ValueError("Root: invalid root type")
-        if isinstance(self.expires, str):
-            self.expires = parse_isoformat(self.expires)
         for k, v in self.keys.items():
             if isinstance(v, dict):
                 self.keys[k] = Key(**v)
@@ -163,7 +159,7 @@ class TargetDesc:
 class Targets:
     _type: str
     custom: Mapping[str, Any]
-    expires: datetime
+    expires: str
     spec_version: str
     targets: Mapping[str, TargetDesc]
     version: int
@@ -173,8 +169,6 @@ def __post_init__(self):
             raise ValueError("Targets: invalid targets type")
         if self.spec_version not in ("1.0", "1.0.0"):
             raise ValueError("Targets: invalid spec version")
-        if isinstance(self.expires, str):
-            self.expires = parse_isoformat(self.expires)
         for k, v in self.targets.items():
             if isinstance(v, dict):
                 self.targets[k] = TargetDesc(**v)

ddtrace/internal/utils/time.py

@@ -1,4 +1,3 @@
-from datetime import datetime
 import time
 from types import TracebackType
 from typing import Optional
@@ -10,20 +9,6 @@
 log = get_logger(__name__)
 
 
-def parse_isoformat(date):
-    # type: (str) -> Optional[datetime]
-    if date.endswith("Z"):
-        try:
-            return datetime.strptime(date, "%Y-%m-%dT%H:%M:%S.%fZ")
-        except ValueError:
-            return datetime.strptime(date, "%Y-%m-%dT%H:%M:%SZ")
-    try:
-        return datetime.fromisoformat(date)
-    except (ValueError, IndexError):
-        log.debug("unsupported isoformat: %s", date)
-    return None
-
-
 class StopWatch(object):
     """A simple timer/stopwatch helper class.
 
@@ -57,7 +42,7 @@ def elapsed(self) -> float:
         """
         # NOTE: datetime.timedelta does not support nanoseconds, so keep a float here
         if self._started_at is None:
-            raise RuntimeError("Can not get the elapsed time of a stopwatch" " if it has not been started/stopped")
+            raise RuntimeError("Can not get the elapsed time of a stopwatch if it has not been started/stopped")
         if self._stopped_at is None:
             now = time.monotonic()
         else:
@@ -80,7 +65,7 @@ def stop(self):
         # type: () -> StopWatch
         """Stops the watch."""
         if self._started_at is None:
-            raise RuntimeError("Can not stop a stopwatch that has not been" " started")
+            raise RuntimeError("Can not stop a stopwatch that has not been started")
         self._stopped_at = time.monotonic()
         return self