feat(tracing): Add helper functions for new traces_sampler option (getsentry#869)

- A function to determine if tracing is enabled
- A function to validate sample rates returned from `traces_sampler`
- A `to_json` method in the `Transaction` class building upon the one already in the `Span` class

Author: lobsterkatie

sentry_sdk/tracing.py

@@ -1,9 +1,11 @@
 import re
 import uuid
 import contextlib
+import math
 import time
 
 from datetime import datetime, timedelta
+from numbers import Real
 
 import sentry_sdk
 
@@ -407,8 +409,8 @@ def finish(self, hub=None):
         _maybe_create_breadcrumbs_from_span(hub, self)
         return None
 
-    def to_json(self, client):
-        # type: (Optional[sentry_sdk.Client]) -> Dict[str, Any]
+    def to_json(self):
+        # type: () -> Dict[str, Any]
         rv = {
             "trace_id": self.trace_id,
             "span_id": self.span_id,
@@ -517,7 +519,7 @@ def finish(self, hub=None):
             return None
 
         finished_spans = [
-            span.to_json(client)
+            span.to_json()
             for span in self._span_recorder.spans
             if span is not self and span.timestamp is not None
         ]
@@ -534,6 +536,47 @@ def finish(self, hub=None):
             }
         )
 
+    def to_json(self):
+        # type: () -> Dict[str, Any]
+        rv = super(Transaction, self).to_json()
+
+        rv["name"] = self.name
+        rv["sampled"] = self.sampled
+        rv["parent_sampled"] = self.parent_sampled
+
+        return rv
+
+
+def _is_valid_sample_rate(rate):
+    # type: (Any) -> bool
+    """
+    Checks the given sample rate to make sure it is valid type and value (a
+    boolean or a number between 0 and 1, inclusive).
+    """
+
+    # both booleans and NaN are instances of Real, so a) checking for Real
+    # checks for the possibility of a boolean also, and b) we have to check
+    # separately for NaN
+    if not isinstance(rate, Real) or math.isnan(rate):
+        logger.warning(
+            "[Tracing] Given sample rate is invalid. Sample rate must be a boolean or a number between 0 and 1. Got {rate} of type {type}.".format(
+                rate=rate, type=type(rate)
+            )
+        )
+        return False
+
+    # in case rate is a boolean, it will get cast to 1 if it's True and 0 if it's False
+    rate = float(rate)
+    if rate < 0 or rate > 1:
+        logger.warning(
+            "[Tracing] Given sample rate is invalid. Sample rate must be between 0 and 1. Got {rate}.".format(
+                rate=rate
+            )
+        )
+        return False
+
+    return True
+
 
 def _format_sql(cursor, sql):
     # type: (Any, str) -> Optional[str]

sentry_sdk/utils.py

@@ -968,3 +968,13 @@ def run(self):
                 integer_configured_timeout
             )
         )
+
+
+def has_tracing_enabled(options):
+    # type: (Dict[str, Any]) -> bool
+    """
+    Returns True if either traces_sample_rate or traces_sampler is
+    non-zero/defined, False otherwise.
+    """
+
+    return bool(options.get("traces_sample_rate") or options.get("traces_sampler"))

tests/tracing/test_sampling.py

@@ -1,4 +1,13 @@
+import pytest
+
 from sentry_sdk import start_span, start_transaction
+from sentry_sdk.tracing import _is_valid_sample_rate
+from sentry_sdk.utils import logger
+
+try:
+    from unittest import mock  # python 3.3 and above
+except ImportError:
+    import mock  # python < 3.3
 
 
 def test_sampling_decided_only_for_transactions(sentry_init, capture_events):
@@ -32,3 +41,35 @@ def test_no_double_sampling(sentry_init, capture_events):
         pass
 
     assert len(events) == 1
+
+
+@pytest.mark.parametrize(
+    "rate",
+    [0.0, 0.1231, 1.0, True, False],
+)
+def test_accepts_valid_sample_rate(rate):
+    with mock.patch.object(logger, "warning", mock.Mock()):
+        result = _is_valid_sample_rate(rate)
+        assert logger.warning.called is False
+        assert result is True
+
+
+@pytest.mark.parametrize(
+    "rate",
+    [
+        "dogs are great",  # wrong type
+        (0, 1),  # wrong type
+        {"Maisey": "Charllie"},  # wrong type
+        [True, True],  # wrong type
+        {0.2012},  # wrong type
+        float("NaN"),  # wrong type
+        None,  # wrong type
+        -1.121,  # wrong value
+        1.231,  # wrong value
+    ],
+)
+def test_warns_on_invalid_sample_rate(rate, StringContaining):  # noqa: N803
+    with mock.patch.object(logger, "warning", mock.Mock()):
+        result = _is_valid_sample_rate(rate)
+        logger.warning.assert_any_call(StringContaining("Given sample rate is invalid"))
+        assert result is False