refactor(tracing): break span-sampling cycle

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

Author: P403n1x87

ddtrace/_trace/processor/__init__.py

@@ -14,15 +14,16 @@
 from ddtrace._trace.span import _is_top_level
 from ddtrace.constants import _APM_ENABLED_METRIC_KEY as MK_APM_ENABLED
 from ddtrace.constants import _SAMPLING_PRIORITY_KEY
+from ddtrace.constants import _SINGLE_SPAN_SAMPLING_MECHANISM
 from ddtrace.constants import USER_KEEP
 from ddtrace.internal import gitmetadata
 from ddtrace.internal import telemetry
 from ddtrace.internal.constants import HIGHER_ORDER_TRACE_ID_BITS
 from ddtrace.internal.constants import LAST_DD_PARENT_ID_KEY
 from ddtrace.internal.constants import MAX_UINT_64BITS
+from ddtrace.internal.constants import SamplingMechanism
 from ddtrace.internal.logger import get_logger
 from ddtrace.internal.sampling import SpanSamplingRule
-from ddtrace.internal.sampling import is_single_span_sampled
 from ddtrace.internal.service import ServiceStatusError
 from ddtrace.internal.telemetry.constants import TELEMETRY_LOG_LEVEL
 from ddtrace.internal.telemetry.constants import TELEMETRY_NAMESPACE
@@ -150,7 +151,12 @@ def process_trace(self, trace: List[Span]) -> Optional[List[Span]]:
                 if priority is not None and priority <= 0:
                     # When any span is marked as keep by a single span sampling
                     # decision then we still send all and only those spans.
-                    single_spans = [_ for _ in trace if is_single_span_sampled(_)]
+
+                    single_spans = [
+                        _
+                        for _ in trace
+                        if _.get_metric(_SINGLE_SPAN_SAMPLING_MECHANISM) == SamplingMechanism.SPAN_SAMPLING_RULE
+                    ]
 
                     return single_spans or None
 
@@ -159,8 +165,8 @@ def process_trace(self, trace: List[Span]) -> Optional[List[Span]]:
                 for span in trace:
                     if span.context.sampling_priority is not None and span.context.sampling_priority <= 0:
                         for rule in self.single_span_rules:
-                            if rule.match(span):
-                                rule.sample(span)
+                            if rule.match(span.name, span.service):
+                                span.sample(rule)
                                 # If stats computation is enabled, we won't send all spans to the agent.
                                 # In order to ensure that the agent does not update priority sampling rates
                                 # due to single spans sampling, we set all of these spans to manual keep.

ddtrace/_trace/sampler.py

@@ -17,8 +17,6 @@
 from ..internal.constants import SamplingMechanism
 from ..internal.logger import get_logger
 from ..internal.rate_limiter import RateLimiter
-from ..internal.sampling import _get_highest_precedence_rule_matching
-from ..internal.sampling import _set_sampling_tags
 from .sampling_rule import SamplingRule
 
 
@@ -169,9 +167,18 @@ def set_sampling_rules(self, rules: str) -> None:
         # Sort the sampling_rules list using a lambda function as the key
         self.rules = sorted(sampling_rules, key=lambda rule: PROVENANCE_ORDER.index(rule.provenance))
 
+    def _get_highest_precedence_rule_matching(self, span: Span) -> Optional[SamplingRule]:
+        if not (rules := self.rules):
+            return None
+
+        for rule in rules:
+            if span.matches(rule):
+                return rule
+        return None
+
     def sample(self, span: Span) -> bool:
         span._update_tags_from_context()
-        matched_rule = _get_highest_precedence_rule_matching(span, self.rules)
+        matched_rule = self._get_highest_precedence_rule_matching(span)
         # Default sampling
         agent_service_based = False
         sampled = True
@@ -197,8 +204,7 @@ def sample(self, span: Span) -> bool:
                 span.set_metric(_SAMPLING_LIMIT_DECISION, self.limiter.effective_rate)
 
         sampling_mechanism = self._get_sampling_mechanism(matched_rule, agent_service_based)
-        _set_sampling_tags(
-            span,
+        span._set_sampling_tags(
             sampled,
             sample_rate,
             sampling_mechanism,

ddtrace/_trace/sampling_rule.py

@@ -10,9 +10,6 @@
 from ddtrace.internal.utils.cache import cachedmethod
 
 
-if TYPE_CHECKING:  # pragma: no cover
-    from ddtrace._trace.span import Span  # noqa:F401
-
 log = get_logger(__name__)
 KNUTH_FACTOR = 1111111111111111111
 
@@ -125,26 +122,6 @@ def _matches(self, key: Tuple[Optional[str], str, Optional[str]]) -> bool:
         else:
             return True
 
-    def matches(self, span):
-        # type: (Span) -> bool
-        """
-        Return if this span matches this rule
-
-        :param span: The span to match against
-        :type span: :class:`ddtrace._trace.span.Span`
-        :returns: Whether this span matches or not
-        :rtype: :obj:`bool`
-        """
-        tags_match = self.tags_match(span)
-        return tags_match and self._matches((span.service, span.name, span.resource))
-
-    def tags_match(self, span):
-        # type: (Span) -> bool
-        tag_match = True
-        if self._tag_value_matchers:
-            tag_match = self.check_tags(span.get_tags(), span.get_metrics())
-        return tag_match
-
     def check_tags(self, meta, metrics):
         if meta is None and metrics is None:
             return False

ddtrace/_trace/span.py

@@ -21,6 +21,7 @@
 from ddtrace._trace._span_pointer import _SpanPointer
 from ddtrace._trace._span_pointer import _SpanPointerDirection
 from ddtrace._trace.context import Context
+from ddtrace._trace.sampling_rule import SamplingRule
 from ddtrace._trace.types import _AttributeValueType
 from ddtrace._trace.types import _MetaDictType
 from ddtrace._trace.types import _MetricDictType
@@ -29,6 +30,10 @@
 from ddtrace.constants import _SAMPLING_AGENT_DECISION
 from ddtrace.constants import _SAMPLING_LIMIT_DECISION
 from ddtrace.constants import _SAMPLING_RULE_DECISION
+from ddtrace.constants import _SINGLE_SPAN_SAMPLING_MAX_PER_SEC
+from ddtrace.constants import _SINGLE_SPAN_SAMPLING_MAX_PER_SEC_NO_LIMIT
+from ddtrace.constants import _SINGLE_SPAN_SAMPLING_MECHANISM
+from ddtrace.constants import _SINGLE_SPAN_SAMPLING_RATE
 from ddtrace.constants import _SPAN_MEASURED_KEY
 from ddtrace.constants import ERROR_MSG
 from ddtrace.constants import ERROR_STACK
@@ -48,10 +53,14 @@
 from ddtrace.internal.compat import NumericType
 from ddtrace.internal.compat import ensure_text
 from ddtrace.internal.compat import is_integer
+from ddtrace.internal.constants import _KEEP_PRIORITY_INDEX
+from ddtrace.internal.constants import _REJECT_PRIORITY_INDEX
 from ddtrace.internal.constants import MAX_UINT_64BITS as _MAX_UINT_64BITS
+from ddtrace.internal.constants import SAMPLING_MECHANISM_TO_PRIORITIES
 from ddtrace.internal.constants import SPAN_API_DATADOG
+from ddtrace.internal.constants import SamplingMechanism
 from ddtrace.internal.logger import get_logger
-from ddtrace.internal.sampling import SamplingMechanism
+from ddtrace.internal.sampling import SpanSamplingRule
 from ddtrace.internal.sampling import set_sampling_decision_maker
 from ddtrace.settings._config import config
 
@@ -334,6 +343,55 @@ def _override_sampling_decision(self, decision: Optional[NumericType]):
                 if key in self._local_root._metrics:
                     del self._local_root._metrics[key]
 
+    def tags_match(self, rule: SamplingRule) -> bool:
+        tag_match = True
+        if rule._tag_value_matchers:
+            tag_match = rule.check_tags(self.get_tags(), self.get_metrics())
+        return tag_match
+
+    def matches(self, rule: SamplingRule) -> bool:
+        """
+        Return if this span matches this rule
+
+        :param span: The span to match against
+        :type span: :class:`ddtrace._trace.span.Span`
+        :returns: Whether this span matches or not
+        :rtype: :obj:`bool`
+        """
+        tags_match = self.tags_match(rule)
+        return tags_match and rule._matches((self.service, self.name, self.resource))
+
+    def apply_span_sampling_tags(self, rule: SpanSamplingRule) -> None:
+        self.set_metric(_SINGLE_SPAN_SAMPLING_MECHANISM, SamplingMechanism.SPAN_SAMPLING_RULE)
+        self.set_metric(_SINGLE_SPAN_SAMPLING_RATE, rule._sample_rate)
+        # Only set this tag if it's not the default -1
+        if rule._max_per_second != _SINGLE_SPAN_SAMPLING_MAX_PER_SEC_NO_LIMIT:
+            self.set_metric(_SINGLE_SPAN_SAMPLING_MAX_PER_SEC, rule._max_per_second)
+
+    def sample(self, rule: SpanSamplingRule) -> bool:
+        if rule._sample(self.span_id):
+            if rule._limiter.is_allowed():
+                self.apply_span_sampling_tags(rule)
+                return True
+        return False
+
+    def _set_sampling_tags(self, sampled: bool, sample_rate: float, mechanism: int) -> None:
+        # Set the sampling mechanism
+        set_sampling_decision_maker(self.context, mechanism)
+        # Set the sampling psr rate
+        if mechanism in (
+            SamplingMechanism.LOCAL_USER_TRACE_SAMPLING_RULE,
+            SamplingMechanism.REMOTE_USER_TRACE_SAMPLING_RULE,
+            SamplingMechanism.REMOTE_DYNAMIC_TRACE_SAMPLING_RULE,
+        ):
+            self.set_metric(_SAMPLING_RULE_DECISION, sample_rate)
+        elif mechanism == SamplingMechanism.AGENT_RATE_BY_SERVICE:
+            self.set_metric(_SAMPLING_AGENT_DECISION, sample_rate)
+        # Set the sampling priority
+        priorities = SAMPLING_MECHANISM_TO_PRIORITIES[mechanism]
+        priority_index = _KEEP_PRIORITY_INDEX if sampled else _REJECT_PRIORITY_INDEX
+        self.context.sampling_priority = priorities[priority_index]
+
     def set_tag(self, key: _TagNameType, value: Any = None) -> None:
         """Set a tag key/value pair on the span.
 

ddtrace/appsec/_trace_utils.py

@@ -25,7 +25,7 @@
 
 def _asm_manual_keep(span: Span) -> None:
     from ddtrace.internal.constants import SAMPLING_DECISION_TRACE_TAG_KEY
-    from ddtrace.internal.sampling import SamplingMechanism
+    from ddtrace.internal.constants import SamplingMechanism
 
     span.set_tag(constants.MANUAL_KEEP_KEY)
     # set decision maker to ASM = -5
@@ -295,7 +295,7 @@ def block_request() -> None:
     meaning that if you capture the exception the request blocking could not work.
     """
     if not asm_config._asm_enabled:
-        log.warning("block_request() is disabled. To use this feature please enable" "Application Security Monitoring")
+        log.warning("block_request() is disabled. To use this feature please enableApplication Security Monitoring")
         return
 
     _asm_request_context.block_request()

ddtrace/internal/sampling.py

@@ -14,18 +14,8 @@
 except ImportError:
     from typing_extensions import TypedDict
 
-from ddtrace._trace.sampling_rule import SamplingRule  # noqa:F401
-from ddtrace.constants import _SAMPLING_AGENT_DECISION
-from ddtrace.constants import _SAMPLING_RULE_DECISION
-from ddtrace.constants import _SINGLE_SPAN_SAMPLING_MAX_PER_SEC
 from ddtrace.constants import _SINGLE_SPAN_SAMPLING_MAX_PER_SEC_NO_LIMIT
-from ddtrace.constants import _SINGLE_SPAN_SAMPLING_MECHANISM
-from ddtrace.constants import _SINGLE_SPAN_SAMPLING_RATE
-from ddtrace.internal.constants import _KEEP_PRIORITY_INDEX
-from ddtrace.internal.constants import _REJECT_PRIORITY_INDEX
 from ddtrace.internal.constants import SAMPLING_DECISION_TRACE_TAG_KEY
-from ddtrace.internal.constants import SAMPLING_MECHANISM_TO_PRIORITIES
-from ddtrace.internal.constants import SamplingMechanism
 from ddtrace.internal.glob_matching import GlobMatcher
 from ddtrace.internal.logger import get_logger
 from ddtrace.settings._config import config
@@ -43,7 +33,6 @@
 
 if TYPE_CHECKING:  # pragma: no cover
     from ddtrace._trace.context import Context  # noqa:F401
-    from ddtrace._trace.span import Span  # noqa:F401
 
 # Big prime number to make hashing better distributed
 KNUTH_FACTOR = 1111111111111111111
@@ -126,28 +115,16 @@ def __init__(
         self._service_matcher = GlobMatcher(service) if service is not None else None
         self._name_matcher = GlobMatcher(name) if name is not None else None
 
-    def sample(self, span):
-        # type: (Span) -> bool
-        if self._sample(span):
-            if self._limiter.is_allowed():
-                self.apply_span_sampling_tags(span)
-                return True
-        return False
-
-    def _sample(self, span):
-        # type: (Span) -> bool
+    def _sample(self, span_id: int) -> bool:
         if self._sample_rate == 1:
             return True
         elif self._sample_rate == 0:
             return False
 
-        return ((span.span_id * KNUTH_FACTOR) % MAX_SPAN_ID) <= self._sampling_id_threshold
+        return ((span_id * KNUTH_FACTOR) % MAX_SPAN_ID) <= self._sampling_id_threshold
 
-    def match(self, span):
-        # type: (Span) -> bool
+    def match(self, name: Optional[str], service: Optional[str]) -> bool:
         """Determines if the span's service and name match the configured patterns"""
-        name = span.name
-        service = span.service
         # If a span lacks a name and service, we can't match on it
         if service is None and name is None:
             return False
@@ -169,14 +146,6 @@ def match(self, span):
                 name_match = self._name_matcher.match(name)
         return service_match and name_match
 
-    def apply_span_sampling_tags(self, span):
-        # type: (Span) -> None
-        span.set_metric(_SINGLE_SPAN_SAMPLING_MECHANISM, SamplingMechanism.SPAN_SAMPLING_RULE)
-        span.set_metric(_SINGLE_SPAN_SAMPLING_RATE, self._sample_rate)
-        # Only set this tag if it's not the default -1
-        if self._max_per_second != _SINGLE_SPAN_SAMPLING_MAX_PER_SEC_NO_LIMIT:
-            span.set_metric(_SINGLE_SPAN_SAMPLING_MAX_PER_SEC, self._max_per_second)
-
 
 def get_span_sampling_rules() -> List[SpanSamplingRule]:
     json_rules = _get_span_sampling_json()
@@ -258,38 +227,3 @@ def _check_unsupported_pattern(string: str) -> None:
     for char in string:
         if char in unsupported_chars and config._raise:
             raise ValueError("Unsupported Glob pattern found, character:%r is not supported" % char)
-
-
-def is_single_span_sampled(span):
-    # type: (Span) -> bool
-    return span.get_metric(_SINGLE_SPAN_SAMPLING_MECHANISM) == SamplingMechanism.SPAN_SAMPLING_RULE
-
-
-def _set_sampling_tags(span, sampled, sample_rate, mechanism):
-    # type: (Span, bool, float, int) -> None
-    # Set the sampling mechanism
-    set_sampling_decision_maker(span.context, mechanism)
-    # Set the sampling psr rate
-    if mechanism in (
-        SamplingMechanism.LOCAL_USER_TRACE_SAMPLING_RULE,
-        SamplingMechanism.REMOTE_USER_TRACE_SAMPLING_RULE,
-        SamplingMechanism.REMOTE_DYNAMIC_TRACE_SAMPLING_RULE,
-    ):
-        span.set_metric(_SAMPLING_RULE_DECISION, sample_rate)
-    elif mechanism == SamplingMechanism.AGENT_RATE_BY_SERVICE:
-        span.set_metric(_SAMPLING_AGENT_DECISION, sample_rate)
-    # Set the sampling priority
-    priorities = SAMPLING_MECHANISM_TO_PRIORITIES[mechanism]
-    priority_index = _KEEP_PRIORITY_INDEX if sampled else _REJECT_PRIORITY_INDEX
-    span.context.sampling_priority = priorities[priority_index]
-
-
-def _get_highest_precedence_rule_matching(span, rules):
-    # type: (Span, List[SamplingRule]) -> Optional[SamplingRule]
-    if not rules:
-        return None
-
-    for rule in rules:
-        if rule.matches(span):
-            return rule
-    return None

ddtrace/propagation/http.py

@@ -17,6 +17,7 @@
 from ddtrace._trace.span import _get_64_lowest_order_bits_as_int
 from ddtrace._trace.span import _MetaDictType
 from ddtrace.appsec._constants import APPSEC
+from ddtrace.internal.constants import SamplingMechanism
 from ddtrace.internal.core import dispatch
 from ddtrace.settings._config import config
 from ddtrace.settings.asm import config as asm_config
@@ -48,7 +49,6 @@
 from ..internal.constants import W3C_TRACESTATE_KEY
 from ..internal.logger import get_logger
 from ..internal.sampling import SAMPLING_DECISION_TRACE_TAG_KEY
-from ..internal.sampling import SamplingMechanism
 from ..internal.sampling import validate_sampling_decision
 from ..internal.utils.http import w3c_tracestate_add_p
 from ._utils import get_wsgi_header

tests/integration/test_sampling.py

@@ -233,7 +233,7 @@ def test_rate_limiter_on_spans(tracer):
     Ensure that the rate limiter is applied to spans
     """
     from ddtrace._trace.sampler import DatadogSampler
-    from ddtrace.internal.sampling import SamplingRule
+    from ddtrace._trace.sampling_rule import SamplingRule
     from ddtrace.trace import tracer
 
     # Rate limit is only applied if a sample rate or trace sample rule is set

tests/tracer/test_sampler.py

@@ -17,9 +17,9 @@
 from ddtrace.constants import USER_KEEP
 from ddtrace.constants import USER_REJECT
 from ddtrace.internal.constants import DEFAULT_SAMPLING_RATE_LIMIT
+from ddtrace.internal.constants import SamplingMechanism
 from ddtrace.internal.rate_limiter import RateLimiter
 from ddtrace.internal.sampling import SAMPLING_DECISION_TRACE_TAG_KEY
-from ddtrace.internal.sampling import SamplingMechanism
 from ddtrace.internal.sampling import set_sampling_decision_maker
 from ddtrace.trace import Context
 from ddtrace.trace import Span

tests/tracer/test_single_span_sampling_rules.py

@@ -6,7 +6,7 @@
 from ddtrace.constants import _SINGLE_SPAN_SAMPLING_MAX_PER_SEC
 from ddtrace.constants import _SINGLE_SPAN_SAMPLING_MECHANISM
 from ddtrace.constants import _SINGLE_SPAN_SAMPLING_RATE
-from ddtrace.internal.sampling import SamplingMechanism
+from ddtrace.internal.constants import SamplingMechanism
 from ddtrace.internal.sampling import SpanSamplingRule
 from ddtrace.internal.sampling import _get_file_json
 from ddtrace.internal.sampling import get_span_sampling_rules