Potel Sampling (#3501)

Add a new SentrySampler that is used for sampling OpenTelemetry spans the Sentry way (using Sentrys traces_sample_rate and traces_sampler config options)

Fixes #3318

sentry_sdk/integrations/opentelemetry/consts.py

@@ -11,6 +11,8 @@
 SENTRY_USE_CURRENT_SCOPE_KEY = create_key("sentry_use_current_scope")
 SENTRY_USE_ISOLATION_SCOPE_KEY = create_key("sentry_use_isolation_scope")
 
+SENTRY_TRACE_STATE_DROPPED = "sentry_dropped"
+
 OTEL_SENTRY_CONTEXT = "otel"
 SPAN_ORIGIN = "auto.otel"
 

sentry_sdk/integrations/opentelemetry/integration.py

@@ -12,6 +12,7 @@
 from sentry_sdk.integrations.opentelemetry.contextvars_context import (
  SentryContextVarsRuntimeContext,
 )
+from sentry_sdk.integrations.opentelemetry.sampler import SentrySampler
 from sentry_sdk.utils import logger
 
 try:
@@ -55,7 +56,7 @@ def _setup_sentry_tracing():
 
  opentelemetry.context._RUNTIME_CONTEXT = SentryContextVarsRuntimeContext()
 
- provider = TracerProvider()
+ provider = TracerProvider(sampler=SentrySampler())
  provider.add_span_processor(PotelSentrySpanProcessor())
  trace.set_tracer_provider(provider)
 

sentry_sdk/integrations/opentelemetry/sampler.py

@@ -0,0 +1,122 @@
+from random import random
+
+from opentelemetry import trace
+
+from opentelemetry.sdk.trace.sampling import Sampler, SamplingResult, Decision
+from opentelemetry.trace.span import TraceState
+
+import sentry_sdk
+from sentry_sdk.integrations.opentelemetry.consts import SENTRY_TRACE_STATE_DROPPED
+from sentry_sdk.tracing_utils import has_tracing_enabled
+from sentry_sdk.utils import is_valid_sample_rate, logger
+
+from typing import TYPE_CHECKING, Optional, Sequence
+
+if TYPE_CHECKING:
+ from opentelemetry.context import Context
+ from opentelemetry.trace import Link, SpanKind
+ from opentelemetry.trace.span import SpanContext
+ from opentelemetry.util.types import Attributes
+
+
+def get_parent_sampled(parent_context, trace_id):
+ # type: (Optional[SpanContext], int) -> Optional[bool]
+ if parent_context is None:
+ return None
+
+ is_span_context_valid = parent_context is not None and parent_context.is_valid
+
+ # Only inherit sample rate if `traceId` is the same
+ if is_span_context_valid and parent_context.trace_id == trace_id:
+ # this is getSamplingDecision in JS
+ if parent_context.trace_flags.sampled:
+ return True
+
+ dropped = parent_context.trace_state.get(SENTRY_TRACE_STATE_DROPPED) == "true"
+ if dropped:
+ return False
+
+ # TODO-anton: fall back to sampling decision in DSC (for this die DSC needs to be set in the trace_state)
+
+ return None
+
+
+def dropped(parent_context=None):
+ # type: (Optional[SpanContext]) -> SamplingResult
+ trace_state = parent_context.trace_state if parent_context is not None else None
+ updated_trace_context = trace_state or TraceState()
+ updated_trace_context = updated_trace_context.update(
+ SENTRY_TRACE_STATE_DROPPED, "true"
+ )
+ return SamplingResult(
+ Decision.DROP,
+ trace_state=updated_trace_context,
+ )
+
+
+class SentrySampler(Sampler):
+ def should_sample(
+ self,
+ parent_context, # type: Optional[Context]
+ trace_id, # type: int
+ name, # type: str
+ kind=None, # type: Optional[SpanKind]
+ attributes=None, # type: Attributes
+ links=None, # type: Optional[Sequence[Link]]
+ trace_state=None, # type: Optional[TraceState]
+ ):
+ # type: (...) -> SamplingResult
+ client = sentry_sdk.get_client()
+
+ parent_span = trace.get_current_span(parent_context)
+ parent_context = parent_span.get_span_context() if parent_span else None
+
+ # No tracing enabled, thus no sampling
+ if not has_tracing_enabled(client.options):
+ return dropped(parent_context)
+
+ sample_rate = None
+
+ # Check if sampled=True was passed to start_transaction
+ # TODO-anton: Do we want to keep the start_transaction(sampled=True) thing?
+
+ # Check if there is a traces_sampler
+ # Traces_sampler is responsible to check parent sampled to have full transactions.
+ has_traces_sampler = callable(client.options.get("traces_sampler"))
+ if has_traces_sampler:
+ # TODO-anton: Make proper sampling_context
+ sampling_context = {
+ "transaction_context": {
+ "name": name,
+ },
+ "parent_sampled": get_parent_sampled(parent_context, trace_id),
+ }
+
+ sample_rate = client.options["traces_sampler"](sampling_context)
+
+ else:
+ # Check if there is a parent with a sampling decision
+ parent_sampled = get_parent_sampled(parent_context, trace_id)
+ if parent_sampled is not None:
+ sample_rate = parent_sampled
+ else:
+ # Check if there is a traces_sample_rate
+ sample_rate = client.options.get("traces_sample_rate")
+
+ # If the sample rate is invalid, drop the span
+ if not is_valid_sample_rate(sample_rate, source=self.__class__.__name__):
+ logger.warning(
+ f"[Tracing] Discarding {name} because of invalid sample rate."
+ )
+ return dropped(parent_context)
+
+ # Roll the dice on sample rate
+ sampled = random() < float(sample_rate)
+
+ if sampled:
+ return SamplingResult(Decision.RECORD_AND_SAMPLE)
+ else:
+ return dropped(parent_context)
+
+ def get_description(self) -> str:
+ return self.__class__.__name__

sentry_sdk/integrations/opentelemetry/scope.py

@@ -97,6 +97,9 @@ def _incoming_otel_span_context(self):
  span_id=int(self._propagation_context.parent_span_id, 16), # type: ignore
  is_remote=True,
  trace_flags=trace_flags,
+ # TODO-anton: add trace_state (mapping[str,str]) with the parentSpanId, dsc and sampled from self._propagation_context
+ # trace_state={
+ # }
  )
 
  return span_context