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fix(sampling): Respect incoming sample rate if not explicitly overridden #8185

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Merged
sentrivana merged 1 commit into from
Nov 5, 2026
Merged

fix(sampling): Respect incoming sample rate if not explicitly overridden #8185

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16 changes: 14 additions & 2 deletions sentry_sdk/scope.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1188,10 +1188,17 @@
"parent_sampled": transaction.parent_sampled,
}
sampling_context.update(custom_sampling_context)

keep_incoming_sample_rate = (
transaction.sampled is None
and transaction.parent_sampled is not None
and not callable(client.options.get("traces_sampler"))
)

transaction._set_initial_sampling_decision(sampling_context=sampling_context)

# update the sample rate in the dsc
if transaction.sample_rate is not None:
if transaction.sample_rate is not None and not keep_incoming_sample_rate:

Check warning on line 1201 in sentry_sdk/scope.py

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@sentry/warden / warden: code-review

Backpressure-adjusted sample rate is not written to DSC 

`keep_incoming_sample_rate` stays true under backpressure, so a downsampled `transaction.sample_rate` never updates baggage/DSC even though this PR says backpressure should override; also gate on `client.monitor.downsample_factor` (or compare rates) and add a regression test.
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propagation_context = self.get_active_propagation_context()
baggage = propagation_context.baggage

Expand Down Expand Up @@ -1337,7 +1344,12 @@
self,
)

if sample_rate is not None:
keep_incoming_sample_rate = (
propagation_context.parent_sampled is not None
and not callable(self.get_client().options.get("traces_sampler"))
)

if sample_rate is not None and not keep_incoming_sample_rate:
self._update_sample_rate(sample_rate)

if sampled is False or sampled is None:
Expand Down
4 changes: 2 additions & 2 deletions tests/integrations/stdlib/test_httplib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -457,7 +457,7 @@ def getresponse(self, *args, **kwargs):
expected_outgoing_baggage = (
"sentry-trace_id=771a43a4192642f0b136d5159a501700,"
"sentry-public_key=49d0f7386ad645858ae85020e393bef3,"
"sentry-sample_rate=1.0,"
"sentry-sample_rate=0.01337,"
"sentry-user_id=Am%C3%A9lie,"
"sentry-sample_rand=0.000005,"
"sentry-sampled=true"
Expand Down Expand Up @@ -487,7 +487,7 @@ def getresponse(self, *args, **kwargs):
expected_outgoing_baggage = (
"sentry-trace_id=771a43a4192642f0b136d5159a501700,"
"sentry-public_key=49d0f7386ad645858ae85020e393bef3,"
"sentry-sample_rate=1.0,"
"sentry-sample_rate=0.01337,"
"sentry-user_id=Am%C3%A9lie,"
"sentry-sample_rand=0.000005,"
"sentry-sampled=true"
Expand Down
8 changes: 4 additions & 4 deletions tests/test_dsc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -201,7 +201,7 @@ def test_dsc_continuation_of_trace(sentry_init, capture_envelopes):
dsn="https://mysecret@o1234.ingest.sentry.io/12312012",
release="myapp@0.0.1",
environment="canary",
traces_sample_rate=1.0,
traces_sample_rate=0.5,
transport=TestTransportWithOptions,
)
envelopes = capture_envelopes()
Expand Down Expand Up @@ -244,7 +244,7 @@ def test_dsc_continuation_of_trace(sentry_init, capture_envelopes):

assert "sample_rate" in envelope_trace_header
assert type(envelope_trace_header["sample_rate"]) == str
assert envelope_trace_header["sample_rate"] == "1.0"
assert envelope_trace_header["sample_rate"] == "0.01337"

assert "sampled" in envelope_trace_header
assert type(envelope_trace_header["sampled"]) == str
Expand Down Expand Up @@ -272,7 +272,7 @@ def test_dsc_continuation_of_trace_span_streaming(sentry_init, capture_envelopes
dsn="https://mysecret@o1234.ingest.sentry.io/12312012",
release="myapp@0.0.1",
environment="canary",
traces_sample_rate=1.0,
traces_sample_rate=0.5,
trace_lifecycle="stream",
transport=TestTransportWithOptions,
)
Expand Down Expand Up @@ -318,7 +318,7 @@ def test_dsc_continuation_of_trace_span_streaming(sentry_init, capture_envelopes

assert "sample_rate" in envelope_trace_header
assert type(envelope_trace_header["sample_rate"]) == str
assert envelope_trace_header["sample_rate"] == "1.0"
assert envelope_trace_header["sample_rate"] == "0.01337"

assert "sampled" in envelope_trace_header
assert type(envelope_trace_header["sampled"]) == str
Expand Down
6 changes: 3 additions & 3 deletions tests/tracing/test_integration_tests.py
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Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,7 @@ def test_continue_trace(sentry_init, capture_envelopes, parent_sampled, sample_r
)

if parent_sampled is not None:
expected_sample_rate = str(float(parent_sampled))
expected_sample_rate = "0.01337"
else:
expected_sample_rate = str(sample_rate)

Expand Down Expand Up @@ -262,7 +262,7 @@ def test_continue_trace_span_streaming(
assert not baggage.mutable

if parent_sampled is not None:
expected_sample_rate = str(float(parent_sampled))
expected_sample_rate = parent_sample_rate
else:
if sample_rate is None:
expected_sample_rate = parent_sample_rate
Expand Down Expand Up @@ -312,7 +312,7 @@ def test_continue_trace_span_streaming(
)

if parent_sampled is not None:
expected_sample_rate = str(float(parent_sampled))
expected_sample_rate = parent_sample_rate
else:
if sample_rate is None:
expected_sample_rate = parent_sample_rate
Expand Down
12 changes: 2 additions & 10 deletions tests/tracing/test_span_streaming.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1082,12 +1082,7 @@ def test_outgoing_traceparent_and_baggage_incoming_trace(
baggage_items = dict(tuple(item.split("=")) for item in baggage.split(","))

# As we've received incoming baggage, we shouldn't modify it ourselves
# and should propagate it as-is. However, in the case where our
# effective sample rate overrides the parent sample rate, we update the
# sample rate in the baggage as a consequence of updating the sample rate
# in the DSC.
if traces_sample_rate is not None:
incoming_baggage["sentry-sample_rate"] = str(float(parent_sampled))
# and should propagate it as-is

assert baggage_items == incoming_baggage

Expand Down Expand Up @@ -1133,12 +1128,9 @@ def test_outgoing_traceparent_and_baggage_inconsistent_incoming_trace(
span_id = span.span_id
assert traceparent == f"{trace_id}-{span_id}-0"

# We shouldn't be updating incoming baggage, but in the case where our
# effective sample rate overrides the parent sample rate, we do this as
# a consequence of updating the sample rate in the DSC.
# We shouldn't be updating incoming baggage
baggage = sentry_sdk.get_baggage()
baggage_items = dict(tuple(item.split("=")) for item in baggage.split(","))
incoming_baggage["sentry-sample_rate"] = "0.0"
assert baggage_items == incoming_baggage


Expand Down
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