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feat: Allow overriding the sampling rate. #1284

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feat: Allow overriding the sampling rate. #1284

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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,5 +1,8 @@
# Changelog

## 0.49.2
- Added `override_sampling_rate` to `ClientOptions` to allow user defined function to override sampling rate when capturing an event. ([#1128](https://github.com/getsentry/sentry-rust/pull/1128)).

## 0.49.1

### Fixes
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10 changes: 8 additions & 2 deletions sentry-core/src/client/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -397,8 +397,14 @@ impl Client {
scope.update_session_from_event(&event);
}

let sample_rate = event_sample_rate(&self.options.event_sampling_strategy);
if !self.sample_should_send(sample_rate) {
let sampling_rate = self
.options()
.override_sampling_rate
.as_ref()
.and_then(|f| f(&event))
.unwrap_or_else(|| event_sample_rate(&self.options.event_sampling_strategy));

if !self.sample_should_send(sampling_rate) {
self.record_lost_event(ClientReportReason::SampleRate);
None
Comment on lines +403 to 409

@sentry sentry Bot Aug 8, 2026

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Bug: The override_sampling_rate callback lacks validation for NaN values, causing sample_should_send to always return false and silently drop all events.
Severity: MEDIUM

Suggested Fix

Validate the f32 value returned from the override_sampling_rate callback. One option is to panic if the value is invalid (e.g., NaN, not in the [0.0, 1.0] range), which would be consistent with other sampling rate setters like sample_rate(). Alternatively, clamp invalid values to a safe default (like 0.0) and document the behavior.

Prompt for AI Agent 
Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: sentry-core/src/client/mod.rs#L403-L409

Potential issue: The `override_sampling_rate` callback does not validate the `f32` value
it returns. If a user's callback returns a `NaN` value (e.g., through a division by
zero), this value is passed to the `sample_should_send` function. Due to IEEE 754
floating-point semantics, all comparisons with `NaN` (`>= 1.0`, `<= 0.0`, and `< rate`)
evaluate to `false`. This causes `sample_should_send` to always return `false`,
resulting in all events being silently dropped. This behavior is inconsistent with other
sampling rate setters in the SDK which panic on invalid values.

Did we get this right? 👍 / 👎 to inform future reviews.

} else {
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19 changes: 19 additions & 0 deletions sentry-core/src/clientoptions.rs
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Expand Up @@ -12,6 +12,9 @@ use crate::{Integration, IntoDsn, TransportFactory};
/// Type alias for before event/breadcrumb handlers.
pub type BeforeCallback<T> = Arc<dyn Fn(T) -> Option<T> + Send + Sync>;

/// Type alias for override sample rate callback.
pub type OverrideSamplingRateCallback = Arc<dyn Fn(&Event<'static>) -> Option<f32> + Send + Sync>;

/// The Session Mode of the SDK.
///
/// Depending on the use-case, the SDK can be set to two different session modes:
Expand Down Expand Up @@ -220,6 +223,8 @@ pub struct ClientOptions {
///
/// See [`before_breadcrumb`](method@ClientOptions::before_breadcrumb) for details.
pub before_breadcrumb: Option<BeforeCallback<Breadcrumb>>,
/// Callback allowing for setting sampling rate based on user defined function.
pub override_sampling_rate: Option<OverrideSamplingRateCallback>,
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/// Callback that is executed for each Log being added.
///
/// See [`before_send_log`](method@ClientOptions::before_send_log) for details.
Expand Down Expand Up @@ -580,6 +585,19 @@ impl ClientOptions {
}
}

/// Sets the [callback](field@ClientOptions::override_sampling_rate) that is used to override the
/// sampling rate.
#[inline]
pub fn override_sampling_rate(
self,
override_func: impl Fn(&Event<'static>) -> Option<f32> + Send + Sync + 'static,
) -> Self {
Self {
override_sampling_rate: Some(Arc::new(override_func)),
..self
}
}

/// Sets the [callback](field@ClientOptions::before_send_log) that is executed before sending
/// each log.
#[cfg(feature = "logs")]
Expand Down Expand Up @@ -860,6 +878,7 @@ impl Default for ClientOptions {
before_send_log: None,
enable_metrics: true,
before_send_metric: None,
override_sampling_rate: None,
}
}
}
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