From dc3d1ef197547637df4209e5eee633e12f8f234a Mon Sep 17 00:00:00 2001
From: Darrell Roberts <droberts0674@gmail.com>
Date: Sat, 16 May 2026 12:35:15 -0400
Subject: [PATCH] feat: Allow overriding the sampling rate.

Allow for a user defined function for setting the sampling rate.
Similar to Python SDK https://docs.sentry.io/platforms/python/sampling/#dynamically-sampling-error-events
---
 CHANGELOG.md                     |  3 +++
 sentry-core/src/client/mod.rs    | 10 ++++++++--
 sentry-core/src/clientoptions.rs | 19 +++++++++++++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d1932164..5a1f4c2b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -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
diff --git a/sentry-core/src/client/mod.rs b/sentry-core/src/client/mod.rs
index bc75919a..fa830eaf 100644
--- a/sentry-core/src/client/mod.rs
+++ b/sentry-core/src/client/mod.rs
@@ -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
         } else {
diff --git a/sentry-core/src/clientoptions.rs b/sentry-core/src/clientoptions.rs
index a67658db..7961bc3e 100644
--- a/sentry-core/src/clientoptions.rs
+++ b/sentry-core/src/clientoptions.rs
@@ -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:
@@ -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>,
     /// Callback that is executed for each Log being added.
     ///
     /// See [`before_send_log`](method@ClientOptions::before_send_log) for details.
@@ -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")]
@@ -860,6 +878,7 @@ impl Default for ClientOptions {
             before_send_log: None,
             enable_metrics: true,
             before_send_metric: None,
+            override_sampling_rate: None,
         }
     }
 }