sentry: Reduce trace sample rate for download endpoint

Author: Turbo87

Diff for: src/sentry/mod.rs

@@ -29,7 +29,18 @@ pub fn init() -> ClientInitGuard {
 
     let traces_sample_rate = env_optional("SENTRY_TRACES_SAMPLE_RATE").unwrap_or(0.0);
 
-    let traces_sampler = move |_ctx: &TransactionContext| -> f32 { traces_sample_rate };
+    let traces_sampler = move |ctx: &TransactionContext| -> f32 {
+        let is_download_endpoint =
+            ctx.name().starts_with("/api/v1/crates/") && ctx.name().ends_with("/download");
+
+        if is_download_endpoint {
+            // Reduce the sample rate for the download endpoint, since we have significantly
+            // more traffic on that endpoint compared to the rest
+            traces_sample_rate / 10.
+        } else {
+            traces_sample_rate
+        }
+    };
 
     let opts = ClientOptions {
         auto_session_tracking: true,