Making performance trace sample rate configurable

crates/symbolicator-service/src/config.rs

@@ -473,6 +473,9 @@ pub struct Config {
     /// cached on disk. The path is created if it doesn't exist. Path must be UTF-8.
     #[serde(default)]
     pub _crash_db: Option<PathBuf>,
+
+    /// The sample rate for transactions. (0.0 - 1.0, defaults to 0.05)
+    pub transaction_sample_rate: f32,
 }
 
 impl Config {
@@ -556,6 +559,7 @@ impl Default for Config {
             max_concurrent_requests: Some(200),
             shared_cache: None,
             _crash_db: None,
+            transaction_sample_rate: 0.05,
         }
     }
 }

crates/symbolicator/src/cli.rs

@@ -87,10 +87,11 @@ pub fn execute() -> Result<()> {
         release,
         session_mode: sentry::SessionMode::Request,
         auto_session_tracking: false,
-        traces_sampler: Some(Arc::new(|ctx| {
+        traces_sampler: Some(Arc::new(move |ctx| {
             if Some(true) == ctx.sampled() {
                 1.0
             } else if ctx.operation() != "http.server" {
+                // TODO: Think about what to do with this comment now:
                 // Symbolicator receives at peak:
                 // - ~3_000 `symbolicate_js`,
                 // - ~800 `symbolicater`, and
@@ -100,7 +101,8 @@ pub fn execute() -> Result<()> {
                 // we end up with ~200 sampled transactions per second, or ~12_000 per minute.
                 // We only do this for the "real" transactions and not the http frontend that
                 // just spawns these computations.
-                0.05
+
+                config.transaction_sample_rate
             } else {
                 0.0
             }

local.example.yml

@@ -13,6 +13,9 @@ cache_dir: cache
 logging:
   level: error
 
+# The sample rate for transactions. (0.0 - 1.0, defaults to 0.05)
+transaction_sample_rate: 0.05
+
 # Configure some default symbol sources:
 sources:
   # You can use symsorter to correctly sort symbols into the local filesystem source: