Add a span property for whether an isolate was reused (#37587)

GitOrigin-RevId: 0bdcc82a07aa2ae3738c186b8eb796e851673a82

Author: goffrie

crates/isolate/src/client.rs

@@ -13,7 +13,10 @@ use std::{
     time::Duration,
 };
 
-use ::metrics::Timer;
+use ::metrics::{
+    IntoLabel,
+    Timer,
+};
 use async_trait::async_trait;
 use common::{
     auth::AuthConfig,
@@ -1417,7 +1420,7 @@ pub trait IsolateWorker<RT: Runtime>: Clone + Send + 'static {
                             return;
                         };
                         let reused = last_client_id.is_some();
-                        // If we receive a request from a different client (i.e. a different backend),
+                        // If we receive a request from a different client (i.e. a different instance),
                         // recreate the isolate. We don't allow an isolate to be reused
                         // across clients for security isolation.
                         if last_client_id.get_or_insert_with(|| {
@@ -1442,6 +1445,7 @@ pub trait IsolateWorker<RT: Runtime>: Clone + Send + 'static {
                             func_path!(),
                             req.parent_trace.clone(),
                         );
+                        root.add_property(|| ("reused_isolate", reused.as_label()));
                         // Require the layer below to opt into isolate reuse by setting `isolate_clean`.
                         let mut isolate_clean = false;
                         let debug_str = self

crates/isolate/src/metrics.rs

@@ -627,17 +627,19 @@ pub fn log_isolate_out_of_memory() {
 }
 
 pub fn record_component_function_path(component_function_path: &ResolvedComponentFunctionPath) {
-    let mut labels = vec![(
-        Cow::Borrowed("udf_path"),
-        Cow::Owned(component_function_path.udf_path.to_string()),
-    )];
-    if let Some(component_path) = &component_function_path.component_path {
-        labels.push((
-            Cow::Borrowed("component"),
-            Cow::Owned(component_path.to_string()),
-        ));
-    }
-    LocalSpan::add_event(Event::new("component_function_path").with_properties(|| labels));
+    LocalSpan::add_event(Event::new("component_function_path").with_properties(|| {
+        let mut labels = vec![(
+            Cow::Borrowed("udf_path"),
+            Cow::Owned(component_function_path.udf_path.to_string()),
+        )];
+        if let Some(component_path) = &component_function_path.component_path {
+            labels.push((
+                Cow::Borrowed("component"),
+                Cow::Owned(component_path.to_string()),
+            ));
+        }
+        labels
+    }));
 }
 
 register_convex_counter!(