efficiently initialize actor ID, remove extra annotation

Signed-off-by: Brooks Townsend <brooks@cosmonic.com>

src/scaler/spreadscaler.rs

@@ -2,6 +2,7 @@ use std::{cmp::Ordering, collections::HashMap};
 
 use anyhow::Result;
 use async_trait::async_trait;
+use tokio::sync::OnceCell;
 use tracing::log::warn;
 
 use crate::{
@@ -18,7 +19,7 @@ const SCALER_VALUE: &str = "spreadscaler";
 const SPREAD_KEY: &str = "wasmcloud/dev/spread_name";
 
 /// Config for an ActorSpreadScaler
-struct ActorSpreadConfig {
+pub struct ActorSpreadConfig {
     /// OCI, Bindle, or File reference for an actor
     actor_reference: String,
     /// Lattice ID that this SpreadScaler monitors
@@ -27,14 +28,16 @@ struct ActorSpreadConfig {
     model_name: String,
     /// Configuration for this SpreadScaler
     spread_config: SpreadScalerProperty,
+    /// Actor ID, stored in a OnceCell to facilitate more efficient fetches
+    actor_id: OnceCell<String>,
 }
 
 /// The ActorSpreadScaler ensures that a certain number of replicas are running,
 /// spread across a number of hosts according to a [SpreadScalerProperty](crate::model::SpreadScalerProperty)
 ///
 /// If no [Spreads](crate::model::Spread) are specified, this Scaler simply maintains the number of replicas
 /// on an available host
-struct ActorSpreadScaler<S: ReadStore + Send + Sync> {
+pub struct ActorSpreadScaler<S: ReadStore + Send + Sync> {
     pub config: ActorSpreadConfig,
     spread_requirements: Vec<(Spread, usize)>,
     store: S,
@@ -168,7 +171,6 @@ impl<S: ReadStore + Send + Sync> Scaler for ActorSpreadScaler<S> {
 }
 
 impl<S: ReadStore + Send + Sync> ActorSpreadScaler<S> {
-    #[allow(unused)]
     /// Construct a new ActorSpreadScaler with specified configuration values
     pub fn new(
         store: S,
@@ -182,38 +184,40 @@ impl<S: ReadStore + Send + Sync> ActorSpreadScaler<S> {
             spread_requirements: compute_spread(&spread_config),
             config: ActorSpreadConfig {
                 actor_reference,
+                actor_id: OnceCell::new(),
                 lattice_id,
                 spread_config,
                 model_name,
             },
         }
     }
 
-    // TODO(brooksmtownsend): Need to consider a better way to grab this. It will fail to find
-    // the actor ID if it's not running in the lattice currently, which seems brittle
     /// Helper function to retrieve the actor ID for the configured actor
     async fn actor_id(&self) -> Result<String> {
         Ok(self
-            .store
-            .list::<Actor>(&self.config.lattice_id)
-            .await?
-            .iter()
-            .find(|(_id, actor)| actor.reference == self.config.actor_reference)
-            .map(|(id, _actor)| id.to_owned())
-            // Default here means the below `get` will find zero running actors, which is fine because
-            // that accurately describes the current lattice having zero instances.
-            .unwrap_or_default())
+            .config
+            .actor_id
+            .get_or_init(|| async {
+                self.store
+                    .list::<Actor>(&self.config.lattice_id)
+                    .await
+                    .unwrap_or_default()
+                    .iter()
+                    .find(|(_id, actor)| actor.reference == self.config.actor_reference)
+                    .map(|(id, _actor)| id.to_owned())
+                    // Default here means the below `get` will find zero running actors, which is fine because
+                    // that accurately describes the current lattice having zero instances.
+                    .unwrap_or_default()
+            })
+            .await
+            .to_string())
     }
 
     /// Helper function to create a predictable annotations map for a spread
     fn annotations(&self, spread_name: &str) -> HashMap<String, String> {
         HashMap::from_iter([
             (SCALER_KEY.to_string(), SCALER_VALUE.to_string()),
             (SPREAD_KEY.to_string(), spread_name.to_string()),
-            (
-                crate::MANAGED_BY_ANNOTATION.to_owned(),
-                crate::MANAGED_BY_IDENTIFIER.to_owned(),
-            ),
         ])
     }
 }