add a default implementation for BanditCache

components/relevancy/src/lib.rs

@@ -23,8 +23,8 @@ use rand_distr::{Beta, Distribution};
 pub use db::RelevancyDb;
 pub use error::{ApiResult, Error, RelevancyApiError, Result};
 pub use interest::{Interest, InterestVector};
-pub use ranker::score;
 use parking_lot::Mutex;
+pub use ranker::score;
 
 use error_support::handle_error;
 
@@ -129,11 +129,7 @@ impl RelevancyStore {
     /// database, creates a Beta distribution, and samples from it to estimate the arm's probability
     /// of success. The arm with the highest sampled probability is selected and returned.
     #[handle_error(Error)]
-    pub fn bandit_select(
-        &self,
-        bandit: String,
-        arms: &[String],
-    ) -> ApiResult<String> {
+    pub fn bandit_select(&self, bandit: String, arms: &[String]) -> ApiResult<String> {
         let mut cache = self.cache.lock();
         let mut best_sample = f64::MIN;
         let mut selected_arm = String::new();
@@ -167,7 +163,9 @@ impl RelevancyStore {
     pub fn bandit_update(&self, bandit: String, arm: String, selected: bool) -> ApiResult<()> {
         let mut cache = self.cache.lock();
 
-        cache.clear(&bandit, &arm).expect("failed to clear cached distribution");
+        cache
+            .clear(&bandit, &arm)
+            .expect("failed to clear cached distribution");
 
         self.db
             .read_write(|dao| dao.update_bandit_arm_data(&bandit, &arm, selected))?;
@@ -180,6 +178,12 @@ pub struct BanditCache {
     cache: HashMap<(String, String), (usize, usize)>,
 }
 
+impl Default for BanditCache {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl BanditCache {
     /// Creates a new, empty `BanditCache`.
     ///
@@ -222,11 +226,7 @@ impl BanditCache {
     ///
     /// This removes the cached values for the specified `bandit` and `arm` from the cache.
     /// Use this method if the cached parameters are no longer valid or need to be refreshed.
-    pub fn clear(
-        &mut self,
-        bandit: &str,
-        arm: &str,
-    ) -> Result<()> {
+    pub fn clear(&mut self, bandit: &str, arm: &str) -> Result<()> {
         let key = (bandit.to_string(), arm.to_string());
 
         self.cache.remove(&key);