move shorteventid_cache to service

src/service/rooms/short.rs

@@ -1,8 +1,12 @@
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 
+use lru_cache::LruCache;
 use ruma::{events::StateEventType, EventId, RoomId};
 
-use crate::utils::error::Result;
+use crate::{
+    observability::{FoundIn, Lookup, METRICS},
+    utils::error::Result,
+};
 
 macro_rules! short_id_type {
     ($name:ident) => {
@@ -33,12 +37,19 @@ pub(crate) use data::Data;
 
 pub(crate) struct Service {
     db: &'static dyn Data,
+    shorteventid_cache: Mutex<LruCache<ShortEventId, Arc<EventId>>>,
 }
 
 impl Service {
-    pub(crate) fn new(db: &'static dyn Data) -> Self {
+    pub(crate) fn new(
+        db: &'static dyn Data,
+        shorteventid_cache_size: usize,
+    ) -> Self {
         Self {
             db,
+            shorteventid_cache: Mutex::new(LruCache::new(
+                shorteventid_cache_size,
+            )),
         }
     }
 
@@ -69,7 +80,25 @@ impl Service {
         &self,
         shorteventid: ShortEventId,
     ) -> Result<Arc<EventId>> {
-        self.db.get_eventid_from_short(shorteventid)
+        let lookup = Lookup::ShortToEventId;
+
+        if let Some(id) =
+            self.shorteventid_cache.lock().unwrap().get_mut(&shorteventid)
+        {
+            METRICS.record_lookup(lookup, FoundIn::Cache);
+            return Ok(Arc::clone(id));
+        }
+
+        let event_id = self.db.get_eventid_from_short(shorteventid)?;
+
+        METRICS.record_lookup(lookup, FoundIn::Database);
+
+        self.shorteventid_cache
+            .lock()
+            .unwrap()
+            .insert(shorteventid, Arc::clone(&event_id));
+
+        Ok(event_id)
     }
 
     pub(crate) fn get_statekey_from_short(