improvement: better memory usage and admin commands to analyze it

src/database/abstraction.rs

@@ -38,6 +38,7 @@ pub trait KeyValueDatabaseEngine: Send + Sync {
     fn memory_usage(&self) -> Result<String> {
         Ok("Current database engine does not support memory usage reporting.".to_owned())
     }
+    fn clear_caches(&self) {}
 }
 
 pub trait KvTree: Send + Sync {

src/database/abstraction/rocksdb.rs

@@ -45,6 +45,10 @@ fn db_options(max_open_files: i32, rocksdb_cache: &rocksdb::Cache) -> rocksdb::O
     db_opts.set_compaction_style(rocksdb::DBCompactionStyle::Level);
     db_opts.optimize_level_style_compaction(10 * 1024 * 1024);
 
+    // https://github.com/facebook/rocksdb/wiki/Setup-Options-and-Basic-Tuning
+    db_opts.set_max_background_jobs(6);
+    db_opts.set_bytes_per_sync(1048576);
+
     let prefix_extractor = rocksdb::SliceTransform::create_fixed_prefix(1);
     db_opts.set_prefix_extractor(prefix_extractor);
 
@@ -121,6 +125,8 @@ impl KeyValueDatabaseEngine for Arc<Engine> {
             self.cache.get_pinned_usage() as f64 / 1024.0 / 1024.0,
         ))
     }
+
+    fn clear_caches(&self) {}
 }
 
 impl RocksDbEngineTree<'_> {

src/database/key_value/globals.rs

@@ -118,8 +118,59 @@ impl service::globals::Data for KeyValueDatabase {
         self._db.cleanup()
     }
 
-    fn memory_usage(&self) -> Result<String> {
-        self._db.memory_usage()
+    fn memory_usage(&self) -> String {
+        let pdu_cache = self.pdu_cache.lock().unwrap().len();
+        let shorteventid_cache = self.shorteventid_cache.lock().unwrap().len();
+        let auth_chain_cache = self.auth_chain_cache.lock().unwrap().len();
+        let eventidshort_cache = self.eventidshort_cache.lock().unwrap().len();
+        let statekeyshort_cache = self.statekeyshort_cache.lock().unwrap().len();
+        let our_real_users_cache = self.our_real_users_cache.read().unwrap().len();
+        let appservice_in_room_cache = self.appservice_in_room_cache.read().unwrap().len();
+        let lasttimelinecount_cache = self.lasttimelinecount_cache.lock().unwrap().len();
+
+        let mut response = format!(
+            "\
+pdu_cache: {pdu_cache}
+shorteventid_cache: {shorteventid_cache}
+auth_chain_cache: {auth_chain_cache}
+eventidshort_cache: {eventidshort_cache}
+statekeyshort_cache: {statekeyshort_cache}
+our_real_users_cache: {our_real_users_cache}
+appservice_in_room_cache: {appservice_in_room_cache}
+lasttimelinecount_cache: {lasttimelinecount_cache}\n"
+        );
+        if let Ok(db_stats) = self._db.memory_usage() {
+            response += &db_stats;
+        }
+
+        response
+    }
+
+    fn clear_caches(&self, amount: u32) {
+        if amount > 0 {
+            self.pdu_cache.lock().unwrap().clear();
+        }
+        if amount > 1 {
+            self.shorteventid_cache.lock().unwrap().clear();
+        }
+        if amount > 2 {
+            self.auth_chain_cache.lock().unwrap().clear();
+        }
+        if amount > 3 {
+            self.eventidshort_cache.lock().unwrap().clear();
+        }
+        if amount > 4 {
+            self.statekeyshort_cache.lock().unwrap().clear();
+        }
+        if amount > 5 {
+            self.our_real_users_cache.write().unwrap().clear();
+        }
+        if amount > 6 {
+            self.appservice_in_room_cache.write().unwrap().clear();
+        }
+        if amount > 7 {
+            self.lasttimelinecount_cache.lock().unwrap().clear();
+        }
     }
 
     fn load_keypair(&self) -> Result<Ed25519KeyPair> {