introduce specific databasemetrics value type

bin/reth/src/node/events.rs

@@ -195,9 +195,9 @@ impl<DB> NodeState<DB> {
     }
 }
 
-impl<DB: DatabaseMetadata<Metadata = usize>> NodeState<DB> {
+impl<DB: DatabaseMetadata> NodeState<DB> {
     fn freelist(&self) -> Option<usize> {
-        self.db.metadata().get("freelist").copied()
+        self.db.metadata().freelist_size()
     }
 }
 
@@ -278,7 +278,7 @@ pub async fn handle_events<E, DB>(
     db: DB,
 ) where
     E: Stream<Item = NodeEvent> + Unpin,
-    DB: DatabaseMetadata<Metadata = usize> + Database + 'static,
+    DB: DatabaseMetadata + Database + 'static,
 {
     let state = NodeState::new(db, network, latest_block_number);
 
@@ -303,7 +303,7 @@ struct EventHandler<E, DB> {
 impl<E, DB> Future for EventHandler<E, DB>
 where
     E: Stream<Item = NodeEvent> + Unpin,
-    DB: DatabaseMetadata<Metadata = usize> + Database + 'static,
+    DB: DatabaseMetadata + Database + 'static,
 {
     type Output = ();
 

crates/storage/db/src/abstraction/database_metrics.rs

@@ -1,5 +1,5 @@
 use metrics::{counter, gauge, histogram, Label};
-use std::{collections::HashMap, sync::Arc};
+use std::sync::Arc;
 
 /// Represents a type that can report metrics, used mainly with the database. The `report_metrics`
 /// method can be used as a prometheus hook.
@@ -41,20 +41,34 @@ impl<DB: DatabaseMetrics> DatabaseMetrics for Arc<DB> {
     }
 }
 
+/// The type used to store metadata about the database.
+#[derive(Debug)]
+pub struct DatabaseMetadataValue {
+    /// The freelist size
+    freelist_size: Option<usize>,
+}
+
+impl DatabaseMetadataValue {
+    /// Creates a new [DatabaseMetadataValue] with the given freelist size.
+    pub fn new(freelist_size: Option<usize>) -> Self {
+        Self { freelist_size }
+    }
+
+    /// Returns the freelist size, if available.
+    pub fn freelist_size(&self) -> Option<usize> {
+        self.freelist_size
+    }
+}
+
 /// Extends [Database] to include a [Metadata] type, which can be used by methods which need to
 /// dynamically retrieve information about the database.
 pub trait DatabaseMetadata {
-    /// The type used to store metadata about the database.
-    type Metadata;
-
-    /// Returns a [HashMap] of [&'static str]-addressable metadata about the database.
-    fn metadata(&self) -> HashMap<&'static str, Self::Metadata>;
+    /// TODO
+    fn metadata(&self) -> DatabaseMetadataValue;
 }
 
 impl<DB: DatabaseMetadata> DatabaseMetadata for Arc<DB> {
-    type Metadata = DB::Metadata;
-
-    fn metadata(&self) -> HashMap<&'static str, Self::Metadata> {
+    fn metadata(&self) -> DatabaseMetadataValue {
         <DB as DatabaseMetadata>::metadata(self)
     }
 }

crates/storage/db/src/implementation/mdbx/mod.rs

@@ -2,7 +2,7 @@
 
 use crate::{
     database::Database,
-    database_metrics::{DatabaseMetadata, DatabaseMetrics},
+    database_metrics::{DatabaseMetadata, DatabaseMetadataValue, DatabaseMetrics},
     tables::{TableType, Tables},
     utils::default_page_size,
     DatabaseError,
@@ -14,7 +14,7 @@ use reth_libmdbx::{
     DatabaseFlags, Environment, EnvironmentFlags, Geometry, Mode, PageSize, SyncMode, RO, RW,
 };
 use reth_tracing::tracing::error;
-use std::{collections::HashMap, ops::Deref, path::Path};
+use std::{ops::Deref, path::Path};
 use tx::Tx;
 
 pub mod cursor;
@@ -133,15 +133,8 @@ impl DatabaseMetrics for DatabaseEnv {
 }
 
 impl DatabaseMetadata for DatabaseEnv {
-    type Metadata = usize;
-
-    fn metadata(&self) -> HashMap<&'static str, Self::Metadata> {
-        let mut metadata = HashMap::new();
-
-        if let Ok(freelist) = self.freelist() {
-            metadata.insert("freelist", freelist);
-        }
-        metadata
+    fn metadata(&self) -> DatabaseMetadataValue {
+        DatabaseMetadataValue::new(self.freelist().ok())
     }
 }
 
@@ -234,7 +227,7 @@ impl DatabaseEnv {
                     LogLevel::Extra => 7,
                 });
             } else {
-                return Err(DatabaseError::LogLevelUnavailable(log_level))
+                return Err(DatabaseError::LogLevelUnavailable(log_level));
             }
         }
 

crates/storage/db/src/lib.rs

@@ -155,9 +155,9 @@ pub mod test_utils {
     use super::*;
     use crate::{
         database::Database,
-        database_metrics::{DatabaseMetadata, DatabaseMetrics},
+        database_metrics::{DatabaseMetadata, DatabaseMetadataValue, DatabaseMetrics},
     };
-    use std::{collections::HashMap, path::PathBuf, sync::Arc};
+    use std::{path::PathBuf, sync::Arc};
 
     /// Error during database open
     pub const ERROR_DB_OPEN: &str = "Not able to open the database file.";
@@ -220,9 +220,7 @@ pub mod test_utils {
     }
 
     impl<DB: DatabaseMetadata> DatabaseMetadata for TempDatabase<DB> {
-        type Metadata = <DB as DatabaseMetadata>::Metadata;
-
-        fn metadata(&self) -> HashMap<&'static str, Self::Metadata> {
+        fn metadata(&self) -> DatabaseMetadataValue {
             self.db().metadata()
         }
     }