Make Storage methods async

This will better support concurrent requests.

core/src/storage.rs

@@ -44,32 +44,35 @@ pub struct Version {
 ///
 /// Changes in a transaction that is dropped without calling `commit` must not appear in any other
 /// transaction.
+#[async_trait::async_trait(?Send)]
 pub trait StorageTxn {
     /// Get information about the client for this transaction
-    fn get_client(&mut self) -> anyhow::Result<Option<Client>>;
+    async fn get_client(&mut self) -> anyhow::Result<Option<Client>>;
 
     /// Create the client for this transaction, with the given latest_version_id. The client must
     /// not already exist.
-    fn new_client(&mut self, latest_version_id: Uuid) -> anyhow::Result<()>;
+    async fn new_client(&mut self, latest_version_id: Uuid) -> anyhow::Result<()>;
 
     /// Set the client's most recent snapshot.
-    fn set_snapshot(&mut self, snapshot: Snapshot, data: Vec<u8>) -> anyhow::Result<()>;
+    async fn set_snapshot(&mut self, snapshot: Snapshot, data: Vec<u8>) -> anyhow::Result<()>;
 
     /// Get the data for the most recent snapshot.  The version_id
     /// is used to verify that the snapshot is for the correct version.
-    fn get_snapshot_data(&mut self, version_id: Uuid) -> anyhow::Result<Option<Vec<u8>>>;
+    async fn get_snapshot_data(&mut self, version_id: Uuid) -> anyhow::Result<Option<Vec<u8>>>;
 
     /// Get a version, indexed by parent version id
-    fn get_version_by_parent(&mut self, parent_version_id: Uuid)
-        -> anyhow::Result<Option<Version>>;
+    async fn get_version_by_parent(
+        &mut self,
+        parent_version_id: Uuid,
+    ) -> anyhow::Result<Option<Version>>;
 
     /// Get a version, indexed by its own version id
-    fn get_version(&mut self, version_id: Uuid) -> anyhow::Result<Option<Version>>;
+    async fn get_version(&mut self, version_id: Uuid) -> anyhow::Result<Option<Version>>;
 
     /// Add a version (that must not already exist), and
     ///  - update latest_version_id
     ///  - increment snapshot.versions_since
-    fn add_version(
+    async fn add_version(
         &mut self,
         version_id: Uuid,
         parent_version_id: Uuid,
@@ -78,12 +81,13 @@ pub trait StorageTxn {
 
     /// Commit any changes made in the transaction.  It is an error to call this more than
     /// once.  It is safe to skip this call for read-only operations.
-    fn commit(&mut self) -> anyhow::Result<()>;
+    async fn commit(&mut self) -> anyhow::Result<()>;
 }
 
 /// A trait for objects able to act as storage.  Most of the interesting behavior is in the
 /// [`crate::storage::StorageTxn`] trait.
+#[async_trait::async_trait]
 pub trait Storage: Send + Sync {
     /// Begin a transaction for the given client ID.
-    fn txn(&self, client_id: Uuid) -> anyhow::Result<Box<dyn StorageTxn + '_>>;
+    async fn txn(&self, client_id: Uuid) -> anyhow::Result<Box<dyn StorageTxn + '_>>;
 }