libsql: add durable_frame_num caching and metadata file

libsql/Cargo.toml

@@ -43,6 +43,9 @@ fallible-iterator = { version = "0.3", optional = true }
 libsql_replication = { version = "0.6", path = "../libsql-replication", optional = true }
 async-stream = { version = "0.3.5", optional = true }
 
+crc32fast = { version = "1", optional = true }
+chrono = { version = "0.4", optional = true }
+
 [dev-dependencies]
 criterion = { version = "0.5", features = ["html_reports", "async", "async_futures", "async_tokio"] }
 pprof = { version = "0.12.1", features = ["criterion", "flamegraph"] }
@@ -105,6 +108,10 @@ sync = [
   "dep:tokio",
   "dep:futures",
   "dep:serde_json",
+  "dep:crc32fast",
+  "dep:chrono",
+  "dep:uuid",
+  "tokio/fs"
 ]
 hrana = [
   "parser",

libsql/src/database.rs

@@ -34,9 +34,12 @@ cfg_core! {
 }
 
 cfg_replication_or_sync! {
+
     pub type FrameNo = u64;
 
     #[derive(Debug)]
+    // TODO(lucio): remove this once we use these fields in our sync code
+    #[allow(dead_code)]
     pub struct Replicated {
         pub(crate) frame_no: Option<FrameNo>,
         pub(crate) frames_synced: usize,
@@ -47,12 +50,16 @@ cfg_replication_or_sync! {
         /// where in the log you might be. Beware that this value can be reset to a lower value by the
         /// server in certain situations. Please use `frames_synced` if you want to track the amount of
         /// work a sync has done.
+        // TODO(lucio): remove this once we use these fields in our sync code
+        #[allow(dead_code)]
         pub fn frame_no(&self) -> Option<FrameNo> {
             self.frame_no
         }
 
         /// The count of frames synced during this call of `sync`. A frame is a 4kB frame from the
         /// libsql write ahead log.
+        // TODO(lucio): remove this once we use these fields in our sync code
+        #[allow(dead_code)]
         pub fn frames_synced(&self) -> usize {
             self.frames_synced
         }

libsql/src/database/builder.rs

@@ -119,7 +119,7 @@ impl Builder<()> {
     }
 }
 
-cfg_replication_or_remote! {
+cfg_replication_or_remote_or_sync! {
     /// Remote configuration type used in [`Builder`].
     pub struct Remote {
         url: String,
@@ -505,7 +505,7 @@ cfg_remote! {
     }
 }
 
-cfg_replication_or_remote! {
+cfg_replication_or_remote_or_sync! {
     impl Remote {
         fn connector<C>(mut self, connector: C) -> Remote
         where

libsql/src/errors.rs

@@ -55,6 +55,8 @@ pub enum Error {
     TransactionalBatchError(String),
     #[error("Invalid blob size, expected {0}")]
     InvalidBlobSize(usize),
+    #[error("sync error: {0}")]
+    Sync(crate::BoxError),
 }
 
 #[cfg(feature = "hrana")]
@@ -64,6 +66,13 @@ impl From<crate::hrana::HranaError> for Error {
     }
 }
 
+#[cfg(feature = "sync")]
+impl From<crate::sync::SyncError> for Error {
+    fn from(e: crate::sync::SyncError) -> Self {
+        Error::Sync(e.into())
+    }
+}
+
 impl From<std::convert::Infallible> for Error {
     fn from(_: std::convert::Infallible) -> Self {
         unreachable!()

libsql/src/local/database.rs

@@ -144,11 +144,11 @@ impl Database {
             endpoint
         };
         let mut db = Database::open(&db_path, flags)?;
-        db.sync_ctx = Some(tokio::sync::Mutex::new(SyncContext::new(
-            connector,
-            endpoint,
-            Some(auth_token),
-        )));
+
+        let sync_ctx =
+            SyncContext::new(connector, db_path.into(), endpoint, Some(auth_token)).await?;
+        db.sync_ctx = Some(tokio::sync::Mutex::new(sync_ctx));
+
         Ok(db)
     }
 
@@ -388,7 +388,7 @@ impl Database {
     #[cfg(feature = "sync")]
     /// Push WAL frames to remote.
     pub async fn push(&self) -> Result<crate::database::Replicated> {
-        let sync_ctx = self.sync_ctx.as_ref().unwrap().lock().await;
+        let mut sync_ctx = self.sync_ctx.as_ref().unwrap().lock().await;
         let conn = self.connect()?;
 
         let page_size = {
@@ -402,7 +402,7 @@ impl Database {
 
         let max_frame_no = conn.wal_frame_count();
 
-        let generation = 1; // TODO: Probe from WAL.
+        let generation = sync_ctx.generation(); // TODO: Probe from WAL.
         let start_frame_no = sync_ctx.durable_frame_num() + 1;
         let end_frame_no = max_frame_no;
 
@@ -423,6 +423,10 @@ impl Database {
             frame_no += 1;
         }
 
+        sync_ctx.write_metadata().await?;
+
+        // TODO(lucio): this can underflow if the server previously returned a higher max_frame_no
+        // than what we have stored here.
         let frame_count = end_frame_no - start_frame_no + 1;
         Ok(crate::database::Replicated {
             frame_no: None,

libsql/src/macros.rs

@@ -10,7 +10,7 @@ macro_rules! cfg_core {
     }
 }
 
-macro_rules! cfg_replication_or_remote {
+macro_rules! cfg_replication_or_remote_or_sync {
     ($($item:item)*) => {
         $(
             #[cfg(any(feature = "replication", feature = "sync", feature = "remote"))]