fix: start datanode instance before frontend services (#634)

src/cmd/src/standalone.rs

@@ -164,8 +164,15 @@ impl StartCommand {
             .context(StartDatanodeSnafu)?;
         let mut frontend = build_frontend(fe_opts, &dn_opts, datanode.get_instance()).await?;
 
+        // Start datanode instance before starting services, to avoid requests come in before internal components are started.
+        datanode
+            .start_instance()
+            .await
+            .context(StartDatanodeSnafu)?;
+        info!("Datanode instance started");
+
         try_join!(
-            async { datanode.start().await.context(StartDatanodeSnafu) },
+            async { datanode.start_services().await.context(StartDatanodeSnafu) },
             async { frontend.start().await.context(StartFrontendSnafu) }
         )?;
 

src/datanode/src/datanode.rs

@@ -88,9 +88,18 @@ impl Datanode {
 
     pub async fn start(&mut self) -> Result<()> {
         info!("Starting datanode instance...");
-        self.instance.start().await?;
-        self.services.start(&self.opts).await?;
-        Ok(())
+        self.start_instance().await?;
+        self.start_services().await
+    }
+
+    /// Start only the internal component of datanode.
+    pub async fn start_instance(&mut self) -> Result<()> {
+        self.instance.start().await
+    }
+
+    /// Start services of datanode. This method call will block until services are shutdown.
+    pub async fn start_services(&mut self) -> Result<()> {
+        self.services.start(&self.opts).await
     }
 
     pub fn get_instance(&self) -> InstanceRef {