Have server notify the client about db connection errors

src/core/protocol/request_response.rs

@@ -73,7 +73,6 @@ pub enum Response {
     UnlockUsers(UnlockUsersOutput),
 
     // Generic responses
-    OperationAborted,
+    Ready,
     Error(String),
-    Exit,
 }

src/main.rs

@@ -9,10 +9,12 @@ use std::path::PathBuf;
 use std::os::unix::net::UnixStream as StdUnixStream;
 use tokio::net::UnixStream as TokioUnixStream;
 
+use futures::StreamExt;
+
 use crate::{
     core::{
         bootstrap::{bootstrap_server_connection_and_drop_privileges, drop_privs},
-        protocol::create_client_to_server_message_stream,
+        protocol::{create_client_to_server_message_stream, Response},
     },
     server::command::ServerArgs,
 };
@@ -205,7 +207,20 @@ fn tokio_run_command(command: Command, server_connection: StdUnixStream) -> anyh
         .unwrap()
         .block_on(async {
             let tokio_socket = TokioUnixStream::from_std(server_connection)?;
-            let message_stream = create_client_to_server_message_stream(tokio_socket);
+            let mut message_stream = create_client_to_server_message_stream(tokio_socket);
+
+            while let Some(Ok(message)) = message_stream.next().await {
+                match message {
+                    Response::Error(err) => {
+                        anyhow::bail!("{}", err);
+                    }
+                    Response::Ready => break,
+                    message => {
+                        eprintln!("Unexpected message from server: {:?}", message);
+                    }
+                }
+            }
+
             match command {
                 Command::User(user_args) => {
                     cli::user_command::handle_command(user_args, message_stream).await

src/server/server_loop.rs

@@ -1,7 +1,7 @@
 use std::{collections::BTreeSet, fs, path::PathBuf};
 
 use futures_util::{SinkExt, StreamExt};
-use tokio::io::AsyncWriteExt;
+use indoc::concatdoc;
 use tokio::net::{UnixListener, UnixStream};
 
 use sqlx::prelude::*;
@@ -57,15 +57,43 @@ pub async fn listen_for_incoming_connections(
 
     sd_notify::notify(true, &[sd_notify::NotifyState::Ready]).ok();
 
-    while let Ok((mut conn, _addr)) = listener.accept().await {
+    while let Ok((conn, _addr)) = listener.accept().await {
-        let uid = conn.peer_cred()?.uid();
+        let uid = match conn.peer_cred() {
+            Ok(cred) => cred.uid(),
+            Err(e) => {
+                log::error!("Failed to get peer credentials from socket: {}", e);
+                let mut message_stream = create_server_to_client_message_stream(conn);
+                message_stream
+                    .send(Response::Error(
+                        (concatdoc! {
+                            "Server failed to get peer credentials from socket\n",
+                            "Please check the server logs or contact the system administrators"
+                        })
+                        .to_string(),
+                    ))
+                    .await
+                    .ok();
+                continue;
+            }
+        };
+
         log::trace!("Accepted connection from uid {}", uid);
 
         let unix_user = match UnixUser::from_uid(uid) {
             Ok(user) => user,
             Err(e) => {
-                eprintln!("Failed to get UnixUser from uid: {}", e);
+                log::error!("Failed to get username from uid: {}", e);
-                conn.shutdown().await?;
+                let mut message_stream = create_server_to_client_message_stream(conn);
+                message_stream
+                    .send(Response::Error(
+                        (concatdoc! {
+                            "Server failed to get user data from the system\n",
+                            "Please check the server logs or contact the system administrators"
+                        })
+                        .to_string(),
+                    ))
+                    .await
+                    .ok();
                 continue;
             }
         };
@@ -73,9 +101,9 @@ pub async fn listen_for_incoming_connections(
         log::info!("Accepted connection from {}", unix_user.username);
 
         match handle_requests_for_single_session(conn, &unix_user, &config).await {
-            Ok(_) => {}
+            Ok(()) => {}
             Err(e) => {
-                eprintln!("Failed to run server: {}", e);
+                log::error!("Failed to run server: {}", e);
             }
         }
     }
@@ -88,8 +116,24 @@ pub async fn handle_requests_for_single_session(
     unix_user: &UnixUser,
     config: &ServerConfig,
 ) -> anyhow::Result<()> {
-    let message_stream = create_server_to_client_message_stream(socket);
+    let mut message_stream = create_server_to_client_message_stream(socket);
-    let mut db_connection = create_mysql_connection_from_config(&config.mysql).await?;
+    let mut db_connection = match create_mysql_connection_from_config(&config.mysql).await {
+        Ok(connection) => connection,
+        Err(err) => {
+            message_stream
+                .send(Response::Error(
+                    (concatdoc! {
+                        "Server failed to connect to database\n",
+                        "Please check the server logs or contact the system administrators"
+                    })
+                    .to_string(),
+                ))
+                .await?;
+            message_stream.flush().await?;
+            return Err(err);
+        }
+    };
+
     log::debug!("Successfully connected to database");
 
     let result = handle_requests_for_single_session_with_db_connection(
@@ -100,9 +144,9 @@ pub async fn handle_requests_for_single_session(
     .await;
 
     if let Err(e) = db_connection.close().await {
-        eprintln!("Failed to close database connection: {}", e);
+        log::error!("Failed to close database connection: {}", e);
-        eprintln!("{}", e);
+        log::error!("{}", e);
-        eprintln!("Ignoring...");
+        log::error!("Ignoring...");
     }
 
     result
@@ -116,6 +160,7 @@ pub async fn handle_requests_for_single_session_with_db_connection(
     unix_user: &UnixUser,
     db_connection: &mut MySqlConnection,
 ) -> anyhow::Result<()> {
+    stream.send(Response::Ready).await?;
     loop {
         // TODO: better error handling
         let request = match stream.next().await {
@@ -133,17 +178,14 @@ pub async fn handle_requests_for_single_session_with_db_connection(
             Request::CreateDatabases(databases_names) => {
                 let result = create_databases(databases_names, unix_user, db_connection).await;
                 stream.send(Response::CreateDatabases(result)).await?;
-                stream.flush().await?;
             }
             Request::DropDatabases(databases_names) => {
                 let result = drop_databases(databases_names, unix_user, db_connection).await;
                 stream.send(Response::DropDatabases(result)).await?;
-                stream.flush().await?;
             }
             Request::ListDatabases => {
                 let result = list_databases_for_user(unix_user, db_connection).await;
                 stream.send(Response::ListAllDatabases(result)).await?;
-                stream.flush().await?;
             }
             Request::ListPrivileges(database_names) => {
                 let response = match database_names {
@@ -161,7 +203,6 @@ pub async fn handle_requests_for_single_session_with_db_connection(
                 };
 
                 stream.send(response).await?;
-                stream.flush().await?;
             }
             Request::ModifyPrivileges(database_privilege_diffs) => {
                 let result = apply_privilege_diffs(
@@ -171,24 +212,20 @@ pub async fn handle_requests_for_single_session_with_db_connection(
                 )
                 .await;
                 stream.send(Response::ModifyPrivileges(result)).await?;
-                stream.flush().await?;
             }
             Request::CreateUsers(db_users) => {
                 let result = create_database_users(db_users, unix_user, db_connection).await;
                 stream.send(Response::CreateUsers(result)).await?;
-                stream.flush().await?;
             }
             Request::DropUsers(db_users) => {
                 let result = drop_database_users(db_users, unix_user, db_connection).await;
                 stream.send(Response::DropUsers(result)).await?;
-                stream.flush().await?;
             }
             Request::PasswdUser(db_user, password) => {
                 let result =
                     set_password_for_database_user(&db_user, &password, unix_user, db_connection)
                         .await;
                 stream.send(Response::PasswdUser(result)).await?;
-                stream.flush().await?;
             }
             Request::ListUsers(db_users) => {
                 let response = match db_users {
@@ -203,22 +240,21 @@ pub async fn handle_requests_for_single_session_with_db_connection(
                     }
                 };
                 stream.send(response).await?;
-                stream.flush().await?;
             }
             Request::LockUsers(db_users) => {
                 let result = lock_database_users(db_users, unix_user, db_connection).await;
                 stream.send(Response::LockUsers(result)).await?;
-                stream.flush().await?;
             }
             Request::UnlockUsers(db_users) => {
                 let result = unlock_database_users(db_users, unix_user, db_connection).await;
                 stream.send(Response::UnlockUsers(result)).await?;
-                stream.flush().await?;
             }
             Request::Exit => {
                 break;
             }
         }
+
+        stream.flush().await?;
     }
 
     Ok(())