From 5bea3c94c197382ceab1ed7fc8dccb6783364843 Mon Sep 17 00:00:00 2001
From: Andras Schmelczer <andras@schmelczer.dev>
Date: Wed, 18 Dec 2024 20:36:38 +0000
Subject: [PATCH] Add write transactions

---
 backend/sync_server/src/database.rs            | 18 ++++++++++++++++--
 .../sync_server/src/server/create_document.rs  |  2 +-
 .../sync_server/src/server/delete_document.rs  |  2 +-
 .../sync_server/src/server/update_document.rs  |  2 +-
 4 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/backend/sync_server/src/database.rs b/backend/sync_server/src/database.rs
index 0241651a..fb1ec1c5 100644
--- a/backend/sync_server/src/database.rs
+++ b/backend/sync_server/src/database.rs
@@ -1,4 +1,4 @@
-use std::str::FromStr;
+use std::{str::FromStr, time::Duration};
 
 use anyhow::{Context, Result};
 use models::{
@@ -21,6 +21,7 @@ impl Database {
     pub async fn try_new(config: &DatabaseConfig) -> Result<Self> {
         let connection_options = SqliteConnectOptions::from_str(&config.sqlite_url)?
             .create_if_missing(true)
+            .busy_timeout(Duration::from_secs(3600))
             .journal_mode(sqlx::sqlite::SqliteJournalMode::Wal);
 
         let pool = SqlitePoolOptions::new()
@@ -49,13 +50,26 @@ impl Database {
             .context("Cannot check for pending migrations")
     }
 
-    pub async fn create_transaction(&self) -> Result<Transaction<'_>> {
+    /// Attempting to write from this transaction might result in a
+    /// database locked error. Use this transaction for read-only operations.
+    pub async fn create_readonly_transaction(&self) -> Result<Transaction<'_>> {
         self.connection_pool
             .begin()
             .await
             .context("Cannot create transaction")
     }
 
+    pub async fn create_write_transaction(&self) -> Result<Transaction<'_>> {
+        let mut transaction = self.create_readonly_transaction().await?;
+
+        // sqlx doesn't support immediate transactions for sqlite: https://github.com/launchbadge/sqlx/issues/481
+        sqlx::query!("END; BEGIN IMMEDIATE;")
+            .execute(&mut *transaction)
+            .await?;
+
+        Ok(transaction)
+    }
+
     /// Return the latest state of all non-deleted documents in the vault
     pub async fn get_latest_documents(
         &self,
diff --git a/backend/sync_server/src/server/create_document.rs b/backend/sync_server/src/server/create_document.rs
index 796443fa..0e1bf8b1 100644
--- a/backend/sync_server/src/server/create_document.rs
+++ b/backend/sync_server/src/server/create_document.rs
@@ -38,7 +38,7 @@ pub async fn create_document(
 
     let mut transaction = state
         .database
-        .create_transaction()
+        .create_write_transaction()
         .await
         .map_err(server_error)?;
 
diff --git a/backend/sync_server/src/server/delete_document.rs b/backend/sync_server/src/server/delete_document.rs
index a966a546..40b87bb2 100644
--- a/backend/sync_server/src/server/delete_document.rs
+++ b/backend/sync_server/src/server/delete_document.rs
@@ -38,7 +38,7 @@ pub async fn delete_document(
 
     let mut transaction = state
         .database
-        .create_transaction()
+        .create_write_transaction()
         .await
         .map_err(server_error)?;
 
diff --git a/backend/sync_server/src/server/update_document.rs b/backend/sync_server/src/server/update_document.rs
index 08d9ac93..0648017c 100644
--- a/backend/sync_server/src/server/update_document.rs
+++ b/backend/sync_server/src/server/update_document.rs
@@ -54,7 +54,7 @@ pub async fn update_document(
 
     let mut transaction = state
         .database
-        .create_transaction()
+        .create_write_transaction()
         .await
         .map_err(server_error)?;