Refactor the diesel pool support

This commit refactors the support for connection pools for diesel.
Instead of only allowing `r2d2` based pools we now abstract the actual
pool away. It also adds support for `deadpool-diesel` based pools as alternative.

.github/workflows/rust.yml

@@ -125,15 +125,15 @@ jobs:
             docker: false
 
           - store: mysql_store
-            features: diesel-store,diesel/mysql
+            features: diesel-store,diesel/mysql,diesel-r2d2
             docker: true
 
           - store: postgres_store
-            features: diesel-store,diesel/postgres
+            features: diesel-store,diesel/postgres,diesel-r2d2
             docker: true
 
           - store: diesel_store
-            features: diesel-store
+            features: diesel-store,diesel-r2d2
             docker: false
 
     steps:

Cargo.toml

@@ -27,6 +27,8 @@ postgres-store = ["sqlx/postgres", "sqlx-store"]
 mysql-store = ["sqlx/mysql", "sqlx-store"]
 moka-store = ["moka"]
 diesel-store = ["dep:diesel", "tokio/rt", "rmp-serde"]
+diesel-r2d2 = ["diesel/r2d2"]
+diesel-deadpool = ["dep:deadpool-diesel", "dep:deadpool"]
 
 [dependencies]
 async-trait = "0.1.73"
@@ -58,9 +60,10 @@ sqlx = { optional = true, version = "0.7.2", features = [
 tokio = { optional = true, version = "1.32.0", default-features = false }
 moka = { optional = true, version = "0.12.0", features = ["future"] }
 diesel = { optional = true, default-features = false, version = "2.1", features = [
-    "r2d2",
     "time",
 ] }
+deadpool-diesel = { version = "0.5", optional = true }
+deadpool = { version ="0.10", optional = true }
 
 [dev-dependencies]
 axum = "0.6.20"
@@ -132,6 +135,7 @@ required-features = [
     "diesel-store",
     "diesel/sqlite",
     "continuously-delete-expired",
+    "diesel-r2d2",
 ]
 
 
@@ -142,4 +146,15 @@ required-features = [
     "diesel-store",
     "diesel/sqlite",
     "continuously-delete-expired",
+    "diesel-r2d2",
+]
+
+[[example]]
+name = "diesel-deadpool"
+required-features = [
+    "axum-core",
+    "diesel-store",
+    "diesel/sqlite",
+    "continuously-delete-expired",
+    "diesel-deadpool",
 ]

examples/diesel-deadpool.rs

@@ -0,0 +1,69 @@
+use std::net::SocketAddr;
+
+use axum::{
+    error_handling::HandleErrorLayer, response::IntoResponse, routing::get, BoxError, Router,
+};
+use deadpool_diesel::{Manager, Pool};
+use diesel::prelude::*;
+use http::StatusCode;
+use serde::{Deserialize, Serialize};
+use time::Duration;
+use tower::ServiceBuilder;
+use tower_sessions::{
+    diesel_store::DieselStore, session_store::ExpiredDeletion, Session, SessionManagerLayer,
+};
+
+const COUNTER_KEY: &str = "counter";
+
+#[derive(Serialize, Deserialize, Default)]
+struct Counter(usize);
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let manager = Manager::<SqliteConnection>::new(":memory:", deadpool_diesel::Runtime::Tokio1);
+    let pool = Pool::builder(manager).max_size(1).build()?;
+    let session_store = DieselStore::new(pool);
+    session_store.migrate().await?;
+
+    let deletion_task = tokio::task::spawn(
+        session_store
+            .clone()
+            .continuously_delete_expired(tokio::time::Duration::from_secs(60)),
+    );
+
+    let session_service = ServiceBuilder::new()
+        .layer(HandleErrorLayer::new(|_: BoxError| async {
+            StatusCode::BAD_REQUEST
+        }))
+        .layer(
+            SessionManagerLayer::new(session_store)
+                .with_secure(false)
+                .with_max_age(Duration::seconds(10)),
+        );
+
+    let app = Router::new()
+        .route("/", get(handler))
+        .layer(session_service);
+
+    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
+    axum::Server::bind(&addr)
+        .serve(app.into_make_service())
+        .await?;
+
+    deletion_task.await??;
+
+    Ok(())
+}
+
+async fn handler(session: Session) -> impl IntoResponse {
+    let counter: Counter = session
+        .get(COUNTER_KEY)
+        .expect("Could not deserialize.")
+        .unwrap_or_default();
+
+    session
+        .insert(COUNTER_KEY, counter.0 + 1)
+        .expect("Could not serialize.");
+
+    format!("Current count: {}", counter.0)
+}