Move to connection pools

Cargo.lock

@@ -113,6 +113,7 @@ checksum = "f7a532c1f99a0f596f6960a60d1e119e91582b24b39e2d83a190e61262c3ef0c"
 dependencies = [
  "diesel_derives",
  "libsqlite3-sys",
+ "r2d2",
  "time",
 ]
 
@@ -798,6 +799,29 @@ dependencies = [
  "system-deps",
 ]
 
+[[package]]
+name = "parking_lot"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3742b2c103b9f06bc9fff0a37ff4912935851bee6d36f3c02bcc755bcfec228f"
+dependencies = [
+ "lock_api",
+ "parking_lot_core",
+]
+
+[[package]]
+name = "parking_lot_core"
+version = "0.9.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93f00c865fe7cabf650081affecd3871070f26767e7b2070a3ffae14c654b447"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "redox_syscall",
+ "smallvec",
+ "windows-targets",
+]
+
 [[package]]
 name = "pin-project"
 version = "1.1.0"
@@ -898,6 +922,26 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "r2d2"
+version = "0.8.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "51de85fb3fb6524929c8a2eb85e6b6d363de4e8c48f9e2c2eac4944abc181c93"
+dependencies = [
+ "log",
+ "parking_lot",
+ "scheduled-thread-pool",
+]
+
+[[package]]
+name = "redox_syscall"
+version = "0.3.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "567664f262709473930a4bf9e51bf2ebf3348f2e748ccc50dea20646858f8f29"
+dependencies = [
+ "bitflags",
+]
+
 [[package]]
 name = "relm4"
 version = "0.6.0"
@@ -993,6 +1037,15 @@ dependencies = [
  "relm4-icons",
 ]
 
+[[package]]
+name = "scheduled-thread-pool"
+version = "0.2.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3cbc66816425a074528352f5789333ecff06ca41b36b0b0efdfbb29edc391a19"
+dependencies = [
+ "parking_lot",
+]
+
 [[package]]
 name = "scopeguard"
 version = "1.1.0"

Cargo.toml

@@ -10,7 +10,7 @@ gtk = { version = "0.6.6", package = "gtk4" }
 relm4 = { version = "0.6.0", features = ["libadwaita"] }
 relm4-components = "0.6.0"
 relm4-icons = { version = "0.6.0", features = ["plus", "minus"] }
-diesel = { version = "2.1.0", features = ["sqlite", "returning_clauses_for_sqlite_3_35"] }
+diesel = { version = "2.1.0", features = ["sqlite", "returning_clauses_for_sqlite_3_35", "r2d2"] }
 libsqlite3-sys = { version = "0.26.0", features = ["bundled"] }
 dotenvy = "0.15"
 nom = "7.1.3"

src/bin/add_sample.rs

@@ -5,7 +5,7 @@ fn main() {
     let suggestions =
         TagSuggestions::read_from_file("tag_terms.txt").expect("expected tag file to load");
 
-    let connection = &mut establish_connection();
+    let connection = &mut get_connection_pool().get().expect("Expected a connection");
 
     let file_str = env::args().nth(1).expect("Need just one argument.");
     let tags = suggestions.get_suggestions(&file_str);

src/bin/create_library.rs

@@ -2,7 +2,7 @@ use sample_amp::*;
 use std::io::{stdin, stdout, Write};
 
 fn main() {
-    let connection = &mut establish_connection();
+    let connection = &mut get_connection_pool().get().expect("Expected a connection.");
 
     let mut name = String::new();
 

src/bin/list_samples.rs

@@ -1,8 +1,8 @@
 use itertools::Itertools;
-use sample_amp::{establish_connection, list_tags};
+use sample_amp::{get_connection_pool, list_tags};
 
 fn main() {
-    let connection = &mut establish_connection();
+    let connection = &mut get_connection_pool().get().expect("Expected a connection");
     println!(
         "Found tags: {}",
         list_tags(connection).iter().map(|t| &t.name).join(", ")

src/bin/list_tags.rs

@@ -1,8 +1,8 @@
 use itertools::Itertools;
-use sample_amp::{establish_connection, list_tags};
+use sample_amp::{get_connection_pool, list_tags};
 
 fn main() {
-    let connection = &mut establish_connection();
+    let connection = &mut get_connection_pool().get().expect("Expected a connection.");
     println!(
         "Found tags: {}",
         list_tags(connection).iter().map(|t| &t.name).join(", ")

src/bin/show_libraries.rs

@@ -5,7 +5,7 @@ use sample_amp::*;
 fn main() {
     use self::schema::libraries::dsl::*;
 
-    let connection = &mut establish_connection();
+    let connection = &mut get_connection_pool().get().expect("Expected a connection");
     let results = libraries
         .limit(5)
         .select(Library::as_select())

src/lib.rs

@@ -1,4 +1,7 @@
-use diesel::prelude::*;
+use diesel::{
+    prelude::*,
+    r2d2::{ConnectionManager, Pool},
+};
 use dotenvy::dotenv;
 use models::{NewSample, Sample, Tag};
 use std::{env, path::Path};
@@ -9,12 +12,17 @@ pub mod models;
 pub mod schema;
 pub mod tag_terms;
 
-pub fn establish_connection() -> SqliteConnection {
+pub fn get_connection_pool() -> Pool<ConnectionManager<SqliteConnection>> {
     dotenv().ok();
 
     let database_url = env::var("DATABASE_URL").expect("DATABASE_URL must be set");
-    SqliteConnection::establish(&database_url)
+
-        .unwrap_or_else(|_| panic!("Error connecting to {}", database_url))
+    let manager = ConnectionManager::<SqliteConnection>::new(database_url);
+
+    Pool::builder()
+        .test_on_check_out(true)
+        .build(manager)
+        .expect("Could not build connection pool")
 }
 
 pub fn create_library(conn: &mut SqliteConnection, name: &str) -> Library {

src/main.rs

@@ -1,4 +1,5 @@
 use diesel::prelude::*;
+use diesel::r2d2::{ConnectionManager, Pool};
 use gtk::gdk::Display;
 use gtk::prelude::*;
 use relm4::{factory::FactoryVecDeque, prelude::*};
@@ -8,7 +9,7 @@ mod sample_list;
 use library_list::LibraryListItem;
 mod app_msg;
 use app_msg::AppMsg;
-use sample_amp::establish_connection;
+use sample_amp::get_connection_pool;
 use sample_amp::models::Library;
 use sample_amp::schema::libraries;
 
@@ -17,7 +18,7 @@ use crate::sample_list::SampleListModel;
 struct AppModel {
     sample_list: Controller<SampleListModel>,
     libraries: FactoryVecDeque<LibraryListItem>,
-    connection: SqliteConnection,
+    pool: Pool<ConnectionManager<SqliteConnection>>,
 }
 
 #[relm4::component]
@@ -33,7 +34,7 @@ impl SimpleComponent for AppModel {
         sender: ComponentSender<Self>,
     ) -> relm4::ComponentParts<Self> {
         let mut model = AppModel {
-            connection: establish_connection(),
+            pool: get_connection_pool(),
             libraries: FactoryVecDeque::new(gtk::ListBox::default(), sender.input_sender()),
             sample_list: SampleListModel::builder().launch(()).detach(),
         };
@@ -43,7 +44,7 @@ impl SimpleComponent for AppModel {
         // todo: cleaner
         let library_results = libraries::dsl::libraries
             .select(Library::as_select())
-            .load(&mut model.connection)
+            .load(&mut model.pool.get().expect("Expected a connection."))
             .expect("Error loading libraries");
 
         model.libraries.guard().push_back("All".to_string());