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#[macro_use] extern crate failure; use diesel::connection::Connection; use diesel::connection::SimpleConnection; use diesel::connection::TransactionManager; use diesel::result::Error as DieselError; use failure::Error as FailureError; use std::sync::Mutex; #[cfg(all(feature = "log_errors_on_drop", feature = "panic_errors_on_drop"))] compile_error!( "Features: \"log_errors_on_drop\" and \"panic_errors_on_drop\" are mutually exclusive!" ); #[cfg(all(nightly, feature = "rollback_hooks"))] pub type RollbackHook = Box<dyn FnOnce() -> Result<(), failure::Error> + Send>; #[cfg(all(not(nightly), feature = "rollback_hooks"))] pub type RollbackHook = Box<fn() -> Result<(), failure::Error>>; #[derive(Debug, Fail)] pub enum Error { #[fail(display = "Diesel Error: {}", _0)] Diesel(DieselError), #[fail(display = "Custom Error: {}", _0)] Failure(FailureError), } impl From<DieselError> for Error { fn from(err: DieselError) -> Self { Error::Diesel(err) } } impl From<FailureError> for Error { fn from(err: FailureError) -> Self { Error::Failure(err) } } #[derive(Debug, Fail)] #[fail(display = "The following errors ocurred: {:?}.", _0)] pub struct ErrorVec(pub Vec<Error>); impl From<Vec<Error>> for ErrorVec { fn from(err_vec: Vec<Error>) -> Self { ErrorVec(err_vec) } } #[cfg(feature = "rollback_hooks")] pub struct TransactionalConnection<T: Connection>(Mutex<T>, Mutex<Vec<RollbackHook>>); #[cfg(not(feature = "rollback_hooks"))] pub struct TransactionalConnection<T: Connection>(Mutex<T>); impl<C: Connection> TransactionalConnection<C> { pub fn new(conn: C) -> Result<TransactionalConnection<C>, Error> { let man = conn.transaction_manager(); man.begin_transaction(&conn)?; #[cfg(feature = "rollback_hooks")] let res = Ok(TransactionalConnection( Mutex::new(conn), Mutex::new(vec![]), )); #[cfg(not(feature = "rollback_hooks"))] let res = Ok(TransactionalConnection(Mutex::new(conn))); res } pub fn rollback(self) -> Result<(), ErrorVec> { let mut errs = vec![]; #[cfg(feature = "rollback_hooks")] { let mut guard = self.1.lock().unwrap(); while !guard.is_empty() { let hook = guard.pop().unwrap(); match hook() { Err(e) => errs.push(Error::from(e)), _ => (), } } } let guard = self.0.lock().unwrap(); let man = guard.transaction_manager(); while TransactionManager::<C>::get_transaction_depth(man) > 0 { match man.rollback_transaction(&*guard) { Err(e) => { errs.push(Error::from(e)); break; } _ => (), } } if !errs.is_empty() { Err(errs)?; } Ok(()) } pub fn commit(self) -> Result<(), Error> { let guard = self.0.lock().unwrap(); let man = guard.transaction_manager(); while TransactionManager::<C>::get_transaction_depth(man) > 0 { man.commit_transaction(&*guard)?; } Ok(()) } pub fn handle_result<T, E>(self, res: Result<T, E>) -> Result<T, failure::Error> where failure::Error: From<E>, { match &res { Ok(_) => self.commit()?, Err(_) => self.rollback()?, }; Ok(res?) } #[cfg(all(nightly, feature = "rollback_hooks"))] pub fn add_rollback_hook(&self, hook: impl FnOnce() -> Result<(), failure::Error> + Send) { self.1.lock().unwrap().push(Box::new(hook)); } #[cfg(all(not(nightly), feature = "rollback_hooks"))] pub fn add_rollback_hook(&self, hook: fn() -> Result<(), failure::Error>) { self.1.lock().unwrap().push(Box::new(hook)); } } impl<C: Connection> std::ops::Drop for TransactionalConnection<C> { fn drop(&mut self) { #[cfg(feature = "rollback_hooks")] { let guard = self.1.lock().unwrap(); for hook in &*guard { let _res = hook(); #[cfg(feature = "log_errors_on_drop")] _res.unwrap_or_else(|e| { eprintln!( "WARNING: Error ocurred while attempting transaction rollback: {}", e ); }); #[cfg(feature = "panic_errors_on_drop")] _res.unwrap_or_else(|e| panic!("{}", e)); } } let guard = self.0.lock().unwrap(); let man = guard.transaction_manager(); while TransactionManager::<C>::get_transaction_depth(man) > 0 { let _res = man.rollback_transaction(&*guard); #[cfg(feature = "log_errors_on_drop")] _res.unwrap_or_else(|e| { eprintln!( "WARNING: Error ocurred while attempting transaction rollback: {}", e ); }); #[cfg(feature = "panic_errors_on_drop")] _res.unwrap_or_else(|e| panic!("{}", e)); } } } impl<C: Connection> SimpleConnection for TransactionalConnection<C> { fn batch_execute(&self, query: &str) -> diesel::QueryResult<()> { self.0.lock().unwrap().batch_execute(query) } } impl<C: Connection> Connection for TransactionalConnection<C> { type Backend = C::Backend; type TransactionManager = Self; fn establish(_: &str) -> diesel::ConnectionResult<Self> { Err(diesel::ConnectionError::BadConnection(String::from( "Cannot directly establish a pooled connection", ))) } fn execute(&self, query: &str) -> diesel::QueryResult<usize> { self.0.lock().unwrap().execute(query) } fn query_by_index<T, U>(&self, source: T) -> diesel::QueryResult<Vec<U>> where T: diesel::query_builder::AsQuery, T::Query: diesel::query_builder::QueryFragment<Self::Backend> + diesel::query_builder::QueryId, Self::Backend: diesel::sql_types::HasSqlType<T::SqlType>, U: diesel::deserialize::Queryable<T::SqlType, Self::Backend>, { self.0.lock().unwrap().query_by_index(source) } fn query_by_name<T, U>(&self, source: &T) -> diesel::QueryResult<Vec<U>> where T: diesel::query_builder::QueryFragment<Self::Backend> + diesel::query_builder::QueryId, U: diesel::deserialize::QueryableByName<Self::Backend>, { self.0.lock().unwrap().query_by_name(source) } fn execute_returning_count<T>(&self, source: &T) -> diesel::QueryResult<usize> where T: diesel::query_builder::QueryFragment<Self::Backend> + diesel::query_builder::QueryId, { self.0.lock().unwrap().execute_returning_count(source) } fn transaction_manager(&self) -> &Self::TransactionManager { &self } } impl<C: Connection> TransactionManager<TransactionalConnection<C>> for TransactionalConnection<C> { fn begin_transaction(&self, conn: &TransactionalConnection<C>) -> diesel::QueryResult<()> { let conn = conn.0.lock().unwrap(); conn.transaction_manager().begin_transaction(&*conn) } fn rollback_transaction(&self, conn: &TransactionalConnection<C>) -> diesel::QueryResult<()> { let conn = conn.0.lock().unwrap(); conn.transaction_manager().rollback_transaction(&*conn) } fn commit_transaction(&self, conn: &TransactionalConnection<C>) -> diesel::QueryResult<()> { let conn = conn.0.lock().unwrap(); conn.transaction_manager().commit_transaction(&*conn) } fn get_transaction_depth(&self) -> u32 { diesel::connection::TransactionManager::<C>::get_transaction_depth( &*self.0.lock().unwrap().transaction_manager(), ) } } #[test] fn multiple_threads() { use diesel::prelude::*; use std::sync::Arc; let pgcon = diesel::PgConnection::establish("localhost:5432/pgdb").unwrap(); let txcon = TransactionalConnection::new(pgcon).unwrap(); let arccon = Arc::new(txcon); let arccon_ = arccon.clone(); let job1 = std::thread::spawn(move || { println!("SELECTing TRUE"); arccon_.add_rollback_hook(|| Ok(println!("Nevermind, rolling back."))); diesel::select(diesel::dsl::sql::<diesel::sql_types::Bool>("TRUE")).load::<bool>(&*arccon_) }); let arccon_ = arccon.clone(); let job2 = std::thread::spawn(move || { diesel::select(diesel::dsl::sql::<diesel::sql_types::Bool>("FALSE")).load::<bool>(&*arccon_) }); let job1res = job1.join().unwrap(); let job2res = job2.join().unwrap(); let res = match (job1res, job2res) { (Ok(a), Ok(b)) => Ok((a, b)), (Err(e), _) => Err(e), (_, Err(e)) => Err(e), }; println!( "{:?}", Arc::try_unwrap(arccon) .map_err(|_| "Arc still held by multiple threads.") .unwrap() .handle_result(res) ); }