Simplify transaction rollback logic

If the attempt to rollback the transaction fails, with Diesel 2.0 it is
now okay to drop the connection as it will be closed instead of being
returned to the pool.

Author: jtgeibel

src/swirl/runner.rs

@@ -172,23 +172,17 @@ impl Runner {
                     // TODO: Replace with flatten() once that stabilizes
                     .and_then(std::convert::identity);
 
+                // If the job panics it could leave the connection inside an inner transaction(s).
+                // Attempt to roll those back so we can mark the job as failed, but if the rollback
+                // fails then there isn't much we can do at this point so return early. `r2d2` will
+                // detect the bad state and drop it from the pool.
                 loop {
-                    let depth = get_transaction_depth(conn);
-                    if depth == Ok(initial_depth) {
+                    let depth = get_transaction_depth(conn)?;
+                    if depth == initial_depth {
                         break;
                     }
                     warn!("Rolling back a transaction due to a panic in a background task");
-                    match <AnsiTransactionManager as TransactionManager<PgConnection>>::rollback_transaction(conn)
-                        {
-                            Ok(_) => (),
-                            Err(e) => {
-                                error!("Leaking a thread and database connection because of an error while rolling back transaction: {e}");
-                                loop {
-                                    std::thread::sleep(Duration::from_secs(24 * 60 * 60));
-                                    error!("How am I still alive?");
-                                }
-                            }
-                        }
+                    AnsiTransactionManager::rollback_transaction(conn)?;
                 }
 
                 match result {
@@ -246,7 +240,7 @@ impl Runner {
 }
 
 fn get_transaction_depth(conn: &mut PgConnection) -> QueryResult<u32> {
-    let transaction_manager = <AnsiTransactionManager as TransactionManager<PgConnection>>::transaction_manager_status_mut(conn);
+    let transaction_manager = AnsiTransactionManager::transaction_manager_status_mut(conn);
     Ok(transaction_manager
         .transaction_depth()?
         .map(u32::from)