store: Simplify with_migration_lock

Author: lutter

store/postgres/src/advisory_lock.rs

@@ -6,7 +6,7 @@
 //! has more details on advisory locks.
 //!
 //! We use the following 64 bit locks:
-//!   * 1,2: to synchronize on migratons
+//!   * 1: to synchronize on migratons
 //!
 //! We use the following 2x 32-bit locks
 //!   * 1, n: to lock copying of the deployment with id n in the destination
@@ -69,41 +69,26 @@ const COPY: Scope = Scope { id: 1 };
 const WRITE: Scope = Scope { id: 2 };
 const PRUNE: Scope = Scope { id: 3 };
 
-/// Get a lock for running migrations. Blocks until we get the lock.
-fn lock_migration(conn: &mut PgConnection) -> Result<(), StoreError> {
-    sql_query("select pg_advisory_lock(1)")
-        .execute(conn)
-        .map_err(|e| {
-            StoreError::from_diesel_error(&e).unwrap_or_else(|| {
-                StoreError::Unknown(anyhow::anyhow!("failed to acquire migration lock: {}", e))
-            })
-        })?;
-
-    Ok(())
-}
-
-/// Release the migration lock.
-fn unlock_migration(conn: &mut PgConnection) -> Result<(), StoreError> {
-    sql_query("select pg_advisory_unlock(1)")
-        .execute(conn)
-        .map_err(|e| {
-            StoreError::from_diesel_error(&e).unwrap_or_else(|| {
-                StoreError::Unknown(anyhow::anyhow!("failed to release migration lock: {}", e))
-            })
-        })?;
-    Ok(())
-}
-
 /// Block until we can get the migration lock, then run `f` and unlock when
 /// it is done. This is used to make sure that only one node runs setup at a
 /// time.
 pub(crate) fn with_migration_lock<F, R>(conn: &mut PgConnection, f: F) -> Result<R, StoreError>
 where
     F: FnOnce(&mut PgConnection) -> Result<R, StoreError>,
 {
-    lock_migration(conn)?;
+    fn execute(conn: &mut PgConnection, query: &str, msg: &str) -> Result<(), StoreError> {
+        sql_query(query).execute(conn).map(|_| ()).map_err(|e| {
+            StoreError::from_diesel_error(&e)
+                .unwrap_or_else(|| StoreError::Unknown(anyhow::anyhow!("{}: {}", msg, e)))
+        })
+    }
+
+    const LOCK: &str = "select pg_advisory_lock(1)";
+    const UNLOCK: &str = "select pg_advisory_unlock(1)";
+
+    execute(conn, LOCK, "failed to acquire migration lock")?;
     let res = f(conn);
-    unlock_migration(conn)?;
+    execute(conn, UNLOCK, "failed to release migration lock")?;
     res
 }