CheckValidConnectionSQL can open a transaction, preventing application from changing transaction isolation level (PostgreSQL) ----------------------------------------------------------------------------------------------------------------------------- Key: WFLY-8032 URL: https://issues.jboss.org/browse/WFLY-8032 Project: WildFly Issue Type: Bug Components: JCA Affects Versions: 10.1.0.Final Reporter: Tomas Hofman Assignee: Tomas Hofman Fix For: 11.0.0.Beta1 PostgreSQL driver only allows changing the transaction isolation level when transaction is not opened. Under certain circumstances, an application can receive a connection with already opened transaction and an attempt to change transaction isolation level will lead to exception. This happens with the PostgreSQL driver and with CheckValidConnectionSQL checker configured to run a select statement to verify connections retrieved from the pool. The scenario is as follows: # A connection is retrieved from the pool for the 1st app and CheckValidConnectionSQL verifies it by running a select statement (autocommit is set to true by default). This statement is run directly via the jdbc connection, not the wrapper. # 1st app receives the connection, sets autocommit=false, perform some work and commits a transaction. # The connection is returned to the pool, {{cleanup()}} method is called on LocalManagedConnection wrapper, which sets autocommit=true. This however doesn't reset autocommit on the wrapped jdbc connection yet, which would only happen just before executing another SQL statement f.i. # The same connection is retrieved from the pool for the 2nd app and CheckValidConnectionSQL runs the query. Because the jdbc connection has still autocommit=false, new transaction is opened. # 2nd app receives the connection and calls {{setTransactionIsolation()}}, which throws an exception because the transaction is open. Possible solution could be that the {{cleanup()}} method propagates the autocommit=true to the wrapped jdbc connection immediately.