postgresql error: canceling statement due to user request

Question

What causes this error in postgresql?

org.postgresql.util.PSQLException: ERROR: canceling statement due to user request

Answer 1

We have figured out the the cause of this issue. It's explained by buggy implementation of setQueryTimeout() in latest JDBC drivers 9.2-100x. It might not happen if you open / close connection manually, but very often happens with connection pooling in place and autocommit set to false. In this case, setQueryTimeout() should be called with non-zero value (as an example, using Spring framework @Transactional( timeout = xxx ) annotation).

It turns out, whenever SQL exception is raised during the statement execution, the cancellation timer hasn't been cancelled and stays alive (that's how it is implemented). Because of pooling, connection behind is not closed but is returned to the pool. Later on, when cancellation timer triggers, it randomly cancels the query currently associated with the connection this timer has been created with. At this moment, it's a totally different query which explains the randomness effect.

The suggested workaround is to give up on setQueryTimeout() and use PostgreSQL configuration instead (statement_timeout). It doesn't provide same level of flexibility but at least always works.