The server is 8.0.3 running on Windows. The client is using the 311 build with some patches we need (from the stable branch). There is nothing we know of which would be canceling things on the server side, and nothing we know of which would be doing so on the JDBC client. (In fact, when this happens during invocation of the Connection.commit method, I don't think there is a way to cancel it programatically.)
A handful of these exceptions may be sprinkled throughout a stream of thousands of queries in the course of a minute. There is nothing we've been able to identify which differentiates the failing queries form those which succeed. There is one clue, though -- except for the case where they happen on Connection.commit, they all seem to happen during attempts to update a row through a ResultSet shortly after an exception (such as a duplicate key) was thrown, resulting in the rollback of the previous database transaction. (That is, Connection.rollback was invoked after catching the exception.) Connection.autoCommit is set to false.
Any suggestions regarding possible causes, possible workarounds, diagnostic steps we should pursue, etc. are welcome.
Below are some typical stack traces, from the point where we invoke a JDBC method. The executeUpdate method was invoked for an UPDATE statement.
java.sql.SQLException: ERROR: canceling query due to user request
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1471)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1256)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:175)
at org.postgresql.jdbc2.AbstractJdbc2Connection.executeTransactionCommand(AbstractJdbc2Connection.java:625)
at org.postgresql.jdbc2.AbstractJdbc2Connection.commit(AbstractJdbc2Connection.java:645)
java.sql.SQLException: ERROR: canceling query due to user request
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1471)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1256)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:175)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:389)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:314)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:221)
at org.postgresql.jdbc2.AbstractJdbc2DatabaseMetaData.getPrimaryKeys(AbstractJdbc2DatabaseMetaData.java:3130)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.isUpdateable(AbstractJdbc2ResultSet.java:1583)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.checkUpdateable(AbstractJdbc2ResultSet.java:2444)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.updateValue(AbstractJdbc2ResultSet.java:2682)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.updateObject(AbstractJdbc2ResultSet.java:1149)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.updateObject(AbstractJdbc2ResultSet.java:1511)
java.sql.SQLException: ERROR: canceling query due to user request
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1471)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1256)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:175)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:389)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:330)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:240)
at org.postgresql.core.Field.getColumnName(Field.java:247)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.updateValue(AbstractJdbc2ResultSet.java:2693)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.updateObject(AbstractJdbc2ResultSet.java:1149)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.updateObject(AbstractJdbc2ResultSet.java:1511)
java.sql.SQLException: ERROR: canceling query due to user request
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1471)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1256)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:175)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:389)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:330)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeUpdate(AbstractJdbc2Statement.java:282)
java.sql.SQLException: ERROR: canceling query due to user request
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1471)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1256)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:175)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:389)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:330)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeUpdate(AbstractJdbc2Statement.java:282)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.updateRow(AbstractJdbc2ResultSet.java:1307)