[Babeldoc-devel] Synchronization problem in GenericSQLJournal

[Stefan K. <ste...@co...>]

Hello,

We are using the SQL journal in a multi-threaded J2EE environment and got
some DB error, because of duplicated IDs in LOG table.
We solved it by making getNextStep and the DB Update a critical section. I
think, this makes sense and should go into the babeldoc code.

Regards,
Stefan

    // copied from GenericSQLJournal with synchronization
    // getNextStep + DB Update is a critical section

    protected void log(IJournalTicket ticket, JournalOperation operation,
                       String other, String stage, Object data) throws
JournalException {
      //getLog().debug("[GenericSqlJournal.log] called");
      // Get the next step for the ticket
      if (!ticket.isDummy()) {
        PreparedStatement pstmt = null;
        Connection con = null;
        String logInsertStmt = SqlQueryManager.getSqlQuery(LOG_INSERT);

        //getLog().debug("[GenericSqlJournal.log] sql: "+logInsertStmt);
        long id = ((JournalTicket)ticket).getValue();

        try {
          con = (Connection) resource.checkOut();

          pstmt = con.prepareStatement(logInsertStmt);
          String pstageName = (stage != null) ? stage : "null";
          String additional = "";

          if (operation.equals(JournalOperation.updateStatus)) {
            additional = (String) data;
          }

          //getLog().debug("[GenericSqlJournal.log] Writing step: "+step);
          pstmt.setLong(1, id);
          pstmt.setLong(3, new java.util.Date().getTime());
          pstmt.setString(4, operation.toString());
          pstmt.setString(5, other);
          pstmt.setString(6, pstageName);
          pstmt.setString(7, additional);

          long step ;
            // without synchronized it is likely to get the same value
		// from getNextStep several times in multiple threads

          synchronized ( this.getClass() ) {
            step = getNextStep(con, id);
            pstmt.setLong(2, step);
            pstmt.executeUpdate();
          }

          if (operation.equals(JournalOperation.updateDocument)) {
            writeDelta(con, id, step,
(com.babeldoc.core.pipeline.PipelineDocument) data);
          }
        } catch (Exception se) {
          LogService.getInstance().logError(se);
        } finally {
          try {
            if (pstmt != null) {
              pstmt.close();
            }

            resource.checkIn(con);
          } catch (Exception se) {
            LogService.getInstance().logError(I18n.get("sql.403"), se);
          }
        }
      }
    }