Error trying to prune DB via Cursor

Question

I'm using JE 3.1.0 and have last-event records in a database and am trying to write a thread to prune the database of old records. The database is not transactional - setTransactional() is set to false in both EnvironmentConfig and DatabaseConfig. Database.put() is being called with a null transaction in the primary writer thread. The background pruning thread opens a cursor with a null transaction as well. The problem is that the pruning thread dies trying to use the cursor, throwing a DatabaseException when cursor.getNext() is called, with the following message:
Exception in thread "Thread-6" java.lang.RuntimeException: Exception attempting to get next record (current record is #0): (JE 3.1.0) A per-thread transaction was created in Thread[main,5,main] but used in Thread[Thread-6,5,main]
The cursor is being opened as follows:
     public EntryRemover(Database db, int chunkSize, int sleepSeconds) {
          this.db = db;
          Transaction txn = null;
          try {
               if (this.db.getEnvironment().getConfig().getTransactional()) {
                    txn = this.db.getEnvironment().beginTransaction(null, null);
                    logger.info("Beginning transaction");
                    cursor = this.db.openCursor(txn, null);
               } else {
                    logger.info("Using null transaction");
                    cursor = this.db.openCursor(null, null);
          } catch (DatabaseException dbe) {
               logger.error("Exception thrown attempting to create transaction: "+dbe.getMessage(),dbe);
               throw new RuntimeException(dbe);
          this.chunkSize = chunkSize;
          this.sleepSeconds = sleepSeconds;
     }And the exception is being thrown from the following method:
     protected int removeEntries(int maxEntriesToRemove) {
          boolean endReached = false;
          int i = 0;
          int entriesRemoved = 0;
          DatabaseEntry key, value;
          while (!endReached && entriesRemoved < maxEntriesToRemove) {
               key = new DatabaseEntry();
               value = new DatabaseEntry();
               OperationStatus status = null;
               try {
                    status = cursor.getNext(key, value, LockMode.DEFAULT);
               } catch (DatabaseException de) {
                    throw new RuntimeException("Exception attempting to get next record (current record is #"+i+"): "+de.getMessage(),de);
               if (status == OperationStatus.SUCCESS) {
                    if (shouldRemove(key.getData(), value.getData())) {
                         try {
                              if (OperationStatus.SUCCESS == cursor.delete()) {
                                   entriesRemoved++;
                              } else {
                                   throw new IllegalStateException("Attempt to delete record did not return success");
                         } catch (DatabaseException de) {
                              throw new RuntimeException("Exception delete record (current record is #"+i+"): "+de.getMessage(),de);
               } else if (status == OperationStatus.NOTFOUND){
                    logger.info("End of db reached");
                    endReached = true;
               else {
                    throw new IllegalStateException("Attempt to get next record did not return success, instead: "+status);
               i++;
          return entriesRemoved;
     }It is using a null transaction in opening the cursor, the database is not transactional, so I'm not sure why it's complaining about a transaction having been created in a different thread?

Answer 1

Hmm, I had seen that but didn't think I was violating it. The way it's working is the main thread is initializing the database and doing the writing, etc. The pruner thread is opening the cursor. I guess this is considered using the cursor across threads? Since the database was initialized in a different thread? Because the pruner thread is the only block of code in which I use cursors, at least explicitly. I'll try it with the db opened transactionally, thanks.
For the record, the EnvironmentConfig is
ERROR 2007-03-27 17:27:09,320 151192 [Thread-6] EntryRemover.java:logEnvConfig  - EnvironmentConfig: allowCreate=true
{je.env.isTransactional=false, je.maxMemoryPercent=25, je.env.isReadOnly=false}