[SNMP4J] ConcurrentModificationException in tabular data

[Frank Fock]

Hi Fabian,

Indeed something strange must have happened.
The following change within the TableUtils
class should avoid the exception:

   class InternalTableListener implements TableListener {

     private List rows = new LinkedList();

     public boolean next(TableEvent event) {
       rows.add(event);
       return true;
     }

     public synchronized void finished(TableEvent event) {
       if ((event.getStatus() != TableEvent.STATUS_OK) ||
           (event.getIndex() != null)) {
         rows.add(event);
       }
       rows = new ArrayList(rows);
       notify();
     }

     public List getRows() {
       return rows;
     }
   }

The change should be also in the next nightly build
available from http://www.agentpp.org/~katzwww/snapshot/
(Note: The CVS snapshots are still experimental)

Best regards,
Frank

Fabian Nart wrote:
> Hi,
> 
> I'm having trouble while retrieving tabular SNMP-data and proceed it 
> with an Iterator. When I iterate through the received list of 
> tableevents I get a ConcurrentModificationException. However, I'm pretty 
> sure that my code doesn't touch the list at all (see code below).
> 
> The exception occurs in the line marked with ###. The _snmp is a 
> reference to the single Snmp-object in my system. Is it possible that 
> somewhere inside SNMP4j the returned List is modified after I've created 
> my Iterator? (I've looked at the source but didn't see anything suspect, 
> but maybe I overlooked something)
> 
> Unfortunately, I cannot reproduce this failure, it just showed up a few 
> times -- but it should never occur, of course.
> 
> I'm grateful for any comments
> Fabian
> 
> 
> --- Code ----------------------------------------------------
> 
> TableUtils tu= new TableUtils(_snmp, new DefaultPDUFactory(PDU.GETBULK));
> 
> List rows= tu.getTable(_target, oids, lowerBoundIndex, upperBoundIndex);
> 
> for (Iterator i= rows.iterator(); i.hasNext();) {
>   TableEvent row= (TableEvent) i.next(); // ###
>   (...)
> }
> 
> --- / Code --------------------------------------------------
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