[SNMP4J] snmp.close() sometimes throws npe

[Frank Fock]

Hello Thanos,

I cannot reproduce this with the current version (1.10.2 snapshot).

Best regards,
Frank

Thanos Panousis wrote:
> Hello all,
> 
> I would like to ask for some advice on why I keep getting a NPE when
> trying to close the snmp instance. In the code bellow, just after
> sending the request and getting back a result, I try to call
> snmp.close(). This sometimes throws the npe. I have "protected" it
> with a check for null, but it does not seem to work(it happens after
> the not null check?).
> 
> Since snmp is never closed before, I don't see why snmp.close() should
> throw an npe. This code is run from within a thread that does this
> task and shares nothing with other threads. I have noticed that this
> npe happens more often when the number of threads is higher.
> 
> protected String getValueFromBase(Sector sector) throws IOException{
>         CommunityTarget tar = new CommunityTarget();//setting up tar
>         Address addr = GenericAddress.parse("udp:" +sector.getIpAddress()
>                 + "/" + sector.getSnmpPort());
>         tar.setCommunity(new
> OctetString(sector.getSnmpCommunity()));//Main.conf.getProperty("community",
> "public")));
>         tar.setAddress(addr);
>         tar.setRetries(Integer.parseInt(Main.conf.getProperty("retry", "4")));
>         tar.setTimeout(Long.parseLong(Main.conf.getProperty("timeout", "400")));
>         tar.setVersion(SnmpConstants.version1);
> 
>         TransportMapping trans = new DefaultUdpTransportMapping();
> //if these fail no fetches will happen
>         trans.listen();
>         Snmp snmp = new Snmp(trans);
>         PDU tempPdu = new PDU();//creating PDU
>         tempPdu.add(new VariableBinding(new OID(oid)));
>         tempPdu.setType(PDU.GETNEXT);
>         ResponseEvent response = snmp.send(tempPdu, tar);
>         PDU responsePdu = response.getResponse();
> 
>        //sometimes the snmp instance throws nullPointer!why?
>         if (snmp != null){
>             snmp.close();
>             trans.close();
>         }
> 
>         //now parse the responsePdu and return result
>     }
> 
> The above code works but sometimes gives this kinf of errors
> (truncated for clarity):
> 
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:205)
>        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:885)
>        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:907)
>        at java.lang.Thread.run(Thread.java:619)
> Caused by: java.lang.NullPointerException
>        at org.snmp4j.Snmp.close(Unknown Source)
>        at wimossCollector.oidType.SectorOid.getValueFromBase(SectorOid.java:68)
> 
> 
> Thank you.
> Thanos Panousis.
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> SNMP4J mailing list
> SNMP4J at agentpp.org
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