[SNMP4J] [SNMP4j] How to determine the correct maxNumOfRowsPerPDU in tableUtils

[Tongjie Li]

Hi Frank
        Thanks for your answer.
        If we can not know the suitable value of maxRepetitions of getBulk
function, how can we use getBulk in a  production environment?
   So we have to use getNext instead of getBulk in production? Since we
have a lot of device need to be monitor by snmp, getNext isn't        very
efficiency.
        I changed pdu.getBulk to pdu.getNext in the example, but I  found
the result table size is 1512 records, and it is also less than the getBulk
with  maxRepetitions set to 20 which is 1528 records.

        public List snmpGetTable(OID[] columnOIDs, OID lowerBoundIndex, OID
upperBoundIndex) throws IOException {
        List result = null;
        TableUtils tableUtils = new TableUtils(this.snmp, new
DefaultPDUFactory(PDU.GETNEXT));
        tableUtils.setMaxNumRowsPerPDU(maxRepetitions);
        result = tableUtils.getTable(this.comtarget, columnOIDs,
lowerBoundIndex, upperBoundIndex);
        return result;
      }

     How can we  get it right?  How to get all rows of a table correctly?
     Thank you very much.

Best Regards,


On Thu, Apr 3, 2014 at 10:33 PM, Frank Fock <fock at agentpp.com> wrote:

> Hi,
>
> There is no "correct" maxRepetitions. Any value is "correct".
> The agent decides how many repetitions it will provide based on
> local contraints and measures. Some agent never return more
> than one, others up to the maximum packet size, others by
> timing constraints.
> Thus, you can never know how many repetitions there will be returned.
>
> BTW, OIDs do NOT start with a dot character. Simply
> write
>
> new OID("1.3.6.1.2.1.47.1.1.1.1.1")
>
> Best regards,
> Frank
>
> Am 03.04.2014 07:11, schrieb Tongjie Li:
>
>  Hi everybody
>>        I was executing a getTable in snmp4j on entitymib. I defined the
>> following columns like  following sample code
>>
>>            public static OID[] getColumnOIDs() {
>>          if (equipmentColumns != null) return equipmentColumns;
>>          equipmentColumns = new OID[11];
>>          equipmentColumns[0] = new OID(".1.3.6.1.2.1.47.1.1.1.1.1");
>> //entPhysicalIndex
>>          equipmentColumns[1] = new OID(".1.3.6.1.2.1.47.1.1.1.1.2");
>> //entPhysicalDescr
>>          equipmentColumns[2] = new OID(".1.3.6.1.2.1.47.1.1.1.1.3");
>> //entPhysicalVendorType
>>          equipmentColumns[3] = new OID(".1.3.6.1.2.1.47.1.1.1.1.4");
>> //entPhysicalContainedIn
>>          equipmentColumns[4] = new OID(".1.3.6.1.2.1.47.1.1.1.1.5");
>> //entPhysicalClass
>>          equipmentColumns[5] = new OID(".1.3.6.1.2.1.47.1.1.1.1.6");
>> //entPhysicalParentRelPos
>>          equipmentColumns[6] = new OID(".1.3.6.1.2.1.47.1.1.1.1.7");
>> //entPhysicalName
>>          equipmentColumns[7] = new OID(".1.3.6.1.2.1.47.1.1.1.1.13");
>> //entPhysicalModelName
>>          equipmentColumns[8] = new OID(".1.3.6.1.2.1.47.1.1.1.1.14");
>> //entPhysicalAlias
>>          equipmentColumns[9] = new OID(".1.3.6.1.2.1.47.1.1.1.1.16");
>> //entPhysicalFru if is fixed
>>          equipmentColumns[10] = new
>> OID(".1.3.6.1.2.1.47.1.1.1.1.11");//entPhysicalSerialNum
>>          return equipmentColumns;
>>           }
>>
>>         when I using it with getTable in the snmp4j with following code (
>> the columnOIDs are equipmentColumns from above example)
>>
>>          public List snmpGetTable(OID[] columnOIDs, OID lowerBoundIndex,
>> OID
>> upperBoundIndex) throws IOException {
>>          List result = null;
>>          TableUtils tableUtils = new TableUtils(this.snmp, new
>> DefaultPDUFactory(PDU.GETBULK));
>>          tableUtils.setMaxNumRowsPerPDU(maxRepetitions);
>>          result = tableUtils.getTable(this.comtarget, columnOIDs,
>> lowerBoundIndex, upperBoundIndex);
>>          return result;
>>        }
>>
>> When i test it,I found that setting different maxRepetitions will get
>> different answers. When I set maxRepetitions to 4
>> ,it return total number of 1428 records. When I set maxRepetitions  to 10,
>> it return total number of 1518 records. When set to 20,it return total
>> number of 1528 records. It made me very crazy.
>>
>> I want to know why and how to set the right maxRepetitions  in order to
>> avoid this. It seems that different types of device need to set different
>>   maxRepetitions. Is there a way to calculate the correct maxRepetitions ?
>>
>> Best regards
>>
>>
>>
>>
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-- 
All the Best!
Li Tongjie