[AGENT++] How to code an Expansion Relationship between 2 tables
Frank Fock
fock at agentpp.com
Thu Oct 16 00:38:32 CEST 2008
Hello Felix,
You can use the MibTable::add_listener method to
create an expansion relationship between two
or more tables. This is an option to facilitate
the synchronization of such tables when dynamic
row creation is supported for one or more those
tables.
The get_next_avail_index does work on simple
index values only (no strings, etc.).
Thus, your approach creating the corresponding
index values directly is OK.
Best regards,
Frank
Schmutz, Felix wrote:
> Hello All!
>
> I am trying to create two tables with Agent++, one of them expanding the other one, so I want to have an expansion relationship.
> Tough I am able to create the tables, I do not think that I got Agent++ to understand the relationship I want to have.
> So the question is: how can I code an expansion table in Agent++ properly representing below MIB
> Maybe one of you can help me out.
>
> Explanation:
>
> Table A (switchTable ) contains a list of all devices and their parameters of my system.
> Table B (slotTable) contains a list of input cards that can be plugged into the devices. Table B shall effectively contain all cards of the whole system.
>
> So Table B shall extend the indexing mechanism of the first table.
>
>
> To maybe make it more clear, my MIB looks like this. (I think these semantics are correct, though it is my first "serious" MIB)
>
> (...)
>
> switchTable OBJECT-TYPE
> SYNTAX SEQUENCE OF SwitchEntry
> MAX-ACCESS not-accessible
> STATUS current
> DESCRIPTION
> "A table containing t a list of all devices and their parameters of my system"
> ::= { companiesOID 10 }
>
> switchEntry OBJECT-TYPE
> SYNTAX SwitchEntry
> MAX-ACCESS not-accessible
> STATUS current
> DESCRIPTION
> "An entry (conceptual row) in the switchTable."
> INDEX { switchTableIndex }
> ::= { switchTable 1 }
>
>
> SwitchEntry ::= SEQUENCE
> {
> switchTableIndex Counter64,
> switchName DisplayString,
> switchFwVersion DisplayString,
> switchFanSpeed Integer32
> }
>
> switchTableIndex OBJECT-TYPE
> SYNTAX Counter64
> MAX-ACCESS not-accessible
> STATUS current
> DESCRIPTION
> "A unique identifier. Each device has one unique 64bit ID that shall be used as an index"
> ::= { switchEntry 1 }
>
> (...)
>
> slotTable OBJECT-TYPE
> SYNTAX SEQUENCE OF SlotEntry
> MAX-ACCESS not-accessible
> STATUS current
> DESCRIPTION
> "extension table containing all cards and their parameters found in the system. The sort-of primary keys are the switchTableIndex(unique Identifier of a device) as well as the slotTableIndex (slot number (unique) in a given device). switchTableIndex shall be the foreign key from switchTable"
> ::= { companiesOID 20 }
>
> slotEntry OBJECT-TYPE
> SYNTAX SlotEntry
> MAX-ACCESS not-accessible
> STATUS current
> DESCRIPTION
> "An entry (conceptual row) in the slotTable."
> INDEX { switchTableIndex , slotTableIndex }
> ::= { slotTable 1 }
>
> SlotEntry ::= SEQUENCE
> {
>
> slotTableIndex Integer32,
> slotName DisplayString,
> slotTemperature Integer32,
> slotCardEnabled INTEGER,
> slotType DisplayString
> }
>
> slotTableIndex OBJECT-TYPE
> SYNTAX INTEGER(0..100)
> MAX-ACCESS not-accessible
> STATUS current
> DESCRIPTION
> "A unique identifier used to identify the slots, generally lower than 30"
> ::= { slotEntry 2 }
>
> (....)
>
> Please note that in the final version the DESCRIPTION will be better.
>
>
> So in Agent++ I now did the following. I created two tables and used the index_info structure, because I think it has something to do with it.
> But how can I tell Agent++ how to fill it?
>
> My code looks like this
>
> ...
> const struct index_info indDynamicTable[1] ={ { theType, FALSE, 1, 1 } };
> const struct index_info indOfSlotTable[2] =
> { { sNMP_SYNTAX_CNTR64, FALSE, 1, 1 }, { sNMP_SYNTAX_INT32, FALSE, 1, 1 } };
>
>
> MibTable switchTable(Oidx(Oids::conceptionalRowOfFrameTable), indDynamicTable , 1,);// conceptionalRowOfFrameTable = a string containing companiesOID::10.1
>
>
> switchTable.add_col(new MibLeaf("1", READONLY, new Counter64(DeviceDaemon::SwitchSerial->Get()))); // this is the switchTableIndex
> switchTable.add_col(new SnmpDisplayString("2", READONLY, new OctetStr( "someName" ) ));
>
> ...
>
>
> MibTable slotTable(Oidx(Oids::conceptionalRowOfSlotTable), indOfSlotTable, 2,); //// conceptionalRowOfFrameTable = string containing absolute OID: companiesOID::20.1
>
> slotTable.add_col(new MibLeaf("1", READONLY, new Counter64(DeviceDaemon::SwitchSerial->Get())));
> slotTable.add_col(new MibLeaf("1", READONLY, new SnmpInt32 (DeviceDaemon::SlotNumber->Get())));
> slotTable .add_col(new SnmpDisplayString(Oids::STnameSlotName, READONLY, new OctetStr("someName")));
>
>
> if I now fill the tables by calling
> Oidx next = table->get_next_avail_index();
> MibTableRow* row = table->add_row(next);
>
> The index column of switchTable is not pre-filled ==> fine.
> I CAN fill it by calling lets say:
>
> switchTableRow->get_nth(0)->replace_value(new Counter64 (switchID)); //I think I fill the index row
> //fill additional values here
>
> as well as
> slotTableRow->get_nth(0)->replace_value(new Counter64 (switchID));
> slotTableRow->get_nth(1)->replace_value(new SnmpInt32 (slotNumber));
> //fill additional values here
>
> That's fine, the way it is implemented, it is working, and by looking at the MIB one will be able to grasp the intended relationship, but I don't think that this is the supposed way how to do it?
> Can one please point me in a direction how one should solve this? I don't find anything about table expansion relationships in Agent++ in any example/document. I'd really appreciate any suggestion and hints!
>
>
> best regards,
>
> Felix
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