[SNMP4J] Fwd: Fwd: Fwd: Table Model
Aiman Farhat
aiman.farhat at gmail.com
Tue May 7 16:41:20 CEST 2013
Hi Frank,
Thank you very much for the clarifications. I think I am going to try to
solve the issue from another angle. As you know the callback function
queryEvent which is the implementation MOServerLookupListener class will
be called multiple times (when using getbulk), hence this will cause
issuing the same query to the DB every time the callback function is
executed.
I am going to update the table only when the DB table is updated, and I am
not going to implement MOServerLookupListener interface.
The only concern I have is when the user sends getbulk request and this
will cause multiple requests being issued, in the meantime I need to update
the snmp table model because the db table is updated.
Do you think it is good approach to lock on the snmp table model for update
while the still processing getbulk? will this cause issues?
Regards
AF
---------- Forwarded message ----------
From: Frank Fock <fock at agentpp.com>
Date: Fri, May 3, 2013 at 5:47 PM
Subject: Re: [SNMP4J] Fwd: Fwd: Table Model
To: snmp4j at agentpp.org
Hi Aiman,
Please reread my answer and then try to explain, why you
think that
"Which is not what I have expected as my model should have either Set1 or
Set2 but not mix of both."
should be true?
If you update the model with each incoming request and each request
can only return 1/3 of the table, then the first third of the resulting
table view in the browser will be from the Set1, the second third from
Set2, and the third from Set3.
This is exactly how it should work.
Best regards,
Frank
Am 03.05.2013 11:57, schrieb Aiman Farhat:
> Hi Frank,
>
> Thanks for your response. According to instrumentation guide I am
> updating
> the table model before the request is processed based on external event.
> Our table will be small tables doesn't exceed 20 row max. The problem we
> are having is not with the order, it is actually with the content. I have
> a test data as follow:
>
> Set1:
> Component_set1_1
> Component_set1_2
> Component_set1_3
>
> Set2:
> Component_set2_1
> Component_set2_2
> Component_set2_3
>
> When I send a request from a Mib browser, the table content gets mixed. For
> example the data in the table could be something like that:
>
> Component_set1_1
> Component_set2_2
> Component_set1_3
>
> Which is not what I have expected as my model should have either Set1 or
> Set2 but not mix of both.
>
> As you know I am implementing MOServerLookupListener interface and in
> queryEvent(MOServerLookupEvent event) I am building my table model. I know
> queryEvent method get called multiple times based on number of columns and
> rows, and maybe that's why I am getting mixed results even though I am
> clearing the model.
>
> I am sure I am doing something wrong, and appricate your help.
>
> Thanks.
> AF
>
>
>
> On Thu, May 2, 2013 at 4:28 PM, Frank Fock <fock at agentpp.com> wrote:
>
> Hi,
>>
>> I think the table works perfectly. The ordering is correct.
>> (I know that this is not what you expected to hear ;-) )
>>
>> OK, first some words on the background: As you might
>> already know, SNMP does not have a PDU or service
>> called "getTable". Instead you have GETNEXT and GETBULK
>> and an absolut upper limit of 64K per PDU (UDP).
>>
>> Thus, medium and large tables will be never fetched with
>> a single Request->Response communication. If you alter
>> your table for each request, the command generator
>> (= sender of the requests) will see "incosistent" data,
>> because you provided incosistent data.
>>
>> Besides, it takes a lot CPU time, to recreate the table
>> for each request.
>>
>> You can improve your code by updating the table only
>> every 2-5 seconds and not more often as a client would
>> typically need to fetch the whole table.
>>
>> Best regards,
>> Frank
>>
>>
>>
>>
>> Am 02.05.2013 14:30, schrieb Aiman Farhat:
>>
>> Hi All,
>>>
>>> The problem I am facing with snmp4j is as follow, I am building a
>>> *dynamic*table model, where every time a request comes I clear the old
>>>
>>> data and then
>>> recreate it. The Issue I am facing is when I am sending subsequent
>>> requests
>>> the data model is not returning the correct rows. Just to give you an
>>> example:
>>>
>>> As a test the data I am sending back to the request either:
>>>
>>>
>>>
>>> Set A:
>>>
>>> Component1
>>>
>>> Component2
>>>
>>> Component3
>>>
>>> Component4
>>>
>>> Component5
>>>
>>> Component6
>>>
>>>
>>> OR
>>>
>>>
>>> Set B:
>>>
>>> Component11
>>>
>>> Component22
>>>
>>> Component33
>>>
>>> Component44
>>>
>>> Component55
>>>
>>> Component66
>>>
>>>
>>>
>>> Now the problem as follow:
>>>
>>> I see the following results in the Mib browser returned:
>>>
>>> Component1
>>>
>>> Component22
>>>
>>> Component3
>>>
>>> Component44
>>>
>>> Component55
>>>
>>> Component6
>>>
>>>
>>> As you can see the values in the table model is not what I have expected.
>>> As when I am building the table model I am clearing the old data then re
>>> populated with either set A or Set B
>>>
>>> of dummy values.
>>>
>>>
>>>
>>> Just to elaborate more from code prospective :
>>>
>>>
>>>
>>> T*his is building the table section:*
>>>
>>>
>>>
>>>
>>> DefaultMOTable table = new DefaultMOTable(tableRootOid, indexDef,
>>>
>>> columns.toArray(new
>>> MOColumn[0]));
>>>
>>> MOMutableTableModel model = (MOMutableTableModel) table.getModel();
>>>
>>>
>>>
>>> int i = 1;
>>>
>>>
>>>
>>> for (Variable[] variables : tableRows) {
>>>
>>> model.addRow(new DefaultMOMutableRow2PC(new OID(String.valueOf(i)),
>>> variables));
>>>
>>> i++;
>>>
>>> }
>>>
>>> table.setVolatile(true);
>>>
>>> return table;
>>>
>>>
>>>
>>> This section details the registration of the managed Table Object
>>>
>>>
>>> server.register(table, null);
>>>
>>> server.addLookupListener(new DeployedComponentListener(****table),
>>> table);
>>>
>>>
>>>
>>>
>>>
>>> And this is my Listener class implementation
>>>
>>>
>>>
>>> @Override
>>>
>>> *public* *void* queryEvent(MOServerLookupEvent event) {
>>>
>>>
>>>
>>> *DefaultMOTable* table = (*DefaultMOTable*) event.getLookupResult();
>>>
>>> MOMutableTableModel<****
>>> DefaultMOMutableRow2PC>
>>> model = *(MOMutableTableModel<****DefaultMOMutableRow2PC>)
>>>
>>> table.getModel()*;
>>>
>>>
>>>
>>> *synchronized* (model) {
>>>
>>>
>>>
>>> model.clear();
>>>
>>> Random r = *new* Random();
>>>
>>>
>>>
>>> *int* rand = r.nextInt(2);
>>>
>>>
>>>
>>> *if* (rand == 0) {
>>>
>>>
>>>
>>> Variable[] var1 = *new*
>>> Variable[]
>>> { *new* Integer32(1),
>>>
>>> *new*
>>> OctetString(
>>> "Component1"),
>>>
>>> *new*
>>> OctetString("Component1
>>> version"),
>>>
>>> *new*
>>> OctetString("Component1
>>> revision"),
>>>
>>> *new*
>>>
>>> OctetString("Component1
>>> insenace id"),
>>>
>>> *new*
>>> OctetString("")
>>> };
>>>
>>>
>>>
>>> more var…..
>>>
>>>
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("1"), var1));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("2"), var2));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("3"), var3));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("4"), var4));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("5"), var5));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("6"), var6));
>>>
>>>
>>>
>>> } *else* {
>>>
>>>
>>>
>>> Variable[] var1 = *new*
>>> Variable[]
>>> { *new* Integer32(1),
>>>
>>> *new*
>>> OctetString(
>>> "Component11"),
>>>
>>> *new*
>>> OctetString(""
>>> ),
>>>
>>> *new*
>>> OctetString(""
>>> ),
>>>
>>> *new*
>>> OctetString(""
>>> ),
>>>
>>> *new*
>>> OctetString("")
>>> };
>>>
>>>
>>>
>>> more var
>>>
>>>
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("1"), var1));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("2"), var2));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("3"), var3));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("4"), var4));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("5"), var5));
>>>
>>>
>>> model.addRow(*new*****DefaultMOMutableRow2PC(
>>>
>>> *new* OID("6"), var6));
>>>
>>>
>>> }
>>>
>>> }
>>>
>>>
>>> I am following the AgentPro instrumentation guide this the only guide I
>>> could find on how to build the table model.
>>>
>>> Thanks
>>>
>>> AF
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