How to know which subrequestId to work with?

[Alex Finogenov]

Frank,

Isn't MibTable::update() called on every subrequest, starting from subrequestId = 0?

Initially I built my agent to pre-populate each table that is hit for the entire request exactly once in the overloaded MibTable::update() for that table.

This approach worked well with all SNMP requests except GetBulk. Upon a closer research of the agentpp internals, I've found that MibTable:: update() is actually called on every single subrequest, and a good way to find out the subrequest Id is to call Request::first_pending(). You can use this method to implement either approach since when it returns 0, it means that the agent is processing a new request.

My agent is not SNMPv3 and is not multi-threaded, although I don't think that this matters.

After reading your reply to the Kjersti's question, I wonder if I am missing anything in my approach.

Thanks,
Alex

> -----Original Message-----
> From: Frank.Fock____t-online.de [mailto:Frank.Fock____t-online.de]
> Sent: Thursday, April 11, 2002 10:48 AM
> To: Kjersti Grønnevik
> Cc: agentpp-dl____agentpp.com
> Subject: Re: How to know which subrequestId to work with?
> 
> 
> Hi Kjersti,
> 
> I have considered to include the subrequest ID in the 
> interface of update.
> I ended up with the current design, because the 
> MibTable::update should
> not operate on a subrequest basis. Rather than, it should 
> update all necessary
> data for the whole request in one go and remember the last 
> transaction IDs
> to avoid duplicate updates. In addition a timer could be used 
> to avoid additional
> updates within a given time interval.
> 
> The MibTable::update method is called from the class Mib when 
> processing
> a request.
> 
> Best regards,
> Frank
> 
> Kjersti Grønnevik wrote:
> 
> > Hi
> >
> > I have a dynamic table which fetches the requested rows 
> from DB when a new request comes. The cache is emptied when a 
> new request comes.
> >
> > My problem is that I need the subrequestId to get the right 
> row from DB and I can't seem to find any function that can 
> give the Id?
> >
> > Any suggenstions will be highly appreciated!
> >
> > I first worked around this by creating this function and call it:
> >
> > ----------------------------------------------------------------
> > void AptEntry::update(Request* req, int subReqIndex)
> > {
> >         start_synch();
> >         currentSubReqIndex = suReqIndex; // 
> currentSubReqIndex is a global variable so the suReqIndex is  
>                                                  // available 
> in the update(req) function
> >         update(req);                       // calls the 
> function, but it is also called elsewhere?
> >         lastReqId = req->get_request_id(); // to see if the 
> subRequest is from the same request or a new                  
>                                    //one
> >         end_synch();
> > }
> > -----------------------------------------------------------------
> > But this function is never called, and I don't know where 
> to call it from. It will not be called from the table index 
> get_request, and where else to put the call?
> >
> > I have filled the update(request req); function with my own 
> code and I think it will work(?), but it depends on the 
> currentSubReqIndex.
> > -----------------------------------------------------------------
> >
> > void lvAptEntry::update(Request* req)
> > {
> > // clear table rows if this is a new request
> > unsigned long currentReqId = req->get_request_id();
> > if( lastReqId != currentReqId )
> > {
> >   removeAllAPTEntries();
> > }
> >
> >   Oidx oid = req->get_oid( currentSubReqIndex );
> >   Oidx oid_aptId = getPrimaryKeyAsOID( oid ); //extract the 
> index/APT.id from the oid
> >
> > //use this index to fetch the corresponding row in the APT 
> table in the DB and cache the row data.
> >   long aptId = getPrimaryKeyAsLong( oid );
> >
> > try
> > {
> >         LVDatabase *db = LVDatabase::getInstance();
> >
> >         APTEntry aptEntry;
> >
> >         // GET
> >         if(req->get_type() == 160)
> >         {
> > //use this index and check cache if corresponding row data 
> already has been loaded from DB in this request
> >           MibTableRow* existingRow = find_index( oid_aptId );
> >
> > // if row data exists in cache - the cached row data are available
> > // else
> >                 if( existingRow == 0 )
> >                 {
> >                         aptEntry = db->getAPTEntry( aptId 
> ); //get the row from db
> >                         if( aptEntry.exists() == true )
> >                         {
> >                                 addEntry( aptEntry, 
> oid_aptId );  //add the row with the row data from db
> >                         }
> >                 }
> >         }
> > // GET NEXT
> >         else if(req->get_type() == 161)
> >         {
> >           Oidx nextOidId = computeNextOID( oid );//Finds 
> out what the next rowIndex would be
> >
> >         MibTableRow* existNextRow = find_index( nextOidId 
> ); //Checks if the row is already fetched
> >
> >           if( existNextRow == 0 )// If not fetched, fetch 
> the row from db
> >           {
> >                 aptEntry = db->getNextAPTEntry( aptId );  
> //get row from db
> >
> >                 if( aptEntry.exists() )
> >                 {
> >                         Oidx oid_nextAptId = 
> getPrimaryKeyAsOID( aptEntry ); //get the rowId
> >                         addEntry( aptEntry, oid_nextAptId 
> );  //add the row with the row data from db
> >                 }
> >                 else
> >                 {
> >                         Oidx oid_collumnNr = oid.cut_right( 
> 1 );//find which collumn that is asked for
> >                         long colNr = oid_collumnNr.last();
> >
> >                         if( colNr < 31 ) //If not the last 
> column in DB table
> >                 {
> >                                 aptEntry = 
> db->getNextAPTEntry( (long)-1 );  //get first row from db
> >                                 if( aptEntry.exists() )
> >                                 {
> >                                         Oidx oid_nextAptId 
> = getPrimaryKeyAsOID( aptEntry ); //get the rowId
> >                                         addEntry( aptEntry, 
> oid_nextAptId );  //add the row with the row data from db
> >                                 }
> >                         }
> >                 }
> >            }
> >         }
> > }
> > catch( exception& e )
> > {
> >         char catchBuffer[200];
> >         sprintf( catchBuffer, "lvAptEntry.update(.) 
> Standard library exception: SQL error %d ", e );
> >         Log::addEvent( Log::INFO, catchBuffer, LOC );
> > }
> > catch( ... )
> > {
> >         char catchBuffer[200];
> >         sprintf( catchBuffer, "lvAptEntry.update(.) 
> Standard library exception: SQL error " );
> >         Log::addEvent( Log::INFO, catchBuffer, LOC );
> > }
> > }
> >
> > ---------------------------------------
> > Oidx lvAptEntry::find_succ(const Oidx& oid, Request* req)
> > {
> >  MibLeaf* leaf = find_next( oid );
> >  if( leaf )
> >  {
> >         return leaf->get_oid();
> >  }
> >  else
> >  {
> >         return Oidx();
> >  }
> > }
> >
> > 
> --------------------------------------------------------------
> ---------
> > void lvAptEntry::removeAllAPTEntries()
> > {
> > //remove old rows from MibTable
> >         clear();
> >         delete_rows.clearAll();
> >         notready_rows.clearAll();
> > }
> > 
> --------------------------------------------------------------
> ---------
> >
> > Hope this is understandable and thanks so much for great 
> help so far!
> >
> > Best regards,
> > Kjersti
> 
> --
> Frank Fock - AGENT++
> Email: fock____agentpp.com
> Fax: +49 7195 177108
> 
> 
> 
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