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query from sqlalchemy returns AttributeError: 'NoneType' object

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  query from sqlalchemy returns AttributeError: 'NoneType' object karthik.sharma@gmail.com - 2013-05-02 15:14 -0700
    Re: query from sqlalchemy returns AttributeError: 'NoneType' object MRAB <python@mrabarnett.plus.com> - 2013-05-03 00:17 +0100
    Re: query from sqlalchemy returns AttributeError: 'NoneType' object Dave Angel <davea@davea.name> - 2013-05-02 19:29 -0400

#44644 — query from sqlalchemy returns AttributeError: 'NoneType' object

from pox.core import core
    import pox.openflow.libopenflow_01 as of
    import re
    import datetime
    
    from sqlalchemy import create_engine, ForeignKey
    from sqlalchemy import Column, Date, Integer, String
    from sqlalchemy.ext.declarative import declarative_base
    from sqlalchemy.orm import relationship, backref
    from sqlalchemy import create_engine
    from sqlalchemy.orm import sessionmaker
    from sqlalchemy.sql.expression import exists
    
    log = core.getLogger()
    
    engine = create_engine('sqlite:///nwtopology.db', echo=False)
    Base = declarative_base()
    Session = sessionmaker(bind=engine)
    session = Session()
    
    ########################################################################
    class SourcetoPort(Base):
        """"""
        __tablename__ = 'source_to_port'
        id = Column(Integer, primary_key=True)
        port_no        = Column(Integer)
        src_address    = Column(String,index=True)
    
        #----------------------------------------------------------------------
        def __init__(self, src_address,port_no):
            """"""
            self.src_address = src_address    
    	self.port_no     = port_no
            
    ########################################################################
    
    #create tables
    Base.metadata.create_all(engine)
    
    class Tutorial (object):
      def __init__ (self, connection):
        self.connection = connection
        connection.addListeners(self)
        # Use this table to keep track of which ethernet address is on
        # which switch port (keys are MACs, values are ports).
        self.mac_to_port = {} 
        self.matrix={} 
    	
        #This will keep track of the traffic matrix. 
        #matrix[i][j]=number of times a packet from i went to j
      
      def send_packet (self, buffer_id, raw_data, out_port, in_port):
        #print "calling send_packet"
        #Sends a packet out of the specified switch port.
        msg = of.ofp_packet_out()
        msg.in_port = in_port
        msg.data = raw_data
        # Add an action to send to the specified port
        action = of.ofp_action_output(port = out_port)
        msg.actions.append(action)
        # Send message to switch
        self.connection.send(msg)
    
      def act_like_hub (self, packet, packet_in):
        #flood packet on all ports
        self.send_packet(packet_in.buffer_id, packet_in.data,
                         of.OFPP_FLOOD, packet_in.in_port)
    
      def act_like_switch (self, packet, packet_in):
        """
        Implement switch-like behavior.
        """
        # Learn the port for the source MAC
        #print "RECIEVED FROM PORT ",packet_in.in_port , "SOURCE ",packet.src
        # create a Session
        #Session = sessionmaker(bind=engine)
        #session = Session()
        self.mac_to_port[packet.src]=packet_in.in_port
        #if self.mac_to_port.get(packet.dst)!=None:
        #print "count for dst",session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).count(),str(packet.dst)
        #if session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).count():
        if session.query(exists().where(SourcetoPort.src_address == str(packet.dst))).scalar() is not None:
          	   #send this packet
    	   print "got info from the database"
    	   q_res = session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).one()
    	   self.send_packet(packet_in.buffer_id, packet_in.data,q_res.port_no, packet_in.in_port)
               #create a flow modification message
          	   msg = of.ofp_flow_mod()
          	   #set the fields to match from the incoming packet
    	   msg.match = of.ofp_match.from_packet(packet)
               #send the rule to the switch so that it does not query the controller again.
               msg.actions.append(of.ofp_action_output(port=q_res.port_no))
               #push the rule
               self.connection.send(msg)
        else:
               #flood this packet out as we don't know about this node.
               print "flooding the first packet"
               self.send_packet(packet_in.buffer_id, packet_in.data,
                           of.OFPP_FLOOD, packet_in.in_port)
    	   #self.matrix[(packet.src,packet.dst)]+=1	 
    	   entry = SourcetoPort(src_address=str(packet.src) , port_no=packet_in.in_port)
               #add the record to the session object
               session.add(entry)
               #add the record to the session object
               session.commit()
    
      def _handle_PacketIn (self, event):
        """
        Handles packet in messages from the switch.
        """
        packet = event.parsed # This is the parsed packet data.
        if not packet.parsed:
          log.warning("Ignoring incomplete packet")
          return
        packet_in = event.ofp # The actual ofp_packet_in message.
    
        #self.act_like_hub(packet, packet_in)
        self.act_like_switch(packet, packet_in)
    
    def launch ():
      """
      Starts the component
      """
      def start_switch (event):
        log.debug("Controlling %s" % (event.connection,))
        Tutorial(event.connection)
      core.openflow.addListenerByName("ConnectionUp", start_switch)



When I run the above code I get the following error:



The problem that I am facing is for some reason if I use 

    if session.query(exists().where(SourcetoPort.src_address == str(packet.dst))).scalar() is not None:

    in place of count query.

    #if session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).count():

The querying from the database

    q_res = session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).first()
    self.send_packet(packet_in.buffer_id, packet_in.data,q_res.port_no, packet_in.in_port)

is giving the following error:

    DEBUG:core:POX 0.1.0 (betta) going up...
    DEBUG:core:Running on CPython (2.7.3/Aug 1 2012 05:14:39)
    DEBUG:core:Platform is Linux-3.5.0-23-generic-x86_64-with-Ubuntu-12.04-precise
    INFO:core:POX 0.1.0 (betta) is up.
    DEBUG:openflow.of_01:Listening on 0.0.0.0:6633
    INFO:openflow.of_01:[00-00-00-00-00-02 1] connected
    DEBUG:tutorial:Controlling [00-00-00-00-00-02 1]
    got info from the database
    ERROR:core:Exception while handling Connection!PacketIn...
    Traceback (most recent call last):
      File "/home/karthik/pox/pox/lib/revent/revent.py", line 234, in raiseEventNoErrors
        return self.raiseEvent(event, *args, **kw)
      File "/home/karthik/pox/pox/lib/revent/revent.py", line 281, in raiseEvent
        rv = event._invoke(handler, *args, **kw)
      File "/home/karthik/pox/pox/lib/revent/revent.py", line 159, in _invoke
        return handler(self, *args, **kw)
      File "/home/karthik/pox/tutorial.py", line 118, in _handle_PacketIn
        self.act_like_switch(packet, packet_in)
      File "/home/karthik/pox/tutorial.py", line 86, in act_like_switch
        self.send_packet(packet_in.buffer_id, packet_in.data,q_res.port_no, packet_in.in_port)
    AttributeError: 'NoneType' object has no attribute 'port_no'
    got info from the database
    ERROR:core:Exception while handling Connection!PacketIn...

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#44646

On 02/05/2013 23:14, karthik.sharma@gmail.com wrote:
[snip]
>
>      ########################################################################
>      class SourcetoPort(Base):
>          """"""
>          __tablename__ = 'source_to_port'
>          id = Column(Integer, primary_key=True)
>          port_no        = Column(Integer)
>          src_address    = Column(String,index=True)
>
>          #----------------------------------------------------------------------
>          def __init__(self, src_address,port_no):
>              """"""
>              self.src_address = src_address

The indentation of this line looks wrong:

>      	   self.port_no     = port_no
>
>      ########################################################################
[snip]

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#44647

On 05/02/2013 06:14 PM, karthik.sharma@gmail.com wrote:
> from pox.core import core
>      import pox.openflow.libopenflow_01 as of
>      import re
>      import datetime
>


You're mixing tabs and space, so all bets are off.  No promise that the 
compiler will interpret the indentations the same way you see them.

Use your editor to expand all the tabs to space, then check whether the 
code still makes sense to you.  Then if you want to post a new question, 
show us the new version of code.

Also this time post the error traceback that matches the version of the 
code you're showing us.

And don't bother double-posting on tutor.

-- 
DaveA

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