l3_agent list_networks should be wrapped in try except

[Koaps]

I was noticing an error in my logs for l3_agent and took a bit to figure out what it was telling me.

2012-10-06 01:10:26 ERROR [quantum.agent.l3_agent] Error running l3_nat daemon_loop
Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/quantum-2013.1-py2.6.egg/quantum/agent/l3_agent.py", line 173, in daemon_loop
    self.do_single_loop()
  File "/usr/lib/python2.6/site-packages/quantum-2013.1-py2.6.egg/quantum/agent/l3_agent.py", line 204, in do_single_loop
    target_ex_net_id = self._fetch_external_net_id()
  File "/usr/lib/python2.6/site-packages/quantum-2013.1-py2.6.egg/quantum/agent/l3_agent.py", line 185, in _fetch_external_net_id
    ex_nets = self.qclient.list_networks(**params)['networks']
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 102, in with_params
    ret = self.function(instance, *args, **kwargs)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 244, in list_networks
    return self.get(self.networks_path, params=_params)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 525, in get
    headers=headers, params=params)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 510, in retry_request
    headers=headers, params=params)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 455, in do_request
    self._handle_fault_response(status_code, replybody)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 436, in _handle_fault_response
    exception_handler_v20(status_code, des_error_body)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 82, in exception_handler_v20
    message=message)
QuantumClientException: [Errno 111] ECONNREFUSED

This happens when the database has no tables created yet.

It can be seen using the code from quantumclient.v2_0.client

>>> from quantumclient.v2_0 import client
>>> client20 = client.Client(username='admin', password='password', auth_url='http://localhost:5000/v2.0', tenant_name='Demo')
>>> client20.tenant = 'default'
>>> client20.format = 'json'
>>> nets = client20.list_networks()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 102, in with_params
    ret = self.function(instance, *args, **kwargs)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 244, in list_networks
    return self.get(self.networks_path, params=_params)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 525, in get
    headers=headers, params=params)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 510, in retry_request
    headers=headers, params=params)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 455, in do_request
    self._handle_fault_response(status_code, replybody)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 436, in _handle_fault_response
    exception_handler_v20(status_code, des_error_body)
  File "/usr/lib/python2.6/site-packages/python_quantumclient-2.1.1-py2.6.egg/quantumclient/v2_0/client.py", line 82, in exception_handler_v20
    message=message)
quantumclient.common.exceptions.QuantumClientException: [Errno 111] Connection refused

Just to make it more friendly, wrapping it in a try except seems to make things much nicer:

>>> from quantumclient.v2_0 import client
>>> client20 = client.Client(username='admin', password='password', auth_url='http://localhost:5000/v2.0', tenant_name='Demo')
>>> client20.tenant = 'default'
>>> client20.format = 'json'
>>> params = {'router:external': True}
>>> try:
... nets = self.client20.list_networks(**params)['networks']
... print nets
... except:
... print "Connection to database failed"
...
Connection to database failed
>>>

To make it so you don't need to wrap a all the returns, it might be a good idea to set ex_net so you don't get an error when doing the len():

    def _fetch_external_net_id(self):
        """Find UUID of single external network for this agent"""
        if self.conf.gateway_external_network_id:
            return self.conf.gateway_external_network_id

        ex_nets = {}
        params = {'router:external': True}
        try:
                ex_nets = self.qclient.list_networks(**params)['networks']
        except:
                LOG.exception("Connection to database failed")

        if len(ex_nets) > 1:
            raise Exception("must configure 'gateway_external_network_id' if "
                            "Quantum has more than one external network.")
        if len(ex_nets) == 0:
            return None
        return ex_nets[0]['id']

This also happens for list_routers:
    def do_single_loop(self):

#............skipped code lines

        # identify and update new or modified routers
        for r in self.qclient.list_routers()['routers']:

I tried wrapping it with a new function:

    def _fetch_routers(self):
        routers = {}
        try:
                routers = self.qclient.list_routers()['routers']
        except:
                LOG.exception("Connection to database failed")

        return routers

    def do_single_loop(self):

#............skipped code lines

        # identify and update new or modified routers
        #for r in self.qclient.list_routers()['routers']:
        for r in routers:

But that didn't catch the error for some reason, my python must be lacking some mojo.

[dan wendlandt (danwent)]

this is a reasonable suggestion I think, but this code should be going away once we update the L3 agent to use RPC: https://blueprints.launchpad.net/quantum/+spec/rpc-for-l3-agent