Getting started with OpenDaylight and Python

I decided to try out my first ODL app using Python, and the REST API. One simple case is to grab flow stats, so that’s what I thought I’d try first. I’m going to tyr and keep track of all my opendaylight scripts on github, feel free to have a look: https://github.com/fredhsu/odl-scripts

First I built up a small network using the very handy tree topolgy that mininet offers:

sudo mn --controller=remote,ip=10.55.17.20 --topo tree,3

This creates a binary tree of depth 3, with two hosts at each leaf node. My ODL controller is running at 10.55.17.20. Now I get a nice diagram on the ODL interface:

Next I want to have some traffic get statistics from. So I need to send some pings between a couple hosts. However, this will not work in its current state. I have to add a ‘Subnet Gateway’, which I hope to dive deeper into later, but it basically responds to ARPs, and creates host flow entries in switches. To do this I click on ‘Add Gateway IP Address’, and fill in an unused IP address for the subnet my hosts are on:

Now I can ping from host to host using Mininet, notice the familiar delay in the first ping due to ARP:

mininet> h1 ping h2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_req=1 ttl=64 time=1010 ms
64 bytes from 10.0.0.2: icmp_req=2 ttl=64 time=4.86 ms
64 bytes from 10.0.0.2: icmp_req=3 ttl=64 time=0.058 ms

After this the diagram in ODL shows my hosts:

Ok, so now we’re all set. I can see the stats that ODL from the web page, this shows me what I’m planning on getting programmatically. Since the web front end uses the REST API, I should be able to get whatever information the website is able to show:

Now its time to start coding. The docs for the Statistics REST API are here. Using that I’m able to go grab stats for all the flows on the controller. My source code is below:

	import httplib2
	import json
	h = httplib2.Http(".cache")
	h.add_credentials('admin', 'admin')
	#resp, content = h.request('http://10.55.17.20:8080/controller/nb/v2/statistics/default/flowstats', "GET")
	# Updated 8 SEP 2013 to reflect new REST API
	resp, content = h.request('http://10.55.17.20:8080/controller/nb/v2/statistics/default/flow', "GET")
	allFlowStats = json.loads(content)
	flowStats = allFlowStats['flowStatistics']
	# These JSON dumps were handy when trying to parse the responses
	#print json.dumps(flowStats[0]['flowStat'][1], indent = 2)
	#print json.dumps(flowStats[4], indent = 2)
	for fs in flowStats:
	print "\nSwitch ID : " + fs['node']['id']
	print '{0:8} {1:8} {2:5} {3:15}'.format('Count', 'Action', 'Port', 'DestIP')
	for aFlow in fs['flowStat']:
	count = aFlow['packetCount']
	actions = aFlow['flow']['actions']
	actionType = ''
	actionPort = ''
	#print actions
	if(type(actions) == type(list())):
	actionType = actions[1]['type']
	actionPort = actions[1]['port']['id']
	else:
	actionType = actions['type']
	actionPort = actions['port']['id']
	dst = aFlow['flow']['match']['matchField'][0]['value']
	print '{0:8} {1:8} {2:5} {3:15}'.format(count, actionType, actionPort, dst)

view raw

odl-stats.py

hosted with ❤ by GitHub

You can see I basically pull in all the flows, parse the JSON, and pull out the stats I want, then print it all out to the command line. Here’s the result:

Switch ID : 00:00:00:00:00:00:00:07
Count    Action   Port  DestIP         
0        output   3     10.0.0.1       
0        output   3     10.0.0.2       

Switch ID : 00:00:00:00:00:00:00:06
Count    Action   Port  DestIP         
0        output   3     10.0.0.1       
0        output   3     10.0.0.2       

Switch ID : 00:00:00:00:00:00:00:05
Count    Action   Port  DestIP         
0        output   3     10.0.0.1       
0        output   3     10.0.0.2       

Switch ID : 00:00:00:00:00:00:00:04
Count    Action   Port  DestIP         
0        output   3     10.0.0.1       
0        output   3     10.0.0.2       

Switch ID : 00:00:00:00:00:00:00:03
Count    Action   Port  DestIP         
6        output   1     10.0.0.1       
6        output   2     10.0.0.2       

Switch ID : 00:00:00:00:00:00:00:02
Count    Action   Port  DestIP         
0        output   1     10.0.0.1       
0        output   1     10.0.0.2       

Switch ID : 00:00:00:00:00:00:00:01
Count    Action   Port  DestIP         
0        output   1     10.0.0.1       
0        output   1     10.0.0.2       

Its not much, but hopefully this serves as a good starting point. I’m going to try and do the same in a couple other languages, just for fun, then work on something more complicated. Any ideas/comments/suggestions are welcome!