pygnmi 2. How to use pyGNMI?

Anton Karneliuk

4 years ago

Hello my friend,

In the previous article we have mentioned that we have started building our own Python package, which will allow you to easily interact with the network functions over gNMI. Today we want to share with you some progress and explain, how you can start benefiting from it right now.


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Brief description

The idea behind pyGNMI is simple. That is a Python package, which you can use in your code to interact with the network functions using the gNMI. There is a number of issue we would need to solve during the development, as we have stated previously:

implementation of both secure and insecure gRPC channels
implementation of all RPCs (Capabilities, Get, Set, Subscribe) in a way it is easy to use them
implementation of all options and arguments, but, again, it should be easy and convenient to use them

So far we have started slowly with the development of the insecure gRPC channel with the Capabilities and Set operations. Per gNMI specification:

Capabilities collects all the details about what the device is capable in terms of supported YANG modules, data encoding types, and gNMI version.
Get allows you to obtain the information from the device, such as configuration and real-time actual operational or state data.

Using this two requests you can already start building a monitoring of your network functions using gNMI or, in general, start exploring how to work with it.

Usage

First thing first, you need to install the pyGNMI. You can do that from the Pypi or GitHub. We are trying to keep them in sync, so both resources should have the most actual stable version of the code. The installation is done using pip:


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$ pip install pygnmi

Collecting pygnmi

  Using cached https://files.pythonhosted.org/packages/a0/5e/00863e634772473e569025648ea5a2aa8cf78dd7d3a3c2e9fe4a1d91c351/pygnmi-0.1.8.tar.gz

Collecting grpcio (from pygnmi)

  Using cached https://files.pythonhosted.org/packages/48/16/d229a9d7d45bafecfe6b4c9ebf2053ec929efc2ffbed0b1a89ef190ef4d9/grpcio-1.32.0-cp37-cp37m-macosx_10_9_x86_64.whl

Collecting grpcio-tools (from pygnmi)

  Using cached https://files.pythonhosted.org/packages/06/c5/2687a0ef17b4444f2ea663572b982728eee93f629f64c6fe08fdae9368a9/grpcio_tools-1.32.0-cp37-cp37m-macosx_10_9_x86_64.whl

Collecting six&gt;=1.5.2 (from grpcio-&gt;pygnmi)

  Using cached https://files.pythonhosted.org/packages/ee/ff/48bde5c0f013094d729fe4b0316ba2a24774b3ff1c52d924a8a4cb04078a/six-1.15.0-py2.py3-none-any.whl

Collecting protobuf&lt;4.0dev,&gt;=3.5.0.post1 (from grpcio-tools-&gt;pygnmi)

  Using cached https://files.pythonhosted.org/packages/9c/d2/10c325d657155ad7bd942f9d2652ae8e3e7a4be66723e9789099283733df/protobuf-3.13.0-cp37-cp37m-macosx_10_9_x86_64.whl

Requirement already satisfied: setuptools in ./venv/lib/python3.7/site-packages (from protobuf&lt;4.0dev,&gt;=3.5.0.post1-&gt;grpcio-tools-&gt;pygnmi) (41.2.0)

Installing collected packages: six, grpcio, protobuf, grpcio-tools, pygnmi

  Running setup.py install for pygnmi ... done

Successfully installed grpcio-1.32.0 grpcio-tools-1.32.0 protobuf-3.13.0 pygnmi-0.1.8 six-1.15.0

As gNMI is based on the gRPC transport, we build it our library on top of the existing gRPC.io. That library under the hood does the gRPC session handling for us.

The next step is to import the appropriate class gNMIclient from pygnmi.client, which handles the session. The class is implemented as a context manager, so it will establish the gRPC session and opening and will close it for you, once job is done:


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$ cat test.py 

#!/usr/bin/env python



# Modules

from pygnmi.client import gNMIclient



# Variables

host = ('169.254.255.64', 57400)



# Body

if __name__ == '__main__':

    with gNMIclient(target=host, username='admin', password='admin', insecure=True) as gc:

         result = gc.get(path=&#91;'openconfig-interfaces:interfaces', 'openconfig-acl:acl'])

         

    print(result)

The parameters you need to provide towards the channel are the following:

Key	Data type	Meaning
target	tuple	gNMI host, IP address is the first key and port is the second
username	string	username to connect to gNMI host
password	string	password to connect to gNMI host
insecure	boolean	type of session: with the SSL encryption (False) or without (True)
path	string	path towards the certificate if insecure=False

Once the object is created, you can perform requests per gNMI specification, which are implemented as methods. So far we have implemented two requests:

request	arguments
capabilities()	no arguments
get()	path, which is a list of strings containing the gNMI paths to resources you want to pull

The result of each call is provided back as a Python dictionary, so you can use it directly a you need without any further conversion. The pygnmi is dealing with the complexity of the Protobuf for you. Here the result of the execution of the capabilities request against Nokia SR OS based network function:


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$ cat test.py 

#!/usr/bin/env python



# Modules

from pygnmi.client import gNMIclient



# Variables

host = ('169.254.255.64', '57400')



# Body

if __name__ == '__main__':

    with gNMIclient(target=host, username='admin', password='admin', insecure=True) as gc:

        result = gc.capabilities()

         

    print(result)





$ python test.py 

{'supported_models': &#91;{'name': 'nokia-conf', 'organization': 'Nokia', 'version': '20.5.R1'}, {'name': 'nokia-state', 'organization': 'Nokia', 'version': '20.5.R1'}, {'name': 'nokia-li-state', 'organization': 'Nokia', 'version': '20.5.R1'}, {'name': 'nokia-li-conf', 'organization': 'Nokia', 'version': '20.5.R1'}, {'name': 'nokia-openconfig-if-ip-augments', 'organization': 'Nokia', 'version': '20.5.R1'}, {'name'...

!

! FURTHER OUTPUT IS OMITTED

Refer to the corresponding article to get info, how to enable gNMI on Nokia SR OS or Arista EOS router.

And the result of the get request for several paths:


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$ cat test.py 

#!/usr/bin/env python



# Modules

from pygnmi.client import gNMIclient



# Variables

host = ('169.254.255.64', '57400')



# Body

if __name__ == '__main__':

    with gNMIclient(target=host, username='admin', password='admin', insecure=True) as gc:

         result = gc.get(path=&#91;'openconfig-interfaces:interfaces', 'openconfig-acl:acl'])

         

    print(result)





$ python test.py 

{'notification': &#91;{'timestamp': 1602618401033156685, 'update': &#91;{'path': 'interfaces', 'json_val': {'interface': &#91;{'name': 'system', 'config': {'name': 'system', 'type': 'softwareLoopback', 'enabled': True}, 'state': {'name': 'system', 'type': 'softwareLoopback'}, 'subinterfaces': {'subinterface': &#91;{'index': 0, 'config': {'index': 0, 'enabled': True}, 'ipv4': {'addresses': {'address': &#91;{'ip': '10.0.255.11', 'config': {'ip': '10.0.255.11', 'prefix-length': 32}}]}}}]}}, {'name': '1/1/c1/1', 'config': {'name': '1/1/c1/1', 'type': 'ethernetCsmacd', 'enabled': True}, 'state': {'name': '1/1/c1/1', 'type': 'ethernetCsmacd', 'mtu': 9212, 'description': '10-Gig Ethernet', 'enabled': True, 'ifindex': 1610899521, 'admin-status': 'UP', 'oper-status': 'UP', 'last-change': '16320000', 'counters': {'in-octets': '46', 'in-unicast-pkts': '0', 'in-broadcast-pkts': '1', 'in-multicast-pkts': '0', 'in-discards': '0', 'in-errors': '0', 'in-unknown-protos': '0', 'in-fcs-errors': '0', 'out-octets': '0', 'out-unicast-pkts': '0', 'out-broadcast-pkts': '0', 'out-multicast-pkts': '0', 'out-discards': '0', 'out-errors': '0', 'carrier-transitions': '0'}}, 'hold-time': {'state': {'up': 0, 'down': 0}}, 'subinterfaces': {'subinterface': &#91;{'index': 0, 'config': {'index': 0, 'enabled': True}, 'ipv4': {'addresses': {'address': &#91;{'ip': '10.0.0.0', 'config': {'ip': '10.0.0.0', 'prefix-length': 31}}]}}}]}, 'ethernet': {'state': {'mac-address': '52:54:00:64:00:01', 'auto-negotiate': False, 'hw-mac-address': '52:54:00:64:00:01', 'negotiated-duplex-mode': 'FULL', 'negotiated-port-speed': 'SPEED_10GB', 'counters': {'in-mac-pause-frames': '0', 'in-oversize-frames': '0', 'in-jabber-frames': '0', 'in-fragment-frames': '0', 'in-crc-errors': '0', 'out-mac-pause-frames': '0'}}}}]}}]}, {'timestamp': 1602618401033657507, 'update': &#91;{'path': 'acl', 'json_val': {'state': {'counter-capability': 'AGGREGATE_ONLY'}}}]}]}

So the first step is done and we encourage you to start using us and give us feedback, what you like, what not and if you see any bugs.

GitHub repository

The latest updates of the pyGNMI, as well as other our products you can find in our GitHub.

Lessons learned

The process of the packaging of the Python modules for Pypi is not trivial. However, there are plenty of the good documents in the Web sharing the step-by-step approach. Personally we have used this one, so thanks author for creating that.

Conclusion

We have created two first calls and have had a lot of fun solving the packaging challenges. Perhaps, they are the most simple one, but we believe it is already a good starting point. Our plan is to cover all calls first and then to add the secure channel capabilities. Stay tuned. Take care and good bye.

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P.S.

If you have further questions or you need help with your networks, I’m happy to assist you, just send me message. Also don’t forget to share the article on your social media, if you like it.

BR,

Anton Karneliuk