Category Archives: python

Docker features for handling Container’s death and resurrection

Containers, Docker, python, Swarm

Docker containers provides an isolated sandbox for the containerized program to execute. One-shot containers accomplishes a particular task and stops. Long running containers runs for an indefinite period till it either gets stopped by the user or when the root process inside container crashes. It is necessary to gracefully handle container’s death and to make sure that the Job running as container does not get impacted in an unexpected manner. When containers are run with Swarm orchestration, Swarm monitors the containers health, exit status and the entire lifecycle including upgrade and rollback. This will be a pretty long blog. I did not want to split it since it makes sense to look at this holistically. You can jump to specific sections by clicking on the links below if needed. In this blog, I will cover the following topics with examples:

Handling Signals and exit codes

Continue reading Docker features for handling Container’s death and resurrection →

Netconf Python ncclient

cisco, devops, devopsnet, ncclient, Netconf, nexus, nxapi, python, VIRL

In my earlier blogs, I had covered basics of Netconf and Yang and how to use Netconf to configure Cisco devices. Recently, I came across this Python ncclient library that simplifies the configuration/monitoring of Networking devices that supports Netconf. Using ncclient library, we can programmatically configure and monitor devices using Netconf. I also found out that Cisco Openstack Neutron plugin uses ncclient library to program the Nexus switches.

I have used Cisco Nexus 3k switch and Cisco VIRL NXOS switch for the examples in this blog.

In my earlier blog on configuring Cisco Nexus devices using Netconf, I covered the following netconf requests.

  1. “get” request using filter to display configuration.
  2. “edit-config” request to change configuration.
  3. “exec-command” to execute raw CLI requests.

In this blog, I will cover the above same tests using Python ncclient library. Even though the examples below are tried from Python interactive shell, the same can be executed as a Python program as well.

First step is to import the ncclient library and create a connection:

Continue reading Netconf Python ncclient →

Cisco UCS Platform Emulator

cisco, devops, python, UCS

Earlier, I had written a blog on Cisco UCS automation using Python SDK. At that time, I used real UCS system to test my scripts. Cisco UCS PE(Platform Emulator) emulates UCSM(UCS Manager) software and we can run this as a VM. Different types of hardware(Fabric Interconnect, FEX/IOM, Servers, adapters, power supply) can be added to create a complex UCS system. We can do majority of the configurations and can trigger different conditions to see how UCSM reacts. Obviously, traffic related testing cannot be done with this. For scripting, UCS PE is a perfect solution. In this blog, I will cover what I did to get UCS PE up and running.

Environment:

VMWare Player 6.05 running on Windows 7.

Installation:

Download the PE zip files. I used version 2.2(3a). Unzip them and import into VMplayer. Choose the default configurations, 3 NAT interfaces are created by default.

Basic configuration:

Continue reading Cisco UCS Platform Emulator →

Ansible for Network Automation – Part 2

Ansible, cisco, devops, devopsnet, Jinja2, Programming, python, UCS, yaml

This blog is part of my series on Devops for Networking. In the previous blog, I covered basics of Ansible and how to get started with it. In this blog, I will cover a sample application that I wrote with Ansible. This Ansible application builds on UCS sdk utility that I covered in a previous blog. The UCS python utility displays the inventory of UCS system. I have made that utility as an Ansible module and extended the application to display the inventory of a list of UCS systems that are defined in the host list. This project is more to illustrate the usecase for Ansible.

The source code for the project can be found here. There are 3 files listed here:

getucs.yml - YAML file that defines the playbook
getucsinfo - New module that is defined. This file needs to be in "usr/share/ansible"
getUcsProp.py - getucsinfo module uses functions in this library. This file needs to be in PYTHONPATH.The library provides utility functions to get UCS inventory.

Continue reading Ansible for Network Automation – Part 2 →

Ansible for Network automation – Part 1

Ansible, devops, devopsnet, Programming, python

This blog is part of my series on Devops for Networking. Ansible is a very popular Devops tool and serves similar purposes as Puppet, Chef etc. Ansible has the unique feature that there is no need to install agent on the device side and this makes it very popular for Network device configuration since Network devices are still predominantly a closed system which does not allow agent installation in the device. In this blog, I will cover how to get started with Ansible and in the next blog, I will cover a sample application that I have written.

Ansible basics:

Ansible modules can be run locally or remotely. With the local approach, the module runs locally using apis to talk to remote devices. In remote scenario ,modules are pushed to remote devices, executed as python script and results are returned. Even though there is no need to install remote agent, remote device should allow execution of Python script. Ansible can either be run in command-line for simple tasks or can be executed using a playbook.

Continue reading Ansible for Network automation – Part 1 →

Network device configuration using templates with Jinja2 and YAML

cisco, devops, devopsnet, Jinja2, Programming, python, yaml

This blog is part of my series on Devops for Networking. Typically, Network device configurations for CLI based systems are stored as text files and when its necessary to change parameters like gateway address, vlan, ntp server etc, the script is manually edited and then reapplied to the device. This process is manual and prone to errors. In this blog, I will cover how to automate generation of configuration scripts using Jinja2 and YAML. I will also provide an sample application that I created. For more details, please refer to the references section below.

Tools overview:

Jinja2:

Jinja2 is a Python library for creating configuration based on templates. Jinja2 defines a templating language with which templates are created. The templates can be as simple as a hostname variable that needs to be updated or it can be an array of vlans that needs to be populated. Jinja2 also provides complex templates to cover different scenarios. Following is a very simple example of a template which says ntp_server is a variable that needs to be updated dynamically. We will see later how we can feed in the dynamic values to update.

ntp server {{ ntp_server }}

Continue reading Network device configuration using templates with Jinja2 and YAML →

Cisco device configuration using OnePK

cisco, devops, nexus, onepk, Programming, python

This blog is part of my series on Devops for Networking. onePK is Cisco’s attempt to expose a standard set of APIs to configure and monitor across multiple different Cisco devices. Orchestration and automation applications can use these standard APIs to talk to Cisco devices. In this blog, I will cover a brief overview of onePK and how to get started with onePK to write applications on top of it.

OnePK overview:

Following block diagram from Cisco gives different blocks involved in onePK.

devops6

Continue reading Cisco device configuration using OnePK →

Nexus devices CLI parsing using Python, XML and JSON

cisco, devops, json, nexus, paramiko, Programming, python, xml

This blog is part of my series on Devops for Networking. As I indicated in 1 of my earlier blog, majority of Network devices still have CLI as the only means of configuration and monitoring. CLI is not automation friendly because of obvious reasons. In the last few years, Cisco NXOS devices provides CLI output in XML and JSON format. This allows much easier ways to parse the CLI output which aids in automation. In this blog, I will cover some examples of monitoring Cisco NXOS devices using Python interface to interact with the device and get useful information.

Prerequisites:

Continue reading Nexus devices CLI parsing using Python, XML and JSON →

Cisco UCS automation using Python SDK

cisco, devops, Programming, python, UCS, xml

This blog is part of my series on Devops for Networking. In this blog, I will cover a brief overview of UCS management model, management tools and how to automate configuration and monitoring of Cisco UCS using Python SDK. UCS is Cisco’s Unified computing system that provides a tightly integrated compute, networking and storage solution.

UCS Management

Cisco UCS management information model is a hierarchical tree with each node in the tree representing either physical or logical entity. The node is referred to as MO(Managed object). Physical entities could be chassis, servers, switches and logical entities could be policies, service profiles etc. XML based interface is provided to set and get managed objects. Following picture shows a sample Management tree with Chassis, blades and adapters.

Continue reading Cisco UCS automation using Python SDK →