Author:Wenjie Chen

Config

• install networkx 1.8
• platform: python 2.7

Run

• There are 3 files can run, command python filename.py :

  • datacenterDemo.py demonstrates how to use datacenter.py module, and will print WARNING to stderr. You can redirect stderr by python datacenterDemo.py 2> error.log

  • testDatacenter.py is the unittest file, which gives more demonstration about datacenter including raise exception

  • linkCheckerDemo.py gives an example that use a thread to check broken links in a data center and terminates in 5 seconds

Files Description

• devicemodels.py : defines all device models used in datacenter module, and provides a factory function to create a device instance

• datacenter.py : defines DataCenter class, a decorator for synchronization, and LinkChecker class, which is a thread

• datacenterDemo.py : demonstration of how to use datacenter module, and prints WARNING to stderr

• testDatacenter.py : unittest cases and further demonstration for raising Exception

• linkCheckerDemo.py : demonstrate of how to use a thread to check broken link in data center

• *.csv: test models of data center, don't delete any csv file

Design and Trade off

• To directly use device object in networkx, each device class in devicemodels.py must override eq and hash method.

• Each device object is identified by its ID attribute, which can't be changed after initialization. Especially for Host class, which contains attribute rack_id, is still uniquely identified by its ID. For example, 2nd host in rack1 is Host2, 2nd host in rack2 is Host12.

• For all public API in datacenter module, there are two ways to refer to a device in data center.

  • Creat a device object. For example, Host(1) refers to Host with id = 1 in a data center, and Spine(2) refers to Spine with id = 2

  • Use a string like: 'spine1', 'leaf-2' or 'host_3', no matter lower or upper case. Only dash or underscore is allowed to be added bewteen device and its id

• data center model in csv file is defined by links between devices. To simplify the model file, and keep the consistency of csv file:

  • the relationship between Host and Rack is explicitly defined in host's id, called complex id. Its pattern like 'r1_2' for host2 in rack1, 'r2_16' for host16 in rack2. Except in model file, don't use complex id in other place, which will cause ValueError.
  • the relationship between Leaf and Rack is implication. For example in model file define a link between Leaf-1 and Host-2, because Host-2 is explicitly placed in Rack1, Leaf-1 is also in Rack-1

• When query a device or a link which is not in data center model, just print a WARNING to stderr and don't raise a Exception to terminate client program. Because query a not exist device or link won't change the structre of data center model. But other wrong operation like add a device with wrong ID will raise Exception.

Public API for requirements in DataCenter Module

This is brief introduction. For details, please see the docstring of modules, classes and methods.

• load topology from csv:

  • load_model_from_files(): can import multiple csv files at once

• delete topology:

  • clean_datacenter(): remove all devices and links
  • remove_link(): remove a link
  • remove_devices: remove multiple devices and their links at once, if device is leaf or host also remove them from their racks

• query device is connnected on a particular port:

  • query_device(): rack of queried device is not required, and print WARNING to stderr if port or device does not exist, or specify a wrong rack

• query ports a particular device is connected on:

  • query_ports(): racks of devices are not required, and print WARNING to stderr if port or device does not exist, or specify a wrong rack. Return a generator of ports.

• query paths to a remote device:

  • query_all_paths(): returns a generator of all paths that have been found

• check broken links:

  • check_link(): synchronized method, can be invoked by other threads

  • LinkChecker class: a thread to check broken links

  • break_link(): Break a link between two devices. Only used for testing check_link(), and don't use for other purpose, which will cause a inconsistent state of data center

• Some APIs and properties are provided to help test the state of data center:

  • synchronized_with(): a decorator for synchronizing methods in a DataCenter instance

  • all_devices: property, read only

  • all_links: property, read only

  • get_device(): get a reference of a device in data center

  • get_devices_in_rack()

  • get_connections_of_device(): get links info of a device

Except check_link(),load_model_from_files() and break_link(), other methods can't be guaranteed as thread-safe. Don't invoke them in other threads.