Allow node cache to be reset.

[da-ar]

As each class inherits directly from node_util, each class has its own cache of node. This removes the per class cache.
Additionally a reset has been added that can be called prior to Environment allowing the new environment settings to be used.

[da-ar]

How this will be used: https://github.com/da-ar/cisco-network-puppet-module/commit/c0b320d09be40eb5a6455074982152406bb2158a

[mikewiebe]

@da-ar Not sure I fully understand the reason for this change. Can you provide more context? Thanks!

[da-ar]

@mikewiebe So the reason for this change is that the module will only be instantiated once and used to access many different devices. The current code allows multiple environments to be created but you cannot specify the specific connection you want to use and class based caches mean that old connections are retained when an environment is changed. This PR will allow a previously set environment to be manually cleared and a new environment to take its place.

For example, this would break like this:

Cisco::Environment.add_new('default', host1)
Cisco::DomainNames.domainnames['something'] = value1
#connect to second device
Cisco::Environment.add_new('default', host2)
Cisco::DomainNames.domainnames['something'] = value2 # changes are made to host1

Take the following code path:
domain_name.domainnames > config_get > NodeUtil.config_get > node.config_get

node is Cisco::Node.instance

Which is Cisco::Node.new

node.config_get calls out to get which accesses @client.get. @client is set when Cisco::Node is initalized and does not pass an environment, so it defaults to nil

[mikewiebe]

@da-ar Thanks for the explanation. Looks pretty straight forward but I kicked of a test against our internal testbed just to be safe. I will have results in the morning and will post back here.

[mikewiebe]

@da-ar Test results looked good. 👍