This guide is intended to discuss the code in detail to assist future modifications without the support of the original authors. The sections below are design to give a clear picture of exactly what the code will do and provide insight into the rational of the design.
In order to maintain state and support rolling back after a VM has been migrated, the tool has three user selectable tasks: migration, state clean up, and rollback.
- Migration - Migrate a set of machines
- Cleanup - Cleanup the state on machines, either after a successful complete migration or from a failure that caused manual cleanup.
- Rollback - Rollback machines back to their original location in the event of a post migration validation failure (see limitations section).
The following list of statements define the guidelines used to develop the tool and resulting code.
- The tool should consist of support documentation and only one file to execute.
- Minimal libraries are required to execute the tool.
- Operate on the VMs as safely as possible while also maintaining the UUID.
- Best effort to provide performance without being overly complex.
- Maintain the state of the migrated VM with vSphere.
- Utilize a common and easy input file format.
The conceptual model below shows the makeup of the "layers" of software. The tool will enter a dispatcher function that will make decisions about which function to call based on the requested task. Each of those tasks start at a controller who has the job to iterate over the VM list and throttle the execution. Inside each controller is a function to handle the task on an individual VM.
Below are the logic flow diagrams for each of the functions defined in the conceptual model.
The dispatcher is the entry point into the tool; it makes decisions based on what task is requested.
The migration controller parses the VM list then manages throttling the number of individual VM tasks being executed at once.
The migration process defines the logic for migrating an individual VM.
The rollback controller parses the VM list then manages throttling the number of individual VM tasks being executed at once.
The rollback process defines the logic for rolling back an individual VM.
The cleanup controller parses the VM list then manages throttling the number of individual VM tasks being executed at once.
The cleanup process defines the logic for cleaning up an individual VM.
