Trove/ResourceManagerInterface

Description
This feature makes three change to the behavior of Trove.

Nova/Cinder/Neutron/Designate aka Natives
Simple interface for the implementation of the resource managements, such as:
 * 1) Instances(instance groups).
 * 2) Volumes (cinder or ephemeral).
 * 3) Network attributes (SGs, floating IPs, NICS).
 * 4) DNS records.

Heat and Nova/Cinder/Designate/Neutron implementation of the Resource manager
Heat and Nova/Cinder/Designate implementation of the Resource manager will cover all methods that are presented in Trove now, such as:
 * 1) Provisioning.
 * 2) Resizing instances (flavor).
 * 3) Resizing volumes.
 * 4) DNS records management.
 * 5) Security group/rules management

Justification

 * Heat allows to work with almost all types of the resources that Trove requires, but Trove does all orchestration over each service expecting to receive/obtain the actual resource from nova/cinder/neutron/designate. Since Heat is a Cloud Orchestration Service, Trove should not do orchestration work over multiple services. It should work with a single service and have only one dependency instead of multiple(one per each service).

Benefits of Resource manager interface

 * 1) The restriction that is being described by the resource manager will make developers to follow provided specification while implementing resource managers (heat or natives).
 * 2) Reducing orchestration logic, delegating all possible tasks to Heat Orchestration Service. As the result - reduced number of the dependecies (heatclient against nova/cinder/neutron/designate).
 * 3) Single point of failure.
 * 4) Recovery procedures are delegated to Heat (Template update: allow rollback).

Scope
Heat should be able to accomplish all tasks required by Trove.

Impacts
From a user’s perspective this feature doesn't change any of the expectations and behavior. From deployer perspective:
 * If updating already running deployed Trove then you would need to use migration manager.
 * If setuping fresh new Trove - use orchestrator manager.

New

 * This configuration parameters are related to trove-taskmanager


 * Native manager - integrated with native services, makes taskmanager act like a orchestration service.
 * Orchestration manager - integrated with cloud orchestration service, less orchestration logic required, all tasks are delegated to cloud orchestration service.
 * Migration manager - combinition of the native and orchestration maanger, works as router - execution task choise depends on how Trove instance was provisioned (native or orchestrator). Route rule based upon new base instance model attribute - provisioning_engine.

Particular Qualities

 * With migration driver each new Trove instance is provisioned by cloud orchestration service.


 * Tasks like: resize flavor/volume and delete were implemented as actual routers with specific rule. Routing based upon how resource was provisioned.


 * Tasks that envolve direct guest interations like: create backup, restart, update_overrides, unassign_configuration - are common to each resource manager.


 * Reboot task. For orchestrator - stack signal. For natives - simple reboot call for server.

Deprecated

 * taskmanager_manager - resource_manager used instead.
 * use_heat - not required any more.

Database
There are no expected changes to the database

Public API
No changes

Internal API
No changes

Guest Agent
No changes

Resource manager under the hood
Resource manager interface is nothing else than class with required methods, each of them raises OperationIsNotSupported exception. Each resource manager implements required tasks from Resource manager interface, such as: provisioning, resizing(instance/volume), security groups management.

Why?
Because cloud orchestrator is ready to cover all required cases.

Way to implement it
Among all services (api, tm, conductor, guestagent) the most suitable please to refactor code is a Trove taskmanager service.

How taskmanager works
Taskmanager works upon manager class that presented inside the configuration file. Default value :
 * resource_manager is set as trove.taskmanager.resources.natives.Natives

Links:

https://github.com/openstack/trove/blob/master/trove/cmd/taskmanager.py#L33

https://github.com/openstack-dev/devstack/blob/master/lib/trove#L166

Current taskmanager manager is the mixing of the orechestration and native resource management. It should be splitted into the three resource management drivers, one for nova/cinder/neutron/designate and another one for heat service, and migration for the combinition of the proposed managers to accomplish successful management with previosly provisioned instances. From the first implementation heat branch will be the experimental branch that requires setup CI job.

Covered by Heat

 * 1) Rollbacks on failed stack updating.
 * 2) Resize instance with confirmation task.
 * 3) Provisioning task.
 * 4) Delete task.
 * 5) Nova-network security group/rules management with Outputs.
 * 6) Neutron security group/rules management with Outputs.
 * 7) Resize volume.