Overview

Scheduler/Device Management is a separate Quantum plugin. It is responsible for:

Management of devices that implement advanced services (load balancers, firewalls, vpn gateways, etc). That includes REST API for CRUD operations on device database.
Binding of service's logical models to devices (ex: schedule vip to load balancer)

Workflow

Example 1. The typical workflow for vip creation:

Details:

The request to create pool is is received by LBaaS Plugin
LBaaS Plugin calls DB plugin to create model and store it to DB, pool_id is returned
LBaaS Plugin responds to API with "HTTP 202 Accepted". The rest of process is done asynchronously
LBaaS Plugin calls Scheduler and passes it service_type, pool_id, pool and other optional parameters.
Scheduler finds device that satisfies service_type and parameters, including those specified in pool.
Scheduler stores mapping between device_id and pool_id in its DB. This mapping will be used in latter requests
Scheduler returns device_info to LBaaS plugin
LBaaS plugin sends rpc message to Agent, specifying command, service_type, logical object (pool) and physical object (device parameters)
Agent reads message and forwards it to driver
Driver is responsible to wire device to tenant network according to service insertion mode and deploy logical object to the device
Agent returns result to LBaaS plugin which updates state of corresponding DB object.

Important note: Agent is common for all services. It delegates processing to drivers[service_type][device_type][version].