Overview

Scheduler is a separate Quantum plugin. It is responsible for:

Management of devices that implement advanced services (load balancers, firewalls, vpn gateways, etc)
Binding of service's logical models to devices (ex: schedule vip to load balancer)
Deployment of configs to devices with help of agents/drivers

Workflow

Example 1. The typical workflow for vip creation:

Details:

The request to create vip is is received by LBaaS Plugin
LBaaS Plugin calls DB plugin to create model and store it to DB, vip_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, vip_id, and other parameters.
Scheduler finds device that satisfies service_type and other filter parameters.
Scheduler stores mapping between device_id and vip_id in its DB. This mapping will be used in latter requests
Scheduler sends message to Agent
Agent reads message and forwards it to driver
Agent returns result to Scheduler, then it is forwarded to LBaaS Plugin.

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