On-Demand Service Architecture
This topic describes the architecture for on-demand MySQL for Pivotal Cloud Foundry (PCF).
For information about architecture of the older, pre-provisioned service, see the Architecture topic for MySQL for PCF v1.9.
Before BOSH 2.0, cloud operators pre-provisioned service instances from Ops Manager. In the Ops Manager Director Networking pane, they allocated a block of IP addresses for the service instance pool, and under Resource Config they provisioned pool VM resources, specifying the CPU, hard disk, and RAM they would use. All instances had to be provisioned at the same level. With each
create-service request from a developer, Ops Manager handed out a static IP address from this block, and with each
delete-service it cleaned up the VM and returned it to the available pool.
With BOSH 2.0 dynamic networking and Cloud Foundry asynchronous service provisioning, operators can now define a dynamically-provisioned service network that hosts instances more flexibly. The service network runs separate from the PCF default network. While the default network hosts VMs launched by Ops Manager, the VMs running in the service network are created and provisioned on-demand by BOSH, and BOSH lets the IaaS assign IP addresses to the service instance VMs. Each dynamic network attached to a job instance is typically represented as its own Network Interface Controller in the IaaS layer.
Operators enable on-demand services when they deploy PCF, by creating one or more service networks in the Ops Manager Director Create Networks pane and selecting the Service Network checkbox. Designating a network as a service network prevents Ops Manager from creating VMs in the network, leaving instance creation to the underlying BOSH.
When they deploy an on-demand service, operators select the service network when configuring the tile for that on-demand service.
Like other on-demand PCF services, on-demand MySQL for PCF relies on the BOSH 2.0 ability to dynamically deploy VMs in a dedicated network. The on-demand service broker uses this capability to create single-tenant service instances in a dedicated service network.
On-demand services use the dynamically-provisioned service network to host the single-tenant worker VMs that run as service instances within development spaces. This architecture lets developers provision IaaS resources for their service instances at creation time, rather than the operator pre-provisioning a fixed quantity of IaaS resources when they deploy the service broker.
By making services single-tenant, where each instance runs on a dedicated VM rather than sharing VMs with unrelated processes, on-demand services eliminate the “noisy neighbor” problem when one application hogs resources on a shared cluster. Single-tenant services can also support regulatory compliance where sensitive data must be compartmentalized across separate machines.
An on-demand service splits its operations between the default network and the service network. Shared components of the service, such as executive controllers and databases, run centrally on the default network along with the Cloud Controller, UAA, and other PCF components. The worker pool deployed to specific spaces runs on the service network.
Prior to deploying any service tile that uses the on-demand broker (ODB), the operator must request the network connections needed to allow various components of Pivotal Cloud Foundry (PCF) to communicate with ODB. The specifics of how to open those connections varies for each IaaS.
The following table shows the responsibilities of the key components in an on-demand architecture.
|Key Components||Their Responsibility|
|BOSH Director||Creates and updates service instances as instructed by ODB|
|BOSH Agent||BOSH includes an Agent on every VM that it deploys. The Agent listens for instructions from the Director and carries out those instructions. The Agent receives job specifications from the Director and uses them to assign a role, or Job, to the VM.|
|BOSH UAA||As an OAuth2 provider, BOSH UAA issues tokens for clients to use when they act on behalf of BOSH users.|
|ERT||Contains the apps that are consuming services|
|ODB||Instructs BOSH to create and update services, and connects to services to create bindings|
|Deployed service instance||Runs the given data service (for example, the deployed Redis for PCF service instance runs the Redis for PCF data service)|