usecases.md

Bind Use Cases

External Service with Bind (mLab and webapp)

The external service use case is where an Ansible Playbook Bundle (APB) is able to connect to a service outside of the cluster. One example, is a webapp that uses mLab as their backend store. There will be a specific APB for the external service.

Catalog Operator does the following:

• Creates a broker resource which calls the AnsibleServiceBroker /catalog endpoint
• The /catalog endpoint response populates the ServiceCatalog's list of ServiceClasses. In our example, this is mLab and Go WebApp

The Service Consumer then utilizes the ServiceClasses for their needs. After getting a list of the available service classes, the Consumer will then:

• Creates an instance of the mLab service.
  • ServiceCatalog calls provision endpoint on AnsibleServiceBroker
  • AnsibleServiceBroker provisions the mLab APB
  • mLab APB configures the mLab instance being made avaiable
  • mLab service ready for consumption
• Create a binding resource for the mLab service
  • ServiceCatalog calls the binding endpoint on the AnsibleServiceBroker
  • AnsibleServiceBroker calls bind on the mLab APB
  • mLab APB will return the credentials, coordinates, & configs for the service.
  • Magic happens
    • ServiceCatalog does something with the bind information such that it can be injected into the applications later
• Creates an instance of the Go WebApp service.
  • ServiceCatalog calls provision endpoint on AnsibleServiceBroker
  • AnsibleServiceBroker provisions the Go WebApp APB
  • The mLab binding information is injected into the Go WebApp APB
  • Go WebApp APB configures itself to use the information
  • Go WebApp service is ready for consumption and utilizing the mLab service

Binding diagram

Binding example sequence diagram

Sequence diagram source

Catalog Operator -> ServiceCatalog: POST broker
ServiceCatalog -> ServiceCatalog: Create Broker resource
Controller -> AnsibleServiceBroker: GET /catalog
AnsibleServiceBroker -> Controller: List of available service classes: mLab, Go WebApp
Controller -> ServiceCatalog: Creates list of service classes available
Service Consumer -> ServiceCatalog: GET /serviceclasses
Service Consumer -> ServiceCatalog: POST /instance (mLab)
Controller -> AnsibleServiceBroker: PUT /provision (mLab)
AnsibleServiceBroker -> mLab APB: docker run provision
mLab APB -> OpenShift: creates Kubernetes service endpoint
ServiceCatalog -> Service Consumer: mLab instance ready
Service Consumer -> ServiceCatalog: PUT /binding
ServiceCatalog -> ServiceCatalog: Create binding resource
Controller -> AnsibleServiceBroker: PUT /binding
AnsibleServiceBroker -> mLab APB: docker run binding
mLab APB -> AnsibleServiceBroker: Returns the binding information for external mLab Service
AnsibleServiceBroker -> Controller: Returns binding information
Controller -> Magic: Store binding information for injection later
Service Consumer -> ServiceCatalog: POST /instance (Go WebApp)
Controller -> AnsibleServiceBroker: PUT /provision (Go WebApp)
AnsibleServiceBroker -> Go WebApp APB: docker run provision
Magic -> Go WebApp APB: INJECT binding information
Go WebApp APB -> mLab Service: Uses
AnsibleServiceBroker -> Controller: Go WebApp service instance ready
ServiceCatalog -> Service Consumer: Go WebApp instance ready

Bindable Database Service

There are services that will be deployed that simply exist to be bound to other applications. Typical use case is a Mariadb database instance.

• provision database APB (stays up to let other bind)
• bind request to app returns connection information,

Database example sequence diagram

Sequence diagram source

Service Consumer -> ServiceCatalog: POST instance
ServiceCatalog -> Ansible Service Broker: PUT provision/instance_id
Ansible Service Broker -> etcd : get database image
etcd -> Ansible Service Broker: return image record
Ansible Service Broker -> Docker Hub: pull database image
Docker Hub -> Ansible Service Broker: return database image
Ansible Service Broker -> Ansible Service Broker: run database image
Ansible Service Broker -> ServiceCatalog: return 200 image
ServiceCatalog -> Service Consumer: ServiceClass
Service Consumer -> ServiceCatalog: PUT /binding
ServiceCatalog -> ServiceCatalog: Create binding resource
Controller -> AnsibleServiceBroker: PUT /binding
Ansible Service Broker -> Controller: return database connection string
Controller -> Magic: Store binding information for injection later

Etherpad wants to connect to database

• provision etherpad
• bind to database
• assume database service previously provisioned

Etherpad sequence diagram

Sequence diagram source

Service Consumer -> ServiceCatalog: POST /instance (Etherpad)
Controller -> AnsibleServiceBroker: PUT /provision (Etherpad)
AnsibleServiceBroker -> Go WebApp APB: docker run provision
Ansible Service Broker -> etcd : get etherpad image
etcd -> Ansible Service Broker: return image record
Ansible Service Broker -> Docker Hub: pull etherpad image
Docker Hub -> Ansible Service Broker: return etherpad image
Ansible Service Broker -> Ansible Service Broker: run etherpad image
Ansible Service Broker -> ServiceCatalog: return 200 OK
Magic -> Go WebApp APB: INJECT binding information
Go WebApp APB -> mLab Service: Uses
AnsibleServiceBroker -> Controller: Go WebApp service instance ready
ServiceCatalog -> Service Consumer: Go WebApp instance ready

Issues

• does the service consumer have to initiate the binds?