Microservice Bus provides a service registration/discovery and routing mechanism to simply the communications between services, The service consumers only need to talk with Microservice Bus without any address information of individual service providers. However, all the service consumers/providers must know the IP and service port of Microservice Bus. MSB suggests the following approach to discover the Microservice Bus.
Each service provider/consumer implementation can get the address of the Microservice Bus from a local config file via the key 'msb.address', the default value consists of a hostname and a service port. The hostname is 'msb.onap.org', which can be resolved by a DNS server in the local network, and the default port is 80. If a DNS server is not available in some deployments, an IP should be used instead.

Examples:

• Default config when a DNS server is available

msb.address: msb.onap.org:80

• An IP if a DNS server is not available

msb.address: 10.74.205.123:80

API Definition and Swagger-UI

ONAP intends to be a microservices-based architecture and every individual service is exposed as a restful API. Microservice Bus provide mechanisms to collect and display the API description(swagger UI) and metrics of services centrally.
The services should provide the information to Microservice Bus by the below approaches:

Swagger

1. REST APIs should be described in a swagger.json file according to Open API Initiative.
2. The swagger.json file should be put at the root path of the service url: http(s)://[hostname][:port]/[ServiceType]/[ServiceName]/[Service Version]/Swagger.json
3. The swagger.json can be automatically generated by JAVA notation, more information can be find at Swagger Annotations.

For example, the swagger description and UI of the services provided by Microservice Bus:
Service: /api/microservices/v1/
Swagger: /api/microservices/v1/swagger.json

Register service to the Microservice Bus

{
  "serviceName": "aai",
  "version": "v8",
  "url": "/aai/v8",
  "protocol": "REST",
  "visualRange": "1",
  "path":"/aai/v8"
  "nodes": [

    {
      "ip": "10.74.56.36",
      "port": "8988",
      "ttl": 0
    }
  ]
}

{
  "serviceName": "catalog",
  "version": "v1",
  "url": "/api/catalog/v1",
  "protocol": "REST",
  "visualRange": "1",
  "nodes": [
    {
      "ip": "10.74.55.66",
      "port": "6666",
      "ttl": 0
    },
    {
      "ip": "10.74.56.37",
      "port": "8989",
      "ttl": 0  
    },
    {
      "ip": "10.74.56.36",
      "port": "8988",
      "ttl": 0
    }
  ]
}

Unregister service from the Microservice Bus

Query service from the Microservice Bus

You can access service by two ways:

First is Point to Point, service consumer can query service instances address from MSB by the following API,and access the service provider directly; - Not recommended, we will lose centralized control capabilities if chose this approach, for example, service call logging, service load balancing policy, etc.

Second is API Gateway, service consumer do not care ip and port of the service provider, it just access the API-Gateway ,and the API-Gateway will route the service call to the appropriate service provider; in this approach, service consumers only need to know the ip and port of API Gateway, it can be stored in a configuration file or an environment property of the service consumer implementation.

MSB support the following access methods:

if the service provider version property is provided when registration, you can use the version before or behind the service name.

/api/[servicename]/v1

/api/v1/[servicename]

if the service did not have version property, you can use the url without version.

/api/[servicename]/

{
  "serviceName": "catalog",
  "version": "v1",
  "url": "/api/catalog/v1",
  "protocol": "REST",
  "visualRange": "1",
  "nodes": [
    {
      "ip": "10.74.55.66",
      "port": "6666",
      "ttl": 0
    },
    {
      "ip": "10.74.56.37",
      "port": "8989",
      "ttl": 0
    },
    {
      "ip": "10.74.56.36",
      "port": "8988",
      "ttl": 0
    }
  ]
}

To be continue