Discover the Microservice Bus
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.
- Default config when a DNS server is available
- An IP if a DNS server is not available
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:
- REST APIs should be described in a swagger.json file according to Open API Initiative.
- The swagger.json file should be put at the root path of the service url, such as: http(s)://[hostname][:port]/[ServiceType]/[ServiceName]/[Service Version]/Swagger.json
- 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:
Register service to the Microservice Bus
|Operation||Register service to the Microservice Bus|
422 Invalid Parameters
Unregister service from the Microservice Bus
|Operation||Unregister service from the Microservice Bus|
404 Can't find the service instance
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.
if the service did not have version property, you can use the url without version.
|Operation||Query service from the Microservice Bus|
404 Can't find the service instance
MSB Client SDK
MSBServiceClient : JAVA SDK for MSB service discovery
RestServiceCreater: JAVA SDK for REST service invocation
MSB Client SDK Example
String MSB_IP="127.0.0.1"; int MSB_Port=10081; MSBServiceClient msbClient = new MSBServiceClient(MSB_IP, MSB_Port); RestServiceCreater restServiceCreater = new RestServiceCreater(msbClient); AnimalServiceClient implProxy = restServiceCreater.createService(AnimalServiceClient.class); Animal animal = implProxy.queryAnimal("panda").execute().body(); System.out.println("animal:" + animal);
Note: In order to test the example application, you need to run MSB following this guide MSB Test Environment Setup
Hello, A very good documentation.
I would suggere that we add design / pattern / registration recommendation for APIs in ONAP.
1/ When using SO we found for instance that it's the root path that is registered in MSB and not the 3 different kind of APIs, for instance as you suggest "url": "/api/catalog/v1". Thus client needs to hardcode specific path, including version, instead of just the resource path like /serviceInstance. When new version has been out in casablanca those hardcoded full path are broken, it would have not occurred if client used the serviceInstance api v7 from MSB, instead of just so api.
instead of unique /
2/ Some find request return 404 when list is empty, that's wrong because the URL is valid, but query parameters returns nothing. It's not an error, it's just an empty list with code 200 and json . The 404 is ambiguous because it suggests that this url doesn't exist, and you MUST update your client code which is wrong..
There are more to add
Good points! We do have suggestion/recommendation for APIs here: RESTful API Design Specification and we encourage projects to follow these suggestions when designing their APIs.
Thank you very much Huabing for pointing to this excellent document.
My remark is not specific to SO, but it's a good example to illustrate why we need centralized service( or api ) repository.SO is not micro services oriented but we can guess 3 different APIs
As SO registers only base hosts we had to hard code 3 paths in casablanca, and we faced with SO, while playing with first integration test to, a change, both in path and version. We had to look into the source code.As an improvement I guess SO might publish 3 different APIs or services with 3 different url parameter while registering to MSB.
I have also seen that services are listed here, but it's still human documentation which doesn't reflect the source code, for instance SO is still v5 in the wiki. ( bad point for externalapi we didn't reference the service here by the way ! )
ONAP Services List#SO
Loop Seshu Kumar Mudiganti in
I checked with OOM deployment yaml file, as Matthieu Geerebaert pointed out, only the infra URL is registered.
We could register 3 different APIs as Matthieu suggested if SO project also think it's reasonable.
For the services list, MSB generates a list of service at http://$MSB_Address:80/msb, you could see all the registered services.