Media Server Discovery Process

Kurento Client discovers KMS with the following procedure:

  1. If there are a system property with the value “kms.url”, its value will be returned
  2. If the file ~/.kurento/config.properties doesn’t exist, the default value ws://127.0.0.1:8888/kurento will be returned
  3. If the file “~/.kurento/config.properties” exists:

  4. If the property “kms.url” exists in the file, its value will be returned. For example, if the file has the following content: kms.url: ws://4.4.4.4:9999/kurento The value “ws://4.4.4.4:9999/kurento” will be returned.

  5. If the property “kms.url.provider” exists in the file, it should contain the name of a class that will be used to obtain the KMS url. In this case:

kms.url.provider:de.fhg.fokus.nubomedia.kmc.KmsUrlProvider The class de.fhg.fokus.nubomedia.kmc.KmsUrlProvider will be instantiated with its default constructor.

This class is a class in the NMC library which implements the interface org.kurento.client.internal.KmsProvider. This interface provides the following methods:

String reserveKms(String id) throws NotEnoughResourcesException;
String reserveKms(String id, int loadPoints) throws NotEnoughResourcesException;
void releaseKms(String id);

The method reserveKms() will be invoked and its value returned. If NotEnoughResourcesException exception is thrown, it will be thrown in KurentoClient.create() method.

REST Interface to NUBOMEDIA Virtual Network Function (VNF)

In conjunction to implementing the org.kurento.client.internal.KmsProvider this library uses a simple REST client to interact with VNF. This section is not necessary important for developing your application, but so you know how everything glues together, here are a few technical explanations.

During deploying on the NUBOMEDIA PaaS, some environment variables are set by the NUBOMEDIA PaaS Manager on the application container with the address on which the VNF can be reached and also a Virtual Network Function Identifier for your application is created. The VNFRService interface provides the following API:


    /**
     * Returns a list of VNFRs managed by the Elastic Media Manager
     * @return a list of all virtual network function records
     */
    public List<VirtualNetworkFunctionRecord> getListRegisteredVNFR();

    /**
     * Returns a list with detailed information about all apps registered to the VNFR with this identifier
     * @param vnfrId - the virtual network function record identifier
     * @return list - the list of application records
     */
    public List<ApplicationRecord> getListRegisteredApplications(String vnfrId);

    /**
     * Registers a new App to the VNFR with a specific VNFR ID
     * @param loadPoints - capacity
     * @param externalAppId - application identifier
     * @return ApplicationRecord - the application's record
     */
    public ApplicationRecord registerApplication(String externalAppId, int loadPoints) 
        throws NotEnoughResourcesException;

    /**
     * Unregisters an App to the VNFR with the specific internal application identify
     * @param internalAppId - identifier of the registered application on the VNFR
     */
    public void unregisterApplication(String internalAppId) throws NotEnoughResourcesException;

    /**
     * Sends a heart beat to the elastic media manager as a keep alive mechanism for registered sessions
     * @param internalAppId - the internal application identifier
     * @param internalAppId
     */
    public void sendHeartBeat(String internalAppId);

And here is the connection:

kurentoClient.Create().reserveKms() -> get instance of de.fhg.fokus.nubomedia.kmc.KmsUrlProvider-> VNFRService.registerApplication() return KMSURL or throws NotEnoughResourcesException

If return KMSURL = TRUE then VNFRService.sendHeartBeat every 1 minute to VNF for the KMS.

Subsequently:

kurentoClient.Create().releaseKms() -> get instance of de.fhg.fokus.nubomedia.kmc.KmsUrlProvider-> VNFRService.unregisterApplication() return void or throws NotEnoughResourcesException -> stopHeartBeatTask();