Use-cases¶

Abstract dependencies between applications¶

In the example above it is also possible to specify a generic class in the contract com.example.databases.SqlDatabase instead of com.example.databases.MySql. It means that an object of any class inherited from com.example.databases.SqlDatabase can be passed to a parameter. In this case you should also use this generic class as a type for a field in the file ui.yaml:

Forms:
  - appConfiguration:
      fields:
        - name: database
          type: com.example.databases.SqlDatabase
          label: Database Server
          description: >-
            Select a database server to host the application`s database

After that you can choose any database package in a drop-down box. The last place, which should be changed in the WordPress package to enable this feature, is manifest file. It should contain the full name of SQL Library package and optionally packages inherited from SQL library if you want them to be downloaded as dependencies. For example:

Require:
  com.example.databases:
  com.example.databases.MySql:
  com.example.databases.PostgreSql:

External load-balancer¶

Suppose, you have powerful load-balancer on a real server. And you want to run the application on an OpenStack VM. Murano can set up new applications to be managed by that external load-balancer (LB). Let’s go into more details.

To implement this case the following apps are used:

• LbApp: its class methods call LB API
• WebApp: runs on the real LB

Several instances of WebApp are deployed with each of them calling two methods:

- $.loadBalancer.createPool()
- $.loadBalancer.addMember($instance)
# where $.loadBalancer is an instance of the LbApp class

The first method creates a pool and associates it with a virtual server. This happens once only. The second one registers a member in the newly created pool.

It is also possible to perform other modifications to the LB configuration, which are only restricted by the LB API functionality.

So, you need to specify the maximum instance number in the UI form related to the WebApp application. All of them are subsequently added to the LB pool. After the deployment, the LB virtual IP, by which an application is accessible, is displayed.

Using existing network as environment’s default¶

This option is available for users when they create a new environment in the Dashboard. A dropdown control is displayed next to the input field prompting for the name of environment. By default this control provides to create a new network, but the user may opt to choose some already existing network to be the default for the environment being created. If the network has more than one subnet, the list will include all the available options with their CIDRs shown. The selected network will be used as environment’s default, so no new network will be created.

Modifying the App UI to prompt user for network¶

The application package may be designed to ask user about the network they want to use for the VMs deployed by this particular application. This allows to override the default environment’s network setting regardless of its value.

To do this, application developer has to include a network field into the Dynamic UI definition of the app. The value returned by this field is a tuple of network_id and a subnet_id. This values may be passed as the input properties for io.murano.resources.ExistingNeutronNetwork object which may be in its turn passed to an instance of io.murano.resources.Instance as its network configuration.

The UI definition may look like this:

Templates:
  customJoinNet:
    - ?:
        type: io.murano.resources.ExistingNeutronNetwork
      internalNetworkName: $.instanceConfiguration.network[0]
      internalSubnetworkName: $.instanceConfiguration.network[1]
Application:
  ?:
    type: com.example.someApplicationName
  instance:
    ?:
      type: io.murano.resources.LinuxMuranoInstance
    networks:
      useEnvironmentNetwork: $.instanceConfiguration.network[0]=null
      useFlatNetwork: false
      customNetworks: switch($.instanceConfiguration.network[0], $=null=>list(), $!=null=>$customJoinNet)
Forms:
  - instanceConfiguration:
      fields:
        - name: network
          type: network
          label: Network
          description: Select a network to join. 'Auto' corresponds to a default environment's network.
          required: false
          murano_networks: translate

For more details on the Dynamic UI its controls and templates please refer to its specification.