Migrate applications to Stable/Newton

In Newton a number of useful features that can be used by developers creating their murano applications were implemented. Also some changes are not backward compatible. This document describes these features, how they may be included into the new apps and what benefits the apps may gain.

1. New syntax for the action declaration

Previously, for declaring action in MuranoPL application, following syntax was used:

  Usage: Action

This syntax is deprecated now for packages with FormatVersion starting from 1.4, and you should use the Scope attribute:

  Scope: Public

For more information about actions in MuranoPL, see Murano actions.

2. Usage of static methods as Action

Now you can declare static method as action with Scope and Usage attributes

  Scope: Public
  Usage: Static

For more information about static methods in MuranoPL, see Static methods and properties.

3. Template contract support

New contract function template was introduced. template works similar to the class in regards to the data validation but does not instantiate objects. The template is just a dictionary with object model representation of the object.

It is useful when you do not necessarily need to pass the actual object as a property or as a method argument and use it right away, but rather to create new objects of this type in runtime from the given template. It is especially beneficial for resources replication or situations when object creation depends on some conditions.

Objects that are assigned to the property or argument with template contract will be automatically converted to their object model representation.

4. Multi-region support

Starting from Newton release cloud resource classes (instances, networks, volumes) can be explicitly put into OpenStack regions other than environment default. Thus it becomes possible to have applications that make use of more than one region including stretching/bursting to other regions.

Each resource class has got new regionName property which controls its placement. If no value is provided, default region for environment is used. Applications wanting to take advantage of multi-region support should access security manager and Heat stacks from regions of their resources rather than from the environment.

Regions need to be configured before they can be used. Please refer to documentation on how to do this: Multi-region application.

Changes in the core library

io.murano.Environment class contains regions property with list of io.murano.CloudRegion objects. Heat stack, networks and agent listener are now owned by io.murano.CloudRegion instances rather than by Environment.

You can not get io.murano.resources.Network objects from Enviromnent::defaultNetworks now. This property only contains templates for io.murano.CloudRegion default networks.

The proper way to retrieve io.murano.resources.Network object is now the following:

$region: $instance.getRegion()
$networks: $region.defaultNetworks

5. Changes to property validation

string() contract no longer converts to string anything but scalar values.

6. Garbage collection

New approach to resource deallocation was introduced.

Previously murano used to load Objects and ObjectsCopy sections of the JSON object model independently which cause for objects that were not deleted between deployments to instantiate twice. If deleted objects were to cause any changes to such alive objects they were made to the objects loaded from ObjectsCopy and immediately discarded before the deployment. Now this behaviour is changed and there are no more duplicates of the same object.

Applications can also make use of the new features. Now it is possible to perform on-demand destruction of the unreferenced MuranoPL objects during the deployment from the application code. The io.murano.system.GC.GarbageCollector.collect() static method may be used for that.

Also objects obtained ability to set up destruction dependencies to the other objects. Destruction dependencies allow to define the preferable order of objects destruction and let objects be aware of other objects destruction, react to this event, including the ability to prevent other objects from being destroyed.

Please refer to the documentation on how to use the Garbage Collector.