Possible Scenario

Conditions.

# The Control Panel is implemented so that it initiates backup procedure for certain application instance periodically and provides the Controller with the path to backup file.

# The Controller is implemented so that it stores all information about package and the application instance:

the application metadata;
information about all application files deployed on the site;
information about all requirements satisfactions;
information about all services installation-only settings, separately from the application files and folders, so that when the application files are removed, the values of old installation-settings are still available.

# The Control Panel is implemented so that the directories tree rooted in the web site home directory represents the URL structure of the hosting environment as it is accessible from the Internet.

Starting Point. Control Panel initiates backup procedure for a particular application instance and points the Controller the location of backup file.

Step 1. The Controller parses application metadata file APP-META.xml.

Sub-step 1.1 The Controller gets information about service backup script ("//service/provision/backup-script/") and checks whether the sufficient element is provided. If the element is present the Controller proceeds to the next step. Otherwise, it backs up application instance resources by its means. If backing up of resources fails, the Controller stops operation and returns error message.

Sub-step 1.2 The Controller gets information about service backup script language ("//service/provision/backup-script/script-language") and checks whether there is an appropriate interpreter in the system and it can be used on the hosting environment to run the script. If the check fails, the Controller refuses to continue the operation.

Step 2. Gathers all the information about environment variables stored (the same set as for configuration script, full instance URL, for example), and creates the variables basing on the rules defined in the Specification.

Step 3. The Controller invokes the application backup script passing to it all required environment variables.

Sub-step 3.1. The Controller checks that backup destination file is writable.

Sub-step 3.2. Runs the backup script in the environment where all the environment variables created.

Sub-step 3.3. If the script invocation succeeds, the Controller returns to Control Panel successful message. If the script invocation fails, the Controller returns error message and deletes backup destination file. If the Controller was responsible for resources back up it is deleted as well.