Feature/skip zero retention

[tarunmenon95]

Added feature to skip creating backups for those with retention types (daily,weekly,monthly,yearly) that are set to 0 in the configuration variables.

Workflow

1. We call the function 'verify_retention' to that verifies the retention type for the current backup resource (Based on date of creation) against the specifed value in the config

if not self._verify_retention(backup_resource=backup_resource):

2. We check whether the retention value is set to '0' in the config

CREATE_DAILY = RuntimeConfig.get_keep_daily(backup_resource.entity_resource_tags(),self) != 0

3. A dict of all retention types and their corresponding boolean on whether we should create them or not is created.

retention = {
            backup_resource.RETENTION_DAILY : CREATE_DAILY,
            backup_resource.RETENTION_WEEKLY : CREATE_WEEKLY,
            backup_resource.RETENTION_MONTHLY : CREATE_MONTHLY,
            backup_resource.RETENTION_YEARLY : CREATE_YEARLY,
        }

4. We then return True/False depending on if the supplied retention value is True/False in the dictionary

return True if retention[retention_value] else False 

5. Lastly in the engine, we call this function and skip any iterations where the retention type is set to '0'

if not self._verify_retention(backup_resource=backup_resource):
                self.logger.info(f"Skipping backup as retention type {backup_resource.retention_type} is disabled")
                continue

EC2AMI 'Daily'Example

1. The current date is 31-Aug-2022, as such we expect that the retention type for the created backup will be 'daily'

2. For a given ec2 instance, we can observe the following specified config defines that the 'daily' retention is set to 0.

3. We call 'shelvery ec2ami create_backups' and can observe the creation of the backup is skipped.

4. Lastly, if we change the value from '0' to '1' in the config then call 'shelvery ec2ami create_backups' again we observe that the backup is created as expected.

[tarunmenon95]

Added the logic to automatically go to the next retention type in the precedence order when the current one is disabled. If the final retention type in the order is disabled (daily) then the backup is skipped.

Examples

• For the purposes of the following examples, the retention type has been hardcoded to force yearly backups.

Yearly Backup (Yearly, Monthly, Weekly disabled)

• Observed in the below screenshot, we can see that yearly, monthly and weekly backups have all been disabled.

- We call 'shelvery ec2ami create_backups' to create the backups for the above instance - Shelvery now checks whether the current retention type is enabled, if not it will move on to the next retention type from Yearly -> Monthly -> Weekly -> Daily. Below we observe that Shelvery detected that yearly, monthly, weekly were all disabled and as such after checking all retention types in order, chose daily as it was allowed.

Skip Backup (All Disabled)

• Here we observe that all retention types are disabled

- When we attempt to create backups, we observe that no backups are created at all as they we're all disabled. When daily is detected as disabled, shelvery will now skip the iteration for that backup_resource.

[tarunmenon95]

Changes

• Added refactor changes to retention type check function
• Added debugging logs

Examples

• For the purposes of the following examples, the retention type has been hardcoded to force yearly backups.
  

Daily Backup (Yearly, Monthly, Weekly disabled, Daily Enabled)

• We observe in the tags the yearly, monthly and weekly retention periods are disabled (Set to 0), only daily is enabled.
  
• We call 'shelvery ec2ami create_backups' which initially detects the retention type as yearly as defined above. It then correctly detects yearly, monthly and weekly as being disabled and finally creates a daily backup as it was the only option enabled.
  

All Disabled

• We observe that all retention types have been set to 0 thus are all disabled.
  
• When we create backups this time we see that shelvery detects that no retention types are enabled as such skips creating a backup for this resource.
  

Custom Retention Type (quarterHourly)

• Here we create a custom retention type by setting "quarterHourly" as an environment variable.
  
• When we call create_backups, we obseve that shelvery detects a custom retention type is being used and skips the validation on the retention type and proceeds directly to creating the backup.
  
• Observe that the backup is created as expected with custom retention type.
  

[Guslington]

lgtm