once-only phases

[craig mcmillan]

is there any way to declare a phase once-only (like :bootstrap) ?

my use-case is this :

i'm installing a cassandra cluster, and after the package install and
configure the data directories (containing default data installed with
the package) need clearing and the server restarting. the clearing of
the data directories should only ever happen once after first
installation, otherwise live data will be deleted

currently i've got a separate phase for this install operation, but this
is unsatisfactory, since if i want to converge new nodes into the
cluster running that phase will delete live data from the existing nodes

a :bootstrap-like once-only phase would be nice : is that possible, or
is there another solution i'm missing ?

thanks

:craig

[Michael Jerger]

Hi,

that's an topic of interest to me also. For only-once phases at the moment I use also a dedicated "installation phase" - what's fitting my current needs.
But another requirement "Installation & Configuration Upgrade" caused me to think about a solution, which could also fit to your needs?

My Idea is to create a configuration-crate which solves the following functions:

• CM System validates configuration ahead of configuration.
• Already working at my prototype: https://github.com/DomainDrivenArchitecture/dda-config-crate
  
• CM System reads version of applied configuration from target system.
• CM System writes version of applied configuration to target system.
• Reading and writing configuration's versions to your servers can be the foundation of an easy solution for your needs. You can in every phase check the version and apply changes only if the configured version is newer ..
• For my Upgrade-Topic I've the chance to choose the appropriate version-old-to-version-new-upgrade steps ..
  

If there will be no better idea here, then feel invited to join my thoughts & discussions (see also https://github.com/DomainDrivenArchitecture/architecture/tree/configmanagement/en/80_config_management/30_requirements :-).

What do you think about?


Best Regards,
Michael

BTW: I write concepts using gitBook at http://dda.gitbooks.io/domaindrivenarchitecture/
So not all MarkDown links will work in plain repository / branch ...