root/trunk/doc/Architecture.txt

$Id$

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ARCHITECTURE
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PLACO is a generator of collaborative platforms.
It use virtualization technics to assume modularity, isolation and security.
For production, PLACO need a dedicated host with a hypervisor. The services run onto virtuals machines hosted on it.

Characteristics
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  - PLACO is open source
  - PLACO only used open source sotfware
  - All the machines (host and virtual machines) run on Linux.
  - The platform is Linux distribution independant : this is planned, but at now, it runs under Linux Debian
  - The platform is hypervisor independant : this is planned, but at now, it runs with Xen

  - all the parameters of the platform are stored in .defines files

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TREE LEVELS OF ABSTRACTION
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  - The platform implements a set of macro services, like web hosting, mailling list, control version system, etc.
  - For that, the platform used several machines : ldap, proxy, www, list, svn, etc.
  - Each macro service used one or more machines : for example, the web hosting macro service needs the machines www, proxy and ldap.
  - Each machine needs its own software : for example, the machine list need apache, sympa, mysql and postfix.

So the 3 levels are : macro service, machine and software. So, the scripts are sorted also in 3 categories :
        - toplevel : OS independant script and file templates, which affects the macro services,
        - middleware : OS independant script and file templates, assuming some tasks on a single machine,
        - repository OS dependant script and file templates, assuming task on a certain type of machine (for example on a Debian machine)