4 Data files

There are 6 main meta-data files share between 3 categories.

• 2 Local server files
• 1 Local collection file
• 3 Remotely shared collection files

All of theses file are locked by the kernel when parsing and serializing using the reader/writer algorithm. This ensure the different processes will not read and modify the same ressource at same time.

The 3 shared collection files are processed to build the same browsable HTML index on each servers (see misc).

Local server files:

Local collection file to index the cache content:

Remotely shared collection files:

Relational schema:

• Entities
  • The SUPPORT entity lists all the local supports.
  • The COLLECTION entity lists all the collections the local server belongs to.

  Below entities are all dupplicated for each collection:

  • The SERVER entity lists all the servers.
  • The IMAGE entity lists on ISO images hold by a server.
  • The ARCHIVE entity lists all archives known at running time.
  • The CONTAINTER entity gives rule to extract archives from each others.
  • The DOCUMENT entity groups archives in order to describe them in a catalog.
  • The RECORD entity lists archives we works with.
• Data in/out

  File	PUBLISHER	CLIENT	cgi	SERVER
  mediatex.conf	rw	rw	r	r
  supports.txt	r	rw	-	r
  md5sums.txt	r	r	-	rw
  catalog.txt	rw	rw	-	-
  extract.txt	rw	rw	-	r
  servers.txt	rw	rw	r	r

• Life cycle for local files:
  • States

    diseased

    data remains on disk (file is up to date)

    loaded

    the file is loaded into memory

    modified

    changes on data only remains in memory

  • Events in

    load

    from <diseased> to <loaded>:
    a Process tells it needs the file to be load

    modify

    from <loaded> to <modified>:
    a Process tells it has modified the data

    save

    from <modified> to <loaded>:
    an ACTIVITY saves all modifications on disk

    free

    from <loaded> to <diseased>:
    an ACTIVITY ends or will reload the data

• Life cycle for shared files:
  • Notice: The <loaded> and <modified> states are grouped into the <inUse> meta-state.
  • States

    diseased

    data remains on disk (file is up to date)

    loaded

    the file is loaded into memory

    modified

    changes on data remains in memory

  • Events in
    Notice: the number of threads using the data (n) is registered in order to know if we may or not release memory.

    load (n+=1)

    from <diseased> to <loaded> if n==0 or
    from <inUse> to <inUse> if n>0
    a Process tells it needs the file to be load

    release (n-=1)

    from <inUse> to <inUse>:
    a Process tells it no more need the file

    modify

    from <loaded> to <modified>:
    a Process tells it has modified the data

    save

    from <modified> to <loaded> if n==0:
    an ACTIVITY saves all modifications on disk

    disease

    from <loaded> to <diseased> if n==0:
    an ACTIVITY that needs place on memory unloads the data

Code:

src/misc/locks.c

src/memory/archive.h

src/common.openClose.c