Intelligent Synching

Thoughts on intelligent synching

Intelligent synching is achieved through a combination of a database of md5 sums and rsync.

Variables

.last_sync a list of md5 sums after last sync

get lists of changes using rsync
use head and tail to avoid the garbage info from rsync
s_to_c: what is listed here exists on server, but is either not on, or in a different version on client
s_to_c=`rsync -vrc -n $GR_SERVER:$GR_SERVERROOT $GR_LOCALROOT | tail —lines=+ 2 | head —lines=-3`
c_to_s: What is listed here exists on local, but is either not on, or in a different version on server
c_to_s=`rsync -vrc -n $GR_LOCALROOT $GR_SERVER:$GR_SERVERROOT | tail —lines=+ 2 | head —lines=-3`

Draft

C_TO_S:
for each $entry (each line in c_to_s)

• if ($entry is a dir) — dir exists on local and not on server
  • if ($entry is not in .last_sync)
    • dir must have been created on local machine
    • copy dir to server.
    • Delete all sub-entries with dir from c_to_s
  • else
    • dir is in .last_sync
    • dir must have been deleted on server
    • if (md5($entry) != .last_sync md5)
      • dir deleted on server, but has been changed locally
      • CONFLICT
    • else dir deleted on server and unchanged locally
      • delete dir locally
        *else it is a file
  • if (file is not in s_to_c)
    • it is a file, exists on local, not on server
    • if (file is in .last_sync)
      • file has been created locally
      • sync to server
    • else file deleted on server
      • if (md5(file) != .last_sync md5)
        • file deleted on server, but modified locally
        • CONFLICT
      • else file deleted on server, untouched locally
        • delete locally
  • else file exists in both places
    • if (md5(local_file) != .last_sync md5)
      • file changed locally
      • if (md5(remote_file) != .last_sync md5)
        • file also changed on server
        • CONFLICT
        • delete entry from s_to_c after resolved conflict
      • else file only changed locally
        • copy to server
        • delete entry from s_to_c
    • else file unchanged locally
      • it is implied from the diff that it must be changed on server then
      • cpy server to local
      • delete entry from s_to_c

In General after sync*

• If file is changed, created, update md5 for dir tree+file
• If file deleted_, change md5 from tree, remove entry from .lastsync
• If dir is changed, created, update md5 for dir tree
• If dir is deleted_, change md5 from tree, remove entry+subdirs/files from .lastsync