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Code Issues Releases Wiki Activity

new logic for determining when to take a full backup

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This commit is contained in:
Joshua Tauberer 2014-09-08 19:42:42 +00:00
parent cce6bc02a8
commit bab8b515ea
1 changed files with 26 additions and 13 deletions
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39
management/backup.py
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@ -46,7 +46,7 @@ def backup_status(env):
"date_str": date.strftime("%x %X"),
"date_delta": reldate(date),
"full": m.group("incbase") is None,
"previous": m.group("incbase") is None,
"previous": m.group("incbase"),
"size": 0,
"encsize": 0,
}
@ -58,6 +58,8 @@ def backup_status(env):
if os.path.exists(encfn):
backups[key]["encsize"] += os.path.getsize(encfn)
# Ensure the rows are sorted reverse chronologically.
# This is relied on by should_force_full().
backups = sorted(backups.values(), key = lambda b : b["date"], reverse=True)
return {
@ -68,6 +70,25 @@ def backup_status(env):
"backups": backups,
}
def should_force_full(env):
# Force a full backup when the total size of the increments
# since the last full backup is greater than half the size
# of that full backup.
inc_size = 0
for bak in backup_status(env)["backups"]:
if not bak["full"]:
# Scan through the incremental backups cumulating
# size...
inc_size += bak["size"]
else:
# ...until we reach the most recent full backup.
# Return if we should to a full backup.
return inc_size > .5*bak["size"]
else:
# If we got here there are no (full) backups, so make one.
# (I love for/else blocks. Here it's just to show off.)
return True
def perform_backup(full_backup):
env = load_environment()
@ -79,18 +100,10 @@ def perform_backup(full_backup):
os.makedirs(backup_duplicity_dir, exist_ok=True)
# On the first run, always do a full backup. Incremental
# will fail.
if len(os.listdir(backup_duplicity_dir)) == 0:
full_backup = True
else:
# When the size of incremental backups exceeds the size of existing
# full backups, take a new full backup. We want to avoid full backups
# because they are costly to synchronize off-site.
full_sz = sum(os.path.getsize(f) for f in glob.glob(backup_duplicity_dir + '/*-full.*'))
inc_sz = sum(os.path.getsize(f) for f in glob.glob(backup_duplicity_dir + '/*-inc.*'))
# (n.b. not counting size of new-signatures files because they are relatively small)
if inc_sz > full_sz * 1.5:
full_backup = True
# will fail. Otherwise do a full backup when the size of
# the increments since the most recent full backup are
# large.
full_backup = full_backup or should_force_full(env)
# Stop services.
shell('check_call', ["/usr/sbin/service", "dovecot", "stop"])