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Fix edge case in backup expiration logic (#166)

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* bugfix - fn_expire_backups function

* add BACKUP_TO_KEEP parameter

* correct PREVIOUS_DEST test

* variables case correction for consistency
This commit is contained in:
kapitainsky 2019-09-25 22:18:06 +01:00 committed by Laurent Cozic
parent eb5fe002e6
commit 48b42bf6ba
1 changed files with 47 additions and 11 deletions
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58
rsync_tmbackup.sh
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@ -96,8 +96,14 @@ fn_expire_backups() {
local current_timestamp=$EPOCH
local last_kept_timestamp=9999999999
# Process each backup dir from most recent to oldest
for backup_dir in $(fn_find_backups | sort -r); do
# we will keep requested backup
backup_to_keep="$1"
# we will also keep the oldest backup
oldest_backup_to_keep="$(fn_find_backups | sort | sed -n '1p')"
# Process each backup dir from the oldest to the most recent
for backup_dir in $(fn_find_backups | sort); do
local backup_date=$(basename "$backup_dir")
local backup_timestamp=$(fn_parse_date "$backup_date")
@ -107,36 +113,60 @@ fn_expire_backups() {
continue
fi
if [ "$backup_dir" == "$backup_to_keep" ]; then
# this is the latest backup requsted to be kept. We can finish pruning
break
fi
if [ "$backup_dir" == "$oldest_backup_to_keep" ]; then
# We dont't want to delete the oldest backup. It becomes first "last kept" backup
last_kept_timestamp=$backup_timestamp
# As we keep it we can skip processing it and go to the next oldest one in the loop
continue
fi
# Find which strategy token applies to this particular backup
for strategy_token in $(echo $EXPIRATION_STRATEGY | tr " " "\n" | sort -r -n); do
IFS=':' read -r -a t <<< "$strategy_token"
# After which date (relative to today) this token applies (X)
# After which date (relative to today) this token applies (X) - we use seconds to get exact cut off time
local cut_off_timestamp=$((current_timestamp - ${t[0]} * 86400))
# Every how many days should a backup be kept past the cut off date (Y)
local cut_off_interval=$((${t[1]} * 86400))
# Every how many days should a backup be kept past the cut off date (Y) - we use days (not seconds)
local cut_off_interval_days=$((${t[1]}))
# If we've found the strategy token that applies to this backup
if [ "$backup_timestamp" -le "$cut_off_timestamp" ]; then
# Special case: if Y is "0" we delete every time
if [ $cut_off_interval -eq "0" ]; then
if [ $cut_off_interval_days -eq "0" ]; then
fn_expire_backup "$backup_dir"
break
fi
# we calculate days number since last kept backup
local last_kept_timestamp_days=$((last_kept_timestamp / 86400))
local backup_timestamp_days=$((backup_timestamp / 86400))
local interval_since_last_kept_days=$((backup_timestamp_days - last_kept_timestamp_days))
# Check if the current backup is in the interval between
# the last backup that was kept and Y
local interval_since_last_kept=$((last_kept_timestamp - backup_timestamp))
if [ "$interval_since_last_kept" -lt "$cut_off_interval" ]; then
# to determine what to keep/delete we use days difference
if [ "$interval_since_last_kept_days" -lt "$cut_off_interval_days" ]; then
# Yes: Delete that one
fn_expire_backup "$backup_dir"
# backup deleted no point to check shorter timespan strategies - go to the next backup
break
else
# No: Keep it
# No: Keep it.
# this is now the last kept backup
last_kept_timestamp=$backup_timestamp
# and go to the next backup
break
fi
break
fi
done
done
@ -450,7 +480,13 @@ while : ; do
# Purge certain old backups before beginning new backup.
# -----------------------------------------------------------------------------
fn_expire_backups
if [ -n "$PREVIOUS_DEST" ]; then
# regardless of expiry strategy keep backup used for --link-dest
fn_expire_backups "$PREVIOUS_DEST"
else
# keep latest backup
fn_expire_backups "$DEST"
fi
# -----------------------------------------------------------------------------
# Start backup