297 lines
10 KiB
Plaintext
297 lines
10 KiB
Plaintext
Dear Nico Schottelius,
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I have started using ccollect and I very much like its design:
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it is elegant and effective.
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In the process of getting ccollect setup and running, I made
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five changes, including one major new feature, that I hope you will
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find useful.
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First, I added the following before any old backup gets deleted:
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> # Verify source is up and accepting connections before deleting any old backups
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> rsync "$source" >/dev/null || _exit_err "Source ${source} is not readable. Skipping."
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I think that this quick test is a much better than, say, pinging
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the source in a pre-exec script: this tests not only that the
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source is up and connected to the net, it also verifies (1) that
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ssh is up and accepting our key (if we are using ssh), and (2) that
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the source directory is mounted (if it needs to be mounted) and
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readable.
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Second, I found ccollect's use of ctime problematic. After
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copying an old backup over to my ccollect destination, I adjusted
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mtime and atime where needed using touch, e.g.:
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touch -d"28 Apr 2009 3:00" destination/daily.01
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However, as far as I know, there is no way to correct a bad ctime.
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I ran into this issue repeatedly while adjusting my backup
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configuration. (For example, "cp -a" preserves mtime but not
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ctime. Even worse, "cp -al old new" also changes ctime on old.)
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Another potential problem with ctime is that it is file-system
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dependent: I have read that Windows sets ctime to create-time not
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last change-time.
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However, It is simple to give a new backup the correct mtime.
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After the rsync step, I added the command:
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553a616,617
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> # Correct the modification time:
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> pcmd touch "${destination_dir}"
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Even if ccollect continues to use ctime for sorting, I see no
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reason not to have the backup directory have the correct mtime.
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To allow the rest of the code to use either ctime or mtime, I
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added definitions:
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44a45,47
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> #TSORT="tc" ; NEWER="cnewer"
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> TSORT="t" ; NEWER="newer"
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(It would be better if this choice was user-configurable because
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those with existing backup directories should continue to use ctime
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until the mtimes of their directories are correct. The correction
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would happen passively over time as new backups created using the
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above touch command and the old ones are deleted.)
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With these definitions, the proper link-dest directory can then be
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found using this minor change (and comment update):
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516,519c579,582
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< # Use ls -1c instead of -1t, because last modification maybe the same on all
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< # and metadate update (-c) is updated by rsync locally.
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< #
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< last_dir="$(pcmd ls -tcp1 "${ddir}" | grep '/$' | head -n 1)" || \
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---
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> # Depending on your file system, you may want to sort on:
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> # 1. mtime (modification time) with TSORT=t, or
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> # 2. ctime (last change time, usually) with TSORT=tc
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> last_dir="$(pcmd ls -${TSORT}p1 "${ddir}" | grep '/$' | head -n 1)" || \
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Thirdly, after I copied my old backups over to my ccollect
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destination directory, I found that ccollect would delete a
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recent backup not an old backup! My problem was that, unknown to
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me, the algorithm to find the oldest backup (for deletion) was
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inconsistent with that used to find the newest (for link-dest). I
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suggest that these two should be consistent. Because time-sorting
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seemed more consistent with the ccollect documentation, I suggest:
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492,493c555,556
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< pcmd ls -p1 "$ddir" | grep "^${INTERVAL}\..*/\$" | \
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< sort -n | head -n "${remove}" > "${TMP}" || \
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---
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> pcmd ls -${TSORT}p1r "$ddir" | grep "^${INTERVAL}\..*/\$" | \
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> head -n "${remove}" > "${TMP}" || \
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Fourthly, in my experience, rsync error code 12 means complete
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failure, usually because the source refuses the ssh connection.
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So, I left the marker in that case:
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558,559c622,625
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< pcmd rm "${destination_dir}.${c_marker}" || \
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< _exit_err "Removing ${destination_dir}/${c_marker} failed."
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---
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> if [ "$ret" -ne 12 ] ; then
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> pcmd rm "${destination_dir}.${c_marker}" || \
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> _exit_err "Removing ${destination_dir}/${c_marker} failed."
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> fi
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(A better solution might allow a user-configurable list of error
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codes that are treated the same as a fail.)
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Fifth, because I was frustrated by the problems of having a
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cron-job decide which interval to backup, I added a major new
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feature: the modified ccollect can now automatically select an
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interval to use for backup.
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Cron-job controlled backup works well if all machines are up and
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running all the time and nothing ever goes wrong. I have, however,
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some machines that are occasionally turned off, or that are mobile
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and only sometimes connected to local net. For these machines, the
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use of cron-jobs to select intervals can be a disaster.
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There are several ways one could automatically choose an
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appropriate interval. The method I show below has the advantage
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that it works with existing ccollect configuration files. The only
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requirement is that interval names be chosen to sort nicely (under
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ls). For example, I currently use:
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$ ls -1 intervals
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a_daily
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b_weekly
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c_monthly
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d_quarterly
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e_yearly
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$ cat intervals/*
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6
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3
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2
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3
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30
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A simpler example would be:
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$ ls -1 intervals
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int1
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int2
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int3
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$ cat intervals/*
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2
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3
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4
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The algorithm works as follows:
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If no backup exists for the least frequent interval (int3 in the
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simpler example), then use that interval. Otherwise, use the
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most frequent interval (int1) unless there are "$(cat
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intervals/int1)" int1 backups more recent than any int2 or int3
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backup, in which case select int2 unless there are "$(cat
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intervals/int2)" int2 backups more recent than any int3 backups
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in which case choose int3.
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This algorithm works well cycling through all the backups for my
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always connected machines as well as for my usually connected
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machines, and rarely connected machines. (For a rarely connected
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machine, interval names like "b_weekly" lose their English meaning
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but it still does a reasonable job of rotating through the
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intervals.)
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In addition to being more robust, the automatic interval
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selection means that crontab is greatly simplified: only one line
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is needed. I use:
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30 3 * * * ccollect.sh AUTO host1 host2 host3 | tee -a /var/log/ccollect-full.log | ccollect_analyse_logs.sh iwe
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Some users might prefer a calendar-driven algorithm such as: do
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a yearly backup the first time a machine is connected during a new
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year; do a monthly backup the first that a machine is connected
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during a month; etc. This, however, would require a change to the
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ccollect configuration files. So, I didn't pursue the idea any
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further.
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The code checks to see if the user specified the interval as
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AUTO. If so, the auto_interval function is called to select the
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interval:
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347a417,420
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> if [ ${INTERVAL} = "AUTO" ] ; then
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> auto_interval
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> _techo "Selected interval: '$INTERVAL'"
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> fi
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The code for auto_interval is as follows (note that it allows 'more
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recent' to be defined by either ctime or mtime as per the TSORT
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variable):
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125a129,182
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> # Select interval if AUTO
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> #
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> # For this to work nicely, you have to choose interval names that sort nicely
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> # such as int1, int2, int3 or a_daily, b_weekly, c_monthly, etc.
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> #
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> auto_interval()
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> {
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> if [ -d "${backup}/intervals" -a -n "$(ls "${backup}/intervals" 2>/dev/null)" ] ; then
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> intervals_dir="${backup}/intervals"
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> elif [ -d "${CDEFAULTS}/intervals" -a -n "$(ls "${CDEFAULTS}/intervals" 2>/dev/null)" ] ; then
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> intervals_dir="${CDEFAULTS}/intervals"
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> else
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> _exit_err "No intervals are defined. Skipping."
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> fi
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> echo intervals_dir=${intervals_dir}
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>
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> trial_interval="$(ls -1r "${intervals_dir}/" | head -n 1)" || \
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> _exit_err "Failed to list contents of ${intervals_dir}/."
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> _techo "Considering interval ${trial_interval}"
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> most_recent="$(pcmd ls -${TSORT}p1 "${ddir}" | grep "^${trial_interval}.*/$" | head -n 1)" || \
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> _exit_err "Failed to list contents of ${ddir}/."
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> _techo " Most recent ${trial_interval}: '${most_recent}'"
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> if [ -n "${most_recent}" ]; then
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> no_intervals="$(ls -1 "${intervals_dir}/" | wc -l)"
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> n=1
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> while [ "${n}" -le "${no_intervals}" ]; do
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> trial_interval="$(ls -p1 "${intervals_dir}/" | tail -n+${n} | head -n 1)"
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> _techo "Considering interval '${trial_interval}'"
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> c_interval="$(cat "${intervals_dir}/${trial_interval}" 2>/dev/null)"
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> m=$((${n}+1))
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> set -- "${ddir}" -maxdepth 1
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> while [ "${m}" -le "${no_intervals}" ]; do
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> interval_m="$(ls -1 "${intervals_dir}/" | tail -n+${m} | head -n 1)"
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> most_recent="$(pcmd ls -${TSORT}p1 "${ddir}" | grep "^${interval_m}\..*/$" | head -n 1)"
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> _techo " Most recent ${interval_m}: '${most_recent}'"
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> if [ -n "${most_recent}" ] ; then
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> set -- "$@" -$NEWER "${ddir}/${most_recent}"
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> fi
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> m=$((${m}+1))
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> done
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> count=$(pcmd find "$@" -iname "${trial_interval}*" | wc -l)
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> _techo " Found $count more recent backups of ${trial_interval} (limit: ${c_interval})"
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> if [ "$count" -lt "${c_interval}" ] ; then
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> break
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> fi
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> n=$((${n}+1))
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> done
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> fi
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> export INTERVAL="${trial_interval}"
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> D_FILE_INTERVAL="${intervals_dir}/${INTERVAL}"
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> D_INTERVAL=$(cat "${D_FILE_INTERVAL}" 2>/dev/null)
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> }
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>
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> #
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While I consider the auto_interval code to be developmental, I have
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been using it for my nightly backups and it works for me.
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One last change: For auto_interval to work, it needs "ddir" to
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be defined first. Consequently, I had to move the following code
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so it gets run before auto_interval is called:
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369,380c442,443
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<
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< #
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< # Destination is a path
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< #
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< if [ ! -f "${c_dest}" ]; then
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< _exit_err "Destination ${c_dest} is not a file. Skipping."
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< else
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< ddir=$(cat "${c_dest}"); ret="$?"
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< if [ "${ret}" -ne 0 ]; then
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< _exit_err "Destination ${c_dest} is not readable. Skipping."
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< fi
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< fi
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345a403,414
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> # Destination is a path
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> #
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> if [ ! -f "${c_dest}" ]; then
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> _exit_err "Destination ${c_dest} is not a file. Skipping."
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> else
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> ddir=$(cat "${c_dest}"); ret="$?"
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> if [ "${ret}" -ne 0 ]; then
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> _exit_err "Destination ${c_dest} is not readable. Skipping."
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> fi
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> fi
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>
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> #
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I have some other ideas but this is all I have implemented at
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the moment. Files are attached.
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Thanks again for developing ccollect and let me know what you
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think.
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Regards,
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John
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--
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John L. Lawless, Ph.D.
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Redwood Scientific, Inc.
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1005 Terra Nova Blvd
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Pacifica, CA 94044-4300
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1-650-738-8083
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