#!/usr/bin/env python2.4

# svn-fast-backup: use rsync snapshots for very fast FSFS repository backup.
#    Multiple FSFS backups share data via hardlinks, meaning old backups are
#    almost free, since a newer revision of a repository is almost a complete
#    superset of an older revision.

# This is good for replacing incremental log-dump+restore-style backups
# because it is just as space-conserving and even faster; there is no
# inter-backup state (old backups are essentially caches); each backup
# directory is self-contained.  It keeps the same interface as svn-hot-backup
# (if you use --force), but only works for FSFS repositories.

# Author: Karl Chen <quarl@quarl.org>

## quarl 2005-08-17 initial version
## quarl 2005-09-01 refactor, documentation; new options: --force, --keep,
##                  --simulate, --trace

# $HeadURL$
# $LastChangedRevision$
# $LastChangedDate$
# $LastChangedBy$

# Originally based on svn-hot-backup.py, whose copyright notice states:

# ====================================================================
# Copyright (c) 2000-2004 CollabNet.  All rights reserved.
#
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution.  The terms
# are also available at http://subversion.tigris.org/license-1.html.
# If newer versions of this license are posted there, you may use a
# newer version instead, at your option.
#
# This software consists of voluntary contributions made by many
# individuals.  For exact contribution history, see the revision
# history and logs, available at http://subversion.tigris.org/.
# ====================================================================

######################################################################

import sys, os, re
import getopt
import subprocess                                   # python2.4

######################################################################
# Global Settings

svnlook = "svnlook"                                 # Path to svnlook
svnadmin = "svnadmin"                               # Path to svnadmin
rsync = "rsync"                                     # Path to rsync

######################################################################
# Command line arguments

def usage():
    raise SystemExit("""Syntax: %s [OPTIONS] repos_path backup_dir

Makes a hot backup of a Subversion FSFS repository at REPOS_PATH to
BACKUP_DIR/repos-rev.

If a previous version exists, make hard links of its files using rsync.
As multiple FSFS backups share data via hardlinks, old backups use
almost no space, since a newer revision of a repository is almost a complete
superset of an older revision (excluding direct repository modifications).

Keeps up to N backups and deletes the rest.  (N includes the current backup.)

OPTIONS:
   -h, --help        This screen
   -q, --quiet       Quieter than usual
   -k, --keep=N      Keep N backups instead of 64
   -k, --keep=all    Keep all backups (never delete any)
   -f, --force       Make a new backup even if one with current revision exists
   -t, --trace       Show actions
   -s, --simulate    Don't perform actions

""" %sys.argv[0])

class Options: pass

def default_options():
    options = Options()
    options.force = False
    options.trace = False
    options.simulate = False
    options.quiet = False
    options.keep = 64                       # Number of backups to keep around
    return options

def parse_commandline():
    options = default_options()

    try:
        opts, args = getopt.getopt(sys.argv[1:], 'qhk:fts', ['quiet', 'help', 'keep=', 'force',
                                                             'trace', 'simulate'])
    except getopt.GetoptError, e:
        print >>sys.stderr, "Error:", e
        usage()

    for (o,a) in opts:
        if o == '-h' or o == '--help':
            usage()
        elif o == '-q' or o == '--quiet':
            options.quiet = True
        elif o == '-f' or o == '--force':
            options.force = True
        elif o == '-t' or o == '--trace':
            options.trace = True
        elif o == '-s' or o == '--simulate':
            options.simulate = True
        elif o == '-k' or o == '--keep':
            if a.strip().lower() == 'all':
                options.keep = 0
            else:
                options.keep = int(a)
        else:
            raise Exception("Internal error")

    if len(args) != 2:
        usage()

    # Path to repository
    options.repo_dir = args[0]

    # Where to store the repository backup.  The backup will be placed in a
    # *subdirectory* of this location, named after the youngest revision.

    options.backup_dir = os.path.abspath(args[1])

    options.repo = os.path.basename(os.path.abspath(options.repo_dir))

    return options

def comparator(a, b):
    # We pass in filenames so there is never a case where they are equal.
    regexp = re.compile("-(?P<revision>[0-9]+)(-(?P<increment>[0-9]+))?$")
    matcha = regexp.search(a)
    matchb = regexp.search(b)
    reva = int(matcha.groupdict()['revision'])
    revb = int(matchb.groupdict()['revision'])
    if (reva < revb):
        return -1
    elif (reva > revb):
        return 1
    else:
        inca = matcha.groupdict()['increment']
        incb = matchb.groupdict()['increment']
    if not inca:
        return -1
    elif not incb:
        return 1;
    elif (int(inca) < int(incb)):
        return -1
    else:
        return 1

def pipe(command):
    return subprocess.Popen(command, stdout=subprocess.PIPE).communicate()[0].strip()

def readfile(filename):
    try:
        return open(filename).read().strip()
    except:
        return ''

def runcmd(cmd):
    if options.trace:
        print >>sys.stderr, '#', cmd
    if options.simulate:
        return 0
    return subprocess.call(cmd)

def deltree(path):
    runcmd(['rm', '-r', path])

def get_youngest_revision():
    if readfile(os.path.join('db', 'fs-type')) != 'fsfs':
        raise SystemExit("Path '%s' doesn't contain a FSFS repository"%options.repo_dir)

    return pipe([svnlook,"youngest","."])

def list_repo_backups():
    '''Return a sorted list of backups for this repository.'''
    regexp = re.compile(options.repo + "-[0-9]+(-[0-9]+)?$")
    directory_list = [x for x in os.listdir(options.backup_dir) if regexp.match(x)]
    directory_list.sort(comparator)
    return directory_list

def delete_old_backups():
    if options.keep <= 0:
        return

    for item in list_repo_backups()[:-options.keep]:
        old_backup_subdir = os.path.join(options.backup_dir, item)
        print "  Removing old backup: ", old_backup_subdir
        deltree(old_backup_subdir)

def find_next_backup_name(youngest):
    # If there is already a backup of this revision, then append the next
    # highest increment to the path.  We still need to do a backup because the
    # repository might have changed despite no new revision having been
    # created.  We find the highest increment and add one rather than start
    # from 1 and increment because the starting increments may have already
    # been removed due to options.keep.

    regexp = re.compile(options.repo + "-" + youngest + "(-(?P<increment>[0-9]+))?$")
    directory_list = os.listdir(options.backup_dir)
    young_list = [ x for x in directory_list if regexp.match(x) ]
    young_list.sort(comparator)

    if not young_list:
        return "%s-%s" %(options.repo, youngest)

    # Backups for this revision exist already.

    if not options.force:
        if not options.quiet:
            print "Backup already exists at",young_list[-1]
        raise SystemExit

    increment = int(regexp.match(young_list[-1]).groupdict()['increment'] or '0')

    return "%s-%s-%d" %(options.repo, youngest, increment+1)

def do_rsync_backup():
    youngest = get_youngest_revision()

    if not options.quiet:
        print "Beginning hot backup of '%s' (youngest revision is %s)..." %(options.repo, youngest),

    backup_subdir = os.path.join(options.backup_dir, find_next_backup_name(youngest))
    backup_tmpdir = backup_subdir + '.tmp'

    if os.path.exists(backup_tmpdir):
        raise SystemExit("%s: Backup in progress?  '%s' exists -- aborting."%(sys.argv[0],backup_tmpdir))

    if not options.simulate:
        os.mkdir(backup_tmpdir)                     # ensures atomicity

    if os.path.exists(backup_subdir):
        # Check again after doing mkdir (which serves as a mutex acquire) --
        # just in case another process just finished the same backup.
        if not options.quiet:
            print "Backup already exists at",backup_subdir
        raise SystemExit

    previous_backups = list_repo_backups()

    ### Use rsync to make a copy.
    # We need to copy the 'current' file first.
    # Don't copy the transactions/ directory.
    # See http://svn.apache.org/repos/asf/subversion/trunk/notes/fsfs

    rsync_dest = os.path.join(backup_tmpdir,'')

    # copy db/current.  -R tells rsync to use relative pathnames.
    if runcmd([rsync, '-aR', 'db/current', rsync_dest]):
        raise "%s: rsync failed" %sys.argv[0]

    # Now copy everything else.
    cmd = [rsync, '-a',
           '--exclude', 'db/current',
           '--exclude', 'db/transactions/*',
           '--exclude', 'db/log.*',
           '.', rsync_dest]
    # If there's a previous backup, make hard links against the latest.
    if previous_backups:
        cmd += ['--link-dest', os.path.join(options.backup_dir, previous_backups[-1])]

    if runcmd(cmd):
        raise "%s: rsync failed" %sys.argv[0]

    # Rename to final name.
    if not options.simulate:
        os.rename(backup_tmpdir, backup_subdir)

    print "Finished backup to", backup_subdir


options = parse_commandline()
os.chdir(options.repo_dir)
do_rsync_backup()
delete_old_backups()