A simple backup script for couchdbs

couch_backup.py

"""
Copyright (c) 2010, Horst Gutmann <zerok@zerokspot.com>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice,
      this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright notice,
      this list of conditions and the following disclaimer in the documentation
      and/or other materials provided with the distribution.

    * Neither the name of the project's author nor the names of its contributors
      may be used to endorse or promote products derived from this software
      without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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-------------------------------------------------------------------------------

This is a simple script for backing up a couchdb with n history steps.
Configuration is handled by a simple configuration file passed as first
argument. It describes what database should be replicated to what machine
and how many historical copies should be created::
    
    [main]
    parts=db1

    [DEFAULT]
    history=3
    source_server=http://localhost:5984/
    target_server=http://whatever.couchone.com/
    
    [db1]
    source=my_database
    target=my_database_backup{0}

Both, source and target, can be either local database names or remote
addresses.  The target has to support one placeholder for the number of the
backup copy. The history-setting allows you to specify how many historical
copies should be preserved. my_database_backup0 is the most recent backup
while my_database_backup3 (if history==3) is the oldest one.

To start the backup simply run `python couch_backup.py mybackup.cfg`,

Note that the script will try to create the target databases if the don't exist
yet.

**WARNING:** The created databases are by default public. If you don't want
that, create the required databases either in advance with the security
settings of your choice or change them after the automatical creation.
"""

import ConfigParser
import couchdb
import optparse


options = optparse.OptionParser()
options.add_option('--dry-run', action='store_true', dest='dryrun',
        default=False)
opts, args = options.parse_args()


cfg = ConfigParser.ConfigParser()
cfg.read(args[0])


def are_same_server(s1, s2):
    if s1.rstrip('/') == s2.rstrip('/'):
        return True
    return False

parts = cfg.get('main', 'parts').split()
for part in parts:
    source = cfg.get(part, 'source')
    source_server = cfg.get(part, 'source_server')
    target = cfg.get(part, 'target')
    target_server = cfg.get(part, 'target_server')
    try:
        handler = cfg.get(part, 'handler')
    except ConfigParser.NoOptionError, e:
        handler = source_server
    history = int(cfg.get(part, 'history'))

    # Produce the final source and target addresses
    if are_same_server(source_server, handler):
        real_source = source
    else:
        real_source = source_server.rstrip('/') + '/' + source
    if are_same_server(target_server, handler):
        real_target = target
    else:
        real_target = target_server.rstrip('/') + '/' + target


    # Open the target server and create all missing datbases
    targetSrv = couchdb.Server(target_server)
    for i in range(history+1):
        print "Creating db {0}".format(target.format(i))
        if not opts.dryrun:
            try:
                targetSrv.create(target.format(i))
            except couchdb.http.PreconditionFailed, e:
                pass

    # Replicate using the handler server
    handlerSrv = couchdb.Server(handler)

    for i in reversed(range(history)):
        print "Replicating {0} to {1}".format(target.format(i),
                target.format(i+1))
        if not opts.dryrun:
            targetSrv.replicate(target.format(i), target.format(i+1))

    print "Replicating {0} to {1}".format(real_source, real_target.format(0))
    if not opts.dryrun:
        handlerSrv.replicate(real_source, real_target.format(0))