mongooplog-alt 0.4.2
Improved alternative to official mongooplog utility.
License: http://www.apache.org/licenses/LICENSE-2.0.html
Keywords: mongodb,mongo,oplog,mongooplog

mongooplog-alt
==============

About
-----

**mongooplog-alt** is the Python remake of `official mongooplog utility`_,
shipped with MongoDB starting from version 2.2.0. It reads oplog of a remote
server, and applies operations to the local server. This can be used to keep
independed replica set loosly synced in a sort of one way replication, and may
be useful in various backup and migration scenarios.

``mongooplog-alt`` implements basic functionality of the official utility and
adds following features:

* tailable oplog reader: runs forever polling new oplog event which is extremly
  useful for keeping two independent replica sets in almost real-time sync.

* option to sync only selected databases/collections.

* option to exclude one or more namespaces (i.e. dbs or collections) from
  being synced.

* ability to "rename" dbs/collections on fly, i.e. destination namespaces can
  differ from the original ones.

* works on mongodb 1.8.x, 2.0.x, and 2.2.x. Official utility only supports
  version 2.2.x and higher.

* save last processed timestamp to file, resume from saved point later.

* at the time of writing (2.2.0), official ``mongooplog`` suffers from bug that
  limits its usage with replica sets (https://jira.mongodb.org/browse/SERVER-6915)


.. _official mongooplog utility: http://docs.mongodb.org/manual/reference/mongooplog/


Installation
------------

Using pip (preferred)::

    pip install --upgrade mongooplog-alt

Using easy_install::

    easy_install -U mongooplog-alt


Command-line options
--------------------

Options common to original ``mongooplog``::

  --from <hostname><:port>
    Hostname of the mongod server from which oplog operations are going to be
    pulled.

  --host <hostname><:port>, -h

    Hostname of the mongod server to which oplog operations are going to be
    applied. Default is "localhost"

  --port <number>

    Port of the mongod server to which oplog operations are going to be
    applied, if not specified in ``--host``. Default is 27017.

  -s SECONDS, --seconds SECONDS

    seconds to go back. If not set, try read timestamp from --resume-file.
    If the file not found, assume --seconds=86400 (24 hours)


Options specific to ``mongooplog-alt``::

 --to
   An alias for ``--host``.

 --follow, -f

   Wait for new data in oplog. Makes the utility polling oplog forever (until
   interrupted). New data is going to be applied immideately with at most one
   second delay.

 --exclude, -x

    List of space separated namespaces which should be ignored. Can be in form
    of ``dname`` or ``dbname.collection``.

  --ns

    Process only these namespaces, ignoring all others. Space separated list of
    strings in form of ``dname`` or ``dbname.collection``.

  --rename [ns_old=ns_new [ns_old=ns_new ...]]

    Rename database(s) and/or collection(s). Operations on namespace ``ns_old``
    from the source server will be applied to namespace ``ns_new`` on the
    destination server.

  --resume-file FILENAME

    resume from timestamp read from this file and write last processed
    timestamp back to this file (default is mongooplog.ts).
    Pass empty string or 'none' to disable this feature.


Example usages
--------------

Consider the following sample usage::

    mongooplog-alt --from prod.example.com:28000 --to dev.example.com:28500 -f --exclude logdb data.transactions --seconds 600

This command is going to take operations from the last 10 minutes from prod,
and apply them to dev. Database ``logdb`` and collection ``transactions`` of
``data`` database will be omitted. After operations for the last minutes will
be applied, command will wait for new changes to come, keep running until
Ctrl+C or other termination signal recieved.


Testing
-------

Tests for ``mongooplog-alt`` are written in javascript using test harness
which is used for testing MongoDB iteself. You can run the whole suite with::

    mongo tests/suite.js

Note, that you will need existing writable ``/data/db`` dir.

Tests produce alot of output. Succesfull execution ends with line like this::

    ReplSetTest stopSet *** Shut down repl set - test worked ****