עידו פרלמוטר (Ido Perlmuter)

NAME

MorboDB - In-memory database, mostly-compatible clone of MongoDB

VERSION

version 1.000000

SYNOPSIS

        use MorboDB;

        # MorboDB usage is meant to refelect MongoDB usage

        my $morbo = MorboDB->new;
        my $database = $morbo->get_database('my_database');
        my $collection = $database->get_collection('users');

        my $id = $collection->insert({
                username => 'someguy98',
                password => 's3cr3t',
                email => 'email at address dot com',
        });

        ...

DESCRIPTION

MorboDB is an in-memory database, meant to be a mostly-compatible clone of Perl's MongoDB driver, in such a way that it can be used to replace or even supplement MongoDB in applications where it might be useful.

USE CASES

An in-memory database can be useful for many purposes. A common use case is testing purposes, where using a "physical" database might be onerous. You can already find a few in-memory databases on CPAN, such as MMapDB, DB_File (has optional support for in-memory databases) and KiokuDB (which has an in-memory hash serializer). I'm sure there are others more.

I decided to develop MorboDB for two main purposes:

  • MongoDB disaster fallback: at work I am currently developing a very critical application that uses MongoDB (with replica-sets setup) as a database backend. This application cannot afford to suffer downtimes. The application's database has some constant data (not too much) that shouldn't change which is completely required for it to work. Most of the data, however, is dynamically written due to user's work and is not as important, so it wouldn't matter if the database won't be able to take such writes for some time.

    Therefore, I have decided to build a fail-safe: when the application is launched (actually I haven't decided yet if on launch or not), the constant data is loaded into MorboDB, which silently waits in the background. If for some reason the MongoDB database crashes, the application switches to MorboDB and the application continues to work - the users don't even notice something happend. Since MorboDB provides mostly the same syntax as MongoDB, this isn't very far-fetched codewise.

  • Delayed writes and undos: I am also working on a content management system in which I want to allow users to undo changes for a certain duration (say 30 seconds) after the changes have been made. MorboDB can work as a bridge between the application and the actual MongoDB database (or whatever actually). So the data will only live in MorboDB for 30 seconds, and if the user decides to undo, the data is removed and nothing happens. Otherwise, the data is moved to MongoDB after the 30 seconds are over.

MOSTLY-COMPATIBLE?

As I've mentioned, MorboDB is mostly-compatible with MongoDB. First of all, a lot of things that are relevant for MongoDB are not relevant for in-memory database. Some things aren't supported and probably never will, like GridFS for example. Otherwise, the syntax is almost completely the same (by relying on MQUL), apart for some changes detailed in both "NOTABLE_DIFFERENCES_FROM_MONGODB" in MQUL::Reference and "INCOMPATIBILITIES WITH MONGODB".

I have provided most methods provided by relevant MongoDB modules, even where they're not really implemented (in which case they either return 1 or an undefined value). Read the documentation of MorboDB's different modules for information on every method and whether it's implemented or not. These methods are only provided to make it possible to use MorboDB as a drop-in replacement of MongoDB where appropriate (so you don't get "undefined subroutine" errors). Please let me know if there are methods you need (even unimplemented) that I haven't provided.

Note that autoloading of database and collection objects has been deprecated since version 1.0.0, in accordance with MongoDB.

STATUS

This module is beta software, not suitable for production use yet. Feel free to test it and let me know how it works for you (of course, not on production), I'd be happy to receive any bug reports, requests, ideas, etc.

OBJECT METHODS

database_names()

Returns a list with the names of all existing databases.

get_database( $name )

Returns a MorboDB::Database object with the given name:

        my $morbodb = MorboDB->new;
        
        my $db = $morbodb->get_database('mydb');

get_master()

Not implemented, simply returns a true value here.

CAVEATS

Currently (not sure if this will change), MorboDB does not work in shared memory, so if your application is multi-threaded, every thread will have its own MorboDB container completely separate and unaware of other threads.

DIAGNOSTICS

This module throws the following errors:

"You must provide the name of the database to get."

Thrown by get_database() if you don't provide it with the name of the database you want to get/create.

CONFIGURATION AND ENVIRONMENT

MorboDB requires no configuration files or environment variables.

DEPENDENCIES

MorboDB depends on the following CPAN modules:

INCOMPATIBILITIES WITH MONGODB

While I hope to make MorboDB as much of a clone of the MongoDB driver as possible (syntax and usage-wise), some changes are inevitable. Currently, only the most essential features of the MongoDB distribution are implemented. That means you can insert documents as you would with MongoDB, update documents and remove documents. You can find documents and work with cursor pretty much the same, including sorting and other cursor modifications.

Syntaxwise, any differences between MorboDB and MongoDB stem from the usage of MQUL as the parser, so read the MQUL documentation for a list of differences.

Another difference worth noting is with OIDs. In MongoDB, OIDs (the automatic ones at least) are 24 characters long hexadecimal strings, and are created by the MongoDB::OID module. In MorboDB, however, OIDs (also, only the automatic ones) are 36 characters long UUIDs. This alone limits your ability to use MorboDB alongside MongoDB in an application if you perform queries on the _id attribute with known MongoDB::OID objects. Other than that, this shouldn't really be a problem.

Featurewise, most differences should be missing or unimplemented methods (and a few missing classes). I have taken some care not to miss any methods provided by the MongoDB distribution, but I may have missed some. Where methods are unimplemented, MorboDB will simply return a true or false value (as appropriate). Please read the documentation of each MorboDB module to learn what to expect from unimplemented methods (and implemented methods of course).

Some features that are native to MongoDB itself (and not just the MongoDB distribution on CPAN) will never be implemented in MorboDB (most of them don't even make sense in an in-memory database).

Here's a (probably incomplete) list of MongoDB features missing from MongoDB:

  • Authentication

  • Indexing (may be supported in the future, don't think so though)

  • Replication

  • Sharding

  • Map/Reduce

  • GridFS

INCOMPATIBILITIES WITH OTHER MODULES

None reported.

BUGS AND LIMITATIONS

No bugs have been reported.

Please report any bugs or feature requests to bug-MorboDB@rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=MorboDB.

SEE ALSO

MongoDB, MongoDB::Connection, MQUL, MQUL::Reference.

AUTHOR

Ido Perlmuter <ido@ido50.net>

LICENSE AND COPYRIGHT

Copyright (c) 2011-2013, Ido Perlmuter ido@ido50.net.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either version 5.8.1 or any later version. See perlartistic and perlgpl.

The full text of the license can be found in the LICENSE file included with this module.

DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.