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https://github.com/mdirolf/mongo-appengine-connector

Connector to use MongoDB with Google's AppEngine
https://github.com/mdirolf/mongo-appengine-connector

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Connector to use MongoDB with Google's AppEngine

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README 

        

===========================

MongoDB AppEngine Connector

===========================

:Info: See `the mongodb site `_ for more  information.  See `github `_ for the latest source.

:Author: Mike Dirolf 



About

=====

The MongoDB AppEngine Connector provides a drop-in replacement for App Engine's

datastore API, using MongoDB as a backend.



Questions and Support

=====================



Questions about the MongoDB AppEngine Connector should be directed to the `mongodb-user

group `_.



Usage

=====



The following steps can be used to get Google AppEngine working with MongoDB:



Install MongoDB

---------------



Instructions for installing MongoDB on your platform can be found on `the mongodb site `_.



After installing, start an instance of **mongod** on the default port::



  $ mongod run



Get the Google AppEngine Code

-----------------------------



In order to use the connector, you must patch the AppEngine source distribution, which can

be found `here `_ and checked out via::



  $ svn checkout http://googleappengine.googlecode.com/svn/trunk/ googleappengine-read-only



Be sure that you meet all the pre-requisites listed in the *README* in the resulting

directory.



Patch the AppEngine Code

------------------------



This adapter has been tested against revision 77 from Google

AppEngine's svn repository. To find the revision number of the repository

that you checked out, go into the root of the repository and type::



  $ svn info



To apply the patch, do the following from a command line::



  $ cd googleappengine-read-only

  $ cd python/ # need to do this if you checked out all the different AE languages

  $ patch -p0 < gae_patch.diff



you should see output similar to::



  patching file dev_appserver.py

  patching file google/appengine/tools/dev_appserver.py



If you see no error messages, your patching was successful.



Set the MongoDB Connector Directory

-----------------------------------



In the AppEngine distribution, we patched *dev_appserver.py* in the previous step, and now we

need to edit it by hand.  Open the file in your favorite editor, and look for the line::



  "PATH/TO/MONGO-APPENGINE-CONNECTOR/DIRECTORY"



and change it to the appropriate value.  Remember to keep the double quotes.



Install PyMongo, the Python Driver for MongoDB

----------------------------------------------



If you've already installed the MongoDB python driver - PyMongo - you can skip this step.



To install PyMongo::



  $ easy_install pymongo



Run the Tests

-------------



Once AppEngine is patched, pymongo is installed, and MongoDB is up and running, you can test

the installation by running the adapter's unit tests.



To do so, simply start AE via the SDK's start script **dev_appserver.py** with the full path to the

*test/test_site* directory in the adapter distribution.  So, starting in the root of the

AppEngine SDK::



  $ ./dev_appserver.py /my/path/to/mongodb-appengine-connector/test/test_site



Then, if you direct your browser to *http://localhost:8080* you should see a single test

page that begins with::



  Datastore API

  Test a simple db example...

  Test that ids get incremented properly between sessions...

  Slightly less simple db test...

  Test db exceptions...

  Test a delete...

  Test a delete on an unsaved object...

  ...



As long as you don't see the word **FAIL** all tests have passed.



Other Notes

===========



- Right now, the Connection cannot be configured. It attempts to

  connect to a standalone MongoDB instance on localhost:27017.



- Transactions are unsupported. When any operation requiring

  transactions is performed a warning will be logged and the operation

  will be performed transaction-less.



- DateTime values get rounded to the nearest millisecond when saved to

  MongoDB. This is a limitation of MongoDB's date representation, and is

  not specific to this adaptor.



- In order to actually create indexes the dev_appserver must be run with

  the --require-indexes option. Running with this option will probably

  add significant overhead, since each time the dev_appserver checks to

  see if it should create an index a query is performed.



- Index creation ignores the "Ancestor" option. This option would just create an

  index on '_id', which MongoDB creates automatically anyway.



Authors

=======

- Mike Dirolf (mdirolf)

  - Original implementation



- Tobias Rodabel (Tobias)

  - Fixes and maintenance for newer versions of AppEngine