.. -*- coding: utf-8 -*-

.. _GoogleAppEngineSource:

CubicWeb in Google AppEngine

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

What is  `Google AppEngine` ?

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

`Google AppEngine`_ is provided with a partial port of the `Django`

framework, but Google stated at Google IO 2008 that it would not

support a specific Python web framework and that all

community-supported frameworks would be more than welcome [1]_.

Therefore `Logilab`_ ported *CubicWeb* to run on top of `Google AppEngine`'s

datastore.

.. _`Google AppEngine`: http://code.google.com/appengine/docs/whatisgoogleappengine.html

.. _Logilab: http://www.logilab.fr/

.. [1] for more on this matter, read our blog at http://www.logilab.org/blogentry/5216

Download the source

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

- The `Google AppEngine SDK` can be downloaded from:

  http://code.google.com/appengine/downloads.html

Please follow instructions on how to install *CubicWeb* framework

(:ref:`SetUpEnv`).

Installation

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

Once ``cubicweb-ctl`` is installed, then you can create a Google

App Engine extension of our framework by running the command ::

   cubicweb-ctl newgapp <myapp>

This will create a directory containing ::

   `-- myapp/

       |-- app.conf

       |-- app.yaml

       |-- bin/

       |    `-- laxctl

       |-- boostrap_cubes

       |-- cubes/

       |    |-- addressbook/

       |    ..

       |    |-- comment

       |    ..

       |    `-- zone/

       |-- cubicweb/

       |-- custom.py

       |-- cw-cubes/

       |-- dateutil/

       |-- docutils/

       |-- fckeditor/

       |-- i18n/

       |-- index.yaml

       |-- loader.py

       |-- logilab/

       |-- main.py

       |-- migration.py

       |-- mx/

       |-- roman.py

       |-- rql/

       |-- schema.py

       |-- simplejson/

       |-- tools/

       |-- views.py

       |-- vobject/

       |-- yams/

       `-- yapps/

This skeleton directory is a working `AppEngine` application. You will

recognize the files ``app.yaml`` and ``main.py``. All the rest is the

*CubicWeb* framework and its third-party libraries. You will notice that

the directory ``cubes`` is a library of reusable cubes.

The main directories that you should know about are:

  - ``cubes`` : this is a library of reusable yams cubes. To use

    those cubes you will list them in the variable

    `included-yams-cubes` of ``app.conf``. See also :ref:`cubes`.

  - [WHICH OTHER ONES SHOULD BE LISTED HERE?]

Dependencies

~~~~~~~~~~~~

Before starting anything, please make sure the following packages are installed:

  - yaml : by default google appengine is providing yaml; make sure you can

    import it. We recommend you create a symbolic link yaml instead of installing

    and using python-yaml:

    yaml -> full/path/to/google_appengine/lib/yaml/lib/yaml/

  - gettext

Setup

~~~~~

Once you executed ``cubicweb-ctl newgapp <myapp>``, you can use that ``myapp/``

as an application directory and do as follows.

This installation directory provides a configuration for an instance of *CubicWeb*

ported for Google App Engine. It is installed with its own command ``laxctl``

which is a port of the command tool ``cubicweb-ctl`` originally developped for

*CubicWeb*.

You can have the details of available commands by running ::

   $ python myapp/bin/laxctl --help

Generating translation files

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

*CubicWeb* is fully internationalized. Translation catalogs are found in

``myapp/i18n``. To compile the translation files, use the `gettext` tools

or the ``laxctl`` command ::

  $ python myapp/bin/laxctl i18ncube

  $ python myapp/bin/laxctl i18ninstance

Ignore the errors that print "No translation file found for domain

'cubicweb'". They disappear after the first run of i18ninstance.

.. note:: The command  myapp/bin/laxctl i18ncube needs to be executed

   only if your instance is using cubes from cubicweb-apps.

   Otherwise, please skip it.

You will never need to add new entries in the translation catalog. Instead we

would recommand you to use ``self._cw._("msgId")`` in your code to flag new

message id to add to the catalog, where ``_`` refers to xgettext that is used to

collect new strings to translate.  While running ``laxctl i18ncube``, new string

will be added to the catalogs.

Generating the data directory

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In order to generate the ``myapp/data`` directory that holds the static

files like stylesheets and icons, you need to run the command::

  $ python myapp/bin/laxctl populatedata

Generating the schema diagram

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There is a view named ``schema`` that displays a diagram of the

entity-relationship graph defined by the schema. This diagram has to

be generated from the command line::

  $ python myapp/bin/laxctl genschema

Instance configuration

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

Authentication

~~~~~~~~~~~~~~

You have the option of using or not google authentication for your instance.

This has to be define in ``app.conf`` and ``app.yaml``.

In ``app.conf`` modify the following variable::

  # does this instance rely on google authentication service or not.

  use-google-auth=no

In ``app.yaml`` comment the `login: required` set by default in the handler::

  - url: .*

  script: main.py

  # comment the line below to allow anonymous access or if you don't want to use

  # google authentication service

  #login: required

Quickstart : launch the instance

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

On Mac OS X platforms, drag that directory on the

`GoogleAppEngineLauncher`.

On Unix and Windows platforms, run it with the dev_appserver::

  $ python /path/to/google_appengine/dev_appserver.py /path/to/myapp/

Once the local server is started, visit `http://MYAPP_URL/_load <http://localhost:8080/_load>`_ and sign in as administrator.

This will initialize the repository and enable you to log in into

the instance and continue the installation.

You should be redirected to a page displaying a message `content initialized`.

Initialize the datastore

~~~~~~~~~~~~~~~~~~~~~~~~

You, then, want to visit  `http://MYAPP_URL/?vid=authinfo <http://localhost:8080/?vid=authinfo>`_ .

If you selected not  to use google authentication, you will be prompted to a

login form where you should initialize the administrator login (recommended

to use admin/admin at first). You will then be redirected to a page providing

you the value to provide to ``./bin/laxctl --cookie``.

If you choosed to use google authentication, then you will not need to set up

and administrator login but you will get the cookie value as well.

This cookie values needs to be provided to ``laxctl`` commands

in order to handle datastore administration requests.

.. image:: ../images/lax-book.02-cookie-values.en.png

   :alt: displaying the detailed view of the cookie values returned

.. note:: In case you are not redirected to a page providing the

   option --cookie value, please visit one more time

   `http://MYAPP_URL/?vid=authinfo <http://localhost:8080/?vid=authinfo>`_ .

Once, you have this value, then return to the shell and execute ::

  $ python myapp/bin/laxctl db-init --cookie='dev_appserver_login=test@example.com:True; __session=7bbe973a6705bc5773a640f8cf4326cc' localhost:8080

.. note:: In the case you are not using google authentication, the value returned

   by `http://MYAPP_URL/?vid=authinfo <http://localhost:8080/?vid=authinfo>`_

   will look like :

   --cookie='__session=2b45d1a9c36c03d2a30cedb04bc37b6d'

Log out by clicking in the menu at the top right corner

and restart browsing from `http://MYAPP_URL/ <http://localhost:8080>`_

as a normal user.

Unless you did something to change it, http://MYAPP_URL should be

http://localhost:8080/