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ophelia / ophelia / CONFIGURATION.txt

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===================
Configuring Ophelia
===================

Configuring Ophelia involves a number of settings variables. They can be
passed as a dictionary to the Ophelia WSGI application,
``ophelia.wsgi.Application``, upon instantiation. The package also comes with
a console script that runs a wsgiref-based server and reads the same settings
variables from an ini-style configuration file, as well as a paste application
factory that lets Ophelia be plugged into any WSGI server that can handle a
paste "ini" file.

Regardless of how the WSGI application is being served, all settings may also
be overridden by accordingly named variables set in the WSGI environment of
each individual request.

The settings variables will end up in the environment namespace stored on the
request object. It is possible to set any number of other variables that are
not recognized by Ophelia using the same configuration mechanism. This allows
configuring Python modules and scripts that belong to your site's content.

The rest of this section contains a description of all variables as well as an
example of a configuration file for the wsgiref server.


Basic configuration
===================

Two variables must always be present:

:template_root:
    The file system path to the template root directory.

:site:
    The absolute URI of the Ophelia site's root, i.e. that part of a page's
    URI that is the same for all pages served from the template directory.

In addition, the variables described below may be specified in order to
influence the request handler's behaviour. All of them have sensible default
values.

For boolean variables such as redirect_index, the values "on", "true", or
"yes" (case-insensitive) are taken to mean True, anything else means False.

:debug:
    Whether to include debug information such as formatted tracebacks in error
    responses. This option is turned off by default.


Delivery of documents straight from disk
========================================

Generally, a site includes documents that are not assembled from templates.
They reside within a directory tree of their own whose root needs to be
configured if needed. Also, if Ophelia sits behind a reverse proxy, documents
from disk may be delivered more efficiently by using something like the
X-Sendfile mechanism:

:document_root:
    Optional, the file system path to the on-disk documents root directory.

:xsendfile:
    One of "standard", "nginx" or "serve". Defaults to "serve" which means
    on-disk documents are delivered directly by the Ophelia application. The
    "standard" value causes an X-Sendfile header to be sent (such as, e.g.,
    Apache understands) while the "nginx" value causes an X-Accel-Redirect
    header for consumption by an nginx reverse proxy to be sent instead. In
    the latter case, the nginx server needs to have the ``/-internal-/``
    location configured as an "internal" alias of the document root directory.


URL canonicalization and redirection
====================================

If a requested URL points to a directory, Ophelia will try to find a template
with a special file name and build the "index" page from that. There are two
configuration options concerned with the index template:

:index_name:
    The name of the index template Ophelia looks for. It defaults to
    "index.html".

:redirect_index:
    Whether to canonicalize the URL and redirect the browser if the path
    portion of the URL ends with the default index page's name. This option is
    turned off by default.


Character encoding
==================

Input encoding
--------------

By default, Ophelia expects Python scripts and TAL templates it reads from
input files to be in 7-bit ASCII encoding. There are several ways to override
this default.

You can declare a character encoding both for the Python script and the
template, and the two encodings may differ. To specify the Python encoding,
just start the script with a Python style encoding declaration like this::

# -*- coding: utf-8 -*-

The template's encoding is determined by looking at the "<?xml?>" tag::

<?xml coding="utf-8" ?>

specifies UTF-8 encoding for the template. The tag itself will be stripped
from the template and will not appear in the rendered page.

You may also specify a default encoding for any scripts and templates to be
read later during traversal. In a Python script, just do something like

::

    __request__.splitter.script_encoding = "utf-8"
    __request__.splitter.template_encoding = "utf-8"

A site-wide default can be set through options:

:script_encoding:
    Encoding of Python scripts found in input files, defaults to "ascii".

:template_encoding:
    Encoding of TAL templates found in input files, defaults to "ascii".

Response encoding
-----------------

Ophelia uses unicode internally, but an HTTP response consists of one-byte
characters, so some encoding has to be applied in the end. This encoding is
automatically declared in the page's XML declaration as well as the response
headers. By default, Ophelia encodes responses using UTF-8.

To set the response encoding to, say, latin-1 for a particular resource, do

::

    __request__.response_encoding = "latin-1"

in a script. To affect the response encoding site-wide, set an option:

:response_encoding:
    Encoding of the HTTP response body, default to "utf-8".


Processing of the result
------------------------

By default, the page body is encoded with the response encoding and prefixed
with an XML declaration before being returned by Request.build(). This can be
prevented by an option if the returned value is going to be processed further
instead of being sent directly to the client:

:immediate_result:
    Whether to use the unprocessed result of template evaluation as the
    response content.


Example configuration for the included WSGI server
==================================================

First of all, note that the wsgiref-based server may be usable for development
but certainly not for production. Therefore, its configuration mechanism is
rather simplistic. Create a configuration file, say, ``wsgiref.cfg``,
containing one section named "DEFAULT" that holds all the settings::

    [DEFAULT]
    host = 127.0.0.1
    port = 8080
    template_root = /var/example/templates
    site = http://localhost:8080/

and run the ophelia-wsgiref script on that file::

    $ ophelia-wsgiref wsgiref.cfg

As the example shows, the wsgiref server needs two pieces of additional
information:

:host:
    The network interface to bind to.

:port:
    The TCP port to listen at on that interface.


Example paste configuration
===========================

The simplest possible paste configuration will just run the paste HTTP server
on the Ophelia WSGI application, without any middleware. Create a file, say,
``paste.ini``::

    [server:main]
    use = egg:paste#http
    host = 127.0.0.1
    port = 8080

    [app:main]
    use = egg:ophelia
    set template_root = /var/example/templates
    set document_root = /var/example/documents
    set site = http://localhost:8080/

and run a paste server from it::

    $ paster serve paste.ini
    Starting server in PID 12345.
    serving on http://127.0.0.1:8080


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