#Hendrix ###Twisted meets Django: Making deployment easy

Hendrix is a multi-threaded, multi-process and asynchronous web server for Django projects. The idea here is to have a highly extensible wsgi deployment tool that is fast, transparent and easy to use.

###Features

• Multi-processing - The WSGI app can be served from multiple processes on a single machine. Meaning that it can leverage multicore servers.
• Optional Resource Caching - Process distributed resource caching, dynamically serving gzipped files. It's also possible to extend the current caching functionality by subclassing the hendrix CacheService and adding a reference to that subclass within a HENDRIX_SERVICES tuple of tuples e.g. (('name', 'app.MyCustomCache'),) in your Django settings file. Just use the --nocache flag to turn caching off.
• Built-in SSL Support - SSL is also process distributed, just provide the options --key /path/to/private.key and --cert /path/to/signed.cert to enable SSL and process distributed TLS
• Multi-threading from within Django - Enables the use of Twisted's defer module and deferToThread and callInThread methods from within Django
• Built-in Websockets Framework
• Daemonize by passing the -d or --daemonize flags to hx

###Installation

pip install -e git+git@github.com:hangarunderground/hendrix.git@master#egg=hendrix

###Deployment/Usage

Hendrix leverages the use of custom django management commands. That and a little bash magic makes hx available as a shortcut to all of the functionality you'd expect from python manage.py hx.

Include hendrix in your project's INSTALLED_APPS list

INSTALLED_APPS = (
    ...,
    'hendrix',
    ...
)

Change your working directory to where manage.py lives:

cd /path/to/project/

#####For help and a complete list of the options:

hx -h

or

hx --help

#####Starting a server with 4 processes (1 parent and 3 child processes):

hx start -w 3

#####Stoping that server:

hx stop

Note that stoping a server is dependent on the settings file and http_port used.

E.g. Running a server on port 8000 with local_settings.py would yield 8000_local_settings.pid which would be used to kill the server. I.e. if you start with hx start --settings local_settings then stop by hx stop --settings local_settings

#####Restarting a server:

hx restart

###Serving Static Files Serving static files via Hendrix is optional but easy.

a default static file handler is built into Hendrix which can be used by adding the following to your settings:

HENDRIX_CHILD_RESOURCES = (
    'hendrix.contrib.resources.static.DefaultDjangoStaticResource',
)

No other configuration is necessary. You don't need to add anything to urls.py.

You can also easily create your own custom static or other handlers by adding them to HENDRIX_CHILD_RESOURCES.

###Running the Development Server

hx start --reload

This will reload your server every time a change is made to a python file in your project.

#####Using "dev" mode You can also use the development mode, which colourfully prints requests.

hx start --dev

You could also mix it up with other options:

hx start --dev --reload --w 2

or

hx start --settings production_settings --dev

etcetera...

###SSL This is made possible by creating a self-signed key. First make sure you have the newest patched version of openssl. Then generate a private key file:

openssl genrsa > key.pem

Then generate a self-signed SSL certificate:

openssl req -new -x509 -key key.pem -out cacert.pem -days 1000

Finally you can run single SSL server by running:

hx start --dev --key key.pem --cert cacert.pem

or a process distributed set of SSL servers:

hx start --dev --key key.pem --cert cacert.pem -w 3

Just go to https://[insert hostname]:4430/ to check it out. N.B. Your browser will warn you not to trust the site... You can also specify which port you want to use by passing the desired number to the --https_port option

###Caching

At the moment a caching server is deployed by default on port 8000. Is serves gzipped content, which is pretty cool - right?

#####How it works

The Hendrix cache server is a reverse proxy that sits in front your Django app. However, if you wanted to switch away from the cache server you can always point to the http port (default 8080).

It works by forwarding requests to the http server running the app and caches the response depending on the availability of max-age [seconds] in a Cache-Control header.

#####Busting the cache

Note that you can bust the cache (meaning force it not to cache) by passing a query in your GET request e.g. http://somesite.com/my/resource?somevar=test. You can also force the query to cache by specifying cache=true in the query e.g. http://somesite.com/my/resource?somevar=test,cache=true (so long as a max-age is specified for the handling view). What this means is that you can let the browser do some or none of the js/css caching if you so want.

#####Caching in Django

In your project view modules use the cache_control decorator to add a max-age of your choosing. e.g.

from django.views.decorators.cache import cache_control

@cache_control(max_age=60*60*24)  # cache it for a day
def homePageView(request):
    ...

and that's it! Hendrix will do the rest. Django docs examples here

#####Turning cache off

You can turn caching off by passing the flags -n or --nocache. You can also change which port you want to use with the --cache_port option.

#####Global Vs Local

If you're running multiple process using the -w or --workers options caching will be process distributed by default. Meaning there will be a reverse proxy cache server for each process. However if you want to run the reverse proxy server on a single process just use the -g or --global_cache flags.

... here "local" means local to the process.

###Testing Tests live in hendrix.tests and are most easily run using nose.

/home/jsmith:~$ nosetests -v
test_multiprocessing (hendrix.tests.deploy_tests.DeployTests) ... ok
A test to ensure that HendrixDeploy.options also has the complete set ... ok
A placeholder test to ensure that instantiating HendrixDeploy through ... ok
...
[insert more tests here... given time]

----------------------------------------------------------------------
Ran >3 tests in >1.012s

OK

Adding tests is pretty straight forward - just add a module under hendrix.tests with the suffix _tests.py e.g. cache_tests.py. Inside that newly created module add any number of unittest.TestCase subclasses as you please. N.B. that in the hendrix.tests __init__.py file a subclass of TestCase called HendrixTestCase has been created to help tests various use cases of hendrix.deploy.HendrixDeploy

###Contributions Contributions are more than welcome. Feedback and bug reports especially.

Unfortunately a majority of the codebase is not covered by tests. This means that if you want to make changes to Hendrix you'll need to click around to see if it works. We're working hard to change this so please bare with us until then.

###Twisted Twisted is what makes this all possible. Mostly. Check it out here.

###Yet to come

• Ensure stability of current implementation of web sockets
• Load Balancing
• Twisted logging
• Cache regex logic/config file
• Ansible deployment utility
• Salt deployment utility
• more tests...

###History It started as a fork of the slashRoot deployment module.

The name is the result of some inane psychological formula wherein the 'twisted' version of Django Reinhardt is Jimi Hendrix.

Hendrix is currently maintained by Reelio.