Hostout gives you:

• the ability to configure your Fabric commands from within buildout
• a framework for integrating different Fabric scripts via setup tools packages
• an out of the box deployment command for buildout based applications
• plugins to integrate deployment further such as hostout.supervisor and hostout.cloud

Hostout is a framework for managing remote buildouts via fabric scripts. It includes many helpful built-in commands to package, deploy and bootstrap a remote server based on your local buildout.

Hostout is built around two ideas:

1. Sharing your deployment configuration for an application in the same buildout you share with your developers in a team, so where and how your applications is deployed is automated rather than documentation. Deployment then becomes a simple command by any member of the team.
2. Sharing fabric scripts via PyPI so we don't have to reinvent ways to deploy or manage hosted applications.

If you are already a user of Fabric and buildout but aren't interested in the hostout's built-in ability to deploy, then skip ahead to Integrating Fabric into buildout.

You don't need to learn Fabric to use hostout but you will need to learn buildout. The good news is that many buildouts and snippets already exist for building django, pylons, pyramid, plone, zope, varnish, apache, haproxy or whichever server-side technology you want to deploy.

To contribute:

• Code repository: http://github.com/collective/collective.hostout
• Questions and comments to http://github.com/collective/collective.hostout/issues
• Report bugs at http://github.com/collective/collective.hostout/issues

Hostout deploy is a built-in Fabric command that packages your buildout and any development eggs you might have, copies them to the server, prepares the server to run and then runs buildout remotely for you. This makes it simple to deploy your application.

For example, let's say we had the worlds simplest wsgi application. You can use paster to create the package. Go to src and type:

../bin/paster create -t basic_package hellowsgi version=0.1
    description="testing hostout" long_description="" keywords=""
    author="" author_email="" url="" license_name="" zip_safe=False

Then edit src/hellowsgi/hellowsgi/__init__.py as follow:

from webob import Request, Response

def main(global_config, **local_conf):
    return MainApplication()

class MainApplication(object):
    """An endpoint"""

    def __call__(self, environ, start_response):
        request = Request(environ)
        response = Response("Powered by collective.hostout!")
        return response(environ, start_response)

Then edit src/hellowsgi/setup.py and update entry_points as follow:

[...]
entry_points="""
      # -*- Entry points: -*-
      [paste.app_factory]
      main = hellowsgi:main
      """,
[...]

We will create a buildout configuration file called base.cfg :

[buildout]
parts = demo pasterini
develop =
  src/hellowsgi

[demo]
recipe=zc.recipe.egg
eggs =
    PasteScript
    webob
    hellowsgi

[pasterini]
recipe = collective.recipe.template
output = parts/demo/paster.ini
port = 8080
input = inline:
    [server:main]
    use = egg:Paste#http
    host = 0.0.0.0
    port = ${:port}

    [pipeline:main]
    pipeline = app

    [app:app]
    use = egg:hellowsgi#main

Once we bootstrap and build this:

$ python bootstrap.py -c base.cfg
$ bin/buildout -c base.cfg

we have a working wsgi app if you run :

$ bin/paster serve parts/demo/paster.ini

Next you will create a "production buildout" which extends your base.cfg. This might contain parts to install webservers, databases, caching servers etc.

Our prod.cfg is very simple :

[buildout]
extends = base.cfg
parts += supervisor

[supervisor]
recipe=collective.recipe.supervisor
programs=
  10 demo ${buildout:directory}/bin/paster [serve ${pasterini:output}] ${buildout:directory} true

[pasterini]
port = 80

Now create a third buildout file, called buildout.cfg. This will be our development/deployment buildout :

[buildout]
extends = base.cfg
parts += host1

[host1]
recipe = collective.hostout
host = myhost.com
hostos = ubuntu
user = myusername
path = /var/buildout/demo
buildout = prod.cfg
post-commands = bin/supervisord
python-version = 2.6
buildout-group = mygroupname

This buildout part will install a script which will deploy prod.cfg along with hellowsgi to the remote path /var/buildout/demo on our server myhost.com :

$ bin/buildout
Develop: '.../src/hellowsgi'
Uninstalling host1.
Installing demo.
Installing host1.

As part of the buildout process, hostout will automatically save the versions of all the eggs in your development buildout in a file called hostoutversions.cfg and will pin them for you during deployment. This ensures that the production buildout will be running the same software as you have tested locally. Remember to manually version pin any additional eggs you use in your prod.cfg as these will not be pinned for you.

The bin/hostout command takes three kinds of parameters :

hostout [hostname(s)] [commands] [command arguments]

in our case we will run :

$ bin/hostout host1 deploy

The first thing this command will do, is to ask you your password and attempt to login in to your server. It will then look for /var/buildout/demo/bin/buildout and when it doesn't find it it will automatically run another hostout command called bootstrap.

Bootstrap is further broken down into three commands: bootstrap_users, bootstrap_python and bootstrap_buildout. These will create an additional buildout-user to build and run your application, install basic system packages needed to run buildout, and install buildout into your remote path. It will attempt to detect which version of linux your server is running to find the system python, but if this fails it will attempt to compile python from source. The version of python used will match the major version of python which your development buildout uses.

Once hostout bootstrap has ensured a working remote buildout, deployment will continue by running the following commands:

1. uploadeggs: Any develop eggs are released as eggs and uploaded to the server. These will be uploaded directly into the buildout's buildout-cache/downloads/dist directory which buildout uses to find packages before looking up the package index.

   It's very important the packages under development work when packaged, i.e. are capable of being packaged via python setup.py sdist. A common mistake is to rely on setuptools to automatically detect which files should be included but not having the correct setuptools SCM helpers installed if you are using git or hg; e.g. for git do easy_install setuptools-git. This will also upload a pinned.cfg which contains the generated version numbers for the packages under development that have been uploaded.

2. uploadbuildout: The relevant .cfg files and any files/directories in the include parameter are synced to the remote server.

3. buildout: Upload a final pinned.cfg which includes the generated development package versions pins and all the versions of all the dependencies of the development buildout from where the system is being deployed from. These discovered pinned versions are recorded during the local buildout process by the hostout recipe and recorded in a local hostoutversions.cfg file. Buildout is then run on the remote production buildout.

   If you continue to develop your application you can run hostout deploy each time and it will only upload the eggs that have changed and buildout will only reinstall changed parts of the buildout.

In our example above, deployment would look something like this :

$ bin/hostout host1 deploy
running clean
...
creating '...example-0.0.0dev_....egg' and adding '...' to it
...
Hostout: Running command 'predeploy' from 'collective.hostout'
...
Hostout: Running command 'uploadeggs' from 'collective.hostout'
Hostout: Preparing eggs for transport
Hostout: Develop egg src/demo changed. Releasing with hash ...
Hostout: Eggs to transport:
    demo = 0.0.0dev-...
...
Hostout: Running command 'uploadbuildout' from 'collective.hostout'
...
Hostout: Running command 'buildout' from 'collective/hostout'
...
Hostout: Running command 'postdeploy' from 'collective/hostout'
...

Now if you visit myhost.com you will see your web application shared with the world.

Hostout comes with a set of helpful commands. You can show this list by not specifying any command at all. The list of commands will vary depending on what fabfiles your hostout references. :

$ bin/hostout host1
cmdline is: bin/hostout host1 [host2...] [all] cmd1 [cmd2...] [arg1 arg2...]
Valid commands are:
  bootstrap        : Install python and users needed to run buildout
  bootstrap_python :
  bootstrap_users  : create buildout and the effective user and allow hostout access
  buildout         : Run the buildout on the remote server
  deploy           : predeploy, uploadeggs, uploadbuildout, buildout and then postdeploy
  postdeploy       : Perform any final plugin tasks
  predeploy        : Install buildout and its dependencies if needed. Hookpoint for plugins
  setowners        : Ensure ownership and permissions are correct on buildout and cache
  run              : Execute cmd on remote as login user
  sudo             : Execute cmd on remote as root user
  uploadbuildout   : Upload buildout pinned to local picked versions + uploaded eggs
  uploadeggs       : Any develop eggs are released as eggs and uploaded to the server

The run command is helpful to run quick remote commands as the buildout user on the remote host :

$> bin/hostout host1 run pwd
Hostout: Running command 'run' from collective.hostout
Logging into the following hosts as root:
    127.0.0.1
[127.0.0.1] run: sh -c "cd /var/host1 && pwd"
[127.0.0.1] out: ...
Done.

We can also use our login user and password to run quick sudo commands :

$> bin/hostout host1 sudo cat /etc/hosts
Hostout: Running command 'sudo' from collective.hostout
Logging into the following hosts as root:
    127.0.0.1
[127.0.0.1] run: sh -c "cd /var/host1 && cat/etc/hosts"
[127.0.0.1] out: ...
Done.

host

the IP or hostname of the host to deploy to. by default it will connect to port 22 using ssh. You can override the port by using hostname:port

user

The user as which hostout will attempt to login to your host. Will read a user's ssh config to get a default.

password

The password for the login user. If not given then hostout will ask each time.

identity-file

A public key for the login user.

extends

Specifies another part which contains defaults for this hostout.

fabfiles

Path to fabric files that contain commands which can then be called from the hostout script. Commands can access hostout options via hostout.options from the fabric environment.

buildout

The configuration file you wish to build on the remote host. Note that this doesn't have to be the same .cfg as the hostout section is in, but the versions of the eggs will be determined from the buildout with the hostout section in. Defaults to buildout.cfg.

path

The absolute path on the remote host where the buildout will be created. Defaults to '/var/buildout/%s'%name, where name is the name of the part which defines this host.

pre-commands

A series of shell commands executed as root before the buildout is run. You can use this to shut down your application, or to help prepare the environment for buildout. If these commands fail they will be ignored.

post-commands

A series of shell commands executed as root after the buildout is run. You can use this to startup your application. If these commands fail they will be ignored.

sudo-parts

Buildout parts which will be installed after the main buildout has been run. These will be run as root.

parts

Runs the buildout with a parts value equal to this.

include

Additional configuration files or directories needed to run this buildout.

buildout-cache

If you want to override the default location for the buildout-cache on the host.

python-version

The version of python to install during bootstrapping. (Mandatory.)

hostos

Over which platform specific bootstrap_python command is called. For instance if hostos=redhat, bootstrap_python_redhat will be called to use "yum" to install python and other developer tools. This paramter is also used in hostout.cloud to pick which VM to create.

The bootstrap_users command is called as part of the bootstrap process which is called if no buildout has already been bootstrapped on the remote server. This command will login using "user" (the user should have sudo rights) and create two additional users and a group which joins them.

effective-user

This user will own the buildouts var files. This allows the application to write to database files in the var directory but not be allowed to write to any other part of the buildout code.

buildout-user

The user which will own the buildout files. During bootstrap this user will be created and be given a ssh key such that hostout can login and run buildout using this account.

buildout-group

A group which will own the buildout files including the var files. This group is created if needed in the bootstrap_users command. (Mandatory.)

In addition the private key will be read from the location identity_file and be used to create a passwordless login for the buildout-user account by copying the public key into the authorized_keys file of the buildout_user account. If no file exists for identity_file a DSA private key is created for you in the file ${hostname}_key in the buildout directory. During a normal deployment all steps are run as the buildout-user so there is no need to use the user account and therefore supply a password. The exception to this is if you specify pre-deploy, post-deploy or sudo-parts steps or have to bootstrap the server. These require the use of the sudo-capable user account. If you'd like to share the ability to deploy your application with others, one way to do this is to simply checkin the private key file specified by identity_file along with your buildout. If you do share deployment, remember to pin your eggs in your buildout so the result is consistent no matter where it is deployed from. One trick you can use to achieve this is to add hostoutversions.cfg to the extends of your buildout and commit hostoutversions.cfg to your source control as well.

Hostout uses fabric files. Fabric is an easy way to write python that calls commands on a host over ssh.

Here is a basic fabfile which will echo two variables on the remote server.

>>> write('fabfile.py',""" ... ... from fabric import api ... from fabric.api import run ... ... def echo(cmdline1): ... option1 = api.env.option1 ... run("echo '%s %s'" % (option1, cmdline1) ) ... ... """)

Using hostout we can predefine some of the fabric scripts parameters as well as install the fabric runner. Each hostout part in your buildout.cfg represents a connection to a server at a given path.

>>> write('buildout.cfg', ... """ ... [buildout] ... parts = host1 ... ... [host1] ... recipe = collective.hostout ... host = 127.0.0.1:10022 ... fabfiles = fabfile.py ... option1 = buildout ... user = root ... password = root ... path = /var/host1 ... ... """ )

If you don't include your password you will be prompted for it later.

When we run buildout a special fabric runner will be installed called bin/hostout

>>> print system('bin/buildout -N') Installing host1. Generated script '/sample-buildout/bin/hostout'.

>>> print system('bin/hostout') cmdline is: bin/hostout host1 [host2...] [all] cmd1 [cmd2...] [arg1 arg2...] Valid hosts are: host1

We can run our fabfile by providing the

• host which refers to the part name in buildout.cfg,
• command which refers to the method name in the fabfile,
• any other options we want to pass to the command.

Note: We can run multiple commands on one or more hosts using a single commandline.

In our example

>>> print system('bin/hostout host1 echo "is cool"') Hostout: Running command 'echo' from 'fabfile.py' Logging into the following hosts as root: 127.0.0.1 [127.0.0.1] run: echo 'cd /var/host1 && buildout is cool' [127.0.0.1] out: ... Done.

Note that we combined information from our buildout with commandline paramaters to determine the exact command sent to our server.

It can be very helpful to package up our fabfiles for others to use.

Hostout Plugins are eggs with three parts:

1. Fabric script
2. A zc.buildout recipe to initialise the parameters of the fabric file commands
3. Entry points for both the recipe and the fabric scripts

>>> entry_points = {'zc.buildout': ['default = hostout.myplugin:Recipe',], ... 'fabric': ['fabfile = hostout.myplugin.fabfile'] ... },

Once packaged and released others can add your plugin to their hostout e.g.

>>> write('buildout.cfg', ... """ ... [buildout] ... parts = host1 ... ... [host1] ... recipe = collective.hostout ... extends = hostout.myplugin ... param1 = blah ... """ )

>>> print system('bin/buildout')

>>> print system('bin/hostout host1') cmdline is: bin/hostout host1 [host2...] [all] cmd1 [cmd2...] [arg1 arg2...] Valid commands are: ... mycommand : example of command from hostout.myplugin

Your fabfile can get access parameters passed in the commandline by defining them in your function; e.g. :

def mycommand(cmdline_param1, cmdline_param2):
    pass

Your fabfile commands can override any of the standard hostout commands. For instance if you which your plugin to hook into the predeploy process then just add a predeploy function to your fabfile.py :

def predeploy():
   api.env.superfun()

It is important when overridding to call the "superfun" function so any overridden functions are also called.

You can also call any other hostout functions from your command :

def mycommand():
  api.env.hostout.deploy()

The options set in the buildout part are available via the Fabric api.env variable and also via api.env.hostout.options.

You use commands others have made via the extends option. Name a buildout recipe egg in the extends option and buildout will download and merge any fabfiles and other configuration options from that recipe into your current hostout configuration. The following are examples of built-in plugins. Others are available on pypi.

hostout.cloud

Will create VM instances automatically for you on many popular hosting services such as Amazon, Rackspace and Slicehost

hostout.supervisor

Will stop a supervisor before buildout is run and restart it afterwards. It provides some short commands to quickly manage your applications from your hostout commandline.

Managing multiple environments can be a real pain and a barrier to development. Hostout puts all of the settings for all of your environments in an easy-to-manage format.

Compared to

SilverLining

Hostout allows you to deploy many different kinds of applications instead of just wsgi-based python apps. Buildout lets you define the installation of almost any kind of application.

Puppet

TODO

mr.awesome

TODO

Fabric

TODO

Egg Proxies

TODO

Hostout itself requires python 2.6. However it is possible to use hostout with a buildout that requires python 2.4 by using buildout's support for different python interpreters.

>>> write('buildout.cfg', ... """ ... [buildout] ... parts = host1 ... ... [host1] ... recipe = collective.hostout ... host = 127.0.0.1:10022 ... python = python26 ... ... [python26] ... executable = /path/to/your/python2.6/binary ... ... """ )

or alternatively if you don't want to use your local python you can get buildout to build it for you.

>>> write('buildout.cfg', ... """ ... [buildout] ... parts = host1 ... ... [host1] ... recipe = collective.hostout ... host = 127.0.0.1:10022 ... python = python26 ... ... [python26] ... recipe = zc.recipe.cmmi ... url = http://www.python.org/ftp/python/2.6.1/Python-2.6.1.tgz ... executable = ${buildout:directory}/parts/python/bin/python2.6 ... extra_options= ... --enable-unicode=ucs4 ... --with-threads ... --with-readline ... ... """ )

Dylan Jay ( software at pretaweb dot com )