Pyramid Deploymentand Maintenance

Carlos de la Guardia

Plone Conference 2011

So, your application is ready and looking good

Time to deploy it and see how it holds up

Deployment with NginXMore information at: http://docs.pylonsproject.org/projects/pyramid_cookbook/dev/deployment/nginx.html

upstream myapp-site { server 127.0.0.1:5000; server 127.0.0.1:5001;}server { server_name example.com; access_log /home/example/env/access.log; location / { proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header X-Forwarded-Proto $scheme; proxy_connect_timeout 60s; proxy_send_timeout 90s; proxy_read_timeout 90s; proxy_buffering off; proxy_pass http://myapp-site; proxy_redirect off; }}

Deployment with Apache and Mod_WSGI

We need to create an app that will call our application with configuration. Then we set up apache to call this app.

More information at:http://docs.pylonsproject.org/projects/pyramid/1.2/tutorials/modwsgi/index.html

#pyramid.wsgifrom pyramid.paster import get_appapplication = get_app('/mydir/modwsgi/env/myapp/production.ini', 'main')

#apache.confWSGIApplicationGroup %{GLOBAL}WSGIPassAuthorization OnWSGIDaemonProcess pyramid user=cguardia group=staff threads=4 \ python-path=/mydir/modwsgi/env/lib/python2.6/site-packagesWSGIScriptAlias /myapp /mydir/modwsgi/env/pyramid.wsgi<Directory /mydir/modwsgi/env> WSGIProcessGroup pyramid Order allow,deny Allow from all</Directory>

To paste or not to paste

Paster is not considered a super fast wsgi server, but it's good enough for many use cases.

We already discussed mod_wsgi. If you are sure that you need something else, people on our mailing lists have reported success with uWSGI and gUnicorn.

If you are using ZODB with paster, consider using Jove to manage multiple sites and settings consistently:

Putting all your eggs in the same basket

Your very own package index

Create an egg directory inside an Apache web server or similar and use a simple script to generate the index in PyPI format.

Create an egg directory using a GitHub site and generate the index with the same script.

Install a PyPI clone like ClueReleaseManager, and configure your .pypirc file to point at the clone. Use setuptools to upload.

Jarn.mkrelease can be used to commit, tag and upload in one step:

Using Buildout with Pyramid

Buildout is a Python system for assembling applications from multiple parts in a repeatable manner.

Recipes are used to define what each part of the buildout will install and/or setup. There are many available recipes on PyPI.

A buildout can have different configurations. For example, deployment and production.

Buildout can be used to setup a Pyramid application and it's dependencies easily.

Sample buildout[buildout]parts = myapp mkrelease

Develop = src/mypackage

index = http://example.github.com/myapp/staging/index/

[myapp]recipe = zc.recipe.eggeggs = some_dependency mypackageinterpreter = py

[mkrelease]recipe = zc.recipe.eggeggs = jarn.mkreleasescripts = mkrelease

Supervisor

Supervisor is a client/server system that allows its users to monitor and control a number of processes on UNIX-like operating systems.

We can use supervisor to control our pyramid applications, either alone or together with other applications or services.

A very easy way to configure it is to simply add the supervisor egg to our buildout and include a configuration file.

Sample supervisor configuration[inet_http_server]port=127.0.0.1:9001

[supervisord]logfile=%(here)s/var/supervisord.loglogfile_maxbytes=50MBlogfile_backups=10loglevel=infopidfile=%(here)s/var/supervisord.pid

[rpcinterface:supervisor]supervisor.rpcinterface_factory = supervisor.rpcinterface:make_main_rpcinterface

[supervisorctl]serverurl=http://127.0.0.1:9001

[program:core]command = %(here)s/bin/paster serve %(here)s/src/inav2_core/development.iniredirect_stderr = true

Useful maintenance tools

Scripting Pyramid

Web applications usually expect to interact with a request object of some kind and return a response.

Importing web application code from a command line script will not work when it depends on a request.

Pyramid offers a facility for generating an environment similar to what the application would get from a real request.

This makes it possible to easily write scripts for

Writing the scriptTo generate the proper environment we use

pyramid.paster.bootstrap, like this:

from pyramid.paster import bootstrapenv = bootstrap('/path/to/my/development.ini')print env['request'].route_url('home')

We get back a dictionary with:

sequest

app

root

registry

Exception logging with pyramid_exclog

[loggers]keys = exc_logger

[handlers]keys = exc_handler

[formatters]keys = exc_formatter

[logger_exc_logger]level = ERRORhandlers = exc_handlerqualname = exc_logger

[handler_exc_handler]class = handlers.SMTPHandlerargs = (('localhost', 25), 'from@example.com', ['to@example.com'], 'myapp Exception')level = ERRORformatter = exc_formatter

[formatter_exc_formatter]format = %(asctime)s %(message)s

Backups

For ZODB based applications:

Collective.recipe.backup

For Postgres based applications:

SQL dump

File system level backup

Continuous archiving

Do not forget about staging

Thinking about staging

A good deployment plan requires a good staging strategy.

It's important to be able to quickly deploy changes to staging before trying them in production.

Ideally, multiple branches could be deployed separately.

Take a look at octomotron:https://github.com/chrisrossi/octomotron

So much to do, so little time

Other deployment related tasks and decisions

Caching

Monitoring

Failover

Replication

Automated deployment

More...

Case Study: KARL

Open source web system for collaboration, organizational intranets, and knowledge management.

Mission-critical application used by organizations such as Open Society Foundations and Oxfam.

5000+ users (no anonymous access).

More than 75,000 Pages of content.

Nearly 100,000 lines of code.

How is KARL deployed?

Toolchain: Nginx, HAProxy, Paste, running under Supervisor.

Buildout for environment creation.

Custom package index stored on GitHub.

1 App Server, 1 DB Server.

Uses ZODB with RelStorage and PGTextIndex.

Deployment is done with a Python script that creates a parallel environment, backs up and evolves data, then restarts the instance.

Thank You!

Email: cguardia@yahoo.com

IRC: #pyramid, #pylons

http://groups.google.com/group/pylons-devel

Goodbye!