I'm writing a Python Flask app to deploy on Heroku. It will use a database. For local development, I'd like to use Sqlite, but when deployed to Heroku I'd like to use Postgresql. How can I achieve this?
I'm stuck because I don't know how to require a different set of packages between my box and the Heroku server.
Were this a Ruby app I would write in my Gemfile
gem "pg", :group => :production
gem "sqlite3", :group => :development
Then Bundler would install the appropriate packages in development and in production. But I don't know any analogous workflow for Python's pip
Well, you have two things to solve.
First, the requirements.txt which isn't that much of a problem. You can either throw all the requirements in the same requirements.txt file, having both database bindings installed doesn't harm anything. If you want to separate, however, just use requirements.txt for deploying, and requirements-dev.txt for local development.
More important is the DB settings itself, and for that you have a one liner solution:
app.config['SQLALCHEMY_DATABASE_URI'] = os.environ.get(
'DATABASE_URL', 'sqlite:////tmp/test.db')
Since DATABASE_URL is set on Heroku, but not on local (make sure this is the case), os.environ.get will not find it, thus reverting to the default, which is the sqlite connection string .
Related
I'm wondering what steps are evolved in moving a django project to a new server.
basicly i'm completely new to Django and have a few questions. The server it is on is now is not stable so I need to act fast. I did not build the app that is there but have pulled down the www folder from the root server. The server is running centOS.
Questions.
is Django backwards compatible or will I need to insure that the same version is installed?
Apart from moving the files what other steps are involved in running the app?
Will I need to use centOS or will any linux server do?
I have a database cluster of PostgreSQL ready to go also.
Start with the docs here - this will give you a good overview.
To your specific questions:
1/ Django is not backwards compatible. You should install 1.6.x. Likely, there's a requirements.txt file in the root directory of your app. On your new server, install pip and then pip install -r requirements.txt will install your dependencies. I would personally use virtualenvwrapper to manage your dependencies on the server
2/ Check the docs, but the main steps are:
Choose a web server. I personally use nginx. You'll need to setup your nginx.conf.
Choose a Python WSGI HTTP Server - I use gunicorn. You'll also need to configure this. This tutorial is a great place to start.
If you use the DigitalOcean tutorial above, any linux server will do. Last, you'll need to upload your Postgres database to the server but sounds like you're able to do that.
3/ You will need to edit your settings.py of the Django project and update certain variables.
If you're changing your database, as well as the app deployment, you'll need to edit the database connection, run ./manage.py syncdb and ./manage.py migrate (if you're using South) to set up the database schema.
It's also recommended to change the SECRET_KEY between deployments.
If you're deploying on a different hosts, you'll need to edit ALLOWED_HOSTS appropriately for your new deployment as well.
Good luck!
Can anyone help to point us to instructions on how to get Django >1.5 working on Google App Engine? I have seen a number of people claim they have Django 1.6 working. We'd like to get 1.6 or 1.7 running. I have searched here for instructions on how to set this up. No luck so far.
Update:
In our development machine we have Django 1.7 installed (both /user/local and on virtualenv). However, if we modify GAE yaml to use Django 1.7 we get the following error messages:
google.appengine.api.yaml_errors.EventError: django version "1.7" is not supported, use one of: "1.2", "1.3", "1.4", "1.5" or "latest" ("latest" recommended for development only) in "./app.yaml",
The version 1.9.12 GoogleAppEngine sdk install in our /Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib directory shows the following Django versions listed:
django-0.96 django-1.2 django-1.3 django-1.4 django-1.5
My question is related to how to get our development environment setup correctly for Django 1.7 on Google App Engine and how to make sure we successfully deploy our app with Django 1.7 when we deploy to Google App Engine in production. How do we get the Django 1.7 to deploy on GAE when we deploy our app?
You can use any pure Python third party libraries in your Google App Engine application. In order to use a third party library, simply include the files in your application's directory, and they will be uploaded with your application when you deploy it to our system. You can import the files as you would any other Python files with your application.
I have application using Django 1.7 this way and everything is working fine. However, sometimes you may need to sort of hack something due to the App Engine limitations and its specifics. But it depends on your use cases.
I would also suggest to use virtual environment for your project. Install each library that is not supported by App Engine directly via pip and then create a symlink in your application directory pointing to the given library.
This way you can keep all required packages in a file (e.g. requirements.txt) that can be stored in SCM system (e.g. Git) along with your source files and other team members can quite easily replicate your working environment.
Provided that you use virtual environment and install all needed libraries (Django, ...) via pip, here is the directory layout that should work for you.
virtual-env-root
.Python
bin
include
lib
app-engine-project-root
app.yaml
django-project-root
django-app-root
symlink-to-django -> lib/python2.7/site-packages/django
symlink-to-another-lib -> lib/python2.7/site-packages/...
Such a layout can be easily deployed with the below command.
$ appcfg.py update app-engine-project-root
Or tested with App Engine development server.
$ dev_appserver.py app-engine-project-root
UPDATE
Since App Engine Python SDK version 1.9.15 you can use the vendoring mechanism to set up third party libraries. You do not have to create symlinks in your application directory pointing to the Python lib folder anymore.
Create lib directory directly in your application root and tell your app how to find libraries in this directory by means of appengine_config.py file.
from google.appengine.ext import vendor
# Add any libraries installed in the "lib" folder.
vendor.add('lib')
New directory layout follows.
virtual-env-root
.Python
bin
include
lib
app-engine-project-root
lib
app.yaml
appengine_config.py
django-project-root
django-app-root
Use pip with the -t lib flag to install libraries in this directory.
$ pip install -t lib [lib-name]
Or
$ pip install -t lib -r requirements.txt
You cannot - GAE only supports 1.5, and even that is marked as experimental. If you need django 1.7, perhaps you should use Google Compute Engine, which is Google's brand name for virtual machines that you can spool up.
If you are not married to Google App Engine, Heroku supports django 1.7 without issues.
Do you have specific a guide on how to move a Django 1.7 project to
Google Compute Engine? There is a bunch of Google stuff without any
guides on how to make them work.
Here are the steps, but they are the same had you deployed on any other server because GCE just gives you a linux instance:
First, make sure your developer account has a billing method attached to it.
Go to the developer console
Create a new project by clicking on Projects, then Create Project.
Wait as the project is being created (you'll see a progress window on the bottom right of your screen).
Once the project is finished creating, the console will automatically shift to that project's settings:
You can create a new instance, or deploy a ready-made template from the second column. You can see there are popular stacks and software applications for which templates are created.
As there is no django template yet, you will start by creating an instance.
Billing is controlled on a per-project basis, so you'll have enable billing at this point if you haven't done so already.
The next page is where you configure the instance. The fields are self-explanatory. You set the type of machine you like (how many virtual CPUs and memory), where (physically) you prefer the machine to be located, if you want both HTTP and HTTPS ports open, and then a disk image from which the instance will boot:
Once you have configured the machine, it will be brought online booted up and then you'll have access to the terminal via SSH.
From this point forward, you should treat this instance like any linux server. Install whatever you need to make your project work using the normal packaging tools; upload your files, etc.
For Amazon, the process is a bit simpler as there is a large library of AMIs that you can use for a one-click deployment process. AMI is Amazon Machine Image - a template from which you can deploy an instance.
For Heroku, as its a PaaS, you don't have to worry about the hardware components; however as with most PaaS platforms, you don't have write access to the filesystem. So to manage your static assets you have to do some extra work. The easiest option is to create a S3 bucket on Amazon and use that with django-storages. The official django tutorial at heroku suggests the use of dj-static to serve files directly from Heroku. This works fine for testing, but if you want to start uploading files, then you need to handle those correctly.
However, once you sort that out the steps are even simpler:
Pre-requisites:
git
heroku toolbelt
dj-database-url Python package
gunicorn Python package
The basic steps:
Create a git repository (if you have not done already) in your source code directory with git init.
Create a requirements.txt at the root of your project. pip freeze > requirements.txt should do it if you are using a virtual environment. Otherwise, you can create a text file and list the packages you need.
Adjust your settings.py, by adding this line at the very bottom: import dj_database_url
DATABASES['default'] = dj_database_url.config()
Create a Procfile (case is important). This is how you tell Heroku what kind of dyno (process) you need for your application. For django, you need a web dyno so in this file the following line should do: web: gunicorn yourproject.wsgi --log-file -
Create an app on Heroku and deploy. You should run these commands from your source code directory:
heroku create --buildpack https://github.com/heroku/heroku-buildpack-python
heroku addons:add heroku-postgresql:dev
git push heroku master
heroku run python yourproject/manage.py migrate --noinput
heroku run python web/manage.py collectstatic
You only do the first two steps once, then whenever you need to update your application simply git push heroku master to create a new revision on Heroku.
App Engine's Python environment currently knows how to provide Django up to version 1.5 via the libraries: configuration mechanism. This doesn't mean that later versions of Django won't work, only that they aren't yet built in. (I'm not sure why the latest built-in version is 1.5. It may have something to do with AE's historical policy of bundling each supported version of Django with the SDK, which probably needs to be revised to keep the SDK from getting too large.)
You can try to include Django 1.7 with your application files. I haven't tried this with 1.7 specifically yet, but it's worked with previous versions. Some adjustments to sys.path will be needed in your main.py.
Note that there is a limit of 10,000 application files. If you're concerned about this limit, one option is to use Python's zipimport and include Django as a zip archive. https://docs.python.org/2/library/zipimport.html
Expanding on this question I am trying to deploy Django on OpenShift but I'm having some problems understanding OpenShift.
I have managed to get as far as setting up a quick app with the git repo https://github.com/openshift/django-example but have the following questions:
Can I develop locally after git cloning to my local? (virtualenv, adding packages)
Packages, what's the deal? local, remote, adding, sycing, virtualenv, git, ...
I came across this line in Nate Aune's PaaS Bakeoff (slide 42) for setup.py and it looks quite useful:
install_requires=open('%s/project.txt' % \
os.environ.get('OPENSHIFT_REPO_DIR', PROJECT_ROOT)).readlines(),
(because I know I can pip freeze > requirments.txt in my virtualenv)
... Is %s/project.txt in wsgi or tthe directory below wsgi? Do I have to set PROJECT_ROOT with some funky os stuff?
EDIT
Basically:
Is it best to ssh into your OpenShift application (lest say you have a dev one) and work there or work off a local copy?
How do you install python packages after you have ssh'ed in to your OpenShift app? (virtualenv)
If you ssh'ed into your OpenShift app do you have to do anything after: creating a project, creating an app (manage.py startapp ...), changing code in your django app
If local is the best option:
How do I use the example locally?
Do I need to setup a virtualenv to work locally?
How do I make sure the python packages django needs are on OpenShift?
How do I add python packages to my OpenShift version (I'm presuming git doesn't do that)
I would suggest developing in a local copy.
In my experience there is no reason to ssh in, unless if you
need to perform one-of operation (migrating databases for example)
The requirements for the openshift app are specified in the setup.py file.
install_requires=['Django>=1.6.0', 'redis>=2.0']
Locally you can of course work in a virtualenv
I was facing a similar situation and found the answer provided by Luis Masuelli to the question posted here very informative. Hope it might help you.
I've got a standard run of the mill Pylons Pyramid application, that uses SQLAlchemy for its database persistence.
I have set up an SQLAlchemy-migrate repo and have it functioning, but I really want to have the ability to use paster to upgrade and downgrade the database, or at least some way of having the user (after installing the egg) upgrade/downgrading the database to the version required.
I've got it built-into my app now, so upon app startup it does the version upgrade, but I would rather go with something where the user explicitly has to upgrade the database so that they know exactly what is going on, and know to make backups beforehand.
How would I go about that? How do I add commands to paste?
The way users would set up the application is:
paste make-config appname production.ini
paste setup-app production.ini#appname
To set it up the first time, to do the database upgrade or upgrade in general I would want:
paste upgrade-app production.ini#appname
Or something along those lines.
You can create your own paster command, e.g. upgrade-app, and then call it from anywhere with paster --plugin=appname upgrade-app /path/to/production.ini appname. You can refer to how pyramid implements the PShellCommand.
It's not quite what you're looking for, but one way I handle this is with Fabric commands. My OSS app I have a fabric command you run that creates a .ini file for your app and then, after you adjust the sqlalchemy.url in it, you run a fabric command that init's SA migrations and runs the upgrade. From then on, to upgrade you run fab db_upgrade.
http://bmark.us/install.html
is an example of the install docs I have setup.
https://github.com/mitechie/Bookie/blob/master/fabfile/database.py
Is the set of db specific commands available through the Fabric interface.
I am trying to create my first site in Django and as I'm looking for example apps out there to draw inspiration from, I constantly stumble upon a term called "reusable apps".
I understand the concept of an app that is reusable easy enough, but the means of reusing an app in Django are quite lost for me. Few questions that are bugging me in the whole business are:
What is the preferred way to re-use an existing Django app? Where do I put it and how do I reference it?
From what I understand, the recommendation is to put it on your "PYTHONPATH", but that breaks as soon as I need to deploy my app to a remote location that I have limited access to (e.g. on a hosting service).
So, if I develop my site on my local computer and intend to deploy it on an ISP where I only have ftp access, how do I re-use 3rd party Django apps so that if I deploy my site, the site keeps working (e.g. the only thing I can count on is that the service provider has Python 2.5 and Django 1.x installed)?
How do I organize my Django project so that I could easily deploy it along with all of the reusable apps I want to use?
In general, the only thing required to use a reusable app is to make sure it's on sys.path, so that you can import it from Python code. In most cases (if the author follows best practice), the reusable app tarball or bundle will contain a top-level directory with docs, a README, a setup.py, and then a subdirectory containing the actual app (see django-voting for an example; the app itself is in the "voting" subdirectory). This subdirectory is what needs to be placed in your Python path. Possible methods for doing that include:
running pip install appname, if the app has been uploaded to PyPI (these days most are)
installing the app with setup.py install (this has the same result as pip install appname, but requires that you first download and unpack the code yourself; pip will do that for you)
manually symlinking the code directory to your Python site-packages directory
using software like virtualenv to create a "virtual Python environment" that has its own site-packages directory, and then running setup.py install or pip install appname with that virtualenv active, or placing or symlinking the app in the virtualenv's site-packages (highly recommended over all the "global installation" options, if you value your future sanity)
placing the application in some directory where you intend to place various apps, and then adding that directory to the PYTHONPATH environment variable
You'll know you've got it in the right place if you can fire up a Python interpreter and "import voting" (for example) without getting an ImportError.
On a server where you have FTP access only, your only option is really the last one, and they have to set it up for you. If they claim to support Django they must provide some place where you can upload packages and they will be available for importing in Python. Without knowing details of your webhost, it's impossible to say how they structure that for you.
An old question, but here's what I do:
If you're using a version control system (VCS), I suggest putting all of the reusable apps and libraries (including django) that your software needs in the VCS. If you don't want to put them directly under your project root, you can modify settings.py to add their location to sys.path.
After that deployment is as simple as cloning or checking out the VCS repository to wherever you want to use it.
This has two added benefits:
Version mismatches; your software always uses the version that you tested it with, and not the version that was available at the time of deployment.
If multiple people work on the project, nobody else has to deal with installing the dependencies.
When it's time to update a component's version, update it in your VCS and then propagate the update to your deployments via it.