如何使用Postgres在Heroku上安装应用

Question

I am trying to install an app in Heroku cloud. This python based app is built on postgresql. I have set up this app in my local machine(Ubuntu). I have following queries.

1. How to install postgresql for this app on heroku?
2. Do I have to make same set up again on Heroku as I did on local machine? Like setting up of Flask etc.?
3. Can I submit code in many stages? eg I have pushed code, after some time modified same code and pushed again.

I have already gone through following url https://devcenter.heroku.com/articles/git#deploying-code but didn't got any satisfactory answer.

Thanks Sanjeev Yadav

Answer 1

Assuming you have heroku belt installed on your computer, create git repository inside your project(which you probably already have) then create Heroku app:

heroku create --stack cedar <name_of_your_app>

First add Postgresql to your project:

heroku addons:add heroku-postgresql

after that check if it has been added succesfully:

heroku pg:info

This should return something like:

HEROKU_POSTGRESQL_WHITE_URL <== Database name
Plan:        Dev
Status:      available

Then promote the database so heroku knows which one you will be using (you can have several databases in one project).

heroku pg:promote HEROKU_POSTGRESQL_WHITE_URL

At this point if you want to configure your database connections you can either get all the connection info from Heroku page of your project or from environment variable DATABASE_URL which was created when you promoted the database. If you use the latter you don't have to provide any info yourself, the function that i use frequently is something in this lines:

if "DATABASE_URL" in os.environ:
        urlparse.uses_netloc.append("postgres")
        url = urlparse.urlparse(os.environ.get("DATABASE_URL"))
        DATABASE = {
             "database" : url.path[1:],
             "user" : url.username,
             "password": url.password,
             "host": url.hostname,
             "port": url.port
               }
        return PostgresqlDatabase(**DATABASE)

This is for peewee ORM , but you can adapt it to any other ORM like SQLAlchemy, just take what's in DATABASE and plug it in to whatever you want.

A far as setting up your application, you need to write requirements.txt file with all dependencies that your app uses, this will automatically be parsed and all libraries installed when you first push your project to Heroku, also you need Procfile file inside your project, this tells Heroku which processes to run at which stage, the most important part is web part for instance:

web: gunicorn main:app

will start gunicorn server serving your site. If you need to run any scripts, for instance script that creates the tables in your database simply type:

heroku run create_tables.py

from within your repository.

As far as last question goes - yes you can push your code in many stages, your app will be restarted and all new code should work same as on your local machine. Hope this helps.