将Django应用迁移到多台服务器

Question

I'd like to migrate a django app to multiple hosts with a fabfile. The problem is all hosts connects to same database (in another server) and migrate command runs for each host.

I may select one host as master and run migrate command only from master but wonder if there is more elegant and proper solution for this.

fabfile.py

def migrate():
    virtualenv('python manage.py makemigrations')
    virtualenv('python manage.py migrate')

def prod():
    env.user = 'myuser'
    env.hosts = ['X1', 'X2']

Answer 1

You have about three options.

There is a @runs_once decorator you can use. Documented here . Where you'd just do something like:

@runs_once
def migrate():
    virtualenv('python manage.py makemigrations')
    virtualenv('python manage.py migrate')

def prod():
    env.user = 'myuser'
    env.hosts = ['X1', 'X2']``

Called like:

$ fab -R myRole migrate update

You can also just apply specific roles to use on said tasks which is shown here :

from fabric.api import run, roles

env.roledefs = {
    'db': ['db1'],
    'web': ['web1', 'web2', 'web3'],
}

@roles('db')
def migrate():
    # Database stuff here.
    pass

@roles('web')
def update():
    # Code updates here.
    pass

Called like:

$ fab migrate update

And if you'd like to get more fine grained those same functions can be coupled with the execute() function (as is shown in that section's docs) and make a deploy function that calls those other tasks for you. Looking like this:

def deploy():
    execute(migrate)
    execute(update)

Called like:

 $ fab deploy