Activate a virtualenv via fabric as deploy user

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I want to run my fabric script locally, which will in turn, log into my server, switch user to deploy, activate the projects .virtualenv, which will change dir to the project and issue a git pull.

def git_pull():
    sudo('su deploy')
    # here i need to switch to the virtualenv
    run('git pull')

I typically use the workon command from virtualenvwrapper which sources the activate file and the postactivate file will put me in the project folder. In this case, it seems that because fabric runs from within shell, control is give over to fabric, so I can't use bash's source built-in to '$source ~/.virtualenv/myvenv/bin/activate'

Anybody have an example and explanation of how they have done this?

10 Answers

Right now, you can do what I do, which is kludgy but works perfectly well* (this usage assumes you're using virtualenvwrapper -- which you should be -- but you can easily substitute in the rather longer 'source' call you mentioned, if not):

def task():
    workon = 'workon myvenv && '
    run(workon + 'git pull')
    run(workon + 'do other stuff, etc')

Since version 1.0, Fabric has a prefix context manager which uses this technique so you can for example:

def task():
    with prefix('workon myvenv'):
        run('git pull')
        run('do other stuff, etc')

* There are bound to be cases where using the command1 && command2 approach may blow up on you, such as when command1 fails (command2 will never run) or if command1 isn't properly escaped and contains special shell characters, and so forth.

This approach worked for me, you can apply this too.

from fabric.api import run 
# ... other code...
def install_pip_requirements():
    run("/bin/bash -l -c 'source venv/bin/activate' "
        "&& pip install -r requirements.txt "
        "&& /bin/bash -l -c 'deactivate'")

Assuming venv is your virtual env directory and add this method wherever appropriate.

I use pyenv with plugin pyenv-virtualenvwrapper. I had no success with workon, instead I use this (fabric 2.5):

with c.prefix('source /home/mirek/.virtualenvs/%s/bin/activate' % PROJECT):
    with c.prefix('cd /home/mirek/%s/%s' % (PROJECT, PROJECT)):
        c.run('python manage.py ....')

For git pull agent forwarding is good, ie. ssh -A .. or better in ~/.ssh/config something like this:

Host forpsi
    HostName xx.xx.xx.xx
    IdentityFile /home/mirek/.ssh/id_ed25519_xxx
    ForwardAgent yes

And now on the development machine if you have a private key in the agent (after ssh-add or if you have AddKeysToAgent yes in ~/.ssh/config after you made git push) then git pull should not ask for the passphrase of the key.

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