fabfile.py

#
# Initial, naive version
#


from fabric.api import *


def _new_rpms():
    """
    Return local filenames for all "new" RPMs.
    """
    return ['some', 'file', 'paths']


@hosts('repository')
def update_repo():
    """
    Push some new RPMs from this workstation to the repository.
    """
    for rpm in _new_rpms():
        put(rpm, '/path/to/repository/root/')
    sudo('/usr/sbin/update_rpm_repo')


@hosts('client1', 'client2', 'client3')
def update_clients():
    """
    Ensure all new RPMs are installed, and update the DB.
    """
    for rpm in _new_rpms():
        sudo('yum install %s' % rpm)
    sudo('/path/to/db/update/script.sh')

fabfile2.py

#
# Version with some rollbacks
#


from fabric.api import *


def _new_rpms():
    """
    Return local filenames for all "new" RPMs.
    """
    return ['some', 'file', 'paths']


@hosts('repository')
def update_repo():
    """
    Push some new RPMs from this workstation to the repository.
    """
    # With no error handling here, any problem will result in termination.
    # If invoked as "fab update_repo update_clients", update_clients will NOT
    # run at all.
    for rpm in _new_rpms():
        put(rpm, '/path/to/repository/root/')
    sudo('/usr/sbin/update_rpm_repo')


@hosts('client1', 'client2', 'client3')
def update_clients():
    """
    Ensure all new RPMs are installed, and update the DB.
    """
    # Keep track of what RPMs have been installed on this host so far.
    installed_rpms = []
    for rpm in _new_rpms():
        with settings(warn_only=True):
            result = sudo('yum install %s' % rpm)
            if result.failed:
                # Rollback: uninstall earlier RPMs, then terminate.
                for rpm in installed_rpms:
                    result = sudo('yum uninstall %s' % rpm)
                    if result.failed:
                        # Rollback failed; tell user to manually clean up.
                        print "Rollback failed on host %s!" % env.host_string
                # Since we return here, any later hosts can still try to run.
                # Change this to abort() to stop completely.
                print "Installation of '%s' failed on host %s! Skipping." % (
                    rpm, env.host_string)
                return
            else:
                # Success: add to list of installed RPMs
                installed_rpms.append(rpm)
    with settings(warn_only=True):
        result = sudo('/path/to/db/update/script.sh')
        if result.failed:
            # Rollback
            print "DB update script failed on host %s! Skipping to next." % env.host_string