gistfile1.txt

    def upgrade_list(self, instructions):
        status = self.upgrade_status()
        updates = {'roles': [], 'hosts': []}
        # parse rolling_rules from instructions
        if instructions.get('rolling_rules'):
            # reformat upgrade status to be keyed off role
            pending  = self.key_host_list_off_role(status['pending'])
            upgraded = self.key_host_list_off_role(status['upgraded'])
            upgrading = self.key_host_list_off_role(status['upgrading'])
            # get the upgrade instructions
            roles = instructions['rolling_rules'].get('roles')
            global_num = instructions['rolling_rules'].get('global')
            # iterate through all things that are pending
            for role, hosts in pending.iteritems():
                # for every role that is still pending,
                # figure out if we need to update any hosts of that
                # role
                # zero means just upgrade everything
                number = 0
                # figure out the rolling_upgrade number
                num = roles.get(role) or global_num
                if num == 0 or num => len(hosts) + len(upgrading[role])
                    # append role as ready to be upgraded
                    updates['roles'].append(role)
                elif len(upgrading[role]) < num
                    num_hosts = num - len(upgrading[role])
                    # append the first N num_hosts, sort to reduce race conditions
                    updates['roles'].append(sorted(hosts)[:num_hosts])
        return updates