python fabric是否支持动态设置env.hosts？

Question

我想动态更改env.hosts,因为有时我想首先部署到一台机器,检查是否可以然后部署到许多机器.目前我需要首先设置env.hosts,如何在方法中设置env.hosts而不在脚本启动时设置为global？

Answer 1

是的,你可以env.hosts动态设置.我们使用的一种常见模式是:

from fabric.api import env

def staging():
    env.hosts = ['XXX.XXX.XXX.XXX', ]

def production():
    env.hosts = ['YYY.YYY.YYY.YYY', 'ZZZ.ZZZ.ZZZ.ZZZ', ]

def deploy():
   # Do something...

您可以使用它来链接诸如fab staging deploy或之类的任务fab production deploy.

Answer 2

有点迟到了,但是我用ec2这样做了(注意在EC2你不知道ip/hostname可能是什么,一般来说 - 所以你几乎要动态去真正考虑环境/系统如何可能会出现 - 另一种选择是使用dyndns,但这仍然有用):

from fabric.api import *
import datetime
import time
import urllib2
import ConfigParser
from platform_util import *

config = ConfigParser.RawConfigParser()

@task
def load_config(configfile=None):
    '''
    ***REQUIRED***  Pass in the configuration to use - usage load_config:</path/to/config.cfg>
    '''
    if configfile != None:
        # Load up our config file
        config.read(configfile)

        # Key/secret needed for aws interaction with boto 
        # (anyone help figure out a better way to do this with sub modules, please don't say classes :-) )
        global aws_key
        global aws_sec

        aws_key = config.get("main","aws_key")
        aws_sec = config.get("main","aws_sec")

         # Stuff for fabric
        env.user                = config.get("main","fabric_ssh_user")
        env.key_filename        = config.get("main","fabric_ssh_key_filename")
        env.parallel            = config.get("main","fabric_default_parallel")

        # Load our role definitions for fabric
        for i in config.sections():
            if i != "main":
                hostlist = []
                if config.get(i,"use-regex") == 'yes':
                    for x in get_running_instances_by_regex(aws_key,aws_sec,config.get(i,"security-group"),config.get(i,"pattern")):
                        hostlist.append(x.private_ip_address)   
                    env.roledefs[i] = hostlist

                else:
                    for x in get_running_instances(aws_key,aws_sec,config.get(i,"security-group")):
                        hostlist.append(x.private_ip_address)   
                    env.roledefs[i] = hostlist

                if config.has_option(i,"base-group"):
                    if config.get(i,"base-group") == 'yes':
                        print "%s is a base group" % i
                        print env.roledefs[i]
#                       env["basegroups"][i] = True

其中get_running_instances和get_running_instances_by_regex是使用boto的实用程序函数(http://code.google.com/p/boto/)

例如:

import logging
import re
from boto.ec2.connection import EC2Connection
from boto.ec2.securitygroup import SecurityGroup
from boto.ec2.instance import Instance
from boto.s3.key import Key

########################################
# B-O-F get_instances
########################################
def get_instances(access_key=None, secret_key=None, security_group=None):
    '''
    Get all instances. Only within a security group if specified., doesnt' matter their state (running/stopped/etc)
    '''
    logging.debug('get_instances()')
    conn = EC2Connection(aws_access_key_id=access_key, aws_secret_access_key=secret_key)

    if security_group:
        sg = SecurityGroup(connection=conn, name=security_group)
        instances = sg.instances()
        return instances
    else:
        instances = conn.get_all_instances()
        return instances

以下是我的配置的示例:

# Config file for fabric toolset
#
#  This specific configuration is for <whatever> related hosts
#  
#
[main]
aws_key = <key>
aws_sec = <secret>
fabric_ssh_user = <your_user>
fabric_ssh_key_filename = /path/to/your/.ssh/<whatever>.pem
fabric_default_parallel = 1

#
# Groupings - Fabric knows them as roledefs (check env dict)
#

# Production groupings
[app-prod]
security-group = app-prod
use-regex = no
pattern = 

[db-prod]
security-group = db-prod
use-regex = no
pattern = 

[db-prod-masters]
security-group = db-prod
use-regex = yes
pattern = mysql-[d-s]01