织物 env.hosts 未被识别

Question

我有一个简单的 fabfile 名称 env_fabfile.py

# env_fabfile.py
# makes use of fab env variables 

from fabric.api import env, run
def login():
    env.hosts = ['user@host1:1234', 'user@host2:2345']
    env.passwords = {'user@host1:1234': 'pass1', 'user@host2:2345': 'pass2'}
    env.parallel=True

def run_lsb_release():
    run('lsb_release -a')

现在我使用 fab 命令运行上述代码：

fab -f env_fabfile.py login run_lsb_release

它完美运行（并行）并提供所需的输出

现在我想实际计算同一脚本串行运行与并行运行之间的时间差。为此，我编写了以下 python 脚本： timecal.py

# timecal.py
# runs the fabfile once in serial and calculates the time
# then runs the same file in parallel and calculates the time

from fabric.api import env, run
import time

def login():
    print "in login"
    env.hosts = ['user@host1:1234', 'user@host2:2345']
    env.passwords = {'user@host1:1234': 'pass1', 'user@host2:2345': 'pass2'}

def parallel(status):
    print "in parallel"
    env.parallel=status

def run_lsb_release():
    print "in run"
    run('lsb_release -a')

def do_serial():
    start_time = time.time()
    parallel(False)
    login()
    run_lsb_release()
    elapsed_time = time.time() - start_time
    return elapsed_time

def do_parallel():
    start_time = time.time()
    parallel(True)
    login()
    run_lsb_release()
    elapsed_time = time.time() - start_time
    return elapsed_time


if __name__ == '__main__':  
    print "Running in serial mode "
    print "Total time taken ", do_serial()

    print "Running in parallel mode"
    print "Total time taken ", do_parallel()

但是当我运行 timecal.py 作为

python timecal.py

我在标准输出上得到以下信息（除了代码中的打印语句）

未找到主机。请指定（单个）主机字符串进行连接：

我不明白为什么？另外如何纠正脚本以便我可以实现我想要的（如上面的问题所述）

如果我尝试不同版本的 timecal.py，如：

from fabric.api import run, settings, env
import time

def do_parallel():
    start_time = time.time()
    env.hosts = ['user@host1:1234', 'user@host2:2345']
    env.passwords = {'user@host1:1234': 'pass1', 'user@host2:2345': 'pass2'}
    env.parallel=True
    run('lsb_release -a')
    elapsed_time = time.time() - start_time
    return elapsed_time

def do_serial():
    start_time = time.time()
    with settings(host_string='host1', port=1234, user='user', password='pass1'):
        run('lsb_release -a')
    with settings(host_string='host2', port=2345, user='user', password='pass2'):
        run('lsb_release -a')
    elapsed_time = time.time() - start_time
    return elapsed_time

if __name__ == '__main__':  
    try:
        print "Running in parallel mode"
        print "Total time taken ", do_parallel()

        print "Running in serial mode "
        print "Total time taken ", do_serial()
    except Exception as e:
        print e

我收到以下错误：

致命错误：需要提示输入目标主机连接字符串（主机：无），但在并行模式下输入会不明确

我不明白为什么主机：这里没有？代码有什么问题？

Answer 1

简短的回答是您不应该按照您当前的方式设置env.hosts 值，env.passowrds 是超级粗略的（可能坏了？），it's recommended to use SSH key-based access，尤其是leveraging native SSH config files。

这是你的 timecal.py 脚本的修改版本，它可以按预期工作，我将在下面列出一些不同之处。

# timecal.py
# runs the fabfile once in serial and calculates the time
# then runs the same file in parallel and calculates the time

from fabric.api import env, run, execute, parallel
import time

env.use_ssh_config = True
env.roledefs = {
    "my_servers": ['server_1', 'server_2']
}


def run_lsb_release():
    print "in run"
    run('lsb_release -a')


def do_task(task_func):
    start_time = time.time()
    execute(task_func, roles=['my_servers'])
    elapsed_time = time.time() - start_time
    return elapsed_time


if __name__ == '__main__':
    print "Running in serial mode "
    print "Total time taken ", do_task(run_lsb_release)

    print "Running in parallel mode"
    print "Total time taken ", do_task(parallel(run_lsb_release))

主要区别在于使用 env.roledefs 和 SSH 配置文件，而不是主机和密码。由于这些任务是在单独的线程中执行的，因此这些值在并行执行模式下将不起作用。 The docs 有点瘦，但这基本上就是你遇到这个问题的原因。