python - 如何仅在单个主机上运行 @roles-decorated 结构任务

Question

我有一个用 @roles 装饰的任务，我偶尔想在单个主机上运行它(用于金丝雀测试部署)。

from fabric.api import *

env.roledefs = {
    'web-workers': ['django@worker1', 'django@worker2'],
    'some-other-role': ['django@worker2'],
}

@task
@roles('web-workers')
def bogomips():
    run('uptime')

docs for @roles指出:

...barring an override on the command line, my_func will be executed against the hosts listed [in the role]...

但是我无法让此处提到的“覆盖”功能起作用......我已经尝试过:

$ fab bogomips -H django@worker2
$ fab bogomips -R some-other-role

但它总是在装饰器中提到的整个角色上执行......

我在这里缺少什么？如何覆盖 @roles 修饰的任务的运行位置？

Answer 1

根据Execution model's Order of Precedence，这实际上是预期的行为，并且在此场景中您必须使用稍微不同的语法。

所以这是不起作用的命令:

$ fab bogomips -R some-other-role # fabric ignores the -R values!

这是有效的版本:

$ fab bogomips:roles=some-other-role

问题如下:#308: @roles and @hosts decorators ignore command line options

文档:http://docs.fabfile.org/en/1.0.0/usage/execution.html#order-of-precedence

• Per-task, command-line host lists (fab mytask:host=host1) override absolutely everything else.
• Per-task, decorator-specified host lists (@hosts('host1')) override the env variables.
• Globally specified host lists set in the fabfile (env.hosts = ['host1']) can override such lists set on the command-line, but only if you’re not careful (or want them to.)
• Globally specified host lists set on the command-line (--hosts=host1) will initialize the env variables, but that’s it.