一、背景说明

基于Ansible1.1源码学习

二、目录结构

ansible核心目录

ansible
├─bin    # 入口命令
│    ├─ansible
│    ├─ansible-doc
│    ├─ansible-playbook
│    ├─ansible-pull
├─lib   # 核心代码
│  └─ansible
│      ├─callback_plugins   # 回调插件
│      ├─inventory
│      │  └─vars_plugins    # 参数
│      ├─playbook           # 剧本
│      ├─runner
│      │  ├─action_plugins
│      │  ├─connection_plugins
│      │  ├─filter_plugins
│      │  └─lookup_plugins
│      └─utils
├─library    # ansible内置模块

三、核心代码

1. ansible获取ansible.cfg的函数

lib/ansible/constants.py

def load_config_file():
    p = ConfigParser.ConfigParser()
    path1 = os.path.expanduser(os.environ.get('ANSIBLE_CONFIG', "~/.ansible.cfg")) # 配置
    path2 = os.getcwd() + "/ansible.cfg" # 命令行传入
    path3 = "/etc/ansible/ansible.cfg"  # 默认路径

    if os.path.exists(path1):
        p.read(path1)
    elif os.path.exists(path2):
        p.read(path2)
    elif os.path.exists(path3):
        p.read(path3)
    else:
        return None
    return p

2. 插件加载函数

主要功能有两个：

• 动态加载插件（py文件）：imp.load_source
  • imp.load_source是python2的方法
  • python3的替代方法是: importlib.import_module
• 通过字典_module_cache 缓存插件
  lib/ansible/utils/plugins.py

import os
import sys
import glob
import imp
import ansible.constants as C
from ansible import errors

_basedirs = []

def push_basedir(basedir):
    _basedirs.insert(0, basedir)

class PluginLoader(object):
    """PluginLoader loads plugins from the best source

    It searches for plugins by iterating through the combined list of
    play basedirs, configured paths, and the installed package directory.
    The first match is used.
    """
    def __init__(self, class_name, package, config, subdir, aliases={}):
        """Create a new PluginLoader"""
        self.class_name = class_name
        self.package = package
        self.config = config
        self.subdir = subdir
        self.aliases = aliases
        self._module_cache = {}
        self._extra_dirs = []

    def _get_package_path(self):
        """Gets the path of a Python package"""
        if not self.package:
            return []
        if not hasattr(self, 'package_path'):
            m = __import__(self.package)
            parts = self.package.split('.')[1:]
            self.package_path = os.path.join(os.path.dirname(m.__file__), *parts)
        return [self.package_path]

    def _get_paths(self):
        """Return a list of paths to search for plugins in

        The list is searched in order."""
        ret = []
        ret += self._extra_dirs
        for basedir in _basedirs:
            fullpath = os.path.join(basedir, self.subdir)
            if fullpath not in ret:
                ret.append(fullpath)
        ret += self.config.split(os.pathsep)
        ret += self._get_package_path()
        return ret

    def add_directory(self, directory, with_subdir=False):
        """Adds an additional directory to the search path"""
        if directory is not None:
            if with_subdir:
                directory = os.path.join(directory, self.subdir)
            self._extra_dirs.append(directory)

    def print_paths(self):
        """Returns a string suitable for printing of the search path"""
        # Uses a list to get the order right
        ret = []
        for i in self._get_paths():
            if i not in ret:
                ret.append(i)
        return os.pathsep.join(ret)

    def find_plugin(self, name):
        """Find a plugin named name"""
        suffix = ".py"
        if not self.class_name:
            suffix = ""
        for i in self._get_paths():
            path = os.path.join(i, "%s%s" % (name, suffix))
            if os.path.exists(path):
                return path
        return None

    def has_plugin(self, name):
        """Checks if a plugin named name exists"""
        return self.find_plugin(name) is not None
    __contains__ = has_plugin

    def get(self, name, *args, **kwargs):
        if name in self.aliases:
            name = self.aliases[name]
        path = self.find_plugin(name)
        if path is None:
            return None
        if path not in self._module_cache:
            self._module_cache[path] = imp.load_source('.'.join([self.package, name]), path)
        return getattr(self._module_cache[path], self.class_name)(*args, **kwargs)

    def all(self, *args, **kwargs):
        for i in self._get_paths():
            for path in glob.glob(os.path.join(i, "*.py")):
                name, ext = os.path.splitext(os.path.basename(path))
                if name.startswith("_"):
                    continue
                if path not in self._module_cache:
                    self._module_cache[path] = imp.load_source('.'.join([self.package, name]), path)
                yield getattr(self._module_cache[path], self.class_name)(*args, **kwargs)

action_loader     = PluginLoader('ActionModule',   'ansible.runner.action_plugins',     C.DEFAULT_ACTION_PLUGIN_PATH,     'action_plugins')
callback_loader   = PluginLoader('CallbackModule', 'ansible.callback_plugins',          C.DEFAULT_CALLBACK_PLUGIN_PATH,   'callback_plugins')
connection_loader = PluginLoader('Connection',     'ansible.runner.connection_plugins', C.DEFAULT_CONNECTION_PLUGIN_PATH, 'connection_plugins', aliases={'paramiko': 'paramiko_ssh'})
module_finder     = PluginLoader('',               '',                                  C.DEFAULT_MODULE_PATH,            'library')
lookup_loader     = PluginLoader('LookupModule',   'ansible.runner.lookup_plugins',     C.DEFAULT_LOOKUP_PLUGIN_PATH,     'lookup_plugins')
vars_loader       = PluginLoader('VarsModule',     'ansible.inventory.vars_plugins',    C.DEFAULT_VARS_PLUGIN_PATH,       'vars_plugins')
filter_loader     = PluginLoader('FilterModule',   'ansible.runner.filter_plugins',     C.DEFAULT_FILTER_PLUGIN_PATH,     'filter_plugins')

四、Ansible命令执行流程