第二天，ansible源码学习

Posted 2020-10-28

按照我的理解，源码学习肯定是一边看代码，一边执行程序验证。执行的命令是：ansible sz003 -a "ls -l"

下面是ansible.py源码，学习分析以注释的形式出现

########################################################
from __future__ import (absolute_import, division, print_function)

# 表示基于type创建类，可以忽略
__metaclass__ = type

# __requires__ 要求按照的模块，可能是因为我没有使用ansible 提供的开发环境脚本的原因，要把这个注释掉才行
#__requires__ = [‘ansible‘]
try:
    import pkg_resources
except Exception:
    # Use pkg_resources to find the correct versions of libraries and set
    # sys.path appropriately when there are multiversion installs.  But we
    # have code that better expresses the errors in the places where the code
    # is actually used (the deps are optional for many code paths) so we don‘t
    # want to fail here.
    pass

import os
import shutil
import sys
import traceback

from ansible.errors import AnsibleError, AnsibleOptionsError, AnsibleParserError
from ansible.module_utils._text import to_text

# 用来显示信息
class LastResort(object):
    # OUTPUT OF LAST RESORT
    def display(self, msg, log_only=None):
        print(msg, file=sys.stderr)

    def error(self, msg, wrap_text=None):
        print(msg, file=sys.stderr)

if __name__ == ‘__main__‘:
    #
    # 从这里开始执行
    #
    display = LastResort()

    try:  # bad ANSIBLE_CONFIG or config options can force ugly stacktrace
        import ansible.constants as C
        from ansible.utils.display import Display
    except AnsibleOptionsError as e:
        display.error(to_text(e), wrap_text=False)
        sys.exit(5)

    #
    # cli 是用来存储ansible 执行命令的对象
    #
    cli = None

    #
    # 获取执行的文件名，在下面的代码中，根据文件名判断是实例adhoc 对象还是 playbook 对象
    # ansible-playbook 这部分代码是类似
    #
    me = os.path.basename(sys.argv[0])
    print("me:"+me)

    try:
        display = Display()
        display.debug("starting run")

        sub = None
        target = me.split(‘-‘)
        if target[-1][0].isdigit():
            # Remove any version or python version info as downstreams
            # sometimes add that
            target = target[:-1]

        if len(target) > 1:
            sub = target[1]
            myclass = "%sCLI" % sub.capitalize()
        elif target[0] == ‘ansible‘:
            sub = ‘adhoc‘
            myclass = ‘AdHocCLI‘
        else:
            raise AnsibleError("Unknown Ansible alias: %s" % me)

        try:
            #
            # 这里是获取 adhoc 还是 playbook
            #
            mycli = getattr(__import__("ansible.cli.%s" % sub, fromlist=[myclass]), myclass)
        except ImportError as e:
            # ImportError members have changed in py3
            if ‘msg‘ in dir(e):
                msg = e.msg
            else:
                msg = e.message
            if msg.endswith(‘ %s‘ % sub):
                raise AnsibleError("Ansible sub-program not implemented: %s" % me)
            else:
                raise

        try:
            #
            # 这里是处理参数，也就是执行命令时输入的 sz003 -a "ls -l"
            #
            args = [to_text(a, errors=‘surrogate_or_strict‘) for a in sys.argv]
        except UnicodeError:
            display.error(‘Command line args are not in utf-8, unable to continue.  Ansible currently only understands utf-8‘)
            display.display(u"The full traceback was:\n\n%s" % to_text(traceback.format_exc()))
            exit_code = 6
        else:
            #
            # 这里就是具体实例化了
            #
            cli = mycli(args)

            #
            # 整理参数
            #
            cli.parse()

            #
            # 执行命令
            #
            exit_code = cli.run()

            #
            # 下面大多数是处理异常代码，最后面有清理临时目录操作
            #

    except AnsibleOptionsError as e:
        cli.parser.print_help()
        display.error(to_text(e), wrap_text=False)
        exit_code = 5
    except AnsibleParserError as e:
        display.error(to_text(e), wrap_text=False)
        exit_code = 4
# TQM takes care of these, but leaving comment to reserve the exit codes
#    except AnsibleHostUnreachable as e:
#        display.error(str(e))
#        exit_code = 3
#    except AnsibleHostFailed as e:
#        display.error(str(e))
#        exit_code = 2
    except AnsibleError as e:
        display.error(to_text(e), wrap_text=False)
        exit_code = 1
    except KeyboardInterrupt:
        display.error("User interrupted execution")
        exit_code = 99
    except Exception as e:
        have_cli_options = cli is not None and cli.options is not None
        display.error("Unexpected Exception, this is probably a bug: %s" % to_text(e), wrap_text=False)
        if not have_cli_options or have_cli_options and cli.options.verbosity > 2:
            log_only = False
            if hasattr(e, ‘orig_exc‘):
                display.vvv(‘\nexception type: %s‘ % to_text(type(e.orig_exc)))
                why = to_text(e.orig_exc)
                if to_text(e) != why:
                    display.vvv(‘\noriginal msg: %s‘ % why)
        else:
            display.display("to see the full traceback, use -vvv")
            log_only = True
        display.display(u"the full traceback was:\n\n%s" % to_text(traceback.format_exc()), log_only=log_only)
        exit_code = 250
    finally:
        #
        # 最后如注释说的，清理临时目录
        #
        # Remove ansible tempdir
        shutil.rmtree(C.DEFAULT_LOCAL_TMP, True)

    sys.exit(exit_code)

明天就转到学习ansible具体执行命令的流程了，也就是下面代码段
cli = mycli(args)
cli.parse()
exit_code = cli.run()