芝麻HTTP:Ansible扩展

2018-02-01 12:08:39来源:cnblogs.com作者:芝麻HTTP代理人点击

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Ansible简介

Ansible是由Python开发的一个运维工具,因为工作需要接触到Ansible,经常会集成一些东西到Ansible,所以对Ansible的了解越来越多。

那Ansible到底是什么呢?在我的理解中,原来需要登录到服务器上,然后执行一堆命令才能完成一些操作。而Ansible就是来代替我们去执行那些命令。并且可以通过Ansible控制多台机器,在机器上进行任务的编排和执行,在Ansible中称为playbook。

那Ansible是如何做到的呢?简单点说,就是Ansible将我们要执行的命令生成一个脚本,然后通过sftp将脚本上传到要执行命令的服务器上,然后在通过ssh协议,执行这个脚本并将执行结果返回。

那Ansible具体是怎么做到的呢?下面从模块和插件来看一下Ansible是如何完成一个模块的执行

PS:下面的分析都是在对Ansible有一些具体使用经验之后,通过阅读源代码进一步得出的执行结论,所以希望在看本文时,是建立在对Ansible有一定了解的基础上,最起码对于Ansible的一些概念有了解,例如inventory,module,playbooks等

Ansible模块

模块是Ansible执行的最小单位,可以是由Python编写,也可以是Shell编写,也可以是由其他语言编写。模块中定义了具体的操作步骤以及实际使用过程中所需要的参数

执行的脚本就是根据模块生成一个可执行的脚本。

那Ansible是怎么样将这个脚本上传到服务器上,然后执行获取结果的呢?

Ansible插件

connection插件

连接插件,根据指定的ssh参数连接指定的服务器,并切提供实际执行命令的接口

shell插件

命令插件,根据sh类型,来生成用于connection时要执行的命令

strategy插件

执行策略插件,默认情况下是线性插件,就是一个任务接着一个任务的向下执行,此插件将任务丢到执行器去执行。

action插件

动作插件,实质就是任务模块的所有动作,如果ansible的模块没有特别编写的action插件,默认情况下是normal或者async(这两个根据模块是否async来选择),normal和async中定义的就是模块的执行步骤。例如,本地创建临时文件,上传临时文件,执行脚本,删除脚本等等,如果想在所有的模块中增加一些特殊步骤,可以通过增加action插件的方式来扩展。

Ansible执行模块流程

  1. ansible命令实质是通过ansible/cli/adhoc.py来运行,同时会收集参数信息
    1. 设置Play信息,然后通过TaskQueueManager进行run,
    2. TaskQueueManager需要Inventory(节点仓库),variable_manager(收集变量),options(命令行中指定的参数),stdout_callback(回调函数)
  2. 在task_queue_manager.py中找到run中
    1. 初始化时会设置队列
    2. 会根据options,,variable_manager,passwords等信息设置成一个PlayContext信息(playbooks/playcontext.py)
    3. 设置插件(plugins)信息callback_loader(回调), strategy_loader(执行策略), module_loader(任务模块)
    4. 通过strategy_loader(strategy插件)的run(默认的strategy类型是linear,线性执行),去按照顺序执行所有的任务(执行一个模块,可能会执行多个任务)
    5. 在strategy_loader插件run之后,会判断action类型。如果是meta类型的话会单独执行(不是具体的ansible模块时),而其他模块时,会加载到队列_queue_task
    6. 在队列中会调用WorkerProcess去处理,在workerproces实际的run之后,会使用TaskExecutor进行执行
    7. 在TaskExecutor中会设置connection插件,并且根据task的类型(模块。或是include等)获取action插件,就是对应的模块,如果模块有自定义的执行,则会执行自定义的action,如果没有的会使用normal或者async,这个是根据是否是任务的async属性来决定
    8. 在Action插件中定义着执行的顺序,及具体操作,例如生成临时目录,生成临时脚本,所以要在统一的模式下,集成一些额外的处理时,可以重写Action的方法
    9. 通过Connection插件来执行Action的各个操作步骤

扩展Ansible实例

执行节点Python环境扩展

实际需求中,我们扩展的一些Ansible模块需要使用三方库,但每个节点中安装这些库有些不易于管理。ansible执行模块的实质就是在节点的python环境下执行生成的脚本,所以我们采取的方案是,指定节点上的Python环境,将局域网内一个python环境作为nfs共享。通过扩展Action插件,增加节点上挂载nfs,待执行结束后再将节点上的nfs卸载。具体实施步骤如下:

扩展代码:

重写ActionBase的execute_module方法

# execute_modulefrom __future__ import (absolute_import, division, print_function)__metaclass__ = typeimport jsonimport pipesfrom ansible.compat.six import text_type, iteritemsfrom ansible import constants as Cfrom ansible.errors import AnsibleErrorfrom ansible.release import __version__try:    from __main__ import displayexcept ImportError:    from ansible.utils.display import Display    display = Display()class MagicStackBase(object):    def _mount_nfs(self, ansible_nfs_src, ansible_nfs_dest):        cmd = ['mount',ansible_nfs_src, ansible_nfs_dest]        cmd = [pipes.quote(c) for c in cmd]        cmd = ' '.join(cmd)        result = self._low_level_execute_command(cmd=cmd, sudoable=True)        return result    def _umount_nfs(self, ansible_nfs_dest):        cmd = ['umount', ansible_nfs_dest]        cmd = [pipes.quote(c) for c in cmd]        cmd = ' '.join(cmd)        result = self._low_level_execute_command(cmd=cmd, sudoable=True)        return result    def _execute_module(self, module_name=None, module_args=None, tmp=None, task_vars=None, persist_files=False, delete_remote_tmp=True):        '''        Transfer and run a module along with its arguments.        '''        # display.v(task_vars)        if task_vars is None:            task_vars = dict()        # if a module name was not specified for this execution, use        # the action from the task        if module_name is None:            module_name = self._task.action        if module_args is None:            module_args = self._task.args        # set check mode in the module arguments, if required        if self._play_context.check_mode:            if not self._supports_check_mode:                raise AnsibleError("check mode is not supported for this operation")            module_args['_ansible_check_mode'] = True        else:            module_args['_ansible_check_mode'] = False        # Get the connection user for permission checks        remote_user = task_vars.get('ansible_ssh_user') or self._play_context.remote_user        # set no log in the module arguments, if required        module_args['_ansible_no_log'] = self._play_context.no_log or C.DEFAULT_NO_TARGET_SYSLOG        # set debug in the module arguments, if required        module_args['_ansible_debug'] = C.DEFAULT_DEBUG        # let module know we are in diff mode        module_args['_ansible_diff'] = self._play_context.diff        # let module know our verbosity        module_args['_ansible_verbosity'] = display.verbosity        # give the module information about the ansible version        module_args['_ansible_version'] = __version__        # set the syslog facility to be used in the module        module_args['_ansible_syslog_facility'] = task_vars.get('ansible_syslog_facility', C.DEFAULT_SYSLOG_FACILITY)        # let module know about filesystems that selinux treats specially        module_args['_ansible_selinux_special_fs'] = C.DEFAULT_SELINUX_SPECIAL_FS        (module_style, shebang, module_data) = self._configure_module(module_name=module_name, module_args=module_args, task_vars=task_vars)        if not shebang:            raise AnsibleError("module (%s) is missing interpreter line" % module_name)        # get nfs info for mount python packages        ansible_nfs_src = task_vars.get("ansible_nfs_src", None)        ansible_nfs_dest = task_vars.get("ansible_nfs_dest", None)        # a remote tmp path may be necessary and not already created        remote_module_path = None        args_file_path = None        if not tmp and self._late_needs_tmp_path(tmp, module_style):            tmp = self._make_tmp_path(remote_user)        if tmp:            remote_module_filename = self._connection._shell.get_remote_filename(module_name)            remote_module_path = self._connection._shell.join_path(tmp, remote_module_filename)            if module_style in ['old', 'non_native_want_json']:                # we'll also need a temp file to hold our module arguments                args_file_path = self._connection._shell.join_path(tmp, 'args')        if remote_module_path or module_style != 'new':            display.debug("transferring module to remote")            self._transfer_data(remote_module_path, module_data)            if module_style == 'old':                # we need to dump the module args to a k=v string in a file on                # the remote system, which can be read and parsed by the module                args_data = ""                for k,v in iteritems(module_args):                    args_data += '%s=%s ' % (k, pipes.quote(text_type(v)))                self._transfer_data(args_file_path, args_data)            elif module_style == 'non_native_want_json':                self._transfer_data(args_file_path, json.dumps(module_args))            display.debug("done transferring module to remote")        environment_string = self._compute_environment_string()        remote_files = None        if args_file_path:            remote_files = tmp, remote_module_path, args_file_path        elif remote_module_path:            remote_files = tmp, remote_module_path        # Fix permissions of the tmp path and tmp files.  This should be        # called after all files have been transferred.        if remote_files:            self._fixup_perms2(remote_files, remote_user)        # mount nfs        if ansible_nfs_src and ansible_nfs_dest:            result = self._mount_nfs(ansible_nfs_src, ansible_nfs_dest)            if result['rc'] != 0:                raise AnsibleError("mount nfs failed!!! {0}".format(result['stderr']))        cmd = ""        in_data = None        if self._connection.has_pipelining and self._play_context.pipelining and not C.DEFAULT_KEEP_REMOTE_FILES and module_style == 'new':            in_data = module_data        else:            if remote_module_path:                cmd = remote_module_path        rm_tmp = None        if tmp and "tmp" in tmp and not C.DEFAULT_KEEP_REMOTE_FILES and not persist_files and delete_remote_tmp:            if not self._play_context.become or self._play_context.become_user == 'root':                # not sudoing or sudoing to root, so can cleanup files in the same step                rm_tmp = tmp        cmd = self._connection._shell.build_module_command(environment_string, shebang, cmd, arg_path=args_file_path, rm_tmp=rm_tmp)        cmd = cmd.strip()        sudoable = True        if module_name == "accelerate":            # always run the accelerate module as the user            # specified in the play, not the sudo_user            sudoable = False        res = self._low_level_execute_command(cmd, sudoable=sudoable, in_data=in_data)        # umount nfs        if ansible_nfs_src and ansible_nfs_dest:            result = self._umount_nfs(ansible_nfs_dest)            if result['rc'] != 0:                raise AnsibleError("umount nfs failed!!! {0}".format(result['stderr']))        if tmp and "tmp" in tmp and not C.DEFAULT_KEEP_REMOTE_FILES and not persist_files and delete_remote_tmp:            if self._play_context.become and self._play_context.become_user != 'root':                # not sudoing to root, so maybe can't delete files as that other user                # have to clean up temp files as original user in a second step                tmp_rm_cmd = self._connection._shell.remove(tmp, recurse=True)                tmp_rm_res = self._low_level_execute_command(tmp_rm_cmd, sudoable=False)                tmp_rm_data = self._parse_returned_data(tmp_rm_res)                if tmp_rm_data.get('rc', 0) != 0:                    display.warning('Error deleting remote temporary files (rc: {0}, stderr: {1})'.format(tmp_rm_res.get('rc'), tmp_rm_res.get('stderr', 'No error string available.')))        # parse the main result        data = self._parse_returned_data(res)        # pre-split stdout into lines, if stdout is in the data and there        # isn't already a stdout_lines value there        if 'stdout' in data and 'stdout_lines' not in data:            data['stdout_lines'] = data.get('stdout', u'').splitlines()        display.debug("done with _execute_module (%s, %s)" % (module_name, module_args))        return data

集成到normal.py和async.py中,记住要将这两个插件在ansible.cfg中进行配置

from __future__ import (absolute_import, division, print_function)__metaclass__ = type from ansible.plugins.action import ActionBasefrom ansible.utils.vars import merge_hash from common.ansible_plugins import MagicStackBase  class ActionModule(MagicStackBase, ActionBase):     def run(self, tmp=None, task_vars=None):        if task_vars is None:            task_vars = dict()         results = super(ActionModule, self).run(tmp, task_vars)        # remove as modules might hide due to nolog        del results['invocation']['module_args']        results = merge_hash(results, self._execute_module(tmp=tmp, task_vars=task_vars))        # Remove special fields from the result, which can only be set        # internally by the executor engine. We do this only here in        # the 'normal' action, as other action plugins may set this.        #        # We don't want modules to determine that running the module fires        # notify handlers.  That's for the playbook to decide.        for field in ('_ansible_notify',):            if field in results:                results.pop(field)         return results
  • 配置ansible.cfg,将扩展的插件指定为ansible需要的action插件
  • 重写插件方法,重点是execute_module
  • 执行命令中需要指定Python环境,将需要的参数添加进去nfs挂载和卸载的参数
    ansible 51 -m mysql_db -a "state=dump name=all target=/tmp/test.sql" -i hosts -u root -v -e "ansible_nfs_src=172.16.30.170:/web/proxy_env/lib64/python2.7/site-packages ansible_nfs_dest=/root/.pyenv/versions/2.7.10/lib/python2.7/site-packages ansible_python_interpreter=/root/.pyenv/versions/2.7.10/bin/python"

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