#程序员# #DevOps# #干货# #自动化运维# #saltstack#

1. 前言

我是一个在北京互联网厂子里996的程序员，一边学习追赶新技术，怕被潮流甩下掉队，一边学习投资理财方法，让自己的薪水滚雪球。我相信，越努力越幸运，虽然刚开始雪球滚起来很慢，但是只要坚持下去，它就会越滚越快，自己的养老就靠它了。在财富自由的道路上，我与你共勉。欢迎来评论区与我交流心得和干货，这样我们就可以收获更多。

2. 概念解释

Salt Client

运行在Salt Master上，给Master发送请求，并且得到结果返回的LocalClient类。

Salt Master有几个重要的类

Publisher：给Minion发送指令EventPublisher：Master上的事件发布总线MWorkers：Salt Master的工作进程ReqServer：实现了一个MWorkers的多进程模型。接收Salt Client的请求或者Minion返回的结果，发送给MWorker去处理3. 任务处理机制 在Master上运行salt '*' test.ping, 原理是通过SaltClient提交任务到ReqServer的TCP：4506端口，并且监听在EventPublisher上获取结果。ReqServer实现了一个MWorkers多进程模型。ReqServer收到请求后发给其中一个MWorker进行处理。MWorker做权限检查后将任务加密发送给Publisher，并且把这个事件发送给EventPublisher。所有Minion都事先连接到了Publisher的TCP：4505端口上，获取到任务后解密处理。Minion处理完毕后将结果发送到Master的ReqServer的TCP：4506端口。ReqServer又把这个结果发给了其中一个MWorker进行处理。MWorker拿到结果后进行解密，然后发送到EventPublisher。此时SaltClient监听在EventPublisher上等待获取结果，碰到结果来了或者超时，命令行返回。3.1. 任务流程图 3.2. 提交任务 入口 salt/scripts/salt.py调用 salt/salt/scripts.py: salt_main() 调用 salt/salt/cli/salt.py: SaltCMD:run()判断是否为异步任务，若是，jid = local.cmd_async(**kwargs)若否，则进行同步执行同步执行

    #    for full_ret in local.cmd_cli(**kwargs):         ret_, out, retcode = self._format_ret(full_ret)         ret.update(ret_)

local.cmd_cli调用 salt/salt/client/__init__.py: LocalClient:cmd_cli()cmd_cli()调用pub_data = self.run_job() -> self.pub() 往ReqServer的ret_port：tcp4506端口提交任务请求。

    #    def pub():        master_uri = 'tcp://' + salt.utils.ip_bracket(self.opts['interface']) + \                     ':' + str(self.opts['ret_port'])        channel = salt.transport.Channel.factory(self.opts,                                                 crypt='clear',                                                 master_uri=master_uri)        try:            payload = channel.send(payload_kwargs, timeout=timeout)        except SaltReqTimeoutError:            raise SaltReqTimeoutError(                'Salt request timed out. The master is not responding. '                'If this error persists after verifying the master is up, '                'worker_threads may need to be increased.'            )

这里的salt.transport.Channel.factory最终会被实例化为AsyncZeroMQReqChannel，而且实例化的参数中有crypt=’clear’, 这就意味着，LocalClient给Master发送的消息都是Clear的，也就是未AES加密的。

任务内容的组装在salt/client/__init__.py的def _prep_pub方法里。其中cmd: 'publish'会在接下来的流程里用到。

    #    def _prep_pub():    ...        payload_kwargs = {'cmd': 'publish',                          'tgt': tgt,                          'fun': fun,                          'arg': arg,                          'key': self.key,                          'tgt_type': expr_form,                          'ret': ret,                          'jid': jid}

最终在payload外包装上’enc’: ‘clear’是在AsyncZeroMQReqChannel 里的send方法实现的，然后调用_crypted_transfer函数里加上。

    #     @tornado.gen.coroutine        def send(self, load, tries=3, timeout=60):            '''            Send a request, return a future which will complete when we send the message            '''            if self.crypt == 'clear':                ret = yield self._uncrypted_transfer(load, tries=tries, timeout=timeout)            else:                ret = yield self._crypted_transfer(load, tries=tries, timeout=timeout)            raise tornado.gen.Return(ret)

最终提交到4506端口的数据变成了类似这样的：

    #    {'enc': 'clear',     'load': {'arg': [],              'cmd': 'publish',              'fun': 'test.ping',              'jid': '',              'key': 'alsdkjfa.,maljf-==adflkjadflkjalkjadfadflkajdflkj',              'kwargs': {'show_jid': False, 'show_timeout': False},              'ret': '',              'tgt': 'client.jacky.com',              'tgt_type': 'glob',              'user': 'sudo_vagrant'}}

提交完任务后，cmd_cli()就调用 self.get_cli_event_returns()调用 self.get_iter_returns()判断是否是MoM结构，若是ret_iter = self.get_returns_no_block('(salt/job|syndic/.*)/{0}'.format(jid), 'regex')若否，ret_iter = self.get_returns_no_block('salt/job/{0}'.format(jid))self.get_returns_no_block中

    #    while True:        raw = self.event.get_event(wait=0.01, tag=tag, match_type=match_type, full=True, no_block=True)        yield raw

调用了salt/utils/event.py：SaltEvent:get_event(), get_event又调用了_get_event(), 在里面其以SUB的角色连接到了EventPublish监听任务结果的消息。

提交的任务的event内容是

    #    [DEBUG   ] Sending event - data = {'tgt_type': 'glob', 'jid': '20151123220104386580', 'tgt': 'client.jacky.com', '_stamp'    : '2015-11-23T14:01:04.386948', 'user': 'sudo_vagrant', 'arg': [], 'fun': 'test.ping', 'minions': ['client.jacky.com']}

这是salt命令后提交任务的debug输出

    #     [root@master base]# salt 'client.jacky.com' test.ping -l debug    [DEBUG   ] Reading configuration from /etc/salt/master    [DEBUG   ] Missing configuration file: /root/.saltrc    [DEBUG   ] Configuration file path: /etc/salt/master    [WARNING ] Insecure logging configuration detected! Sensitive data may be logged.    [DEBUG   ] Reading configuration from /etc/salt/master    [DEBUG   ] Missing configuration file: /root/.saltrc    [DEBUG   ] MasterEvent PUB socket URI: ipc:///var/run/salt/master/master_event_pub.ipc    [DEBUG   ] MasterEvent PULL socket URI: ipc:///var/run/salt/master/master_event_pull.ipc    [DEBUG   ] Initializing new AsyncZeroMQReqChannel for ('/etc/salt/pki/master', 'master.jacky.com_master', 'tcp://127.0.0.1:4506', 'clear')    [DEBUG   ] LazyLoaded config.option    [DEBUG   ] get_iter_returns for jid 20151124092621201574 sent to set(['client.jacky.com']) will timeout at 09:26:26.241828    [DEBUG   ] jid 20151124092621201574 return from client.jacky.com    client.jacky.com:    	True    [DEBUG   ] jid 20151124092621201574 found all minions set(['client.jacky.com'])

3.3. ReqServer实现的多进程模型

ReqServer的启动入口在salt/master.py里。

    #    req_channels = []    for transport, opts in iter_transport_opts(self.opts):        chan = salt.transport.server.ReqServerChannel.factory(opts)        chan.pre_fork(self.process_manager)        req_channels.append(chan)

利用ReqServerChannel的工厂函数实例化ZeroMQ或Raet等其他协议的通信通道，具体的实现在salt/transport/zeromq.py里。 chan.pre_fork(self.process_manager) -> process_manager.add_process(self.zmq_device), 在zmq_device实现了Router＋Dealer的模型，并且Client(Router)绑定了tcp://ip:4506端口，Worker(Dealer)根据ipc_mode的配置绑定了tcp://127.0.0.1:4515或者ipc://workers.ipc。

    #    while True:        try:            zmq.device(zmq.QUEUE, self.clients, self.workers)        except zmq.ZMQError as exc:            if exc.errno == errno.EINTR:                continue            raise exc

zmq.device对clients和worker之间的消息传递进行了代理。

    #    for ind in range(int(self.opts['worker_threads'])):        self.process_manager.add_process(MWorker,                                         args=(self.opts,                                               self.master_key,                                               self.key,                                               req_channels,                                               ),                                         )    self.process_manager.run()

根据配置文件里worker_threads 的配置启动相应个数的MWorker。

关于ZeroMQReqServerChannel的实现在salt/transport/zeromq.py中。客户端会通过AsyncReqMessageClient往Router：4506端口提交请求。MWorker继承自multiprocessing.Process，每个MWorker被创建的时候都传入了req_channels ，在run()方法里调用了self.__bind(), 通过post_fork()创建了REP类型的连接到Dealer上，等待处理任务。

    #    def __bind(self):        '''        Bind to the local port        '''        # using ZMQIOLoop since we *might* need zmq in there        zmq.eventloop.ioloop.install()        self.io_loop = zmq.eventloop.ioloop.ZMQIOLoop()        for req_channel in self.req_channels:            req_channel.post_fork(self._handle_payload, io_loop=self.io_loop)  # TODO: cleaner? Maybe lazily?        self.io_loop.start()

至此，这样一个多进程模型就创建完毕。(该图来自ZeroMQ官网)

3.4. MWorker的处理逻辑

MWorker的启动入口在salt/master.py里。

程序入口是run()方法。设置了self.clear_funcs和self.aes_funcs方法，并且调用__bind方法，通过post_fork()传入了self._handle_payload任务处理函数，并且创建了REP类型的连接到Dealer上，等待处理任务。

    ＃    def __bind(self):        '''        Bind to the local port        '''        # using ZMQIOLoop since we *might* need zmq in there        zmq.eventloop.ioloop.install()        self.io_loop = zmq.eventloop.ioloop.ZMQIOLoop()        for req_channel in self.req_channels:            req_channel.post_fork(self._handle_payload, io_loop=self.io_loop)  # TODO: cleaner? Maybe lazily?        self.io_loop.start()

post_fork()里调用ZeroMQReqServerChannel或者其他ReqServerChannel的实现，以ZeroMQReqServerChannel的post_fork为例，处理任务的入口在这几行代码, 设置了任务处理函数 payload_handler。self.handle_message是MWorker在接收到消息时的一个回调函数，在里面调用了payload_handler去处理任务。

    ＃    salt.transport.mixins.auth.AESReqServerMixin.post_fork(self, payload_handler, io_loop)    self.stream = zmq.eventloop.zmqstream.ZMQStream(self._socket, io_loop=self.io_loop)    self.stream.on_recv_stream(self.handle_message)

通过_handle_payload方法，我们可以看到cmd: 'publish', 那么MWorker就会调用self._handle_clear.publish方法，将任务load发送到PubServerChannel的PULL接口。

    ＃    @tornado.gen.coroutine    def _handle_payload(self, payload):        '''        The _handle_payload method is the key method used to figure out what        needs to be done with communication to the server        Example cleartext payload generated for 'salt myminion test.ping':        {'enc': 'clear',         'load': {'arg': [],                  'cmd': 'publish',                  'fun': 'test.ping',                  'jid': '',                  'key': 'alsdkjfa.,maljf-==adflkjadflkjalkjadfadflkajdflkj',                  'kwargs': {'show_jid': False, 'show_timeout': False},                  'ret': '',                  'tgt': 'myminion',                  'tgt_type': 'glob',                  'user': 'root'}}        :param dict payload: The payload route to the appropriate handler        '''        key = payload['enc']        load = payload['load']        ret = {'aes': self._handle_aes,               'clear': self._handle_clear}[key](load)        raise tornado.gen.Return(ret)    def _handle_clear(self, load):        '''        Process a cleartext command        :param dict load: Cleartext payload        :return: The result of passing the load to a function in ClearFuncs corresponding to                 the command specified in the load's 'cmd' key.        '''        log.trace('Clear payload received with command {cmd}'.format(**load))        if load['cmd'].startswith('__'):            return False        return getattr(self.clear_funcs, load['cmd'])(load), {'fun': 'send_clear'}

3.5. Publisher实现的Pub-Sub任务分发机制

Publisher的入口在salt/master.py里。

在Master的启动过程中start()函数里，创建了PubServerChannel，根据传入参数不同创建ZeroMQPubServerChannel或者其他协议的实现，具体的实现在salt/transport/zeromq.py里。这里以PubServerChannel为例。

    ＃    for transport, opts in iter_transport_opts(self.opts):        chan = salt.transport.server.PubServerChannel.factory(opts)        chan.pre_fork(process_manager)        pub_channels.append(chan)

    ＃    def pre_fork(self, process_manager):        '''        Do anything necessary pre-fork. Since this is on the master side this will        primarily be used to create IPC channels and create our daemon process to        do the actual publishing        :param func process_manager: A ProcessManager, from salt.utils.process.ProcessManager        '''        process_manager.add_process(self._publish_daemon)

实例化chan后，调用pre_fork方法，利用_publish_daemon方法启动新Daemon进程，监听了pull_uri, pub_uri，并且在while循环里将pull_uri接收到的任务转发到pub_uri里。

    #    def _publish_daemon(self):    ...       while True:            # Catch and handle EINTR from when this process is sent            # SIGUSR1 gracefully so we don't choke and die horribly            try:                package = pull_sock.recv()                unpacked_package = salt.payload.unpackage(package)                payload = unpacked_package['payload']                if self.opts['zmq_filtering']:                    # if you have a specific topic list, use that                    if 'topic_lst' in unpacked_package:                        for topic in unpacked_package['topic_lst']:                            # zmq filters are substring match, hash the topic                            # to avoid collisions                            htopic = hashlib.sha1(topic).hexdigest()                            pub_sock.send(htopic, flags=zmq.SNDMORE)                            pub_sock.send(payload)                            # otherwise its a broadcast                    else:                        # TODO: constants file for "broadcast"                        pub_sock.send('broadcast', flags=zmq.SNDMORE)                        pub_sock.send(payload)                else:                    pub_sock.send(payload)            except zmq.ZMQError as exc:                if exc.errno == errno.EINTR:                    continue                raise exc

MWorker将任务提交到Publisher是在self._handle_clear.publish方法里实现的。

    #    def publish():    ...         # Send it!        self._send_pub(payload)    ...    def _send_pub(self, load):        '''        Take a load and send it across the network to connected minions        '''        for transport, opts in iter_transport_opts(self.opts):            chan = salt.transport.server.PubServerChannel.factory(opts)            chan.publish(load)

这里的chan就是ZeroMQPubServerChannel的实例，调用该实例的publish方法，将payload加密，然后发送给Publisher的pull_uri，即publish_pull.ipc端口。

    #    payload = {'enc': 'aes'}    crypticle = salt.crypt.Crypticle(self.opts, salt.master.SMaster.secrets['aes']['secret'].value)    payload['load'] = crypticle.dumps(load)    ...    pub_sock.connect(pull_uri)    ...    pub_sock.send(self.serial.dumps(int_payload))    ...

这是Master上的debug输出

    #    [DEBUG   ] Sending event - data = {'_stamp': '2015-11-24T00:39:00.185467', 'minions': ['client.jacky.com']}    [DEBUG   ] Sending event - data = {'tgt_type': 'glob', 'jid': '20151124083900185051', 'tgt': 'client.jacky.com', '_stamp': '2015-11-24T00:39:00.186134', 'user': 'sudo_vagrant', 'arg': [], 'fun': 'test.ping', 'minions': ['client.jacky.com']}    [INFO    ] User sudo_vagrant Published command test.ping with jid 20151124083900185051    [DEBUG   ] Published command details {'tgt_type': 'glob', 'jid': '20151124083900185051', 'tgt': 'client.jacky.com', 'ret': 'mysql', 'user': 'sudo_vagrant', 'arg': [], 'fun': 'test.ping'}    [INFO    ] Got return from client.jacky.com for job 20151124083900185051    [DEBUG   ] Sending event - data = {'fun_args': [], 'jid': '20151124083900185051', 'return': True, 'retcode': 0, 'success': True, 'cmd': '_return', '_stamp': '2015-11-24T00:39:00.303857', 'fun': 'test.ping', 'id': 'client.jacky.com'}

3.6. Minion连接到Publisher获取和处理任务

Minion在启动过程中最终会进入tune_in方法，然后陷入无限循坏，不断处理任务和返回结果。实现在salt/minion.py里。

tune_in调用self.connect_masterconnect_master调用self.eval_master(self.opts, self.timeout, self.safe)eval_master中利用AsyncPubChannel的factory方法，根据不同参数实例化相应的pub_channel，这里以AsyncZeroMQPubChannel为例，具体的实现在salt/transport/zeromq.py里。

    #    try:        pub_channel = salt.transport.client.AsyncPubChannel.factory(opts, **factory_kwargs)        yield pub_channel.connect()        conn = True        break    except SaltClientError:        msg = ('Master {0} could not be reached, trying '               'next master (if any)'.format(opts['master']))        log.info(msg)        continue

调用AsyncZeroMQPubChannel的connect方法，以SUB的角色连接到Master的PUB端口4505。

        #        def connect(self):            if not self.auth.authenticated:                yield self.auth.authenticate()            self.publish_port = self.auth.creds['publish_port']            self._socket.connect(self.master_pub)    

tune_in方法里，连接到Master之后，设置任务处理的回调函数

    #    # add handler to subscriber    self.pub_channel.on_recv(self._handle_payload)

在pub_channel.on_recv其实就是AsyncZeroMQPubChannel.on_recv()方法，封装了对收到的message进行解密。

     #     def on_recv():             @tornado.gen.coroutine            def wrap_callback(messages):                payload = yield self._decode_messages(messages)                if payload is not None:                    callback(payload)

self._decode_messages()调用了self._decode_payload()进行解密。见salt/transport/mixins/auth.py的class AESPubClientMixin(object)。

    #    @tornado.gen.coroutine    def _decode_payload(self, payload):        # we need to decrypt it        log.trace('Decoding payload: {0}'.format(payload))        if payload['enc'] == 'aes':            self._verify_master_signature(payload)            try:                payload['load'] = self.auth.crypticle.loads(payload['load'])            except salt.crypt.AuthenticationError:                yield self.auth.authenticate()                payload['load'] = self.auth.crypticle.loads(payload['load'])        raise tornado.gen.Return(payload)

self._handle_payload调用了_handle_decoded_payload，根据data['fun']的类型初始化target，接下来以target创建新的进程或者线程去处理这个任务（根据master里multiprocessing参数来判断是创建新进程还是线程）。具体处理逻辑在_thread_return或者_thread_multi_return里，这里以_thread_return为例。

        #        if isinstance(data['fun'], tuple) or isinstance(data['fun'], list):            target = Minion._thread_multi_return        else:            target = Minion._thread_return    

_thread_return中对任务进行处理，然后用minion_instance._return_pub返回结果给Master的4506端口。

    #    try:        func = minion_instance.functions[data['fun']]        args, kwargs = load_args_and_kwargs(            func,            data['arg'],            data)        minion_instance.functions.pack['__context__']['retcode'] = 0        if opts.get('sudo_user', ''):            sudo_runas = opts.get('sudo_user')            if 'sudo.salt_call' in minion_instance.functions:                return_data = minion_instance.functions['sudo.salt_call'](                        sudo_runas,                        data['fun'],                        *args,                        **kwargs)        else:            return_data = func(*args, **kwargs)

_return_pub方法中调用salt.transport.Channel的factory工厂方法实例化到master到连接，这里的channel就是AsyncZeroMQReqChannel，使用channel.send方法将结果发送。

    #    def _return_pub():    ...        channel = salt.transport.Channel.factory(self.opts)    ...            try:            ret_val = channel.send(load, timeout=timeout)        except SaltReqTimeoutError:            msg = ('The minion failed to return the job information for job '                   '{0}. This is often due to the master being shut down or '                   'overloaded. If the master is running consider increasing '                   'the worker_threads value.').format(jid)            log.warn(msg)            return ''

这里的AsyncZeroMQReqChannel.send默认会使用aes加密的方式对消息进行发送。

    #     @tornado.gen.coroutine        def send(self, load, tries=3, timeout=60):            '''            Send a request, return a future which will complete when we send the message            '''            if self.crypt == 'clear':                ret = yield self._uncrypted_transfer(load, tries=tries, timeout=timeout)            else:                ret = yield self._crypted_transfer(load, tries=tries, timeout=timeout)            raise tornado.gen.Return(ret)

这是Minion上的debug输出

    #     [INFO    ] User sudo_vagrant Executing command test.ping with jid 20151124083900185051    [DEBUG   ] Command details {'tgt_type': 'glob', 'jid': '20151124083900185051', 'tgt': 'client.jacky.com', 'ret': 'mysql', 'user': 'sudo_vagrant', 'arg': [], 'fun': 'test.ping'}    [INFO    ] Starting a new job with PID 27556    [DEBUG   ] LazyLoaded test.ping    [DEBUG   ] Minion return retry timer set to 2 seconds (randomized)    [INFO    ] Returning information for job: 20151124083900185051    [DEBUG   ] Initializing new AsyncZeroMQReqChannel for ('/etc/salt/pki/minion', 'client.jacky.com', 'tcp://192.168.33.20:4506', 'aes')    [DEBUG   ] Initializing new SAuth for ('/etc/salt/pki/minion', 'client.jacky.com', 'tcp://192.168.33.20:4506')

3.7. SaltClient将结果返回

在3.1里讲到了Client以SUB的角色连接到了Master的EventPublisher上监听结果。自此，执行一个命令的闭环就完成了。

4. 小结

分析完这个流程，几点值得学习的地方是

如何利用ZeroMQ实现各种进程通信模型如何用Python实现大型基础架构软件5. 参考资料PermalinkSalt Development Architecture OverviewSaltstack github

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