DevOps干货：Saltstack任务处理机制源码分析

#saltstack#

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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

1. Publisher：给Minion发送指令
2. EventPublisher：Master上的事件发布总线
3. MWorkers：Salt Master的工作进程
4. 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

1. 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。
2. 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。
3. 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。
4. 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。
5. ReqServer又把这个结果发给了其中一个MWorker进行处理。
6. MWorker拿到结果后进行解密，然后发送到EventPublisher。
7. 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。

• 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)

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_master
• connect_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。

分析完这个流程，几点值得学习的地方是

1. 如何利用ZeroMQ实现各种进程通信模型
2. 如何用Python实现大型基础架构软件

1. Salt Development Architecture Overview
2. Saltstack github

好了，今天的分享就到这里。 如果大家觉得我的分享对你有用，还请点一点关注，在评论区跟我交流，我会持续分享一些有用的知识点和心得。