feature(wgt): add barrier middleware

.coveragerc

@@ -1,4 +1,5 @@
 [run]
+concurrency = multiprocessing,thread
 omit =
   ding/utils/slurm_helper.py
   ding/utils/file_helper.py

ding/framework/middleware/__init__.py

@@ -3,3 +3,4 @@
 from .learner import OffPolicyLearner, HERLearner
 from .ckpt_handler import CkptSaver
 from .distributer import ContextExchanger, ModelExchanger
+from .barrier import Barrier, BarrierRuntime

ding/framework/middleware/barrier.py

@@ -0,0 +1,227 @@
+from time import sleep, time
+from ditk import logging
+from ding.framework import task
+from ding.utils.lock_helper import LockContext, LockContextType
+from ding.utils.design_helper import SingletonMetaclass
+
+
+class BarrierRuntime(metaclass=SingletonMetaclass):
+
+    def __init__(self, node_id: int, max_world_size: int = 100):
+        """
+        Overview:
+            'BarrierRuntime' is a singleton class. In addition, it must be initialized before the
+            class 'Parallel' starts MQ, otherwise the messages sent by other nodes may be lost after
+            the detection is completed. We don't have a message retransmission mechanism, and losing
+            a message means deadlock.
+        Arguments:
+            - node_id (int): Process ID.
+            - max_world_size (int, optional): The maximum total number of processes that can be
+                synchronized, the defalut value is 100.
+        """
+        self.node_id = node_id
+        self._has_detected = False
+        self._range_len = len(str(max_world_size)) + 1
+
+        self._barrier_epoch = 0
+        self._barrier_recv_peers_buff = dict()
+        self._barrier_recv_peers = dict()
+        self._barrier_ack_peers = []
+        self._barrier_lock = LockContext(LockContextType.THREAD_LOCK)
+
+        self.mq_type = task.router.mq_type
+        self._connected_peers = dict()
+        self._connected_peers_lock = LockContext(LockContextType.THREAD_LOCK)
+        self._keep_alive_daemon = False
+
+        self._event_name_detect = "b_det"
+        self.event_name_req = "b_req"
+        self.event_name_ack = "b_ack"
+
+    def _alive_msg_handler(self, peer_id):
+        with self._connected_peers_lock:
+            self._connected_peers[peer_id] = time()
+
+    def _add_barrier_req(self, msg):
+        peer, epoch = self._unpickle_barrier_tag(msg)
+        logging.debug("Node:[{}] recv barrier request from node:{}, epoch:{}".format(self.node_id, peer, epoch))
+        with self._barrier_lock:
+            if peer not in self._barrier_recv_peers:
+                self._barrier_recv_peers[peer] = []
+            self._barrier_recv_peers[peer].append(epoch)
+
+    def _add_barrier_ack(self, peer):
+        logging.debug("Node:[{}] recv barrier ack from node:{}".format(self.node_id, peer))
+        with self._barrier_lock:
+            self._barrier_ack_peers.append(peer)
+
+    def _unpickle_barrier_tag(self, msg):
+        return msg % self._range_len, msg // self._range_len
+
+    def pickle_barrier_tag(self):
+        return int(self._barrier_epoch * self._range_len + self.node_id)
+
+    def reset_all_peers(self):
+        with self._barrier_lock:
+            for peer, q in self._barrier_recv_peers.items():
+                if len(q) != 0:
+                    assert q.pop(0) == self._barrier_epoch
+            self._barrier_ack_peers = []
+            self._barrier_epoch += 1
+
+    def get_recv_num(self):
+        count = 0
+        with self._barrier_lock:
+            if len(self._barrier_recv_peers) > 0:
+                for _, q in self._barrier_recv_peers.items():
+                    if len(q) > 0 and q[0] == self._barrier_epoch:
+                        count += 1
+        return count
+
+    def get_ack_num(self):
+        with self._barrier_lock:
+            return len(self._barrier_ack_peers)
+
+    def detect_alive(self, expected, timeout):
+        # The barrier can only block other nodes within the visible range of the current node.
+        # If the 'attch_to' list of a node is empty, it does not know how many nodes will attach to him,
+        # so we cannot specify the effective range of a barrier in advance.
+        assert task._running
+        task.on(self._event_name_detect, self._alive_msg_handler)
+        task.on(self.event_name_req, self._add_barrier_req)
+        task.on(self.event_name_ack, self._add_barrier_ack)
+        start = time()
+        while True:
+            sleep(0.1)
+            task.emit(self._event_name_detect, self.node_id, only_remote=True)
+            # In case the other node has not had time to receive our detect message,
+            # we will send an additional round.
+            if self._has_detected:
+                break
+            with self._connected_peers_lock:
+                if len(self._connected_peers) == expected:
+                    self._has_detected = True
+
+            if time() - start > timeout:
+                raise TimeoutError("Node-[{}] timeout when waiting barrier! ".format(task.router.node_id))
+
+        task.off(self._event_name_detect)
+        logging.info(
+            "Barrier detect node done, node-[{}] has connected with {} active nodes!".format(self.node_id, expected)
+        )
+
+
+class BarrierContext:
+
+    def __init__(self, runtime: BarrierRuntime, detect_timeout, expected_peer_num: int = 0):
+        self._runtime = runtime
+        self._expected_peer_num = expected_peer_num
+        self._timeout = detect_timeout
+
+    def __enter__(self):
+        if not self._runtime._has_detected:
+            self._runtime.detect_alive(self._expected_peer_num, self._timeout)
+
+    def __exit__(self, exc_type, exc_value, tb):
+        if exc_type is not None:
+            import traceback
+            traceback.print_exception(exc_type, exc_value, tb)
+        self._runtime.reset_all_peers()
+
+
+class Barrier:
+
+    def __init__(self, attch_from_nums: int, timeout: int = 60):
+        """
+        Overview:
+            Barrier() is a middleware for debug or profiling. It can synchronize the task step of each
+            process within the scope of all visible processes. When using Barrier(), you need to pay
+            attention to the following points:
+
+            1. All processes must call the same number of Barrier(), otherwise a deadlock occurs.
+
+            2. 'attch_from_nums' is a very important variable, This value indicates the number of times
+                the current process will be attached to by other processes (the number of connections
+                established).
+                For example:
+                    Node0: address: 127.0.0.1:12345, attach_to = []
+                    Node1: address: 127.0.0.1:12346, attach_to = ["tcp://127.0.0.1:12345"]
+                    For Node0, the 'attch_from_nums' value is 1. (It will be acttched by Node1)
+                    For Node1, the 'attch_from_nums' value is 0. (No one will attach to Node1)
+                Please note that this value must be given correctly, otherwise, for a node whose 'attach_to'
+                list is empty, it cannot perceive how many processes will establish connections with it,
+                resulting in any form of synchronization cannot be performed.
+
+            3. Barrier() is thread-safe, but it is not recommended to use barrier in multithreading. You need
+                to carefully calculate the number of times each thread calls Barrier() to avoid deadlock.
+
+            4. In normal training tasks, please do not use Barrier(), which will force the step synchronization
+                between each process, so it will greatly damage the training efficiency. In addition, if your
+                training task has dynamic processes, do not use Barrier() to prevent deadlock.
+
+        Arguments:
+            - attch_from_nums (int): [description]
+            - timeout (int, optional): The timeout for successful detection of 'expected_peer_num'
+                number of nodes, the default value is 60 seconds.
+        """
+        self.node_id = task.router.node_id
+        self.timeout = timeout
+        self._runtime: BarrierRuntime = task.router.barrier_runtime
+        self._barrier_peers_nums = task.get_attch_to_len() + attch_from_nums
+
+        logging.info(
+            "Node:[{}], attach to num is:{}, attach from num is:{}".format(
+                self.node_id, task.get_attch_to_len(), attch_from_nums
+            )
+        )
+
+    def __call__(self, ctx):
+        self._wait_barrier(ctx)
+        yield
+        self._wait_barrier(ctx)
+
+    def _wait_barrier(self, ctx):
+        self_ready = False
+        with BarrierContext(self._runtime, self.timeout, self._barrier_peers_nums):
+            logging.debug("Node:[{}] enter barrier".format(self.node_id))
+            # Step1: Notifies all the attached nodes that we have reached the barrier.
+            task.emit(self._runtime.event_name_req, self._runtime.pickle_barrier_tag(), only_remote=True)
+            logging.debug("Node:[{}] sended barrier request".format(self.node_id))
+
+            # Step2: We check the number of flags we have received.
+            # In the current CI design of DI-engine, there will always be a node whose 'attach_to' list is empty,
+            # so there will always be a node that will send ACK unconditionally, so deadlock will not occur.
+            if self._runtime.get_recv_num() == self._barrier_peers_nums:
+                self_ready = True
+
+            # Step3: Waiting for our own to be ready.
+            # Even if the current process has reached the barrier, we will not send an ack immediately,
+            # we need to wait for the slowest directly connected or indirectly connected peer to
+            # reach the barrier.
+            start = time()
+            if not self_ready:
+                while True:
+                    if time() - start > self.timeout:
+                        raise TimeoutError("Node-[{}] timeout when waiting barrier! ".format(task.router.node_id))
+
+                    if self._runtime.get_recv_num() != self._barrier_peers_nums:
+                        sleep(0.1)
+                    else:
+                        break
+
+            # Step4: Notifies all attached nodes that we are ready.
+            task.emit(self._runtime.event_name_ack, self.node_id, only_remote=True)
+            logging.debug("Node:[{}] sended barrier ack".format(self.node_id))
+
+            # Step5: Wait until all directly or indirectly connected nodes are ready.
+            start = time()
+            while True:
+                if time() - start > self.timeout:
+                    raise TimeoutError("Node-[{}] timeout when waiting barrier! ".format(task.router.node_id))
+
+                if self._runtime.get_ack_num() != self._barrier_peers_nums:
+                    sleep(0.1)
+                else:
+                    break
+
+            logging.info("Node-[{}] env_step:[{}] barrier finish".format(self.node_id, ctx.env_step))

ding/framework/middleware/tests/test_barrier.py

@@ -0,0 +1,144 @@
+import random
+import time
+import socket
+import pytest
+import multiprocessing as mp
+from ditk import logging
+from ding.framework import task
+from ding.framework.parallel import Parallel
+from ding.framework.context import OnlineRLContext
+from ding.framework.middleware.barrier import Barrier
+
+PORTS_LIST = ["1235", "1236", "1237"]
+
+
+class EnvStepMiddleware:
+
+    def __call__(self, ctx):
+        yield
+        ctx.env_step += 1
+
+
+class SleepMiddleware:
+
+    def __init__(self, node_id):
+        self.node_id = node_id
+
+    def random_sleep(self, diection, step):
+        random.seed(self.node_id + step)
+        sleep_second = random.randint(1, 5)
+        logging.info("Node:[{}] env_step:[{}]-{} will sleep:{}s".format(self.node_id, step, diection, sleep_second))
+        for i in range(sleep_second):
+            time.sleep(1)
+            print("Node:[{}] sleepping...".format(self.node_id))
+        logging.info("Node:[{}] env_step:[{}]-{} wake up!".format(self.node_id, step, diection))
+
+    def __call__(self, ctx):
+        self.random_sleep("forward", ctx.env_step)
+        yield
+        self.random_sleep("backward", ctx.env_step)
+
+
+def star_barrier():
+    with task.start(ctx=OnlineRLContext()):
+        node_id = task.router.node_id
+        if node_id == 0:
+            attch_from_nums = 3
+        else:
+            attch_from_nums = 0
+        barrier = Barrier(attch_from_nums)
+        task.use(barrier, lock=False)
+        task.use(SleepMiddleware(node_id), lock=False)
+        task.use(barrier, lock=False)
+        task.use(EnvStepMiddleware(), lock=False)
+        try:
+            task.run(2)
+        except Exception as e:
+            logging.error(e)
+            assert False
+
+
+def mesh_barrier():
+    with task.start(ctx=OnlineRLContext()):
+        node_id = task.router.node_id
+        attch_from_nums = 3 - task.router.node_id
+        barrier = Barrier(attch_from_nums)
+        task.use(barrier, lock=False)
+        task.use(SleepMiddleware(node_id), lock=False)
+        task.use(barrier, lock=False)
+        task.use(EnvStepMiddleware(), lock=False)
+        try:
+            task.run(2)
+        except Exception as e:
+            logging.error(e)
+            assert False
+
+
+def unmatch_barrier():
+    with task.start(ctx=OnlineRLContext()):
+        node_id = task.router.node_id
+        attch_from_nums = 3 - task.router.node_id
+        task.use(Barrier(attch_from_nums, 5), lock=False)
+        if node_id != 2:
+            task.use(Barrier(attch_from_nums, 5), lock=False)
+        try:
+            task.run(2)
+        except TimeoutError as e:
+            assert node_id != 2
+            logging.info("Node:[{}] timeout with barrier".format(node_id))
+        else:
+            time.sleep(5)
+            assert node_id == 2
+            logging.info("Node:[{}] finish barrier".format(node_id))
+
+
+def launch_barrier(args):
+    i, topo, fn, test_id = args
+    address = socket.gethostbyname(socket.gethostname())
+    topology = "alone"
+    attach_to = []
+    port_base = PORTS_LIST[test_id]
+    port = port_base + str(i)
+    if topo == 'star':
+        if i != 0:
+            attach_to = ['tcp://{}:{}{}'.format(address, port_base, 0)]
+    elif topo == 'mesh':
+        for j in range(i):
+            attach_to.append('tcp://{}:{}{}'.format(address, port_base, j))
+
+    Parallel.runner(
+        node_ids=i,
+        ports=int(port),
+        attach_to=attach_to,
+        topology=topology,
+        protocol="tcp",
+        n_parallel_workers=1,
+        startup_interval=0
+    )(fn)
+
+
+@pytest.mark.unittest
+def test_star_topology_barrier():
+    ctx = mp.get_context("spawn")
+    with ctx.Pool(processes=4) as pool:
+        pool.map(launch_barrier, [[i, 'star', star_barrier, 0] for i in range(4)])
+        pool.close()
+        pool.join()
+
+
+@pytest.mark.unittest
+def test_mesh_topology_barrier():
+    ctx = mp.get_context("spawn")
+    with ctx.Pool(processes=4) as pool:
+        pool.map(launch_barrier, [[i, 'mesh', mesh_barrier, 1] for i in range(4)])
+        pool.close()
+        pool.join()
+
+
+@pytest.mark.unittest
+def test_unmatch_barrier():
+    ctx = mp.get_context("spawn")
+    with ctx.Pool(processes=4) as pool:
+        pool.map(launch_barrier, [[i, 'mesh', unmatch_barrier, 2] for i in range(4)])
+        pool.close()
+        pool.join()