# Adapted from https://github.com/vllm-project/vllm/blob/v0.6.4.post1/vllm/distributed/device_communicators/shm_broadcast.py import logging import os import pickle import time from contextlib import contextmanager from dataclasses import dataclass, field from multiprocessing import shared_memory from typing import List, Optional from unittest.mock import patch import torch import torch.distributed as dist from torch.distributed import ProcessGroup from zmq import IPV6 # type: ignore from zmq import SUB, SUBSCRIBE, XPUB, XPUB_VERBOSE, Context # type: ignore from sglang.srt.utils import ( format_tcp_address, get_local_ip_auto, get_open_port, is_valid_ipv6_address, ) # SGLANG_RINGBUFFER_WARNING_INTERVAL can be set to 60 SGLANG_RINGBUFFER_WARNING_INTERVAL = int( os.environ.get("SGLANG_RINGBUFFER_WARNING_INTERVAL", "60") ) logger = logging.getLogger(__name__) class ShmRingBuffer: def __init__( self, n_reader: int, max_chunk_bytes: int, max_chunks: int, name: Optional[str] = None, ): """ A shared memory ring buffer implementation for broadcast communication. Essentially, it is a queue where only one will `enqueue` and multiple will `dequeue`. The max size of each item, together with the max number of items that can be stored in the buffer are known in advance. In this case, we don't need to synchronize the access to the buffer. Buffer memory layout: data metadata | | | (current_idx) | (current_idx) v v +-------------------------------+----------------------------------------+ | chunk0 | chunk1 | ... | chunk | metadata0 | metadata1 | ... | metadata | +-------------------------------+----------------------------------------+ | max_chunks x max_chunk_bytes | max_chunks x (1 + n_reader) bytes | metadata memory layout: each byte is a flag, the first byte is the written flag, and the rest are reader flags. The flags are set to 0 by default. +--------------+--------------+--------------+-----+--------------+ | written_flag | reader0_flag | reader1_flag | ... | readerN_flag | +--------------+--------------+--------------+-----+--------------+ The state of metadata is as follows: (case 1) 0???...???: the block is not written yet, cannot read, can write (case 2) 1000...000: the block is just written, can read, cannot write (case 3) 1???...???: the block is written and read by some readers, can read if not read, cannot write (case 4) 1111...111: the block is written and read by all readers, cannot read, can write State transition for readers: When a reader finds a block that it can read (case 2 or 3), it can yield the block for caller to read. Only after the caller finishes reading the block, the reader can mark the block as read. Readers only mark the block as read (from 0 to 1), the writer marks the block as ready to read (from 1 to 0). State transition for writer: When the writer writes to a block (case 1 or 4), it first resets the written flag to 0, converting either case to case 1. Then it can yield the block for caller to write. After the caller finishes writing the block, the writer can reset the reader flags to 0, and mark the block as written (from 0 to 1). NOTE: the order is important here, first reset the reader flags (so that we are still in case 1), then mark the block as written. The state transition is atomic. If we do it in the reverse order, it will go through case 3 and then back to case 2, and readers might read the intermediate case 3, which is not correct. During creation, `name` is None and the buffer is created. We can pass the created object to other processes by pickling it. The other processes will get the name of the shared memory and open it, so that they can access the same shared memory buffer. """ # noqa self.n_reader = n_reader self.metadata_size = 1 + n_reader self.max_chunk_bytes = max_chunk_bytes self.max_chunks = max_chunks self.total_bytes_of_buffer = ( self.max_chunk_bytes + self.metadata_size ) * self.max_chunks self.data_offset = 0 self.metadata_offset = self.max_chunk_bytes * self.max_chunks if name is None: # we are creating a buffer self.is_creator = True self.shared_memory = shared_memory.SharedMemory( create=True, size=self.total_bytes_of_buffer ) # initialize the metadata section to 0 with memoryview( self.shared_memory.buf[self.metadata_offset :] ) as metadata_buffer: torch.frombuffer(metadata_buffer, dtype=torch.uint8).fill_(0) else: # we are opening an existing buffer self.is_creator = False # fix to https://stackoverflow.com/q/62748654/9191338 # Python incorrectly tracks shared memory even if it is not # created by the process. The following patch is a workaround. with patch( "multiprocessing.resource_tracker.register", lambda *args, **kwargs: None, ): try: self.shared_memory = shared_memory.SharedMemory(name=name) assert self.shared_memory.size == self.total_bytes_of_buffer except FileNotFoundError: # we might deserialize the object in a different node # in this case, this object is not used, # and we should suppress the error pass def __reduce__(self): return ( self.__class__, ( self.n_reader, self.max_chunk_bytes, self.max_chunks, self.shared_memory.name, ), ) def __del__(self): if hasattr(self, "shared_memory"): self.shared_memory.close() if self.is_creator: self.shared_memory.unlink() @contextmanager def get_data(self, current_idx: int): start = self.data_offset + current_idx * self.max_chunk_bytes end = start + self.max_chunk_bytes with memoryview(self.shared_memory.buf[start:end]) as buf: yield buf @contextmanager def get_metadata(self, current_idx: int): start = self.metadata_offset + current_idx * self.metadata_size end = start + self.metadata_size with memoryview(self.shared_memory.buf[start:end]) as buf: yield buf @dataclass class Handle: connect_ip: str local_reader_ranks: List[int] = field(default_factory=list) buffer: Optional[ShmRingBuffer] = None local_subscribe_port: Optional[int] = None remote_subscribe_port: Optional[int] = None class MessageQueue: def __init__( self, n_reader, # number of all readers n_local_reader, # number of local readers through shared memory local_reader_ranks: Optional[List[int]] = None, max_chunk_bytes: int = 1024 * 1024 * 10, max_chunks: int = 10, connect_ip: Optional[str] = None, ): if local_reader_ranks is None: local_reader_ranks = list(range(n_local_reader)) else: assert len(local_reader_ranks) == n_local_reader self.n_local_reader = n_local_reader n_remote_reader = n_reader - n_local_reader self.n_remote_reader = n_remote_reader if connect_ip is None: connect_ip = ( get_local_ip_auto("0.0.0.0") if n_remote_reader > 0 else "127.0.0.1" ) context = Context() if n_local_reader > 0: # for local readers, we will: # 1. create a shared memory ring buffer to communicate small data # 2. create a publish-subscribe socket to communicate large data self.buffer = ShmRingBuffer(n_local_reader, max_chunk_bytes, max_chunks) # XPUB is very similar to PUB, # except that it can receive subscription messages # to confirm the number of subscribers self.local_socket = context.socket(XPUB) # set the verbose option so that we can receive every subscription # message. otherwise, we will only receive the first subscription # see http://api.zeromq.org/3-3:zmq-setsockopt for more details self.local_socket.setsockopt(XPUB_VERBOSE, True) local_subscribe_port = get_open_port() socket_addr = f"tcp://127.0.0.1:{local_subscribe_port}" logger.debug("Binding to %s", socket_addr) self.local_socket.bind(socket_addr) self.current_idx = 0 else: self.buffer = None # type: ignore local_subscribe_port = None self.local_socket = None self.current_idx = -1 if n_remote_reader > 0: # for remote readers, we will: # create a publish-subscribe socket to communicate large data self.remote_socket = context.socket(XPUB) self.remote_socket.setsockopt(XPUB_VERBOSE, True) remote_subscribe_port = get_open_port() if is_valid_ipv6_address(connect_ip): self.remote_socket.setsockopt(IPV6, 1) address = format_tcp_address(connect_ip, remote_subscribe_port) logger.debug(f"class MessageQueue: Binding remote socket to {address=}") self.remote_socket.bind(address) else: remote_subscribe_port = None self.remote_socket = None self._is_writer = True self._is_local_reader = False self.local_reader_rank = -1 # rank does not matter for remote readers self._is_remote_reader = False self.handle = Handle( connect_ip=connect_ip, local_reader_ranks=local_reader_ranks, buffer=self.buffer, local_subscribe_port=local_subscribe_port, remote_subscribe_port=remote_subscribe_port, ) logger.debug("Message queue communication handle: %s", self.handle) def export_handle(self) -> Handle: return self.handle @staticmethod def create_from_handle(handle: Handle, rank) -> "MessageQueue": self = MessageQueue.__new__(MessageQueue) self.handle = handle self._is_writer = False context = Context() if rank in handle.local_reader_ranks: assert handle.buffer is not None self.buffer = handle.buffer self.current_idx = 0 self.local_reader_rank = handle.local_reader_ranks.index(rank) self._is_local_reader = True self._is_remote_reader = False self.local_socket = context.socket(SUB) self.local_socket.setsockopt_string(SUBSCRIBE, "") socket_addr = f"tcp://127.0.0.1:{handle.local_subscribe_port}" logger.debug("Connecting to %s", socket_addr) self.local_socket.connect(socket_addr) self.remote_socket = None else: self.buffer = None # type: ignore self.current_idx = -1 self.local_reader_rank = -1 self._is_local_reader = False self._is_remote_reader = True self.local_socket = None self.remote_socket = context.socket(SUB) self.remote_socket.setsockopt_string(SUBSCRIBE, "") if is_valid_ipv6_address(handle.connect_ip): self.remote_socket.setsockopt(IPV6, 1) socket_addr = format_tcp_address( handle.connect_ip, handle.remote_subscribe_port ) logger.debug("Connecting to %s", socket_addr) self.remote_socket.connect(socket_addr) return self def wait_until_ready(self): """This is a collective operation. All processes (including the readers and the writer) should call this function. """ if self._is_writer: # wait for all readers to connect # local readers for i in range(self.n_local_reader): # wait for subscription messages from all local readers self.local_socket.recv() if self.n_local_reader > 0: # send a message to all local readers # to make sure the publish channel is working self.local_socket.send(b"READY") # remote readers for i in range(self.n_remote_reader): # wait for subscription messages from all remote readers self.remote_socket.recv() if self.n_remote_reader > 0: # send a message to all remote readers # to make sure the publish channel is working self.remote_socket.send(b"READY") elif self._is_local_reader: # wait for the writer to send a message recv = self.local_socket.recv() assert recv == b"READY" elif self._is_remote_reader: # wait for the writer to send a message recv = self.remote_socket.recv() assert recv == b"READY" @contextmanager def acquire_write(self): assert self._is_writer, "Only writers can acquire write" start_time = time.monotonic() n_warning = 1 while True: with self.buffer.get_metadata(self.current_idx) as metadata_buffer: read_count = sum(metadata_buffer[1:]) written_flag = metadata_buffer[0] if written_flag and read_count != self.buffer.n_reader: # this block is written and not read by all readers # for writers, `self.current_idx` is the next block to write # if this block is not ready to write, # we need to wait until it is read by all readers # Release the processor to other threads os.sched_yield() # if we wait for a long time, we should warn the user if ( time.monotonic() - start_time > SGLANG_RINGBUFFER_WARNING_INTERVAL * n_warning ): logger.warning( "No available block found in %s second. ", SGLANG_RINGBUFFER_WARNING_INTERVAL, ) n_warning += 1 continue # found a block that is either # (1) not written # (2) read by all readers # mark the block as not written metadata_buffer[0] = 0 # let caller write to the buffer with self.buffer.get_data(self.current_idx) as buf: yield buf # caller has written to the buffer # NOTE: order is important here # first set the read flags to 0 # then set the written flag to 1 # otherwise, the readers may think they already read the block for i in range(1, self.buffer.n_reader + 1): # set read flag to 0, meaning it is not read yet metadata_buffer[i] = 0 # mark the block as written metadata_buffer[0] = 1 self.current_idx = (self.current_idx + 1) % self.buffer.max_chunks break @contextmanager def acquire_read(self): assert self._is_local_reader, "Only readers can acquire read" start_time = time.monotonic() n_warning = 1 while True: with self.buffer.get_metadata(self.current_idx) as metadata_buffer: read_flag = metadata_buffer[self.local_reader_rank + 1] written_flag = metadata_buffer[0] if not written_flag or read_flag: # this block is either # (1) not written # (2) already read by this reader # for readers, `self.current_idx` is the next block to read # if this block is not ready, # we need to wait until it is written # Release the processor to other threads os.sched_yield() # if we wait for a long time, we should warn the user if ( time.monotonic() - start_time > SGLANG_RINGBUFFER_WARNING_INTERVAL * n_warning ): logger.warning( "No available block found in %s second. ", SGLANG_RINGBUFFER_WARNING_INTERVAL, ) n_warning += 1 continue # found a block that is not read by this reader # let caller read from the buffer with self.buffer.get_data(self.current_idx) as buf: yield buf # caller has read from the buffer # set the read flag metadata_buffer[self.local_reader_rank + 1] = 1 self.current_idx = (self.current_idx + 1) % self.buffer.max_chunks break def enqueue(self, obj): assert self._is_writer, "Only writers can enqueue" serialized_obj = pickle.dumps(obj, protocol=pickle.HIGHEST_PROTOCOL) if self.n_local_reader > 0: if len(serialized_obj) >= self.buffer.max_chunk_bytes: with self.acquire_write() as buf: buf[0] = 1 # overflow self.local_socket.send(serialized_obj) else: with self.acquire_write() as buf: buf[0] = 0 # not overflow buf[1 : len(serialized_obj) + 1] = serialized_obj if self.n_remote_reader > 0: self.remote_socket.send(serialized_obj) def dequeue(self): if self._is_local_reader: with self.acquire_read() as buf: overflow = buf[0] == 1 if not overflow: # no need to know the size of serialized object # pickle format contains the size information internally # see https://docs.python.org/3/library/pickle.html obj = pickle.loads(buf[1:]) if overflow: recv = self.local_socket.recv() obj = pickle.loads(recv) elif self._is_remote_reader: recv = self.remote_socket.recv() obj = pickle.loads(recv) else: raise RuntimeError("Only readers can dequeue") return obj def broadcast_object(self, obj=None): if self._is_writer: self.enqueue(obj) return obj else: return self.dequeue() @staticmethod def create_from_process_group( pg: ProcessGroup, max_chunk_bytes, max_chunks, writer_rank=0 ) -> "MessageQueue": group_rank = dist.get_rank(pg) group_world_size = dist.get_world_size(pg) global_ranks = dist.get_process_group_ranks(pg) from sglang.srt.distributed.parallel_state import in_the_same_node_as status = in_the_same_node_as(pg, source_rank=writer_rank) same_node_ranks = [i for i, s in enumerate(status) if s] n_reader = group_world_size - 1 n_local_reader = len(same_node_ranks) - 1 local_reader_ranks = [i for i in same_node_ranks if i != writer_rank] buffer_io: MessageQueue if group_rank == writer_rank: buffer_io = MessageQueue( n_reader=n_reader, n_local_reader=n_local_reader, local_reader_ranks=local_reader_ranks, max_chunk_bytes=max_chunk_bytes, max_chunks=max_chunks, ) handle = buffer_io.export_handle() dist.broadcast_object_list( [handle], src=global_ranks[writer_rank], group=pg ) else: recv = [None] dist.broadcast_object_list(recv, src=global_ranks[writer_rank], group=pg) handle = recv[0] # type: ignore buffer_io = MessageQueue.create_from_handle(handle, group_rank) buffer_io.wait_until_ready() return buffer_io