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sglang/python/sglang/srt/ray/engine.py
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Python

# Copyright 2023-2024 SGLang Team
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""RayEngine - Engine subclass that launches schedulers as Ray actors."""
from __future__ import annotations
import dataclasses
import logging
import threading
from typing import Callable
import ray
from ray.util.scheduling_strategies import PlacementGroupSchedulingStrategy
from sglang.srt.entrypoints.engine import (
Engine,
SchedulerInitResult,
_calculate_rank_ranges,
_compute_parallelism_ranks,
)
from sglang.srt.ray.scheduler_actor import SchedulerActor
from sglang.srt.server_args import ZMQ_TCP_PORT_DELTA, PortArgs, ServerArgs
logger = logging.getLogger(__name__)
@dataclasses.dataclass
class RaySchedulerInitResult(SchedulerInitResult):
"""SchedulerInitResult that also holds Ray actor handles for cleanup."""
scheduler_actors: list = dataclasses.field(default_factory=list)
def _find_engine_bundle(placement_group, nnodes: int) -> tuple[int, str]:
"""Find which placement group bundle is on the same node as the Engine.
Rank0 scheduler must be co-located with the Engine. Returns (bundle_index, engine_ip).
"""
engine_ip = ray.util.get_node_ip_address()
@ray.remote(num_cpus=0, num_gpus=0)
def get_node_ip():
return ray.util.get_node_ip_address()
bundle_ips = ray.get(
[
get_node_ip.options(
scheduling_strategy=PlacementGroupSchedulingStrategy(
placement_group=placement_group,
placement_group_bundle_index=i,
),
).remote()
for i in range(nnodes)
]
)
try:
return bundle_ips.index(engine_ip), engine_ip
except ValueError:
raise RuntimeError(
f"Engine node {engine_ip} not found in any placement group bundle {bundle_ips}. "
f"Rank-0 scheduler must be co-located with the Engine."
)
class RayEngine(Engine):
"""Engine using Ray actors for scheduler processes."""
def shutdown(self):
"""Shutdown the engine — kill Ray scheduler actors then local processes."""
for actor in self._scheduler_init_result.scheduler_actors:
try:
ray.kill(actor)
except Exception:
logger.error(f"Failed to kill Ray scheduler actor: {actor}")
super().shutdown()
@classmethod
def _launch_scheduler_processes(
cls,
server_args: ServerArgs,
port_args: PortArgs,
run_scheduler_process_func: Callable,
) -> tuple[SchedulerInitResult, None]:
"""Launch schedulers as Ray actors.
Returns:
Tuple of (RaySchedulerInitResult, None).
scheduler_procs is None since Ray uses actors instead of mp.Process.
"""
pg = ray.util.get_current_placement_group()
if pg is None:
raise RuntimeError(
"use_ray=True requires a placement group, but none was detected. "
"Schedule the Engine actor onto a placement group"
)
nnodes = server_args.nnodes
# co-located with the Engine and rank0 scheduler at the same node
engine_bundle, engine_ip = _find_engine_bundle(pg, nnodes)
bundle_for_node = [engine_bundle] + [
i for i in range(nnodes) if i != engine_bundle
]
rank0_node_ip = engine_ip
if server_args.dp_size == 1:
# Launch tensor parallel scheduler actors
world_size = server_args.tp_size * server_args.pp_size
gpus_per_node = world_size // nnodes
logger.info(
f"Ray cluster: {nnodes} nodes, "
f"Use {gpus_per_node} GPUs/node, world_size={world_size}"
)
dist_init_addr = f"{rank0_node_ip}:{server_args.port + ZMQ_TCP_PORT_DELTA}"
logger.info(f"dist_init_addr: {dist_init_addr}")
scheduler_actors = []
for node_idx in range(nnodes):
bundle_idx = bundle_for_node[node_idx]
pp_range, tp_range, pp_per_node, tp_per_node = _calculate_rank_ranges(
nnodes,
server_args.pp_size,
server_args.tp_size,
node_rank=node_idx,
)
for pp_rank in pp_range:
for tp_rank in tp_range:
local_gpu_idx = (pp_rank % pp_per_node) * tp_per_node + (
tp_rank % tp_per_node
)
attn_cp_rank, moe_dp_rank, moe_ep_rank = (
_compute_parallelism_ranks(server_args, tp_rank)
)
actor = SchedulerActor.options(
num_cpus=0,
num_gpus=1,
name=f"sglang_scheduler_rank0node={rank0_node_ip}_pp{pp_rank}_tp{tp_rank}",
scheduling_strategy=PlacementGroupSchedulingStrategy(
placement_group=pg,
placement_group_bundle_index=bundle_idx,
),
).remote(
server_args=server_args,
port_args=port_args,
gpu_id=local_gpu_idx,
tp_rank=tp_rank,
attn_cp_rank=attn_cp_rank,
moe_dp_rank=moe_dp_rank,
moe_ep_rank=moe_ep_rank,
pp_rank=pp_rank,
dp_rank=0,
dist_init_addr=dist_init_addr,
)
scheduler_actors.append(actor)
try:
scheduler_infos = ray.get(
[actor.get_info.remote() for actor in scheduler_actors]
)
except ray.exceptions.RayActorError as e:
for actor in scheduler_actors:
try:
ray.kill(actor)
except Exception:
logger.error(f"Failed to kill Ray scheduler actor: {actor}")
raise RuntimeError(f"Scheduler actor failed to initialize: {e}")
event_loop_refs = [
actor.run_event_loop.remote() for actor in scheduler_actors
]
def wait_for_completion():
try:
ray.get(event_loop_refs)
except Exception as e:
logger.error(f"Ray scheduler actor terminated with error: {e}")
return (
RaySchedulerInitResult(
scheduler_infos=scheduler_infos,
wait_for_completion=wait_for_completion,
scheduler_actors=scheduler_actors,
),
None,
)
else:
# Launch the data parallel controller
return (
cls._launch_dp_scheduler_processes(
server_args, port_args, pg, bundle_for_node, rank0_node_ip
),
None,
)
@classmethod
def _launch_dp_scheduler_processes(
cls,
server_args: ServerArgs,
port_args: PortArgs,
pg,
bundle_for_node: list,
rank0_node_ip: str,
) -> RaySchedulerInitResult:
"""Launch DP schedulers via RayDataParallelController."""
from sglang.srt.ray.data_parallel_controller import (
RayDataParallelController,
)
if server_args.enable_dp_attention:
# DP attention folds DP into TP — total GPUs = tp_size * pp_size
total_gpus = server_args.tp_size * server_args.pp_size
else:
total_gpus = server_args.dp_size * server_args.tp_size * server_args.pp_size
gpus_per_node = total_gpus // server_args.nnodes
logger.info(
f"Ray DP cluster: {server_args.nnodes} nodes, "
f"{gpus_per_node} GPUs/node, dp_size={server_args.dp_size}, "
f"tp_size={server_args.tp_size}, pp_size={server_args.pp_size}, "
f"enable_dp_attention={server_args.enable_dp_attention}"
)
# Set dist_init_addr on server_args so PortArgs.init_new() can compute
# TCP addresses correctly (required for DP attention path).
dp_server_args = dataclasses.replace(
server_args,
dist_init_addr=f"{rank0_node_ip}:{server_args.port + ZMQ_TCP_PORT_DELTA}",
)
# Create the DP controller in-process. This blocks until all actors
# are initialized and their event loops have started.
controller = RayDataParallelController(
dp_server_args, port_args, pg, bundle_for_node, rank0_node_ip
)
# Start the DP controller's event loop in a daemon thread.
# It routes requests from the tokenizer to per-DP-rank schedulers.
dp_thread = threading.Thread(
target=controller.event_loop, daemon=True, name="dp_controller"
)
dp_thread.start()
scheduler_infos = [
{
"max_total_num_tokens": controller.max_total_num_tokens,
"max_req_input_len": controller.max_req_input_len,
}
]
event_loop_refs = controller.event_loop_refs
def wait_for_completion():
try:
ray.get(event_loop_refs)
except Exception as e:
logger.error(f"Ray scheduler actor terminated with error: {e}")
return RaySchedulerInitResult(
scheduler_infos=scheduler_infos,
wait_for_completion=wait_for_completion,
scheduler_actors=controller.scheduler_actors,
)