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[Session] Add streaming mode with SessionAwareCache fast path (#19171)

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Co-authored-by: hnyls2002 <lsyincs@gmail.com>
This commit is contained in:
Aurick Qiao
2026-02-27 16:31:08 -08:00
committed by GitHub
parent 2bd2b60b5c
commit c6cb0c9649
12 changed files with 999 additions and 30 deletions
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60
python/sglang/srt/managers/session_controller.py
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@@ -11,6 +11,7 @@
# ==============================================================================
import logging
import time
import uuid
from typing import Dict, Optional
@@ -65,25 +66,59 @@ class SessionReqNode:
class Session:
def __init__(self, capacity_of_str_len: int, session_id: Optional[str] = None):
def __init__(
self,
capacity_of_str_len: int,
session_id: Optional[str] = None,
streaming: bool = False,
timeout: Optional[float] = None,
):
self.session_id = session_id if session_id is not None else uuid.uuid4().hex
self.capacity_of_str_len = capacity_of_str_len
self.streaming = streaming
self.timeout = timeout
self.last_active_time: float = time.monotonic()
self.req_nodes: Dict[str, SessionReqNode] = {}
def is_timed_out(self) -> bool:
if self.timeout is None:
return False
return time.monotonic() - self.last_active_time > self.timeout
def create_req(self, req: TokenizedGenerateReqInput, tokenizer, vocab_size: int):
assert req.session_params is not None
self.last_active_time = time.monotonic()
session_params = req.session_params
last_req_node = None
last_req = None
abort = False
if session_params.replace:
abort_message = ""
if self.streaming:
# Streaming sessions: only simple appends allowed; reject otherwise.
if session_params.replace:
abort = True
abort_message = "Streaming sessions do not support replace."
elif session_params.drop_previous_output:
abort = True
abort_message = (
"Streaming sessions do not support drop_previous_output."
)
elif session_params.offset and session_params.offset != 0:
abort = True
abort_message = "Streaming sessions do not support offset."
elif self.req_nodes:
assert len(self.req_nodes) == 1
_, last_req_node = self.req_nodes.popitem()
last_req = last_req_node.req
elif session_params.replace:
if session_params.rid is None:
for _, req_node in self.req_nodes.items():
req_node.clear(self.req_nodes)
else:
if session_params.rid not in self.req_nodes:
abort = True
abort_message = "Invalid request session id"
else:
last_req_node = self.req_nodes[session_params.rid]
last_req_node.abort()
@@ -93,18 +128,22 @@ class Session:
if session_params.rid is not None:
if session_params.rid not in self.req_nodes:
abort = True
abort_message = "Invalid request session id"
else:
last_req_node = self.req_nodes[session_params.rid]
last_req = last_req_node.req
if not last_req.finished():
logging.warning(
"The request in a session is appending to a request that hasn't finished."
)
abort = True
abort_message = "Session request is appending to a request that hasn't finished."
logging.warning(abort_message)
if last_req is not None:
# trim bos token if it is an append
if tokenizer is not None and req.input_ids[0] == tokenizer.bos_token_id:
if (
tokenizer is not None
and req.input_ids
and req.input_ids[0] == tokenizer.bos_token_id
):
req.input_ids = req.input_ids[1:]
input_ids = (
@@ -136,6 +175,7 @@ class Session:
else:
input_ids = req.input_ids
input_ids_unpadded = req.input_ids
new_req = Req(
rid=req.rid,
origin_input_text=None,
@@ -143,7 +183,7 @@ class Session:
origin_input_ids_unpadded=input_ids_unpadded,
sampling_params=req.sampling_params,
lora_id=req.lora_id,
session_id=self.session_id,
session=self,
custom_logit_processor=req.custom_logit_processor,
stream=req.stream,
return_logprob=req.return_logprob,
@@ -156,7 +196,11 @@ class Session:
new_req.tokenizer = tokenizer
if abort:
new_req.set_finish_with_abort("Invalid request session id")
new_req.set_finish_with_abort(abort_message)
elif self.streaming:
if last_req is not None:
last_req.session = None
self.req_nodes[req.rid] = SessionReqNode(new_req)
else:
new_req_node = SessionReqNode(new_req, last_req_node)
self.req_nodes[req.rid] = new_req_node