Support HTTP2 server (#21700)

python/pyproject.toml

@@ -129,6 +129,10 @@ tracing = [
   "opentelemetry-sdk",
 ]
 
+http2 = [
+  "granian>=2.6.0",
+]
+
 test = [
   "accelerate",
   "addict",
@@ -146,6 +150,7 @@ test = [
   "diff-cover",
   "sentence_transformers",
   "tabulate",
+  "granian>=2.6.0",
 ]
 
 dev = ["sglang[test]"]
@@ -153,6 +158,7 @@ dev = ["sglang[test]"]
 all = [
   "sglang[diffusion]",
   "sglang[tracing]",
+  "sglang[http2]",
 ]
 
 [tool.uv.extra-build-dependencies]

python/sglang/srt/entrypoints/http_server.py

@@ -206,6 +206,32 @@ def get_global_state() -> _GlobalState:
     return _global_state
 
 
+async def _init_granian_worker() -> ServerArgs:
+    main_pid = get_main_process_id()
+    port_args, server_args, scheduler_info = read_from_shared_memory(
+        f"multi_tokenizer_args_{main_pid}"
+    )
+
+    tokenizer_manager = TokenizerManager(server_args, port_args)
+    template_manager = TemplateManager()
+    template_manager.initialize_templates(
+        tokenizer_manager=tokenizer_manager,
+        model_path=server_args.model_path,
+        chat_template=server_args.chat_template,
+        completion_template=server_args.completion_template,
+    )
+    tokenizer_manager.max_req_input_len = scheduler_info["max_req_input_len"]
+
+    set_global_state(
+        _GlobalState(
+            tokenizer_manager=tokenizer_manager,
+            template_manager=template_manager,
+            scheduler_info=scheduler_info,
+        )
+    )
+    return server_args
+
+
 async def init_multi_tokenizer() -> ServerArgs:
     """
     Initialization function for multi-process tokenizer mode.
@@ -263,6 +289,10 @@ async def lifespan(fast_api_app: FastAPI):
         server_args = fast_api_app.server_args
         warmup_thread_kwargs = fast_api_app.warmup_thread_kwargs
         thread_label = "Tokenizer"
+    elif envs.SGLANG_GRANIAN_PARENT_PID.get() is not None:
+        server_args = await _init_granian_worker()
+        warmup_thread_kwargs = dict(server_args=server_args)
+        thread_label = "Tokenizer"
     else:
         # Initialize multi-tokenizer support for worker processes
         server_args = await init_multi_tokenizer()
@@ -2017,6 +2047,53 @@ def _wait_weights_ready():
     )
 
 
+def _close_main_process_sockets():
+    """Close the main process's ZMQ sockets before spawning Granian workers.
+
+    Granian workers create their own TokenizerManager with fresh ZMQ sockets.
+    The main process must release its sockets first to avoid binding conflicts
+    on the same IPC addresses.
+    """
+    if _global_state is None or _global_state.tokenizer_manager is None:
+        return
+    tm = _global_state.tokenizer_manager
+    for attr in ("recv_from_detokenizer", "send_to_scheduler"):
+        sock = getattr(tm, attr, None)
+        if sock is None:
+            continue
+        inner = getattr(sock, "socket", None)
+        if inner is not None:
+            inner.close()
+        elif hasattr(sock, "close"):
+            sock.close()
+        setattr(tm, attr, None)
+
+
+def _run_granian_server(server_args: ServerArgs):
+    """Launch Granian with HTTP/2 support"""
+    from granian import Granian
+    from granian.constants import HTTPModes, Interfaces, Loops
+
+    granian_kwargs = dict(
+        target="sglang.srt.entrypoints.http_server:app",
+        address=server_args.host,
+        port=server_args.port,
+        interface=Interfaces.ASGI,
+        http=HTTPModes.auto,
+        loop=Loops.uvloop,
+        log_level=server_args.log_level_http or server_args.log_level or "info",
+        workers=1,
+    )
+
+    ssl_enabled = server_args.ssl_certfile and server_args.ssl_keyfile
+    if ssl_enabled:
+        granian_kwargs["ssl_cert"] = server_args.ssl_certfile
+        granian_kwargs["ssl_key"] = server_args.ssl_keyfile
+
+    server = Granian(**granian_kwargs)
+    server.serve()
+
+
 def _setup_and_run_http_server(
     server_args: ServerArgs,
     tokenizer_manager,
@@ -2047,6 +2124,35 @@ def _setup_and_run_http_server(
     if server_args.enable_metrics:
         add_prometheus_track_response_middleware(app)
 
+    # Use Granian for HTTP/2 server
+    if server_args.enable_http2:
+        # Reuse the multi-tokenizer shared memory mechanism to pass
+        # init args (port_args, server_args, scheduler_info) to
+        # Granian workers, which are independent processes.
+        multi_tokenizer_args_shm = write_data_for_multi_tokenizer(
+            port_args, server_args, scheduler_infos[0]
+        )
+        try:
+            if server_args.ssl_certfile:
+                logger.info(
+                    f"SSL enabled: certfile={server_args.ssl_certfile}, "
+                    f"keyfile={server_args.ssl_keyfile}"
+                )
+            logger.info(
+                f"Starting Granian HTTP/2 server on "
+                f"{server_args.host}:{server_args.port}"
+            )
+            # Propagate the main process PID via os.environ so Granian
+            # workers (forked or spawned) can locate the shared memory
+            # segment created above.
+            envs.SGLANG_GRANIAN_PARENT_PID.set(os.getpid())
+            _close_main_process_sockets()
+            _run_granian_server(server_args)
+        finally:
+            if multi_tokenizer_args_shm is not None:
+                multi_tokenizer_args_shm.unlink()
+        return
+
     # Pass additional arguments to the lifespan function.
     # They will be used for additional initialization setups.
     if server_args.tokenizer_worker_num == 1:

python/sglang/srt/environ.py

@@ -489,6 +489,9 @@ class Envs:
     # HTTP Server
     SGLANG_TIMEOUT_KEEP_ALIVE = EnvInt(5)
 
+    # HTTP/2 Server
+    SGLANG_GRANIAN_PARENT_PID = EnvInt(None)
+
     # Health Check
     SGLANG_ENABLE_HEALTH_ENDPOINT_GENERATION = EnvBool(True)
 

python/sglang/srt/managers/multi_tokenizer_mixin.py

@@ -433,7 +433,16 @@ async def print_exception_wrapper(func):
 
 
 def get_main_process_id() -> int:
-    """Get the main process ID"""
+    """Get the main process ID.
+
+    Supports override via SGLANG_GRANIAN_PARENT_PID for workers whose
+    multiprocessing parent PID differs from the shared-memory owner.
+    """
+    from sglang.srt.environ import envs
+
+    override = envs.SGLANG_GRANIAN_PARENT_PID.get()
+    if override is not None:
+        return override
     return multiprocessing.current_process()._parent_pid
 
 

python/sglang/srt/server_args.py

@@ -326,6 +326,7 @@ class ServerArgs:
     ssl_ca_certs: Optional[str] = None
     ssl_keyfile_password: Optional[str] = None
     enable_ssl_refresh: bool = False
+    enable_http2: bool = False
 
     # Quantization and data type
     dtype: str = "auto"
@@ -923,6 +924,26 @@ class ServerArgs:
                 "to be specified."
             )
 
+        if self.enable_http2:
+            try:
+                import granian  # noqa: F401
+            except ImportError:
+                raise ValueError(
+                    "--enable-http2 requires the 'granian' package. "
+                    'Install it with: pip install "sglang[http2]"'
+                )
+            if self.enable_ssl_refresh:
+                raise ValueError(
+                    "--enable-ssl-refresh is not supported with --enable-http2. "
+                    "Granian does not support SSL certificate hot-reloading. "
+                    "Use Uvicorn (the default) or handle certificate rotation externally."
+                )
+            if self.tokenizer_worker_num > 1:
+                raise ValueError(
+                    "--enable-http2 does not yet support --tokenizer-worker-num > 1. "
+                    "Multi-worker HTTP/2 support will be added in a future release."
+                )
+
     def _handle_deprecated_args(self):
         # Handle deprecated tool call parsers
         deprecated_tool_call_parsers = {"qwen25": "qwen", "glm45": "glm"}
@@ -3865,6 +3886,14 @@ class ServerArgs:
             help="Enable automatic SSL certificate hot-reloading when cert/key "
             "files change on disk. Requires --ssl-certfile and --ssl-keyfile.",
         )
+        parser.add_argument(
+            "--enable-http2",
+            action="store_true",
+            default=ServerArgs.enable_http2,
+            help="Use Granian instead of Uvicorn as the ASGI server, enabling HTTP/1.1 and "
+            "HTTP/2 auto-negotiation. Clients may use h2c (cleartext HTTP/2) or plain HTTP/1.1. "
+            "Requires 'pip install sglang[http2]'.",
+        )
 
         # Quantization and data type
         parser.add_argument(