Support HTTP2 server (#21700)

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(