[infer] support lora adapter for SGLang backend (#8067)

src/llamafactory/chat/sglang_engine.py

@@ -79,6 +79,10 @@ class SGLangEngine(BaseEngine):
         self.template = get_template_and_fix_tokenizer(self.tokenizer, data_args)
         self.template.mm_plugin.expand_mm_tokens = False  # for sglang generate
         self.generating_args = generating_args.to_dict()
+        if model_args.adapter_name_or_path is not None:
+            self.lora_request = True
+        else:
+            self.lora_request = False
 
         launch_cmd = [
             "python3 -m sglang.launch_server",
@@ -90,6 +94,15 @@ class SGLangEngine(BaseEngine):
             f"--download-dir {model_args.cache_dir}",
             "--log-level error",
         ]
+        if self.lora_request:
+            launch_cmd.extend(
+                [
+                    "--max-loras-per-batch 1",
+                    f"--lora-backend {model_args.sglang_lora_backend}",
+                    f"--lora-paths lora0={model_args.adapter_name_or_path[0]}",
+                    "--disable-radix-cache",
+                ]
+            )
         launch_cmd = " ".join(launch_cmd)
         logger.info_rank0(f"Starting SGLang server with command: {launch_cmd}")
         try:
@@ -202,6 +215,8 @@ class SGLangEngine(BaseEngine):
                 "sampling_params": sampling_params,
                 "stream": True,
             }
+            if self.lora_request:
+                json_data["lora_request"] = ["lora0"]
             response = requests.post(f"{self.base_url}/generate", json=json_data, stream=True)
             if response.status_code != 200:
                 raise RuntimeError(f"SGLang server error: {response.status_code}, {response.text}")

src/llamafactory/hparams/model_args.py

@@ -364,6 +364,12 @@ class SGLangArguments:
         default=None,
         metadata={"help": "Config to initialize the SGLang engine. Please use JSON strings."},
     )
+    sglang_lora_backend: Literal["triton", "flashinfer"] = field(
+        default="triton",
+        metadata={
+            "help": "The backend of running GEMM kernels for Lora modules. Recommend using the Triton LoRA backend for better performance and stability."
+        },
+    )
 
     def __post_init__(self):
         if isinstance(self.sglang_config, str) and self.sglang_config.startswith("{"):

tests/e2e/test_sglang.py

@@ -20,7 +20,7 @@ from llamafactory.chat import ChatModel
 from llamafactory.extras.packages import is_sglang_available
 
 
-MODEL_NAME = "meta-llama/Llama-3.2-1B-Instruct"
+MODEL_NAME = "Qwen/Qwen2.5-0.5B"
 
 
 INFER_ARGS = {