Add token processor plugin support (#4059)

* Add token processor plugin support

* fix import

* fix import

fastdeploy/engine/common_engine.py

@@ -42,10 +42,16 @@ from fastdeploy.inter_communicator import (
 from fastdeploy.metrics.metrics import main_process_metrics
 from fastdeploy.metrics.trace_util import start_span, start_span_request
 from fastdeploy.model_executor.guided_decoding import schema_checker
-from fastdeploy.output.token_processor import TokenProcessor
+from fastdeploy.plugins.token_processor import load_token_processor_plugins
 from fastdeploy.splitwise.splitwise_connector import SplitwiseConnector
 from fastdeploy.utils import EngineError, envs, llm_logger
 
+try:
+    TokenProcessor = load_token_processor_plugins()
+    llm_logger.info(f"TokenProcessor plugin {TokenProcessor} loaded")
+except:
+    from fastdeploy.output.token_processor import TokenProcessor
+
 
 class EngineService:
     """

fastdeploy/plugins/__init__.py

@@ -18,10 +18,12 @@ from .input_processor import load_input_processor_plugins
 from .model_register import load_model_register_plugins
 from .model_runner import load_model_runner_plugins
 from .reasoning_parser import load_reasoning_parser_plugins
+from .token_processor import load_token_processor_plugins
 
 __all__ = [
     "load_model_register_plugins",
     "load_model_runner_plugins",
     "load_input_processor_plugins",
     "load_reasoning_parser_plugins",
+    "load_token_processor_plugins",
 ]

fastdeploy/plugins/token_processor/__init__.py

@@ -0,0 +1,27 @@
+"""
+# Copyright (c) 2025  PaddlePaddle Authors. All Rights Reserved.
+#
+# 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.
+"""
+
+from fastdeploy.plugins.utils import load_plugins_by_group
+
+# make sure one process only loads plugins once
+PLUGINS_GROUP = "fastdeploy.token_processor_plugins"
+
+
+def load_token_processor_plugins():
+    """load_token_processor_plugins"""
+    plugins = load_plugins_by_group(group=PLUGINS_GROUP)
+    assert len(plugins) <= 1, "Most one plugin is allowed to be loaded."
+    return next(iter(plugins.values()))()