chore: import upstream snapshot with attribution

cpp/serve/threaded_engine.h

@@ -0,0 +1,90 @@
+/*!
+ *  Copyright (c) 2023-2025 by Contributors
+ * \file serve/threaded_engine.h
+ * \brief The header of threaded serving engine in MLC LLM.
+ */
+#ifndef MLC_LLM_SERVE_THREADED_ENGINE_H_
+#define MLC_LLM_SERVE_THREADED_ENGINE_H_
+
+#include "data.h"
+#include "engine.h"
+#include "request.h"
+
+namespace mlc {
+namespace llm {
+namespace serve {
+
+using namespace tvm::runtime;
+
+/*!
+ * \brief The interface threaded engine in MLC LLM.
+ * The threaded engine keeps running a background request processing
+ * loop on a standalone thread. Ensuring thread safety, it exposes
+ * `AddRequest` and `AbortRequest` to receive new requests or
+ * abortions from other threads, and the internal request processing
+ * is backed by a normal engine wrapped inside.
+ */
+class ThreadedEngine {
+ public:
+  /*! \brief Create a ThreadedEngine. */
+  static std::unique_ptr<ThreadedEngine> Create();
+
+  virtual ~ThreadedEngine() = default;
+
+  /*!
+   * \brief Initialize the threaded engine from packed arguments in PackedArgs.
+   * \param device The device where to run models.
+   * \param request_stream_callback The request stream callback function to.
+   * \param trace_recorder Event trace recorder for requests.
+   */
+  virtual void InitThreadedEngine(Device device, Optional<Function> request_stream_callback,
+                                  Optional<EventTraceRecorder> trace_recorder) = 0;
+
+  /*!
+   * \brief Reload the engine with the new engine config.
+   * \param engine_config_json_str The engine config JSON string.
+   */
+  virtual void Reload(String engine_config_json_str) = 0;
+
+  /*! \brief Unload the background engine. */
+  virtual void Unload() = 0;
+
+  /*! \brief Reset the engine to the initial state. */
+  virtual void Reset() = 0;
+
+  /*! \brief Starts the background request processing loop. */
+  virtual void RunBackgroundLoop() = 0;
+
+  /*! \brief Starts the request stream callback loop. */
+  virtual void RunBackgroundStreamBackLoop() = 0;
+
+  /*!
+   * \brief Notify the ThreadedEngine to exit the background
+   * request processing loop. This method is invoked by threads
+   * other than the engine-driving thread.
+   */
+  virtual void ExitBackgroundLoop() = 0;
+
+  /*! \brief Add a new request to the engine. */
+  virtual void AddRequest(Request request) = 0;
+
+  /*! \brief Abort the input request (specified by id string) from engine. */
+  virtual void AbortRequest(const String& request_id) = 0;
+
+  /************** Query/Profile/Debug **************/
+
+  /*! \brief Return the default generation config. */
+  virtual GenerationConfig GetDefaultGenerationConfig() const = 0;
+
+  /*! \brief Return the complete engine config. */
+  virtual EngineConfig GetCompleteEngineConfig() const = 0;
+
+  /*! \brief Call the given global function on all workers. Only for debug purpose. */
+  virtual void DebugCallFuncOnAllAllWorker(const String& func_name, Optional<String> func_args) = 0;
+};
+
+}  // namespace serve
+}  // namespace llm
+}  // namespace mlc
+
+#endif  // MLC_LLM_SERVE_THREADED_ENGINE_H_