Add logic to handle Python-based backends instead of platform handlers

CMakeLists.txt

@@ -309,13 +309,6 @@ install(
     ${INSTALL_CONFIGDIR}
 )
 
-install(
-  DIRECTORY
-    src/resources/platform_handlers
-  DESTINATION
-    ${CMAKE_INSTALL_PREFIX}/backends/python
-)
-
 install(
   FILES
     src/resources/triton_python_backend_utils.py

src/pb_stub.cc

@@ -82,9 +82,10 @@ Stub::Instantiate(
     const std::string& shm_region_name, const std::string& model_path,
     const std::string& model_version, const std::string& triton_install_path,
     bi::managed_external_buffer::handle_t ipc_control_handle,
-    const std::string& name, const std::string& platform)
+    const std::string& name, const std::string& python_runtime_model)
 {
-  model_context_.Init(model_path, platform, triton_install_path, model_version);
+  model_context_.Init(
+      model_path, python_runtime_model, triton_install_path, model_version);
   name_ = name;
   health_mutex_ = nullptr;
   initialized_ = false;
@@ -1659,57 +1660,29 @@ PYBIND11_EMBEDDED_MODULE(c_python_backend_utils, module)
 
 void
 ModelContext::Init(
-    const std::string& model_path, const std::string& platform,
+    const std::string& model_path, const std::string& runtime_modeldir,
     const std::string& triton_install_path, const std::string& model_version)
 {
-  bool python_model_found = false;
-  std::string platform_model_path;
-
-  if (platform != "NONE") {
-    platform_model_path =
-        triton_install_path + "/platform_handlers/" + platform + "/model.py";
-    // Check if model file exists in the path.
-    struct stat buffer;
-    if (stat(platform_model_path.c_str(), &buffer) == 0) {
-      // Use the Platform model for serving the model.
-      python_model_found = true;
-      type_ = ModelType::PLATFORM;
-      python_model_path_ = platform_model_path;
-      // Trimming the model name from the model path, the platform model
-      // will populate the expected default model file name into model_path_.
-      model_dir_ = model_path.substr(0, model_path.find_last_of("\\/"));
-    } else {
-      LOG_WARN << "Unable to find model(handler) \'" << platform_model_path
-               << "\' for platform field \'" << platform << "\'";
-    }
-  }
-
-  if (!python_model_found) {
+  type_ = ModelType::DEFAULT;
+  if (runtime_modeldir != "DEFAULT") {
+    // For python based backends, existence of `model.py` in the corresponding
+    // backend folder happens on the core side, so we can omit this check here.
+    python_model_path_ = runtime_modeldir + "/model.py";
+    type_ = ModelType::BACKEND;
+  } else {
     python_model_path_ = model_path;
     // Check if model file exists in this path.
     struct stat buffer;
-    if (stat(python_model_path_.c_str(), &buffer) == 0) {
-      python_model_found = true;
-      type_ = ModelType::DEFAULT;
-    }
-    // Initializing here for consistency with platform model case.
-    model_dir_ = model_path.substr(0, model_path.find_last_of("\\/"));
-  }
-
-  if (!python_model_found) {
-    if (platform != "NONE") {
-      throw PythonBackendException(
-          ("Python model file not found in neither \'" + platform_model_path +
-           "\' nor \'" + model_path + "\'"));
-    } else {
+    if (stat(python_model_path_.c_str(), &buffer) != 0) {
       throw PythonBackendException(
           ("Python model file not found in \'" + model_path + "\'"));
     }
   }
 
+  model_dir_ = model_path.substr(0, model_path.find_last_of("\\/"));
   python_backend_folder_ = triton_install_path;
   model_version_ = model_version;
-  platform_ = platform;
+  runtime_modeldir_ = runtime_modeldir;
 }
 
 void
@@ -1740,9 +1713,10 @@ ModelContext::StubSetup(py::module& sys)
     sys = py::module_::import(
         (std::string(model_version_) + "." + model_name_trimmed).c_str());
   } else {
-    std::string platform_model_dir(
-        python_backend_folder_ + "/platform_handlers/" + platform_ + "/");
-    sys.attr("path").attr("append")(platform_model_dir);
+    std::string model_path_parent =
+        python_model_path_.substr(0, python_model_path_.find_last_of("/"));
+    std::string backend_model_dir(model_path_parent);
+    sys.attr("path").attr("append")(backend_model_dir);
     sys.attr("path").attr("append")(python_backend_folder_);
     sys = py::module_::import(model_name_trimmed.c_str());
   }
@@ -1791,14 +1765,14 @@ main(int argc, char** argv)
   int64_t shm_growth_size = std::stol(argv[4]);
   std::string triton_install_path = argv[6];
   std::string name = argv[8];
-  std::string platform = argv[9];
+  std::string runtime_modeldir = argv[9];
 
   std::unique_ptr<Stub>& stub = Stub::GetOrCreateInstance();
   try {
     stub->Instantiate(
         shm_growth_size, shm_default_size, shm_region_name, model_path,
         model_version, argv[6] /* triton install path */,
-        std::stoi(argv[7]) /* IPCControl handle */, name, platform);
+        std::stoi(argv[7]) /* IPCControl handle */, name, runtime_modeldir);
   }
   catch (const PythonBackendException& pb_exception) {
     LOG_INFO << "Failed to preinitialize Python stub: " << pb_exception.what();

src/pb_stub.h

@@ -180,9 +180,15 @@ class ModelContext {
   std::string model_dir_;
   std::string model_version_;
   std::string python_backend_folder_;
-  std::string platform_;
-
-  enum ModelType { DEFAULT, PLATFORM };
+  std::string runtime_modeldir_;
+
+  // Triton supports python-based backends,
+  // i.e. backends that provide common `model.py`, that can be re-used
+  // between different models. `ModelType` helps to differentiate
+  // between models running with c++ python backend (ModelType::DEFAULT)
+  // and models running with python-based backend (ModelType::BACKEND)
+  // at the time of ModelContext::StubSetup to properly set up paths.
+  enum ModelType { DEFAULT, BACKEND };
   ModelType type_;
 };
 
@@ -210,7 +216,8 @@ class Stub {
       const std::string& shm_region_name, const std::string& model_path,
       const std::string& model_version, const std::string& triton_install_path,
       bi::managed_external_buffer::handle_t ipc_control_handle,
-      const std::string& model_instance_name, const std::string& platform);
+      const std::string& model_instance_name,
+      const std::string& runtime_modeldir);
 
   /// Get the health of the stub process.
   bool& Health();

src/python_be.cc

@@ -1771,11 +1771,12 @@ ModelState::ModelState(TRITONBACKEND_Model* triton_model)
   python_execution_env_ = "";
   force_cpu_only_input_tensors_ = true;
   decoupled_ = false;
-  platform_ = "";
 
   void* bstate;
   THROW_IF_BACKEND_MODEL_ERROR(TRITONBACKEND_BackendState(backend, &bstate));
   backend_state_ = reinterpret_cast<BackendState*>(bstate);
+
+  runtime_modeldir_ = backend_state_->runtime_modeldir;
   triton::common::TritonJson::Value params;
   common::TritonJson::Value model_config;
   if (model_config_.Find("parameters", &params)) {
@@ -1812,14 +1813,6 @@ ModelState::ModelState(TRITONBACKEND_Model* triton_model)
       }
     }
 
-    triton::common::TritonJson::Value platform;
-    if (model_config_.Find("platform", &platform)) {
-      auto error = platform.AsString(&platform_);
-      if (error != nullptr) {
-        throw BackendModelException(error);
-      }
-    }
-
     // Skip the FORCE_CPU_ONLY_INPUT_TENSORS variable if it doesn't exits.
     std::string force_cpu_only_input_tensor;
     error = nullptr;
@@ -1948,8 +1941,11 @@ TRITONBACKEND_Initialize(TRITONBACKEND_Backend* backend)
   backend_state->shm_message_queue_size = 1000;
   backend_state->number_of_instance_inits = 0;
   backend_state->thread_pool_size = 32;
+  // Initialize shared memory region prefix to include backend's name
+  // to avoid collision between python backend and python-based backends.
   backend_state->shared_memory_region_prefix =
-      "triton_python_backend_shm_region_";
+      "triton_" + name + "_backend_shm_region_";
+  std::string default_backend_dir_string;
 
   if (backend_config.Find("cmdline", &cmdline)) {
     triton::common::TritonJson::Value shm_growth_size;
@@ -2059,6 +2055,12 @@ TRITONBACKEND_Initialize(TRITONBACKEND_Backend* backend)
         return TRITONSERVER_ErrorNew(TRITONSERVER_ERROR_INVALID_ARG, ia.what());
       }
     }
+
+    triton::common::TritonJson::Value default_backend_dir;
+    if (cmdline.Find("backend-directory", &default_backend_dir)) {
+      RETURN_IF_ERROR(
+          default_backend_dir.AsString(&default_backend_dir_string));
+    }
   }
 
   LOG_MESSAGE(
@@ -2076,7 +2078,50 @@ TRITONBACKEND_Initialize(TRITONBACKEND_Backend* backend)
   TRITONBACKEND_ArtifactType artifact_type;
   RETURN_IF_ERROR(
       TRITONBACKEND_BackendArtifacts(backend, &artifact_type, &location));
-  backend_state->python_lib = location;
+
+  // Check if `triton_python_backend_stub` and `triton_python_backend_utils.py`
+  // are located under `location`.
+  // DLIS-5596: Add forward slash to be platform agnostic
+  // (i.e. For Windows, we need to use backward slash).
+  std::string default_python_backend_dir =
+      default_backend_dir_string + "/python";
+  std::string backend_stub_path =
+      std::string(location) + "/triton_python_backend_stub";
+  std::string backend_utils =
+      std::string(location) + "/triton_python_backend_utils.py";
+  // Both, stub and utils should be in the same location
+  if (FileExists(backend_stub_path) && FileExists(backend_utils)) {
+    backend_state->python_lib = location;
+    // If `location` is default location of a python backend,
+    // then we are using default python backend.
+    if (default_python_backend_dir == std::string(location)) {
+      backend_state->runtime_modeldir = "";
+    } else {
+      // If `location` is not default location of a python backend,
+      // then we are using a python backend based backend and model.py stored
+      // in the received location.
+      backend_state->runtime_modeldir = location;
+    }
+  } else {
+    // If stub and utils are not found in received `location`,
+    // then we are using a python backend based backend and stub and utils are
+    // stored in the default python backend location.
+    if (!default_backend_dir_string.empty()) {
+      std::string backend_stub_path =
+          default_backend_dir_string + "/python/triton_python_backend_stub";
+      if (!FileExists(backend_stub_path)) {
+        return TRITONSERVER_ErrorNew(
+            TRITONSERVER_ERROR_NOT_FOUND,
+            (std::string("triton_python_backend_stub") +
+             " is not found. Searched paths: " + default_backend_dir_string +
+             "/python and" + std::string(location))
+                .c_str());
+      }
+    }
+    backend_state->runtime_modeldir = location;
+    backend_state->python_lib = default_backend_dir_string + "/python";
+  }
+
   backend_state->env_manager = std::make_unique<EnvironmentManager>();
 
   RETURN_IF_ERROR(TRITONBACKEND_BackendSetState(

src/python_be.h

@@ -218,6 +218,7 @@ struct BackendState {
   std::string shared_memory_region_prefix;
   int64_t thread_pool_size;
   std::unique_ptr<EnvironmentManager> env_manager;
+  std::string runtime_modeldir;
 };
 
 class ModelState : public BackendModel {
@@ -237,8 +238,8 @@ class ModelState : public BackendModel {
   // Is decoupled API being used.
   bool IsDecoupled() { return decoupled_; }
 
-  // Returns the value in the platform field
-  std::string Platform() { return platform_; }
+  // Returns the value in the `runtime_modeldir_` field
+  std::string RuntimeModelDir() { return runtime_modeldir_; }
 
   // Launch auto-complete stub process.
   TRITONSERVER_Error* LaunchAutoCompleteStubProcess();
@@ -255,7 +256,7 @@ class ModelState : public BackendModel {
   std::string python_execution_env_;
   bool force_cpu_only_input_tensors_;
   bool decoupled_;
-  std::string platform_;
+  std::string runtime_modeldir_;
   std::unique_ptr<StubLauncher> auto_complete_stub_;
 };