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Core API Documentation

Overview​

The Content Transfer Engine (CTE) Core is a high-performance distributed storage middleware system built on the Clio framework. It provides a flexible blob storage API with advanced features including:

  • Multi-target Storage Management: Register and manage multiple storage backends (file, RAM, NVMe)
  • Blob Storage with Tags: Store and retrieve data blobs with tag-based organization
  • Block-based Data Management: Efficient block-level data placement across multiple targets
  • Performance Monitoring: Built-in telemetry and performance metrics collection
  • Configurable Data Placement: Multiple data placement algorithms (random, round-robin, max bandwidth)
  • Asynchronous Operations: Async-only API with C++20 coroutine support

CTE Core implements a Module (CLIO Runtime Module) that integrates with the CLIO Runtime distributed runtime system, providing scalable data management across multiple nodes in a cluster.

Installation & Linking​

Prerequisites​

  • CMake 3.20 or higher
  • C++17 compatible compiler
  • Clio framework (clio-core umbrella package, which provides clio::run::cxx and the admin Module)
  • yaml-cpp library
  • Python 3.7+ (for Python bindings)
  • nanobind (for Python bindings)

Building CTE Core​

# Clone the repository
git clone <repository-url>
cd content-transfer-engine

# Create build directory
mkdir build && cd build

# Configure with CMake (using debug preset as recommended)
cmake .. -DCMAKE_BUILD_TYPE=Debug

# Build the project
make -j

# Install (optional)
sudo make install

Linking to CTE Core in CMake Projects​

To use CTE Core in your CMake project, follow the patterns established in the MODULE_DEVELOPMENT_GUIDE.md. Add the following to your CMakeLists.txt:

# Find required Clio framework packages
find_package(clio-core CONFIG REQUIRED)      # Core Clio framework + admin Module

# Find CTE Core Module package
find_package(clio_cte_core REQUIRED)          # CTE Core Module

# Create your executable or library
add_executable(my_app main.cpp)

# Link against CTE Core libraries using modern target aliases
target_link_libraries(my_app 
  PRIVATE 
    clio_cte::core_client                     # CTE Core client library
    # clio_cte::core_runtime                  # Optional - if you need runtime functionality
    # clio::run::admin_client                # Optional - if you need admin functionality
)

# Note: Include directories are handled automatically by the Module targets
# No manual target_include_directories() call needed

Package and Target Naming​

CTE Core follows the CLIO Runtime Module naming conventions:

  • Package Name: clio_cte_core (for find_package(clio_cte_core REQUIRED))
  • Target Aliases: clio_cte::core_client, clio_cte::core_runtime (recommended for linking)
  • Actual Targets: clio_cte_core_client, clio_cte_core_runtime
  • Library Files: libclio_cte_core_client.so, libclio_cte_core_runtime.so
  • Include Path: clio_cte/core/ (e.g., #include <clio_cte/core/core_client.h>)

Dependency Management​

The CTE Core Module targets automatically include all required dependencies:

  • Core CLIO Runtime Framework: Automatically linked via clio_cte::core_client target
  • Admin Module: Available via clio::run::admin_client if needed
  • Include Paths: Automatically configured by Module targets
  • System Dependencies: Handled by the build system (threading, YAML, etc.)

External applications only need to link against the CTE Core targets - all framework dependencies are resolved automatically.

Runtime Dependencies​

The CTE Core runtime library (libclio_cte_core_runtime.so) must be available at runtime. It will be automatically loaded by the Clio framework when the CTE Core container is created.

External Application Example​

For external applications using CTE Core, follow these patterns (based on the MODULE_DEVELOPMENT_GUIDE.md):

# External application CMakeLists.txt
cmake_minimum_required(VERSION 3.20)
project(my_cte_application)

set(CMAKE_CXX_STANDARD_20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

# Find required packages
find_package(clio-core CONFIG REQUIRED)      # Core Clio framework + admin Module
find_package(clio_cte_core REQUIRED)          # CTE Core Module

# Find additional dependencies
find_package(yaml-cpp REQUIRED)
find_package(Threads REQUIRED)

# Create your application
add_executable(my_cte_app main.cpp)

# Link with CTE Core - dependencies are automatically included
target_link_libraries(my_cte_app
  clio_cte::core_client                       # CTE Core client (required)
  # clio_cte::core_runtime                    # Optional - if needed
  # clio::run::admin_client                  # Optional - if needed
  ${CMAKE_THREAD_LIBS_INIT}                 # Threading support
)

API Reference​

Core Client Class​

The main entry point for CTE Core functionality is the clio_cte::core::Client class.

Class Definition​

The CTE client provides an async-only API. All methods return clio::run::Future<TaskType> for asynchronous completion.

namespace clio::cte::core {

class Client : public clio::run::ContainerClient {
public:
  // Constructors
  Client();
  explicit Client(const clio::run::PoolId &pool_id);

  // Container lifecycle
  clio::run::Future<CreateTask> AsyncCreate(
      const clio::run::PoolQuery &pool_query,
      const std::string &pool_name,
      const clio::run::PoolId &custom_pool_id,
      const CreateParams &params = CreateParams());

  // Target management
  clio::run::Future<RegisterTargetTask> AsyncRegisterTarget(
      const std::string &target_name,
      clio::run::bdev::BdevType bdev_type,
      clio::run::u64 total_size,
      const clio::run::PoolQuery &target_query = clio::run::PoolQuery::Local(),
      const clio::run::PoolId &bdev_id = clio::run::PoolId::GetNull(),
      const clio::run::PoolQuery &pool_query = clio::run::PoolQuery::Dynamic());

  clio::run::Future<UnregisterTargetTask> AsyncUnregisterTarget(
      const std::string &target_name);

  clio::run::Future<ListTargetsTask> AsyncListTargets();

  clio::run::Future<StatTargetsTask> AsyncStatTargets();

  // Tag management
  clio::run::Future<GetOrCreateTagTask<CreateParams>> AsyncGetOrCreateTag(
      const std::string &tag_name,
      const TagId &tag_id = TagId::GetNull());

  clio::run::Future<DelTagTask> AsyncDelTag(const TagId &tag_id);
  clio::run::Future<DelTagTask> AsyncDelTag(const std::string &tag_name);

  clio::run::Future<GetTagSizeTask> AsyncGetTagSize(const TagId &tag_id);

  // Blob operations. score defaults to -1.0f (auto tier); a Context and
  // flags follow. GetBlob takes flags BEFORE the output buffer pointer.
  clio::run::Future<PutBlobTask> AsyncPutBlob(
      const TagId &tag_id,
      const std::string &blob_name,
      clio::run::u64 offset, clio::run::u64 size,
      ctp::ipc::ShmPtr<> blob_data,
      float score = -1.0f,
      const Context &context = Context(),
      clio::run::u32 flags = 0);

  clio::run::Future<GetBlobTask> AsyncGetBlob(
      const TagId &tag_id,
      const std::string &blob_name,
      clio::run::u64 offset, clio::run::u64 size,
      clio::run::u32 flags,
      ctp::ipc::ShmPtr<> blob_data);

  clio::run::Future<DelBlobTask> AsyncDelBlob(
      const TagId &tag_id,
      const std::string &blob_name);

  clio::run::Future<ReorganizeBlobTask> AsyncReorganizeBlob(
      const TagId &tag_id,
      const std::string &blob_name,
      float new_score);

  // Blob metadata operations
  clio::run::Future<GetBlobScoreTask> AsyncGetBlobScore(
      const TagId &tag_id,
      const std::string &blob_name);

  clio::run::Future<GetBlobSizeTask> AsyncGetBlobSize(
      const TagId &tag_id,
      const std::string &blob_name);

  clio::run::Future<GetContainedBlobsTask> AsyncGetContainedBlobs(
      const TagId &tag_id);

  // Telemetry
  clio::run::Future<PollTelemetryLogTask> AsyncPollTelemetryLog(
      std::uint64_t minimum_logical_time);

  // Query operations
  clio::run::Future<TagQueryTask> AsyncTagQuery(
      const std::string &tag_regex,
      clio::run::u32 max_tags = 0,
      const clio::run::PoolQuery &pool_query = clio::run::PoolQuery::Broadcast());

  clio::run::Future<BlobQueryTask> AsyncBlobQuery(
      const std::string &tag_regex,
      const std::string &blob_regex,
      clio::run::u32 max_blobs = 0,
      const clio::run::PoolQuery &pool_query = clio::run::PoolQuery::Broadcast());
};

}  // namespace clio::cte::core

Tag Wrapper Class​

The clio_cte::core::Tag class provides a simplified, object-oriented interface for blob operations within a specific tag. This wrapper class eliminates the need to pass TagId parameters for each operation, making the API more convenient and less error-prone.

Class Definition​

namespace clio::cte::core {

class Tag {
private:
  TagId tag_id_;
  std::string tag_name_;

public:
  // Constructors
  explicit Tag(const std::string &tag_name);  // Creates or gets existing tag
  explicit Tag(const TagId &tag_id);          // Uses existing TagId directly

  // Blob storage operations (synchronous wrappers)
  void PutBlob(const std::string &blob_name, const char *data, size_t data_size,
               size_t off = 0, float score = 1.0f, const Context &context = Context());
  void PutBlob(const std::string &blob_name, const ctp::ipc::ShmPtr<> &data, size_t data_size,
               size_t off = 0, float score = -1.0f, const Context &context = Context());

  // Asynchronous blob storage
  clio::run::Future<PutBlobTask> AsyncPutBlob(const std::string &blob_name,
                                              const ctp::ipc::ShmPtr<> &data,
                                              size_t data_size, size_t off = 0,
                                              float score = -1.0f,
                                              const Context &context = Context());

  // Blob retrieval operations (synchronous wrappers)
  void GetBlob(const std::string &blob_name, char *data, size_t data_size, size_t off = 0);
  void GetBlob(const std::string &blob_name, ctp::ipc::ShmPtr<> data, size_t data_size, size_t off = 0);

  // Blob metadata operations (synchronous wrappers)
  float GetBlobScore(const std::string &blob_name);
  clio::run::u64 GetBlobSize(const std::string &blob_name);
  std::vector<std::string> GetContainedBlobs();

  // Blob reorganization
  void ReorganizeBlob(const std::string &blob_name, float new_score);

  // Tag accessor
  const TagId& GetTagId() const { return tag_id_; }
};

}  // namespace clio::cte::core

Key Features​

  • Automatic Tag Management: Constructor with tag name automatically creates or retrieves existing tags
  • Simplified API: No need to pass TagId for each operation
  • Memory Management: Raw data variant automatically handles shared memory allocation and cleanup
  • Exception Safety: Operations throw exceptions on failure for clear error handling
  • Score Support: Blob scoring for intelligent data placement across storage targets
  • Blob Enumeration: GetContainedBlobs() method returns all blob names in the tag
  • Reorganization Support: ReorganizeBlob() method for data tier migration

Memory Management Guidelines​

For Synchronous Tag Wrapper Operations:

  • Raw data variant (const char*) automatically manages shared memory lifecycle
  • Shared memory variant requires caller to manage ctp::ipc::ShmPtr<> lifecycle

For Asynchronous Operations:

  • Only shared memory variant available to avoid memory lifecycle issues
  • Caller must keep shared memory buffers alive until async task completes
  • See usage examples below for proper async memory management patterns

Data Structures​

CreateParams​

Configuration parameters for CTE container creation:

struct CreateParams {
  // CTE configuration object (loaded server-side from the pool config /
  // YAML file passed to CLIO_CTE_CLIENT_INIT).
  Config config_;

  // OUT: managed-USM pointer to the GPU metadata cache header (0 when the
  // GPU metadata cache is disabled).
  clio::run::u64 gpu_cache_ptr_ = 0;

  // Required: chimod library name for the module manager.
  static constexpr const char *chimod_lib_name = "clio_cte_core";

  CreateParams();
};

ListTargets Return Type​

The AsyncListTargets method returns a Future. Access target names via task->target_names_ after Wait():

clio::run::Future<ListTargetsTask> AsyncListTargets();

Example usage:

#include <clio_cte/core/core_client.h>
#include <iostream>

void example() {
  using namespace clio::cte::core;
  auto *cte_client = CLIO_CTE_CLIENT;

  auto task = cte_client->AsyncListTargets();
  task.Wait();
  for (const auto &target_name : task->target_names_) {
    std::cout << "Target: " << target_name << "\n";
  }
}

GetOrCreateTag Return Type​

The AsyncGetOrCreateTag method returns a Future. Access the TagId via task->tag_id_ after Wait():

clio::run::Future<GetOrCreateTagTask<CreateParams>> AsyncGetOrCreateTag(
    const std::string &tag_name,
    const TagId &tag_id = TagId::GetNull());

Example usage:

#include <clio_cte/core/core_client.h>

void example() {
  using namespace clio::cte::core;
  auto *cte_client = CLIO_CTE_CLIENT;

  auto task = cte_client->AsyncGetOrCreateTag("my_dataset");
  task.Wait();
  TagId tag_id = task->tag_id_;
  (void)tag_id;
}

BlobInfo​

Blob metadata and block management:

struct BlobInfo {
  clio::run::priv::string blob_name_;
  clio::run::priv::vector<BlobBlock> blocks_;  // Ordered blocks making up the blob
  float score_;                                // 0-1 score for reorganization
  Timestamp last_modified_;
  Timestamp last_read_;

  clio::run::u64 GetTotalSize() const;         // Total size from all blocks
};

Note: Individual blob sizes can be queried efficiently using Client::GetBlobSize() or Tag::GetBlobSize() without needing to retrieve full BlobInfo.

BlobBlock​

Individual block within a blob:

struct BlobBlock {
  clio::run::bdev::Client bdev_client_;  // Bdev client for this block's target
  clio::run::PoolQuery target_query_;    // Target pool query for bdev API calls
  clio::run::u64 target_offset_;         // Offset within target
  clio::run::u64 size_;                  // Size of this block
};

CteTelemetry​

Telemetry data for performance monitoring:

struct CteTelemetry {
  CteOp op_;                    // Operation type
  size_t off_;                  // Offset within blob
  size_t size_;                 // Size of operation
  TagId tag_id_;                // Tag ID involved
  Timestamp mod_time_;          // Last modification time
  Timestamp read_time_;         // Last read time
  std::uint64_t logical_time_;  // For ordering entries
};

enum class CteOp : clio::run::u32 {
  kPutBlob = 0,
  kGetBlob = 1,
  kDelBlob = 2,
  kGetOrCreateTag = 3,
  kDelTag = 4,
  kGetTagSize = 5
};

Global Access​

CTE Core provides singleton access patterns:

// Initialize CTE client (must be called once)
// NOTE: This automatically calls clio::run::CLIO_INIT internally
// config_path: Optional path to YAML configuration file
// pool_query: Pool query type for CTE container creation (default: Dynamic)
namespace clio::cte::core {
bool CLIO_CTE_CLIENT_INIT(const std::string &config_path = "",
                          const clio::run::PoolQuery &pool_query = clio::run::PoolQuery::Dynamic());
}

// Access global CTE client instance (returns clio::cte::core::Client*)
auto *client = CLIO_CTE_CLIENT;

Important Notes:

  • CLIO_CTE_CLIENT_INIT automatically calls clio::run::CLIO_INIT(clio::run::RuntimeMode::kClient, true) internally
  • You do NOT need to call clio::run::CLIO_INIT separately when using CTE Core
  • Configuration is managed per-Runtime instance (no global ConfigManager singleton)
  • The config file path can also be specified via the CLIO_SERVER_CONF environment variable

Usage Examples​

Basic Initialization​

#include <clio_cte/core/core_client.h>
#include <clio_cte/core/core_tasks.h>

int main() {
  // Initialize CTE subsystem
  // NOTE: CLIO_CTE_CLIENT_INIT automatically calls clio::run::CLIO_INIT internally
  // You do NOT need to call clio::run::CLIO_INIT separately
  clio::cte::core::CLIO_CTE_CLIENT_INIT("/path/to/config.yaml");

  // Get global CTE client instance (created during initialization)
  auto *cte_client = CLIO_CTE_CLIENT;
  (void)cte_client;

  // The CTE client is now ready to use - no need to call Create() again
  // The client is automatically initialized with the pool specified during
  // CLIO_CTE_CLIENT_INIT

  return 0;
}

Registering Storage Targets​

#include <clio_cte/core/core_client.h>
#include <iostream>
#include <string>

void example() {
  using namespace clio::cte::core;

  // Get global CTE client
  auto *cte_client = CLIO_CTE_CLIENT;

  // Register a file-based storage target
  std::string target_path = "/mnt/nvme/cte_storage.dat";
  clio::run::u64 target_size = 100ULL * 1024 * 1024 * 1024;  // 100GB

  auto reg_task = cte_client->AsyncRegisterTarget(
      target_path, clio::run::bdev::BdevType::kFile, target_size);
  reg_task.Wait();

  if (reg_task->return_code_ == 0) {
    std::cout << "Target registered successfully\n";
  }

  // Register a RAM-based cache target
  auto cache_task = cte_client->AsyncRegisterTarget(
      "ram::cte_cache", clio::run::bdev::BdevType::kRam,
      8ULL * 1024 * 1024 * 1024);  // 8GB
  cache_task.Wait();

  // List all registered targets
  auto list_task = cte_client->AsyncListTargets();
  list_task.Wait();
  for (const auto &target_name : list_task->target_names_) {
    std::cout << "Target: " << target_name << "\n";
  }
}
From the dashboard

The runtime's web dashboard gives every CTE core pool a management page at /viz/clio_cte_core/: the target roster (score, free space, capacity, latency, bandwidth, bytes read/written) with register and unregister buttons, backed by GET /api/mod/clio_cte_core/{pool}/targets and POST …/register_target / …/unregister_target. register_target takes a fresh name + bdev_type + capacity, or name + attach_pool_id to attach an existing pool such as a safe-bdev array.

Working with Tags and Blobs​

Using the Core Client Directly​

#include <clio_cte/core/core_client.h>
#include <algorithm>
#include <cstring>
#include <iostream>
#include <vector>

void example() {
  using namespace clio::cte::core;

  // Get global CTE client
  auto *cte_client = CLIO_CTE_CLIENT;

  // Create or get a tag for grouping related blobs
  auto tag_task = cte_client->AsyncGetOrCreateTag("dataset_v1");
  tag_task.Wait();
  TagId tag_id = tag_task->tag_id_;

  // Prepare data for storage
  std::vector<char> data(1024 * 1024);  // 1MB of data
  std::fill(data.begin(), data.end(), 'A');

  // Allocate shared memory for the data
  ctp::ipc::FullPtr<char> shm_buffer = CLIO_IPC->AllocateBuffer(data.size());
  memcpy(shm_buffer.ptr_, data.data(), data.size());

  auto put_task = cte_client->AsyncPutBlob(
      tag_id,
      "blob_001",                  // Blob name
      0,                           // Offset
      data.size(),                 // Size
      shm_buffer.shm_.Cast<void>(),  // Shared memory pointer
      0.8f,                        // Score (0-1, higher = hotter data)
      Context(),                   // Compression context
      0);                          // Flags
  put_task.Wait();

  if (put_task->return_code_ == 0) {
    std::cout << "Blob stored successfully\n";

    // Get blob size
    auto size_task = cte_client->AsyncGetBlobSize(tag_id, "blob_001");
    size_task.Wait();
    std::cout << "Stored blob size: " << size_task->size_ << " bytes\n";

    // Get blob score
    auto score_task = cte_client->AsyncGetBlobScore(tag_id, "blob_001");
    score_task.Wait();
    std::cout << "Blob score: " << score_task->score_ << "\n";
  }

  // Retrieve the blob
  auto retrieve_buffer = CLIO_IPC->AllocateBuffer(data.size());
  auto get_task = cte_client->AsyncGetBlob(
      tag_id,
      "blob_001",                       // Blob name for lookup
      0,                                // Offset
      data.size(),                      // Size to read
      0,                                // Flags
      retrieve_buffer.shm_.Cast<void>());  // Buffer for data
  get_task.Wait();

  // Get all blob names in the tag
  auto blobs_task = cte_client->AsyncGetContainedBlobs(tag_id);
  blobs_task.Wait();
  std::cout << "Tag contains " << blobs_task->blob_names_.size() << " blobs\n";
  for (const auto &name : blobs_task->blob_names_) {
    std::cout << "  - " << name << "\n";
  }

  // Get total size of all blobs in tag
  auto tag_size_task = cte_client->AsyncGetTagSize(tag_id);
  tag_size_task.Wait();
  std::cout << "Tag total size: " << tag_size_task->tag_size_ << " bytes\n";

  // Delete a specific blob
  auto del_blob_task = cte_client->AsyncDelBlob(tag_id, "blob_001");
  del_blob_task.Wait();

  // Delete entire tag (removes all blobs)
  auto del_tag_task = cte_client->AsyncDelTag(tag_id);
  del_tag_task.Wait();
}
#include <clio_cte/core/core_client.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>

void example() {
  using namespace clio::cte::core;

  // Create tag wrapper - automatically creates or gets existing tag
  Tag dataset_tag("dataset_v1");

  // Prepare data for storage
  std::vector<char> data(1024 * 1024);  // 1MB of data
  std::fill(data.begin(), data.end(), 'A');

  try {
    // Store blob - automatically handles shared memory management
    dataset_tag.PutBlob("blob_001", data.data(), data.size());
    std::cout << "Blob stored successfully\n";

    // Get blob size
    clio::run::u64 blob_size = dataset_tag.GetBlobSize("blob_001");
    std::cout << "Stored blob size: " << blob_size << " bytes\n";

    // Get blob score
    float blob_score = dataset_tag.GetBlobScore("blob_001");
    std::cout << "Blob score: " << blob_score << "\n";

    // Retrieve the blob using automatic memory management (recommended)
    std::vector<char> retrieve_data(blob_size);
    dataset_tag.GetBlob("blob_001", retrieve_data.data(), blob_size);

    // Alternative: Retrieve using manual shared memory management
    // auto retrieve_buffer = CLIO_IPC->AllocateBuffer(blob_size);
    // dataset_tag.GetBlob("blob_001", retrieve_buffer.shm_.Cast<void>(), blob_size);

    std::cout << "Blob retrieved successfully\n";

    // Get all blobs in the tag
    std::vector<std::string> blob_names = dataset_tag.GetContainedBlobs();
    std::cout << "Tag contains " << blob_names.size() << " blobs\n";

    // Reorganize blob with new score
    dataset_tag.ReorganizeBlob("blob_001", 0.95f);  // Move to hot tier

  } catch (const std::exception &e) {
    std::cerr << "Error: " << e.what() << "\n";
  }

  // For tag-level operations, you can use the core client:
  auto *cte_client = CLIO_CTE_CLIENT;

  // Get total size of all blobs in tag
  auto tag_size_task = cte_client->AsyncGetTagSize(dataset_tag.GetTagId());
  tag_size_task.Wait();
  std::cout << "Tag total size: " << tag_size_task->tag_size_ << " bytes\n";

  // Delete entire tag (removes all blobs)
  auto del_task = cte_client->AsyncDelTag(dataset_tag.GetTagId());
  del_task.Wait();
}

Tag Wrapper Usage Examples​

The Tag wrapper class provides a more convenient interface for blob operations within a specific tag. Here are comprehensive examples showing different usage patterns:

Basic Tag Wrapper Operations​

#include <clio_cte/core/core_client.h>
#include <algorithm>
#include <iostream>
#include <vector>

void example() {
  using namespace clio::cte::core;

  // Initialize CTE system (same as before)
  // ... initialization code ...

  // Create a tag wrapper - automatically creates or gets existing tag
  Tag dataset_tag("dataset_v1");

  // Store data using the simple raw data interface
  std::vector<char> data(1024 * 1024);  // 1MB of data
  std::fill(data.begin(), data.end(), 'X');

  try {
    // Simple PutBlob - automatically manages shared memory
    dataset_tag.PutBlob("sample_blob", data.data(), data.size());
    std::cout << "Blob stored successfully\n";

    // Get blob size without retrieving data
    clio::run::u64 blob_size = dataset_tag.GetBlobSize("sample_blob");
    std::cout << "Blob size: " << blob_size << " bytes\n";

    // Get blob score (data temperature)
    float blob_score = dataset_tag.GetBlobScore("sample_blob");
    std::cout << "Blob score: " << blob_score << "\n";

  } catch (const std::exception &e) {
    std::cerr << "Error: " << e.what() << "\n";
  }
}

Memory Management: Automatic vs Manual​

The Tag class provides two GetBlob variants to suit different memory management preferences:

#include <clio_cte/core/core_client.h>
#include <iostream>
#include <string>
#include <vector>

void example() {
  using namespace clio::cte::core;

  Tag data_tag("performance_data");

  try {
    // Store some test data
    std::string test_data = "Sample blob data for retrieval testing";
    data_tag.PutBlob("test_blob", test_data.c_str(), test_data.size());

    clio::run::u64 blob_size = data_tag.GetBlobSize("test_blob");
    std::cout << "Blob size: " << blob_size << " bytes\n";

    // Method 1: Automatic memory management (recommended for most use cases)
    std::vector<char> auto_buffer(blob_size);
    data_tag.GetBlob("test_blob", auto_buffer.data(), blob_size);
    std::cout << "Retrieved with automatic memory management\n";

    // Method 2: Manual shared memory management (for advanced use cases)
    auto shm_buffer = CLIO_IPC->AllocateBuffer(blob_size);
    if (!shm_buffer.IsNull()) {
      data_tag.GetBlob("test_blob", shm_buffer.shm_.Cast<void>(), blob_size);
      std::cout << "Retrieved with manual shared memory management\n";
      // shm_buffer automatically freed when it goes out of scope
    }

    // Method 1 is preferred because:
    // - No shared memory allocation required
    // - Automatic cleanup via RAII
    // - Works with standard C++ containers
    // - Simpler error handling

  } catch (const std::exception &e) {
    std::cerr << "Memory management example error: " << e.what() << "\n";
  }
}

Advanced Tag Wrapper with Scoring​

#include <clio_cte/core/core_client.h>
#include <algorithm>
#include <cstring>
#include <iostream>
#include <string>
#include <vector>

void example() {
  using namespace clio::cte::core;

  // Create tag wrapper for time-series data
  Tag timeseries_tag("timeseries_2024");

  // Store multiple data chunks with different scores (data temperatures)
  std::vector<std::vector<char>> chunks;
  std::vector<float> scores = {0.9f, 0.7f, 0.5f, 0.2f};  // Hot to cold data
  std::vector<std::string> chunk_names = {"latest", "recent", "old", "archived"};

  for (size_t i = 0; i < 4; ++i) {
    chunks.emplace_back(1024 * 512);  // 512KB chunks
    std::fill(chunks[i].begin(), chunks[i].end(), static_cast<char>('A' + i));

    try {
      // For custom scoring, use shared memory version:
      auto shm_ptr = CLIO_IPC->AllocateBuffer(chunks[i].size());
      memcpy(shm_ptr.ptr_, chunks[i].data(), chunks[i].size());
      timeseries_tag.PutBlob(chunk_names[i], shm_ptr.shm_.Cast<void>(),
                             chunks[i].size(), 0, scores[i]);

      std::cout << "Stored chunk '" << chunk_names[i] << "' with score "
                << scores[i] << "\n";

    } catch (const std::exception &e) {
      std::cerr << "Failed to store chunk " << chunk_names[i] << ": "
                << e.what() << "\n";
    }
  }
}

Blob Retrieval with Tag Wrapper​

#include <clio_cte/core/core_client.h>
#include <iostream>
#include <stdexcept>

static void ProcessBlobData(const char *data, clio::run::u64 size) {
  (void)data;
  (void)size;
}

void example() {
  using namespace clio::cte::core;

  // Create tag wrapper from an existing TagId (obtained from a prior
  // AsyncGetOrCreateTag call, for example).
  TagId existing_tag_id = TagId::GetNull();
  Tag existing_tag(existing_tag_id);

  try {
    // First, check if blob exists and get its size
    clio::run::u64 blob_size = existing_tag.GetBlobSize("target_blob");
    if (blob_size == 0) {
      std::cout << "Blob 'target_blob' not found or empty\n";
      return;
    }

    std::cout << "Blob size: " << blob_size << " bytes\n";

    // Allocate shared memory buffer for retrieval
    auto retrieve_buffer = CLIO_IPC->AllocateBuffer(blob_size);
    if (retrieve_buffer.IsNull()) {
      throw std::runtime_error("Failed to allocate retrieval buffer");
    }

    // Retrieve the blob
    existing_tag.GetBlob("target_blob", retrieve_buffer.shm_.Cast<void>(),
                         blob_size);

    // Process the retrieved data
    ProcessBlobData(retrieve_buffer.ptr_, blob_size);

    std::cout << "Successfully retrieved and processed blob\n";

  } catch (const std::exception &e) {
    std::cerr << "Blob retrieval error: " << e.what() << "\n";
  }
}

Asynchronous Operations with Tag Wrapper​

#include <clio_cte/core/core_client.h>
#include <clio_cte/core/core_tasks.h>
#include <algorithm>
#include <cstring>
#include <iostream>
#include <string>
#include <vector>

void example() {
  using namespace clio::cte::core;

  Tag async_tag("async_operations");

  // Prepare data for async operations
  std::vector<std::vector<char>> async_data;
  std::vector<ctp::ipc::FullPtr<char>> shm_buffers;
  std::vector<clio::run::Future<PutBlobTask>> async_tasks;

  for (int i = 0; i < 5; ++i) {
    // Prepare data
    async_data.emplace_back(1024 * 256);  // 256KB each
    std::fill(async_data[i].begin(), async_data[i].end(),
              static_cast<char>('Z' - i));

    // Allocate shared memory (must keep alive until async operation completes)
    auto shm_buffer = CLIO_IPC->AllocateBuffer(async_data[i].size());
    if (shm_buffer.IsNull()) {
      std::cerr << "Failed to allocate shared memory for async operation " << i
                << "\n";
      continue;
    }

    // Copy data to shared memory
    memcpy(shm_buffer.ptr_, async_data[i].data(), async_data[i].size());

    try {
      // Start async operation (returns immediately)
      auto task = async_tag.AsyncPutBlob("async_blob_" + std::to_string(i),
                                         shm_buffer.shm_.Cast<void>(),
                                         async_data[i].size(),
                                         0,     // offset
                                         0.6f);  // score

      // Store references to keep alive
      shm_buffers.push_back(std::move(shm_buffer));
      async_tasks.push_back(std::move(task));

      std::cout << "Started async put for blob " << i << "\n";

    } catch (const std::exception &e) {
      std::cerr << "Failed to start async put " << i << ": " << e.what() << "\n";
    }
  }

  // Wait for all async operations to complete
  std::cout << "Waiting for async operations to complete...\n";
  for (size_t i = 0; i < async_tasks.size(); ++i) {
    try {
      async_tasks[i].Wait();  // Note: Wait() on Future, not pointer
      if (async_tasks[i]->return_code_ == 0) {
        std::cout << "Async operation " << i << " completed successfully\n";
      } else {
        std::cout << "Async operation " << i << " failed with code "
                  << async_tasks[i]->return_code_ << "\n";
      }
      // Task is automatically cleaned up when Future goes out of scope

    } catch (const std::exception &e) {
      std::cerr << "Error waiting for async operation " << i << ": " << e.what()
                << "\n";
    }
  }

  // Note: shm_buffers will be automatically cleaned up when they go out of scope
}

Asynchronous Operations​

#include <clio_cte/core/core_client.h>
#include <clio_cte/core/core_tasks.h>
#include <cstring>
#include <iostream>
#include <string>
#include <vector>

static void ProcessOtherData() {}

void example() {
  using namespace clio::cte::core;

  // Get global CTE client
  auto *cte_client = CLIO_CTE_CLIENT;

  // A tag to store into, and some data to store.
  auto tag_task = cte_client->AsyncGetOrCreateTag("async_dataset");
  tag_task.Wait();
  TagId tag_id = tag_task->tag_id_;
  std::vector<char> data(1024 * 1024, 'A');

  // Allocate shared memory for the data
  ctp::ipc::FullPtr<char> shm_buffer = CLIO_IPC->AllocateBuffer(data.size());
  memcpy(shm_buffer.ptr_, data.data(), data.size());

  // Asynchronous blob operations for better performance
  auto put_task = cte_client->AsyncPutBlob(
      tag_id, "async_blob", 0, data.size(), shm_buffer.shm_.Cast<void>(), 0.5f);

  // Do other work while blob is being stored
  ProcessOtherData();

  // Wait for completion
  put_task.Wait();
  if (put_task->return_code_ == 0) {
    std::cout << "Async put completed successfully\n";
  }
  // Task is automatically cleaned up when Future goes out of scope

  // Multiple async operations
  std::vector<clio::run::Future<PutBlobTask>> tasks;
  std::vector<ctp::ipc::FullPtr<char>> buffers;  // Keep buffers alive

  for (int i = 0; i < 10; ++i) {
    // Allocate buffer for each task
    auto buffer = CLIO_IPC->AllocateBuffer(data.size());
    memcpy(buffer.ptr_, data.data(), data.size());

    auto task = cte_client->AsyncPutBlob(tag_id, "blob_" + std::to_string(i), 0,
                                         data.size(), buffer.shm_.Cast<void>(),
                                         0.5f);

    buffers.push_back(std::move(buffer));  // Keep buffer alive
    tasks.push_back(std::move(task));
  }

  // Wait for all to complete
  for (auto &task : tasks) {
    task.Wait();
  }
  // buffers and tasks automatically cleaned up here
}

Performance Monitoring​

#include <clio_cte/core/core_client.h>
#include <cstdint>
#include <iostream>

void example() {
  using namespace clio::cte::core;

  // Get global CTE client
  auto *cte_client = CLIO_CTE_CLIENT;

  // Poll telemetry log for performance analysis
  std::uint64_t last_logical_time = 0;

  auto telemetry_task = cte_client->AsyncPollTelemetryLog(last_logical_time);
  telemetry_task.Wait();

  for (const auto &entry : telemetry_task->entries_) {
    std::cout << "Operation: ";
    switch (entry.op_) {
      case CteOp::kPutBlob: std::cout << "PUT"; break;
      case CteOp::kGetBlob: std::cout << "GET"; break;
      case CteOp::kDelBlob: std::cout << "DEL"; break;
      case CteOp::kGetOrCreateTag: std::cout << "GET_TAG"; break;
      case CteOp::kDelTag: std::cout << "DEL_TAG"; break;
      case CteOp::kGetTagSize: std::cout << "TAG_SIZE"; break;
      default: std::cout << "OTHER"; break;
    }
    std::cout << " Size: " << entry.size_ << " Offset: " << entry.off_
              << " LogicalTime: " << entry.logical_time_ << "\n";

    // Update last_logical_time for next poll
    if (entry.logical_time_ > last_logical_time) {
      last_logical_time = entry.logical_time_;
    }
  }

  // Update target statistics
  auto stat_task = cte_client->AsyncStatTargets();
  stat_task.Wait();

  // List all targets
  auto list_task = cte_client->AsyncListTargets();
  list_task.Wait();
  for (const auto &target_name : list_task->target_names_) {
    std::cout << "Target: " << target_name << "\n";
  }
}

Blob Reorganization​

#include <clio_cte/core/core_client.h>
#include <iostream>
#include <string>
#include <vector>

void example() {
  using namespace clio::cte::core;

  // Reorganize blobs based on new access patterns
  // Higher scores (closer to 1.0) indicate hotter data
  auto *cte_client = CLIO_CTE_CLIENT;

  auto tag_task = cte_client->AsyncGetOrCreateTag("my_dataset");
  tag_task.Wait();
  TagId tag_id = tag_task->tag_id_;

  // Reorganize multiple blobs by calling AsyncReorganizeBlob once per blob
  std::vector<std::string> blob_names = {"blob_001", "blob_002", "blob_003"};
  std::vector<float> new_scores = {0.95f, 0.7f, 0.3f};  // Hot, warm, cold

  for (size_t i = 0; i < blob_names.size(); ++i) {
    auto reorg_task =
        cte_client->AsyncReorganizeBlob(tag_id, blob_names[i], new_scores[i]);
    reorg_task.Wait();
    if (reorg_task->return_code_ == 0) {
      std::cout << "Blob " << blob_names[i] << " reorganized successfully\n";
    }
  }

  // Example: Reorganize single blob
  auto single_task =
      cte_client->AsyncReorganizeBlob(tag_id, "important_blob", 0.95f);
  single_task.Wait();
  if (single_task->return_code_ == 0) {
    std::cout << "Single blob reorganized successfully\n";
  }

  // Using Tag wrapper (simpler API)
  Tag my_tag("my_dataset");
  my_tag.ReorganizeBlob("hot_data", 0.95f);     // Move to hot tier
  my_tag.ReorganizeBlob("cold_archive", 0.2f);  // Move to cold tier
}

Configuration​

CTE Core uses YAML configuration files for runtime parameters. Configuration can be loaded from:

  1. A file path specified during initialization
  2. Environment variable CLIO_SERVER_CONF
  3. Programmatically via the Config API

Configuration File Format​

# Worker thread configuration
worker_count: 4

# Target management settings
targets:
  max_targets: 100
  default_target_timeout_ms: 30000
  auto_unregister_failed: true

# Performance tuning
performance:
  target_stat_interval_ms: 5000      # Target statistics update interval
  blob_cache_size_mb: 512            # Cache size for blob operations
  max_concurrent_operations: 64      # Max concurrent I/O operations
  score_threshold: 0.7               # Threshold for blob reorganization

# Queue configuration for different operation types
queues:
  target_management:
    lane_count: 2
    priority: "low_latency"
  
  tag_management:
    lane_count: 2
    priority: "low_latency"
  
  blob_operations:
    lane_count: 4
    priority: "high_latency"
  
  stats:
    lane_count: 1
    priority: "high_latency"

# Storage device configuration
storage:
  # Primary high-performance storage with manual tier score
  - path: "/mnt/nvme/cte_primary"
    bdev_type: "file"
    capacity_limit: "1TB"
    score: 0.9                # Optional: Manual tier score (0.0-1.0)
  
  # RAM-based cache (highest tier)
  - path: "/tmp/cte_cache"
    bdev_type: "ram"
    capacity_limit: "8GB"
    score: 1.0                # Optional: Manual tier score for fastest access
  
  # Secondary storage (uses automatic scoring)
  - path: "/mnt/ssd/cte_secondary"
    bdev_type: "file"
    capacity_limit: "500GB"
    # No score specified - uses automatic bandwidth-based scoring

# Data Placement Engine configuration
dpe:
  dpe_type: "max_bw"  # Options: "random", "round_robin", "max_bw"

Programmatic Configuration​

Configuration in CTE Core is now managed per-Runtime instance, not through a global singleton. Configuration is loaded during initialization through the CLIO_CTE_CLIENT_INIT function.

#include <clio_cte/core/core_client.h>

void example() {
  // Initialize CTE with configuration file
  // Configuration is passed to the Runtime during creation
  bool success = clio::cte::core::CLIO_CTE_CLIENT_INIT("/path/to/config.yaml");

  // Or use environment variable CLIO_SERVER_CONF
  // export CLIO_SERVER_CONF=/path/to/config.yaml
  success = clio::cte::core::CLIO_CTE_CLIENT_INIT();
  (void)success;

  // Configuration is now embedded in the Runtime instance
  // and cannot be modified after initialization
}

Note: The ConfigManager singleton has been removed. Configuration is now:

  • Loaded once during CLIO_CTE_CLIENT_INIT
  • Embedded in the CTE Runtime instance via CreateParams
  • Immutable after initialization
  • Can be specified via file path parameter or CLIO_SERVER_CONF environment variable

Queue Priority Options​

  • "low_latency" - Optimized for minimal latency (clio::run::kLowLatency)
  • "high_latency" - Optimized for throughput (clio::run::kHighLatency)

Storage Device Types​

  • "file" - File-based block device
  • "ram" - RAM-based block device (for caching)
  • "dev_dax" - Persistent memory device
  • "posix" - POSIX file system interface

Manual Tier Scoring​

Storage devices support optional manual tier scoring to override automatic bandwidth-based tier assignment:

Configuration Parameters​

  • score (optional, float 0.0-1.0): Manual tier score for the storage device
    • 1.0: Highest tier (fastest access, e.g., RAM, high-end NVMe)
    • 0.8-0.9: High-performance tier (e.g., NVMe SSDs)
    • 0.5-0.7: Medium-performance tier (e.g., SATA SSDs)
    • 0.1-0.4: Low-performance tier (e.g., HDDs, network storage)
    • Not specified: Uses automatic bandwidth-based scoring

Behavior​

  • Manual scores are preserved during target statistics updates
  • Targets with manual scores will not be overwritten by automatic scoring algorithms
  • Data placement engines use these scores for intelligent tier selection
  • Mixed configurations (some manual, some automatic) are fully supported

Example Configuration​

storage:
  # Fastest tier - manual score
  - path: "/mnt/ram/cache"
    bdev_type: "ram"
    capacity_limit: "16GB"
    score: 1.0
  
  # High-performance tier - manual score  
  - path: "/mnt/nvme/primary"
    bdev_type: "file"
    capacity_limit: "1TB"
    score: 0.85
  
  # Medium tier - automatic scoring
  - path: "/mnt/ssd/secondary"
    bdev_type: "file"
    capacity_limit: "2TB"
    # Uses automatic bandwidth measurement

Data Placement Engine Types​

  • "random" - Random placement across targets
  • "round_robin" - Round-robin placement
  • "max_bw" - Place on target with maximum available bandwidth

Python Bindings​

CTE Core provides Python bindings for easy integration with Python applications.

Installation​

# Build Python bindings
cd build
cmake .. -DBUILD_PYTHON_BINDINGS=ON
make

# Install Python module
pip install ./wrapper/python

Python API Usage​

import clio_cte_core_ext as cte

# Initialize CTE
# NOTE: This automatically calls clio::run::CLIO_INIT() internally
cte.initialize_cte("/path/to/config.yaml")

# Get global CTE client
client = cte.get_cte_client()

# Create or get a tag
tag_task = client.async_get_or_create_tag("my_dataset")
tag_task.wait()
tag_id = tag_task.tag_id

# Poll telemetry log
minimum_logical_time = 0
telemetry_task = client.async_poll_telemetry_log(minimum_logical_time)
telemetry_task.wait()

for entry in telemetry_task.telemetry:
    print(f"Operation: {entry.op}")
    print(f"Size: {entry.size}")
    print(f"Offset: {entry.off}")
    print(f"Logical Time: {entry.logical_time}")

# Reorganize blobs with new scores
blob_names = ["blob_001", "blob_002", "blob_003"]
new_scores = [0.95, 0.85, 0.75]  # Different tier assignments

# Call async_reorganize_blob once per blob
for blob_name, new_score in zip(blob_names, new_scores):
    task = client.async_reorganize_blob(tag_id, blob_name, new_score)
    task.wait()
    if task.return_code == 0:
        print(f"Blob {blob_name} reorganized successfully")
    else:
        print(f"Reorganization of {blob_name} failed with error code: {task.return_code}")

Python Data Types​

# Create unique IDs
tag_id = cte.TagId.GetNull()
blob_id = cte.BlobId.GetNull()

# Check if ID is null
if tag_id.IsNull():
    print("Tag ID is null")

# Access ID components
print(f"Major: {tag_id.major_}, Minor: {tag_id.minor_}")

# Operation types
print(cte.CteOp.kPutBlob)    # Put blob operation
print(cte.CteOp.kGetBlob)    # Get blob operation
print(cte.CteOp.kDelBlob)    # Delete blob operation

Python Blob Reorganization​

The Python bindings support blob reorganization for dynamic data placement optimization using the async API:

import clio_cte_core_ext as cte

# Initialize CTE system (as shown in previous examples)
cte.initialize_cte("/path/to/config.yaml")
client = cte.get_cte_client()

# Get or create tag for the blobs
tag_task = client.async_get_or_create_tag("my_dataset")
tag_task.wait()
tag_id = tag_task.tag_id

# Example 1: Reorganize multiple blobs to different tiers
blob_names = ["hot_data", "warm_data", "cold_archive"]
new_scores = [0.95, 0.6, 0.2]  # Hot, warm, and cold tiers

# Call async_reorganize_blob once per blob
for blob_name, new_score in zip(blob_names, new_scores):
    task = client.async_reorganize_blob(tag_id, blob_name, new_score)
    task.wait()
    if task.return_code == 0:
        print(f"Blob {blob_name} reorganized successfully")
    else:
        print(f"Reorganization of {blob_name} failed with error code: {task.return_code}")

# Example 2: Promote frequently accessed blobs based on telemetry
telemetry_task = client.async_poll_telemetry_log(0)
telemetry_task.wait()
access_counts = {}

# Count accesses per blob name (requires tracking blob names from telemetry)
for entry in telemetry_task.telemetry:
    if entry.op == cte.CteOp.kGetBlob:
        # Track access patterns
        blob_key = (entry.blob_id.major, entry.blob_id.minor)
        access_counts[blob_key] = access_counts.get(blob_key, 0) + 1

# Batch reorganize based on access frequency
# Assuming you have a mapping of blob IDs to names
blob_id_to_name = {
    (0, 1): "dataset_001",
    (0, 2): "dataset_002",
    (0, 3): "dataset_003"
}

blobs_to_reorganize = []
new_scores_list = []

for blob_key, count in access_counts.items():
    if blob_key in blob_id_to_name and count > 10:
        blob_name = blob_id_to_name[blob_key]
        blobs_to_reorganize.append(blob_name)

        # Calculate score based on access frequency
        score = min(0.5 + (count / 100.0), 1.0)
        new_scores_list.append(score)

# Perform reorganization for each blob
if blobs_to_reorganize:
    for blob_name, new_score in zip(blobs_to_reorganize, new_scores_list):
        task = client.async_reorganize_blob(tag_id, blob_name, new_score)
        task.wait()
        if task.return_code == 0:
            print(f"Reorganized blob {blob_name} successfully")

# Example 3: Tier-based reorganization strategy
# Organize blobs into three tiers based on size and access patterns

# Small, frequently accessed -> Hot tier (0.9)
small_hot_blobs = ["config", "index", "metadata"]
for blob_name in small_hot_blobs:
    task = client.async_reorganize_blob(tag_id, blob_name, 0.9)
    task.wait()
    if task.return_code == 0:
        print(f"Hot tier blob {blob_name} reorganized")

# Medium, occasionally accessed -> Warm tier (0.5-0.7)
warm_blobs = ["dataset_recent_01", "dataset_recent_02"]
warm_scores = [0.6, 0.5]
for blob_name, score in zip(warm_blobs, warm_scores):
    task = client.async_reorganize_blob(tag_id, blob_name, score)
    task.wait()
    if task.return_code == 0:
        print(f"Warm tier blob {blob_name} reorganized")

# Large, rarely accessed -> Cold tier (0.1-0.3)
cold_blobs = ["archive_2023", "backup_full"]
cold_scores = [0.2, 0.1]
for blob_name, score in zip(cold_blobs, cold_scores):
    task = client.async_reorganize_blob(tag_id, blob_name, score)
    task.wait()
    if task.return_code == 0:
        print(f"Cold tier blob {blob_name} reorganized")

Score Guidelines for Python:

  • 0.9 - 1.0: Highest tier (RAM cache, frequently accessed)
  • 0.7 - 0.8: High tier (NVMe, recently accessed)
  • 0.4 - 0.6: Medium tier (SSD, occasionally accessed)
  • 0.1 - 0.3: Low tier (HDD, archival data)
  • 0.0: Lowest tier (cold storage, rarely accessed)

Method Pattern:

# All Python client methods use async pattern
task = client.async_reorganize_blob(
    tag_id,         # Tag ID containing the blob
    blob_name,      # Blob name (string)
    new_score       # New score (float, 0.0 to 1.0)
)
task.wait()
result = task.return_code  # 0 = success

Return Codes:

  • 0: Success - blob reorganized successfully
  • Non-zero: Error - reorganization failed (tag not found, blob not found, insufficient space, etc.)

Important Notes:

  • All Python client methods follow the async pattern with .wait() completion
  • All blobs must belong to the specified tag_id
  • Scores must be in the range [0.0, 1.0]
  • Higher scores indicate hotter data that should be placed on faster storage tiers

Advanced Topics​

Best Practices​

Choosing Between Tag Wrapper and Direct Client API​

Generally, the tag wrapper class is preferred over the direct API.

Memory Management Best Practices​

For Raw Data Operations:

#include <clio_cte/core/core_client.h>
#include <vector>

static std::vector<char> LoadData() { return std::vector<char>(1024, 'x'); }

void example() {
  using namespace clio::cte::core;
  // Tag wrapper automatically manages shared memory for sync operations
  Tag tag("my_data");
  std::vector<char> data = LoadData();
  tag.PutBlob("item", data.data(), data.size());  // Safe - automatic cleanup
}

For Shared Memory Operations:

#include <clio_cte/core/core_client.h>
#include <cstring>

void example() {
  using namespace clio::cte::core;
  Tag tag("my_data");
  size_t data_size = 1024;
  const char *raw_data = "some bytes";
  float score = 0.8f;

  // Manual shared memory management - more control
  // NOTE: AllocateBuffer is NOT templated - it returns ctp::ipc::FullPtr<char>
  auto shm_buffer = CLIO_IPC->AllocateBuffer(data_size);
  memcpy(shm_buffer.ptr_, raw_data, data_size);
  tag.PutBlob("item", shm_buffer.shm_.Cast<void>(), data_size, 0, score);
  // shm_buffer automatically cleaned up when it goes out of scope
}

For Asynchronous Operations:

#include <clio_cte/core/core_client.h>
#include <clio_cte/core/core_tasks.h>
#include <cstring>
#include <vector>

void example() {
  using namespace clio::cte::core;
  Tag tag("my_data");
  std::vector<std::vector<char>> data_chunks(3, std::vector<char>(256, 'y'));

  // Always keep shared memory alive until async task completes
  std::vector<ctp::ipc::FullPtr<char>> buffers;  // Keep alive
  std::vector<clio::run::Future<PutBlobTask>> tasks;

  for (auto &data_chunk : data_chunks) {
    auto buffer = CLIO_IPC->AllocateBuffer(data_chunk.size());
    memcpy(buffer.ptr_, data_chunk.data(), data_chunk.size());

    auto task =
        tag.AsyncPutBlob("chunk", buffer.shm_.Cast<void>(), data_chunk.size());

    buffers.push_back(std::move(buffer));  // Keep alive!
    tasks.push_back(std::move(task));
  }

  // Wait for completion and cleanup
  for (auto &task : tasks) {
    task.Wait();  // Note: Wait() on Future, not pointer
  }
  // buffers and tasks automatically cleaned up here
}

Performance Optimization​

Blob Scoring Guidelines:

  • Use scores 0.8-1.0 for frequently accessed "hot" data
  • Use scores 0.4-0.7 for occasionally accessed "warm" data
  • Use scores 0.0-0.3 for archival "cold" data
  • CTE uses scores for intelligent placement across storage tiers

Batch Operations:

#include <clio_cte/core/core_client.h>
#include <string>
#include <vector>

void example() {
  using namespace clio::cte::core;

  struct Item {
    std::string name;
    const char *data;
    size_t size;
  };
  std::vector<Item> batch_items;

  // Efficient: Group related operations
  Tag batch_tag("batch_job");
  for (const auto &item : batch_items) {
    batch_tag.PutBlob(item.name, item.data, item.size);
  }

  // Less efficient: Multiple tags with few operations each
  // Creates overhead for tag lookup and context switching
}

Size Queries:

#include <clio_cte/core/core_client.h>

void example() {
  using namespace clio::cte::core;
  Tag tag("my_data");

  // Efficient: Check size before allocating retrieval buffer
  clio::run::u64 blob_size = tag.GetBlobSize("large_blob");
  if (blob_size > 0) {
    auto buffer = CLIO_IPC->AllocateBuffer(blob_size);
    tag.GetBlob("large_blob", buffer.shm_.Cast<void>(), blob_size);
  }

  // Less efficient: Allocate maximum possible size
  // auto buffer = CLIO_IPC->AllocateBuffer(MAX_SIZE);  // Wasteful
}

Error Handling Patterns​

Tag Wrapper (Exception-based):

#include <clio_cte/core/core_client.h>
#include <iostream>
#include <stdexcept>
#include <vector>

void example() {
  using namespace clio::cte::core;
  std::vector<char> buffer(1024, 'z');
  size_t size = buffer.size();

  try {
    Tag tag("dataset");
    tag.PutBlob("data", buffer.data(), size);

    clio::run::u64 stored_size = tag.GetBlobSize("data");
    if (stored_size != size) {
      throw std::runtime_error("Size mismatch after storage");
    }

  } catch (const std::exception &e) {
    std::cerr << "Storage operation failed: " << e.what() << "\n";
    // Automatic cleanup via RAII
  }
}

Direct Client (Async with Return Code):

#include <clio_cte/core/core_client.h>
#include <cstring>
#include <iostream>
#include <vector>

bool example() {
  using namespace clio::cte::core;
  auto *client = CLIO_CTE_CLIENT;

  std::vector<char> data(1024, 'z');
  clio::run::u64 size = data.size();
  auto buffer = CLIO_IPC->AllocateBuffer(size);
  memcpy(buffer.ptr_, data.data(), size);

  auto tag_task = client->AsyncGetOrCreateTag("dataset");
  tag_task.Wait();
  TagId tag_id = tag_task->tag_id_;

  auto put_task = client->AsyncPutBlob(tag_id, "data", 0, size,
                                       buffer.shm_.Cast<void>(), 0.5f);
  put_task.Wait();

  if (put_task->return_code_ != 0) {
    std::cerr << "PutBlob failed with code: " << put_task->return_code_ << "\n";
    return false;
  }

  auto size_task = client->AsyncGetBlobSize(tag_id, "data");
  size_task.Wait();
  if (size_task->size_ != size) {
    std::cerr << "Size mismatch: expected " << size << ", got "
              << size_task->size_ << "\n";
    return false;
  }
  return true;
}

Thread Safety Considerations​

  • Both Tag wrapper and Client are thread-safe
  • Multiple threads can safely share the same Tag or Client instance
  • Shared memory buffers (ctp::ipc::FullPtr) should not be shared between threads
  • Each thread should maintain its own buffer allocations for optimal performance

Multi-Node Deployment​

CTE Core supports distributed deployment across multiple nodes:

  1. Configure CLIO Runtime for multi-node operation
  2. Use appropriate PoolQuery values:
    • clio::run::PoolQuery::Local() - Local node only
    • clio::run::PoolQuery::Broadcast() - All nodes
    • Custom pool queries for specific node groups

Custom Data Placement Algorithms​

Extend the DPE (Data Placement Engine) by implementing custom placement strategies:

  1. Inherit from the base DPE class
  2. Implement placement logic based on target metrics
  3. Register the new DPE type in configuration

Performance Optimization​

  1. Batch Operations: Use async APIs for multiple operations
  2. Score-based Placement: Set appropriate scores (0-1) for data temperature
  3. Target Balancing: Monitor and rebalance based on target metrics
  4. Queue Tuning: Adjust lane counts and priorities based on workload

Error Handling​

All async operations return a Future. After calling Wait(), check the return_code_ field:

  • 0: Success
  • Non-zero: Error (specific codes depend on operation)

Always check return values and handle errors appropriately:

#include <clio_cte/core/core_client.h>
#include <iostream>
#include <string>

void example() {
  using namespace clio::cte::core;
  auto *cte_client = CLIO_CTE_CLIENT;
  std::string target_name = "/mnt/nvme/cte_storage.dat";
  clio::run::bdev::BdevType bdev_type = clio::run::bdev::BdevType::kFile;
  clio::run::u64 size = 1024ULL * 1024 * 1024;

  auto task = cte_client->AsyncRegisterTarget(target_name, bdev_type, size);
  task.Wait();
  if (task->return_code_ != 0) {
    // Handle error
    std::cerr << "Failed to register target, error code: "
              << task->return_code_ << "\n";
  }
}

Thread Safety​

  • CTE Core client operations are thread-safe
  • Multiple threads can share a client instance
  • Async operations are particularly suitable for multi-threaded usage

Memory Management​

  • CTE Core uses shared memory for zero-copy data transfer
  • The ctp::ipc::ShmPtr<> type represents shared memory locations
  • ctp::ipc::FullPtr<char> manages allocation lifecycle with RAII cleanup
  • Use CLIO_IPC->AllocateBuffer(size) to allocate shared memory buffers

Troubleshooting​

Common Issues​

  1. Initialization Failures

    • Ensure CLIO Runtime is initialized first
    • Check configuration file path and format
    • Verify storage paths have appropriate permissions

  2. Target Registration Errors

    • Confirm target path exists and is writable
    • Check available disk space
    • Verify bdev type matches storage medium

  3. Blob Operations Failing

    • Ensure tag exists before blob operations
    • Check target has sufficient space
    • Verify data pointers are valid shared memory

  4. Performance Issues

    • Monitor target statistics regularly
    • Adjust worker count based on workload
    • Tune queue configurations
    • Consider data placement strategy

Debug Logging​

Enable debug logging by setting environment variables:

export CTP_LOG_LEVEL=debug
export CTE_LOG_LEVEL=DEBUG

Metrics Collection​

Use the telemetry API to collect performance metrics:

#include <clio_cte/core/core_client.h>
#include <chrono>
#include <cstdint>
#include <thread>

static void ProcessTelemetry(
    const clio::run::priv::vector<clio::cte::core::CteTelemetry> &entries) {
  (void)entries;
}

void example() {
  using namespace clio::cte::core;
  auto *cte_client = CLIO_CTE_CLIENT;

  bool running = true;
  std::uint64_t last_logical_time = 0;

  // Continuous monitoring loop
  while (running) {
    auto telemetry_task = cte_client->AsyncPollTelemetryLog(last_logical_time);
    telemetry_task.Wait();

    ProcessTelemetry(telemetry_task->entries_);

    if (!telemetry_task->entries_.empty()) {
      last_logical_time = telemetry_task->entries_.back().logical_time_;
    }

    std::this_thread::sleep_for(std::chrono::seconds(1));
    running = false;  // (example: run one iteration)
  }
}

API Stability and Versioning​

CTE Core follows semantic versioning:

  • Major version: Breaking API changes
  • Minor version: New features, backward compatible
  • Patch version: Bug fixes

Check version compatibility:

// Version macros (defined in headers)
#if CTE_CORE_VERSION_MAJOR >= 1 && CTE_CORE_VERSION_MINOR >= 0
    // Use newer API features
#endif

Support and Resources​

  • Documentation: This document and inline API documentation
  • Examples: See test/unit/ directory for comprehensive examples
  • Configuration: Example configs in config/ directory
  • Issues: Report bugs via project issue tracker