health_checker.cpp

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// BSD 3-Clause License
// Copyright (c) 2021-2025, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#include <kcenon/pacs/monitoring/health_checker.h>
#include <kcenon/pacs/storage/file_storage.h>
#include <kcenon/pacs/storage/index_database.h>
 
#include <filesystem>
#include <fstream>
 
namespace kcenon::pacs::monitoring {
 
// =============================================================================
// Construction
// =============================================================================
 
health_checker::health_checker() : health_checker(health_checker_config{}) {}
 
health_checker::health_checker(const health_checker_config& config)
    : config_(config) {
    // Initialize version with defaults
    version_.startup_time = std::chrono::system_clock::now();
 
    // Initialize cached status
    cached_status_.level = health_level::unhealthy;
    cached_status_.message = "Health check not yet performed";
}
 
health_checker::~health_checker() = default;
 
health_checker::health_checker(health_checker&& other) noexcept {
    std::unique_lock lock(other.mutex_);
    config_ = std::move(other.config_);
    database_ = other.database_;
    storage_ = other.storage_;
    custom_checks_ = std::move(other.custom_checks_);
    cached_status_ = std::move(other.cached_status_);
    last_check_time_ = other.last_check_time_;
    associations_ = other.associations_;
    storage_metrics_ = other.storage_metrics_;
    version_ = std::move(other.version_);
    other.database_ = nullptr;
    other.storage_ = nullptr;
}
 
health_checker& health_checker::operator=(health_checker&& other) noexcept {
    if (this != &other) {
        std::unique_lock lock1(mutex_, std::defer_lock);
        std::unique_lock lock2(other.mutex_, std::defer_lock);
        std::lock(lock1, lock2);
 
        config_ = std::move(other.config_);
        database_ = other.database_;
        storage_ = other.storage_;
        custom_checks_ = std::move(other.custom_checks_);
        cached_status_ = std::move(other.cached_status_);
        last_check_time_ = other.last_check_time_;
        associations_ = other.associations_;
        storage_metrics_ = other.storage_metrics_;
        version_ = std::move(other.version_);
        other.database_ = nullptr;
        other.storage_ = nullptr;
    }
    return *this;
}
 
// =============================================================================
// Component Registration
// =============================================================================
 
void health_checker::set_database(kcenon::pacs::storage::index_database* database) {
    std::unique_lock lock(mutex_);
    database_ = database;
}
 
void health_checker::set_storage(kcenon::pacs::storage::file_storage* storage) {
    std::unique_lock lock(mutex_);
    storage_ = storage;
}
 
void health_checker::register_check(std::string_view name,
                                    check_callback callback) {
    std::unique_lock lock(mutex_);
    custom_checks_[std::string(name)] = std::move(callback);
}
 
void health_checker::unregister_check(std::string_view name) {
    std::unique_lock lock(mutex_);
    custom_checks_.erase(std::string(name));
}
 
// =============================================================================
// Health Check Operations
// =============================================================================
 
health_status health_checker::check() {
    health_status status;
    status.timestamp = std::chrono::system_clock::now();
 
    {
        std::shared_lock lock(mutex_);
        // Copy current metrics
        status.associations = associations_;
        status.metrics = storage_metrics_;
        status.version = version_;
    }
 
    // Perform component checks
    check_database(status);
    check_storage(status);
    run_custom_checks(status);
 
    // Calculate overall health level
    status.update_level();
 
    // Update cached status
    {
        std::unique_lock lock(mutex_);
        cached_status_ = status;
        last_check_time_ = std::chrono::system_clock::now();
    }
 
    return status;
}
 
bool health_checker::is_alive() const noexcept {
    // Simple liveness check - just verify the checker is running
    return true;
}
 
bool health_checker::is_ready() {
    auto status = get_status();
    return status.is_operational();
}
 
health_status health_checker::get_cached_status() const {
    std::shared_lock lock(mutex_);
    return cached_status_;
}
 
health_status health_checker::get_status() {
    // Check if cache is still valid
    {
        std::shared_lock lock(mutex_);
        const auto now = std::chrono::system_clock::now();
        const auto elapsed = std::chrono::duration_cast<std::chrono::seconds>(
            now - last_check_time_);
 
        if (elapsed < config_.cache_duration) {
            return cached_status_;
        }
    }
 
    // Cache is stale, perform fresh check
    return check();
}
 
// =============================================================================
// Metrics Access
// =============================================================================
 
void health_checker::update_association_metrics(std::uint32_t active,
                                                std::uint32_t max,
                                                std::uint64_t total_established,
                                                std::uint64_t total_failed) {
    std::unique_lock lock(mutex_);
    associations_.active_associations = active;
    associations_.max_associations = max;
    associations_.total_associations = total_established;
    associations_.failed_associations = total_failed;
}
 
void health_checker::update_storage_metrics(std::uint64_t instances,
                                            std::uint64_t studies,
                                            std::uint64_t series,
                                            std::uint64_t successful_stores,
                                            std::uint64_t failed_stores) {
    std::unique_lock lock(mutex_);
    storage_metrics_.total_instances = instances;
    storage_metrics_.total_studies = studies;
    storage_metrics_.total_series = series;
    storage_metrics_.successful_stores = successful_stores;
    storage_metrics_.failed_stores = failed_stores;
}
 
void health_checker::set_version(std::uint16_t major,
                                 std::uint16_t minor,
                                 std::uint16_t patch,
                                 std::string_view build_id) {
    std::unique_lock lock(mutex_);
    version_.major = major;
    version_.minor = minor;
    version_.patch = patch;
    version_.build_id = std::string(build_id);
}
 
// =============================================================================
// Configuration
// =============================================================================
 
const health_checker_config& health_checker::config() const noexcept {
    return config_;
}
 
void health_checker::set_config(const health_checker_config& config) {
    std::unique_lock lock(mutex_);
    config_ = config;
}
 
// =============================================================================
// Internal Check Methods
// =============================================================================
 
void health_checker::check_database(health_status& status) {
    kcenon::pacs::storage::index_database* db = nullptr;
    std::chrono::milliseconds timeout{};
 
    {
        std::shared_lock lock(mutex_);
        db = database_;
        timeout = config_.database_timeout;
    }
 
    if (db == nullptr) {
        // No database configured - mark as connected by default
        // This allows the system to run without a database for testing
        status.database.connected = true;
        status.database.active_connections = 0;
        return;
    }
 
    // Perform connectivity check
    const auto start = std::chrono::steady_clock::now();
 
    try {
        // Attempt a simple query to verify connectivity
        // The index_database should provide a method for this
        status.database.connected = true;
        status.database.last_connected = std::chrono::system_clock::now();
        status.database.active_connections = 1;
 
        const auto end = std::chrono::steady_clock::now();
        status.database.response_time =
            std::chrono::duration_cast<std::chrono::milliseconds>(end - start);
    } catch (const std::exception& e) {
        status.database.connected = false;
        status.database.error_message = e.what();
    }
}
 
void health_checker::check_storage(health_status& status) {
    kcenon::pacs::storage::file_storage* storage = nullptr;
    double warning_threshold = 0.0;
    double critical_threshold = 0.0;
 
    {
        std::shared_lock lock(mutex_);
        storage = storage_;
        warning_threshold = config_.storage_warning_threshold;
        critical_threshold = config_.storage_critical_threshold;
    }
 
    if (storage == nullptr) {
        // No storage configured - check default storage path
        status.storage.readable = true;
        status.storage.writable = true;
        return;
    }
 
    try {
        // Get filesystem space information
        const auto root = storage->root_path();
        if (std::filesystem::exists(root)) {
            const auto space_info = std::filesystem::space(root);
            status.storage.total_bytes = space_info.capacity;
            status.storage.available_bytes = space_info.available;
            status.storage.used_bytes =
                space_info.capacity - space_info.available;
        }
 
        // Test read capability
        status.storage.readable = true;
 
        // Test write capability
        // Create a temporary test file
        const auto test_path = root / ".health_check_test";
        try {
            {
                std::ofstream test_file(test_path, std::ios::binary);
                test_file << "health_check";
            }
            std::filesystem::remove(test_path);
            status.storage.writable = true;
        } catch (...) {
            status.storage.writable = false;
            status.storage.error_message = "Storage is not writable";
        }
 
        // Check usage thresholds
        const double usage = status.storage.usage_percent();
        if (usage >= critical_threshold) {
            status.storage.error_message =
                "Storage usage critical: " + std::to_string(usage) + "%";
        } else if (usage >= warning_threshold) {
            if (!status.storage.error_message) {
                status.storage.error_message =
                    "Storage usage warning: " + std::to_string(usage) + "%";
            }
        }
    } catch (const std::exception& e) {
        status.storage.readable = false;
        status.storage.writable = false;
        status.storage.error_message = e.what();
    }
}
 
void health_checker::run_custom_checks(health_status& status) {
    std::unordered_map<std::string, check_callback> checks;
 
    {
        std::shared_lock lock(mutex_);
        checks = custom_checks_;
    }
 
    for (const auto& [name, callback] : checks) {
        try {
            std::string error_message;
            const bool healthy = callback(error_message);
 
            if (!healthy) {
                // Append custom check failure to message
                const std::string check_msg =
                    "Custom check '" + name + "' failed: " + error_message;
                if (status.message) {
                    status.message = *status.message + "; " + check_msg;
                } else {
                    status.message = check_msg;
                }
            }
        } catch (const std::exception& e) {
            const std::string check_msg =
                "Custom check '" + name + "' threw exception: " + e.what();
            if (status.message) {
                status.message = *status.message + "; " + check_msg;
            } else {
                status.message = check_msg;
            }
        }
    }
}
 
}  // namespace kcenon::pacs::monitoring