multi_service_tracing_example.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 <iostream>
#include <memory>
#include <string>
#include <chrono>
#include <thread>
#include <iomanip>
 
#include "kcenon/monitoring/tracing/distributed_tracer.h"
 
using namespace kcenon::monitoring;
using namespace std::chrono_literals;
 
// Forward declarations
void display_span(const trace_span& span, int depth);
void display_children(const std::vector<trace_span>& spans,
                     const std::string& parent_id,
                     int depth);
 
class ApiGatewayService {
private:
    std::string service_name_ = "api_gateway";
 
public:
    trace_span handle_request(const std::string& endpoint, const std::string& method) {
        std::cout << "\n[" << service_name_ << "] Processing " << method << " " << endpoint << std::endl;
 
        // Create root span for this request
        trace_span span;
        span.trace_id = generate_trace_id();
        span.span_id = generate_span_id();
        span.operation_name = "http_request";
        span.service_name = service_name_;
        span.start_time = std::chrono::system_clock::now();
 
        // Add HTTP-specific tags
        span.tags["http.method"] = method;
        span.tags["http.url"] = endpoint;
        span.tags["http.target"] = endpoint;
        span.tags["component"] = "http_server";
 
        // Add baggage for cross-cutting concerns
        span.baggage["user.id"] = "user-12345";
        span.baggage["session.id"] = "sess-67890";
        span.baggage["request.priority"] = "high";
 
        std::cout << "   → Created root span: " << span.span_id << std::endl;
        std::cout << "     Trace ID: " << span.trace_id << std::endl;
        std::cout << "     Baggage: user.id=" << span.baggage["user.id"] << std::endl;
 
        return span;
    }
 
    trace_context create_context(const trace_span& span) {
        trace_context ctx;
        ctx.trace_id = span.trace_id;
        ctx.span_id = span.span_id;
        ctx.trace_flags = "01";  // Sampled
        ctx.baggage = span.baggage;
 
        std::cout << "   → Context for propagation: "
                  << ctx.to_w3c_traceparent() << std::endl;
 
        return ctx;
    }
 
private:
    static std::string generate_trace_id() {
        // Generate 32-character hex string (16 bytes)
        std::string id;
        for (int i = 0; i < 32; ++i) {
            id += "0123456789abcdef"[rand() % 16];
        }
        return id;
    }
 
    static std::string generate_span_id() {
        // Generate 16-character hex string (8 bytes)
        std::string id;
        for (int i = 0; i < 16; ++i) {
            id += "0123456789abcdef"[rand() % 16];
        }
        return id;
    }
};
 
class AuthService {
private:
    std::string service_name_ = "auth_service";
 
public:
    trace_span verify_token(const trace_context& parent_ctx, const std::string& /* token */) {
        std::cout << "\n[" << service_name_ << "] Verifying authentication token" << std::endl;
        std::cout << "   Received context: " << parent_ctx.to_w3c_traceparent() << std::endl;
 
        // Create child span
        trace_span span;
        span.trace_id = parent_ctx.trace_id;         // Same trace ID
        span.span_id = generate_span_id();           // New span ID
        span.parent_span_id = parent_ctx.span_id;    // Link to parent
        span.operation_name = "verify_token";
        span.service_name = service_name_;
        span.start_time = std::chrono::system_clock::now();
 
        // Inherit baggage from parent
        span.baggage = parent_ctx.baggage;
 
        // Add service-specific tags
        span.tags["auth.token_type"] = "bearer";
        span.tags["auth.method"] = "jwt";
 
        std::cout << "   → Created child span: " << span.span_id << std::endl;
        std::cout << "     Parent span: " << span.parent_span_id << std::endl;
        std::cout << "     Inherited baggage: user.id=" << span.baggage["user.id"] << std::endl;
 
        // Simulate authentication work
        std::this_thread::sleep_for(5ms);
 
        span.end_time = std::chrono::system_clock::now();
        span.calculate_duration();
        span.status = trace_span::status_code::ok;
        span.tags["auth.result"] = "success";
 
        std::cout << "   ✓ Authentication successful (duration: "
                  << span.duration.count() << "µs)" << std::endl;
 
        return span;
    }
 
private:
    static std::string generate_span_id() {
        std::string id;
        for (int i = 0; i < 16; ++i) {
            id += "0123456789abcdef"[rand() % 16];
        }
        return id;
    }
};
 
class UserService {
private:
    std::string service_name_ = "user_service";
 
public:
    trace_span get_user_profile(const trace_context& parent_ctx, const std::string& user_id) {
        std::cout << "\n[" << service_name_ << "] Fetching user profile" << std::endl;
        std::cout << "   User ID from baggage: " << parent_ctx.baggage.at("user.id") << std::endl;
 
        // Create child span
        trace_span span;
        span.trace_id = parent_ctx.trace_id;
        span.span_id = generate_span_id();
        span.parent_span_id = parent_ctx.span_id;
        span.operation_name = "get_user_profile";
        span.service_name = service_name_;
        span.start_time = std::chrono::system_clock::now();
 
        // Inherit baggage
        span.baggage = parent_ctx.baggage;
 
        // Add database query tags
        span.tags["db.system"] = "postgresql";
        span.tags["db.name"] = "users_db";
        span.tags["db.statement"] = "SELECT * FROM users WHERE id = ?";
        span.tags["db.user_id"] = user_id;
 
        std::cout << "   → Created child span: " << span.span_id << std::endl;
        std::cout << "     Parent span: " << span.parent_span_id << std::endl;
 
        // Simulate database query
        std::this_thread::sleep_for(15ms);
 
        span.end_time = std::chrono::system_clock::now();
        span.calculate_duration();
        span.status = trace_span::status_code::ok;
        span.tags["db.rows_returned"] = "1";
 
        std::cout << "   ✓ User profile fetched (duration: "
                  << span.duration.count() << "µs)" << std::endl;
 
        return span;
    }
 
private:
    static std::string generate_span_id() {
        std::string id;
        for (int i = 0; i < 16; ++i) {
            id += "0123456789abcdef"[rand() % 16];
        }
        return id;
    }
};
 
class CacheService {
private:
    std::string service_name_ = "cache_service";
 
public:
    trace_span cache_lookup(const trace_context& parent_ctx, const std::string& key) {
        std::cout << "\n[" << service_name_ << "] Cache lookup" << std::endl;
 
        // Create child span
        trace_span span;
        span.trace_id = parent_ctx.trace_id;
        span.span_id = generate_span_id();
        span.parent_span_id = parent_ctx.span_id;
        span.operation_name = "cache_get";
        span.service_name = service_name_;
        span.start_time = std::chrono::system_clock::now();
 
        // Inherit baggage
        span.baggage = parent_ctx.baggage;
 
        // Add cache-specific tags
        span.tags["cache.type"] = "redis";
        span.tags["cache.key"] = key;
 
        std::cout << "   → Created child span: " << span.span_id << std::endl;
 
        // Simulate cache miss
        std::this_thread::sleep_for(2ms);
 
        span.end_time = std::chrono::system_clock::now();
        span.calculate_duration();
        span.status = trace_span::status_code::ok;
        span.tags["cache.hit"] = "false";
 
        std::cout << "   ○ Cache miss (duration: "
                  << span.duration.count() << "µs)" << std::endl;
 
        return span;
    }
 
private:
    static std::string generate_span_id() {
        std::string id;
        for (int i = 0; i < 16; ++i) {
            id += "0123456789abcdef"[rand() % 16];
        }
        return id;
    }
};
 
void display_trace_tree(const std::vector<trace_span>& spans) {
    std::cout << "\n=== Trace Tree Structure ===" << std::endl;
 
    // Find root span
    const trace_span* root = nullptr;
    for (const auto& span : spans) {
        if (span.parent_span_id.empty()) {
            root = &span;
            break;
        }
    }
 
    if (!root) {
        std::cout << "No root span found" << std::endl;
        return;
    }
 
    std::cout << "\nTrace ID: " << root->trace_id << "\n" << std::endl;
 
    // Display root
    display_span(*root, 0);
 
    // Display children
    display_children(spans, root->span_id, 1);
 
    std::cout << "\n=== Total Spans: " << spans.size() << " ===" << std::endl;
    std::cout << "Total trace duration: " << root->duration.count() << "µs" << std::endl;
}
 
void display_span(const trace_span& span, int depth) {
    std::string indent(depth * 2, ' ');
    std::string prefix = depth == 0 ? "┌─" : "├─";
 
    std::cout << indent << prefix << " [" << span.service_name << "] "
              << span.operation_name << std::endl;
    std::cout << indent << "   Span ID: " << span.span_id << std::endl;
    std::cout << indent << "   Duration: " << span.duration.count() << "µs" << std::endl;
 
    if (!span.tags.empty()) {
        std::cout << indent << "   Tags:";
        int count = 0;
        for (const auto& [key, value] : span.tags) {
            if (count++ < 3) {  // Show first 3 tags
                std::cout << " " << key << "=" << value;
            }
        }
        if (span.tags.size() > 3) {
            std::cout << " +" << (span.tags.size() - 3) << " more";
        }
        std::cout << std::endl;
    }
}
 
void display_children(const std::vector<trace_span>& spans,
                     const std::string& parent_id,
                     int depth) {
    for (const auto& span : spans) {
        if (span.parent_span_id == parent_id) {
            display_span(span, depth);
            display_children(spans, span.span_id, depth + 1);
        }
    }
}
 
void simulate_multi_service_request() {
    std::cout << "=== Multi-Service Distributed Tracing Example ===" << std::endl;
 
    std::vector<trace_span> collected_spans;
 
    // Step 1: API Gateway receives request
    std::cout << "\n--- Step 1: API Gateway ---" << std::endl;
    ApiGatewayService gateway;
    auto gateway_span = gateway.handle_request("/api/user/profile", "GET");
    auto gateway_ctx = gateway.create_context(gateway_span);
 
    // Step 2: Check cache (parallel to auth)
    std::cout << "\n--- Step 2: Cache Lookup ---" << std::endl;
    CacheService cache;
    auto cache_span = cache.cache_lookup(gateway_ctx, "user:user-12345");
    collected_spans.push_back(cache_span);
 
    // Step 3: Authenticate request
    std::cout << "\n--- Step 3: Authentication ---" << std::endl;
    AuthService auth;
    auto auth_span = auth.verify_token(gateway_ctx, "eyJhbGc...");
    collected_spans.push_back(auth_span);
 
    // Create context for user service call
    trace_context user_ctx;
    user_ctx.trace_id = gateway_ctx.trace_id;
    user_ctx.span_id = gateway_span.span_id;
    user_ctx.baggage = gateway_ctx.baggage;
 
    // Step 4: Fetch user profile (after cache miss)
    std::cout << "\n--- Step 4: User Profile Service ---" << std::endl;
    UserService user_service;
    auto user_span = user_service.get_user_profile(user_ctx, "user-12345");
    collected_spans.push_back(user_span);
 
    // Complete gateway span
    std::this_thread::sleep_for(5ms);
    gateway_span.end_time = std::chrono::system_clock::now();
    gateway_span.calculate_duration();
    gateway_span.status = trace_span::status_code::ok;
    gateway_span.tags["http.status_code"] = "200";
    collected_spans.insert(collected_spans.begin(), gateway_span);
 
    // Display complete trace
    display_trace_tree(collected_spans);
 
    // Show baggage propagation
    std::cout << "\n=== Baggage Propagation ===" << std::endl;
    std::cout << "Baggage items propagated across all services:" << std::endl;
    for (const auto& [key, value] : gateway_span.baggage) {
        std::cout << "   " << key << " = " << value << std::endl;
    }
 
    std::cout << "\n=== Example completed successfully ===" << std::endl;
}
 
int main() {
    std::cout << "Multi-Service Distributed Tracing Example\n" << std::endl;
 
    simulate_multi_service_request();
 
    std::cout << "\n" << std::string(60, '=') << std::endl;
    std::cout << "\nKey Concepts Demonstrated:" << std::endl;
    std::cout << "1. Trace context propagation across services" << std::endl;
    std::cout << "2. Parent-child span relationships" << std::endl;
    std::cout << "3. Baggage propagation for cross-cutting data" << std::endl;
    std::cout << "4. W3C Trace Context standard" << std::endl;
    std::cout << "5. Service-specific span tags and metadata" << std::endl;
 
    return 0;
}