Distributed Observability: OpenTelemetry & Grafana Tempo

// W3C Trace Context Header
traceparent: 00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01

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// OpenTelemetry Distributed Trace Context Propagation Engine
class DistributedTraceContext {
    constructor() {
        this.traceId = this._generateHex(16); // 128-bit Trace ID (Shared across all microservices!)
        this.spanId = this._generateHex(8);   // 64-bit Current Span ID
    }
 
    _generateHex(bytes) {
        let result = '';
        for (let i = 0; i < bytes; i++) {
            result += Math.floor(Math.random() * 256).toString(16).padStart(2, '0');
        }
        return result;
    }
 
    // Format into standard W3C 'traceparent' header (RFC 00-traceId-spanId-flags)
    toW3CHeader() {
        return `00-${this.traceId}-${this.spanId}-01`;
    }
 
    // Create child span for downstream RPC call
    createChildSpan() {
        const child = new DistributedTraceContext();
        child.traceId = this.traceId; // Retains global trace ID!
        child.parentSpanId = this.spanId;
        return child;
    }
}
 
// 1. Inbound Request at API Gateway
const gatewaySpan = new DistributedTraceContext();
console.log("=== OpenTelemetry Distributed Tracing Engine ===");
console.log("[API GATEWAY] Generated Trace ID:  ", gatewaySpan.traceId);
console.log("[API GATEWAY] Outgoing W3C Header: ", gatewaySpan.toW3CHeader());
 
// 2. Downstream Payment Microservice receives header & continues trace
const paymentSpan = gatewaySpan.createChildSpan();
console.log("\n[PAYMENT SERVICE] Ingested Trace ID: ", paymentSpan.traceId);
console.log("[PAYMENT SERVICE] New Child Span ID:  ", paymentSpan.spanId);
console.log("[PAYMENT SERVICE] Parent Span ID:     ", paymentSpan.parentSpanId);
 
console.log("\n✅ Distributed context propagated seamlessly across network boundaries!");