How to Add a Correlation ID Tracing Header in Python

import uuid
import json
from dataclasses import dataclass, field
from typing import Optional

@dataclass
class Request:
    headers: dict = field(default_factory=dict)

    def get(self, key, default=None):
        return self.headers.get(key, default)

class CorrelationIdMiddleware:
    def __init__(self, header_name: str = "X-Correlation-ID"):
        self.header_name = header_name

    def process(self, request: Request) -> Request:
        corr_id = request.get(self.header_name)
        if corr_id is None:
            corr_id = str(uuid.uuid4())
            request.headers[self.header_name] = corr_id
        return request

    def log_with_correlation(self, request: Request, message: str) -> str:
        corr_id = request.get(self.header_name, "N/A")
        return json.dumps({
            "correlation_id": corr_id,
            "message": message
        })

if __name__ == "__main__":
    middleware = CorrelationIdMiddleware()
    
    request1 = Request()
    request1 = middleware.process(request1)
    
    request2 = Request(headers={"X-Correlation-ID": "existing-id-123"})
    request2 = middleware.process(request2)
    
    print(middleware.log_with_correlation(request1, "Processing request 1"))
    print(middleware.log_with_correlation(request2, "Processing request 2"))