service_b.py

from flask import Flask, request, jsonify, g, has_request_context
import logging
from pythonjsonlogger import jsonlogger
import time
import sys
import uuid
from datetime import datetime, timezone

app = Flask(__name__)
SERVICE_NAME = "service-b"


class RequestContextFilter(logging.Filter):
    def filter(self, record):
        record.timestamp = datetime.now(timezone.utc).isoformat()
        record.level = record.levelname
        if not hasattr(record, "service"):
            record.service = SERVICE_NAME
        if not hasattr(record, "correlation_id"):
            if has_request_context():
                record.correlation_id = getattr(g, "correlation_id", "no-correlation-id")
            else:
                record.correlation_id = "no-request-context"
        return True


def setup_logging():
    """Configure JSON logging for service B"""
    log_handler = logging.StreamHandler(sys.stdout)
    formatter = jsonlogger.JsonFormatter(
        "%(timestamp)s %(level)s %(name)s %(service)s %(correlation_id)s %(message)s"
    )
    log_handler.setFormatter(formatter)
    log_handler.addFilter(RequestContextFilter())

    logger = logging.getLogger(SERVICE_NAME)
    logger.handlers.clear()
    logger.addHandler(log_handler)
    logger.setLevel(logging.INFO)
    logger.propagate = False

    return logger


logger = setup_logging()


@app.before_request
def before_request():
    """Extract correlation ID from incoming requests"""
    g.correlation_id = request.headers.get("X-Correlation-ID", str(uuid.uuid4()))
    g.request_start_time = time.time()


@app.after_request
def after_request(response):
    response.headers["X-Correlation-ID"] = getattr(g, "correlation_id", "")
    return response


def log_with_context(level, message, **kwargs):
    extra = {
        "correlation_id": getattr(g, "correlation_id", "no-correlation-id"),
        "timestamp": datetime.now(timezone.utc).isoformat(),
        "service": SERVICE_NAME
    }
    extra.update(kwargs)

    log_method = getattr(logger, level.lower(), logger.info)
    log_method(message, extra=extra)


@app.route('/api/inventory/check', methods=['POST'])
def check_inventory():
    """Check inventory availability"""
    data = request.get_json(silent=True) or {}
    product_id = data.get('product_id')

    log_with_context(
        "info",
        "Inventory check request received",
        method=request.method,
        path=request.path,
        product_id=product_id
    )

    if not product_id:
        log_with_context(
            "warning",
            "Inventory validation failed",
            status_code=400,
            missing_field="product_id"
        )
        return jsonify({"error": "product_id is required"}), 400

    # Simulate inventory check
    time.sleep(0.05)

    result = {
        "product_id": product_id,
        "available": True,
        "quantity": 50
    }

    duration_ms = round((time.time() - g.request_start_time) * 1000, 2)

    log_with_context(
        "info",
        "Inventory check completed",
        status_code=200,
        product_id=product_id,
        available=result["available"],
        quantity=result["quantity"],
        duration_ms=duration_ms
    )

    return jsonify(result)


if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5001, debug=False)