microservices-expert

Microservices Expert

Expert guidance for microservices architecture, design patterns, service communication, and distributed system challenges.

Core Concepts

Microservices Principles

• Single responsibility per service
• Independently deployable
• Decentralized data management
• Infrastructure automation
• Design for failure
• Evolutionary design

Architecture Patterns

• API Gateway
• Service Discovery
• Circuit Breaker
• Saga Pattern
• Event Sourcing
• CQRS

Communication

• Synchronous (HTTP/REST, gRPC)
• Asynchronous (Message queues, Events)
• Service mesh
• API composition
• Backend for Frontend (BFF)

Service Design

from fastapi import FastAPI, HTTPException
from pydantic import BaseModel
import httpx
from typing import List, Optional
from circuitbreaker import circuit
import asyncio

# Individual Microservice
app = FastAPI(title="Order Service", version="1.0.0")

class Order(BaseModel):
    id: str
    user_id: str
    items: List[dict]
    total: float
    status: str

class OrderService:
    def __init__(self, inventory_url: str, payment_url: str):
        self.inventory_url = inventory_url
        self.payment_url = payment_url
        self.client = httpx.AsyncClient()

    @circuit(failure_threshold=5, recovery_timeout=60)
    async def check_inventory(self, items: List[dict]) -> bool:
        """Check inventory availability with circuit breaker"""
        try:
            response = await self.client.post(
                f"{self.inventory_url}/check",
                json={"items": items},
                timeout=5.0
            )
            return response.json()["available"]
        except Exception as e:
            print(f"Inventory service error: {e}")
            raise

    @circuit(failure_threshold=5, recovery_timeout=60)
    async def process_payment(self, user_id: str, amount: float) -> dict:
        """Process payment with circuit breaker"""
        try:
            response = await self.client.post(
                f"{self.payment_url}/charge",
                json={"user_id": user_id, "amount": amount},
                timeout=10.0
            )
            return response.json()
        except Exception as e:
            print(f"Payment service error: {e}")
            raise

    async def create_order(self, order: Order) -> Order:
        """Create order with coordination"""
        # 1. Check inventory
        inventory_available = await self.check_inventory(order.items)
        if not inventory_available:
            raise HTTPException(400, "Items not available")

        # 2. Process payment
        payment = await self.process_payment(order.user_id, order.total)
        if payment["status"] != "success":
            raise HTTPException(400, "Payment failed")

        # 3. Reserve inventory
        await self.reserve_inventory(order.items)

        # 4. Create order record
        order.status = "confirmed"
        await self.save_order(order)

        return order

@app.post("/orders", response_model=Order)
async def create_order(order: Order):
    service = OrderService(
        inventory_url="http://inventory-service",
        payment_url="http://payment-service"
    )
    return await service.create_order(order)