Microservices Communication Introduction — Complete Guide

# patterns_overview.py
# Microservices communication patterns

def communication_patterns():
    patterns = {
        "Synchronous": "Client sends request and waits for response. REST, gRPC, GraphQL.",
        "Asynchronous": "Client sends message and continues. Message queues, pub/sub, event buses.",
        "Hybrid": "Combines sync for queries, async for commands and events.",
    }
    
    strengths = {
        "Synchronous": "Simple to implement, immediate response, easy debugging",
        "Asynchronous": "Loose coupling, fault tolerance, better scalability",
        "Hybrid": "Best of both approaches when designed carefully",
    }
    
    print("Microservices Communication Patterns")
    print("=" * 45)
    for pattern, desc in patterns.items():
        print(f"\n{pattern}:")
        print(f"  Description: {desc}")
        print(f"  Strength:    {strengths[pattern]}")

communication_patterns()

# sync_communication.py
# Synchronous communication characteristics

def sync_characteristics():
    print("Synchronous Communication Characteristics")
    print("=" * 40)
    print()
    print("Protocols: HTTP/REST, gRPC, GraphQL")
    print()
    print("Flow:")
    print("  1. Service A sends request to Service B")
    print("  2. Service A blocks until response arrives")
    print("  3. Service B processes and returns response")
    print("  4. Service A continues execution")
    print()
    print("Pros:")
    print("  + Simple request-response model")
    print("  + Immediate feedback")
    print("  + Easy to debug and trace")
    print()
    print("Cons:")
    print("  - Tight coupling between services")
    print("  - Cascading failures if downstream is down")
    print("  - Latency accumulates with chain calls")

sync_characteristics()

# async_communication.py
# Asynchronous communication characteristics

def async_characteristics():
    print("Asynchronous Communication Characteristics")
    print("=" * 42)
    print()
    print("Brokers: RabbitMQ, Apache Kafka, AWS SQS, Redis Pub/Sub")
    print()
    print("Flow:")
    print("  1. Service A publishes message to broker")
    print("  2. Service A continues executing immediately")
    print("  3. Service B consumes message when ready")
    print("  4. Service B processes and may publish result")
    print()
    print("Pros:")
    print("  + Loose coupling between services")
    print("  + Fault isolation")
    print("  + Better scalability and elasticity")
    print()
    print("Cons:")
    print("  - Harder to debug and trace")
    print("  - Eventual consistency only")
    print("  - Message ordering challenges")

async_characteristics()

# choose_pattern.py
# Decision factors for communication pattern

def choose_pattern():
    scenarios = [
        {
            "requirement": "Real-time user request",
            "pattern": "Synchronous (REST/gRPC)",
            "reason": "User expects immediate response"
        },
        {
            "requirement": "Background processing",
            "pattern": "Asynchronous (message queue)",
            "reason": "Task can complete without blocking user"
        },
        {
            "requirement": "Event broadcast to multiple services",
            "pattern": "Async (pub/sub event bus)",
            "reason": "Multiple consumers need notification"
        },
        {
            "requirement": "Data consistency across services",
            "pattern": "Saga pattern (async choreography/orchestration)",
            "reason": "Distributed transaction coordination"
        },
    ]
    
    print("Communication Pattern Selection Guide")
    print("=" * 45)
    for s in scenarios:
        print(f"\nRequirement: {s['requirement']}")
        print(f"Pattern:      {s['pattern']}")
        print(f"Reason:       {s['reason']}")

choose_pattern()

def document_system_design():
    print("Document Processing System - Communication Design")
    print("=" * 50)
    print()
    print("Services:")
    print("  Upload Service    - Receives files from users")
    print("  Conversion Service - Converts file formats")
    print("  Storage Service   - Saves to object storage")
    print("  Notification      - Sends email/SMS to users")
    print()
    print("Communication Plan:")
    print()
    print("  Upload -> Conversion: Async (RabbitMQ)")
    print("    Reason: Conversion takes time; user should not wait")
    print()
    print("  Conversion -> Storage: Async (RabbitMQ)")
    print("    Reason: Storage is independent step after conversion")
    print()
    print("  Storage -> Notification: Async (Event Bus)")
    print("    Reason: Multiple notification channels may listen")
    print()
    print("  User -> Upload: Sync (REST)")
    print("    Reason: User needs upload confirmation immediately")
    
document_system_design()