Messaging System Architectures Overview¶

This document provides an overview of common messaging system architectures and their use cases.

Common Messaging Architectures¶

1. Publish-Subscribe (Pub-Sub)¶

Publishers send messages to a topic; subscribers receive messages from topics asynchronously.

graph TD
    P1[Publisher 1] -->|Message| T[Topic/Channel]
    P2[Publisher 2] -->|Message| T
    T -->|Message| S1[Subscriber 1]
    T -->|Message| S2[Subscriber 2]
    T -->|Message| S3[Subscriber 3]

Use Cases: - Event-driven architectures - Real-time notifications - Broadcasting information to multiple consumers

Examples: Kafka, RabbitMQ, Solace

2. Request-Reply¶

Clients send requests and await replies, often used in service bus architectures.

sequenceDiagram
    participant C as Client
    participant S as Service
    C->>S: Request
    S->>C: Reply

Use Cases: - Synchronous communication - RPC-style messaging - Service-to-service communication

Examples: IBM MQ, RabbitMQ, TIBCO

3. Push-Pull (Work Queue)¶

Tasks are distributed among multiple consumers for parallel processing.

graph TD
    P[Producer] -->|Task| Q[Queue]
    Q -->|Task| C1[Consumer 1]
    Q -->|Task| C2[Consumer 2]
    Q -->|Task| C3[Consumer 3]

Use Cases: - Task distribution - Load balancing - Background job processing

Examples: RabbitMQ, Amazon SQS, Redis

4. Fanout¶

A message sent to an exchange is delivered to all bound queues.

graph TD
    P[Producer] -->|Message| E[Fanout Exchange]
    E -->|Message| Q1[Queue 1]
    E -->|Message| Q2[Queue 2]
    E -->|Message| Q3[Queue 3]

Use Cases: - Broadcasting updates - Event replication - Multi-consumer scenarios

Examples: RabbitMQ, Apache Pulsar

5. Streaming¶

Continuous data flow processing with ordered message sequences.

graph LR
    P[Producer] -->|Stream| T[Topic/Partition]
    T -->|Stream| C1[Consumer Group 1]
    T -->|Stream| C2[Consumer Group 2]

Use Cases: - Real-time analytics - Event sourcing - Log aggregation

Examples: Apache Kafka, Apache Pulsar, AWS Kinesis

Architecture Selection Guide¶

Hybrid Architectures¶

Many modern systems combine multiple patterns:

graph TD
    subgraph "Microservices"
        MS1[Service A] -->|Request-Reply| MS2[Service B]
        MS2 -->|Event| ES[Event Store]
    end

    subgraph "Event Processing"
        ES -->|Stream| SP[Stream Processor]
        SP -->|Notification| NS[Notification Service]
    end

    subgraph "Task Processing"
        MS1 -->|Task| TQ[Task Queue]
        TQ -->|Task| W1[Worker 1]
        TQ -->|Task| W2[Worker 2]
    end

Choosing the Right Architecture¶

Consider these factors when selecting an architecture:

1. Communication Pattern: Synchronous vs. asynchronous
2. Message Volume: Low, medium, or high throughput
3. Durability Requirements: Temporary vs. persistent messages
4. Ordering Requirements: Strict ordering vs. parallel processing
5. Scalability Needs: Horizontal scaling requirements
6. Latency Tolerance: Real-time vs. batch processing

Next Steps¶

Once you've identified the appropriate architecture pattern, proceed to the Product Comparison to evaluate specific implementations.