Exchange Chains

Exchange chains allow a message to move from one exchange to another.

This is useful when routing must be composed in multiple steps.

---

Topology

graph LR
    Publisher --> Orders["orders"]
    Orders --> Integration["orders.integration"]
    Integration --> Audit["orders.audit"]
    Integration --> Analytics["orders.analytics"]

---

Descriptor

var descriptor = new PublisherBoundDescriptor
{
    Exchanges =
    {
        new ExchangeBoundDescriptor
        {
            Name = "orders",
            Type = ExchangeTypes.Direct,
            Durable = true,
            Exchanges =
            {
                new ExchangeBoundDescriptor
                {
                    Name = "orders.integration",
                    Type = ExchangeTypes.Direct,
                    Durable = true,
                    Exchanges =
                    {
                        new ExchangeBoundDescriptor
                        {
                            Name = "orders.audit",
                            Type = ExchangeTypes.Direct,
                            Durable = true
                        },
                        new ExchangeBoundDescriptor
                        {
                            Name = "orders.analytics",
                            Type = ExchangeTypes.Direct,
                            Durable = true
                        }
                    }
                }
            }
        }
    }
};

---

Exchange Chain With Queue

graph LR
    Publisher --> Orders["orders"]
    Orders --> Integration["orders.integration"]
    Integration --> Queue["orders.integration.queue"]

var descriptor = new PublisherBoundDescriptor
{
    Exchanges =
    {
        new ExchangeBoundDescriptor
        {
            Name = "orders",
            Type = ExchangeTypes.Direct,
            Durable = true,
            Exchanges =
            {
                new ExchangeBoundDescriptor
                {
                    Name = "orders.integration",
                    Type = ExchangeTypes.Direct,
                    Durable = true,
                    Queues =
                    {
                        new QueueBoundDescriptor
                        {
                            Name = "orders.integration.queue",
                            Durable = true,
                            AutoDelete = false
                        }
                    }
                }
            }
        }
    }
};

---

When To Use

Use exchange chains when:

• routing should be layered;
• integration routing must be separated from internal routing;
• messages must be replicated to downstream exchanges;
• topology should be configured without changing publisher code.