Single Active Consumer (Go)

Ensure only one consumer processes messages from a queue at a time.

Basic Usage

easyrmq.NewWorkerBuilder(easyrmq.ExchangeKindDirect).
    WithPool(client).
    WithExchange("order.events.v1").
    Queue("order.process").
    SingleActiveConsumer(true).
    Build(handler)

What is Single Active Consumer?

Single Active Consumer ensures that only one consumer receives messages from a queue at any time:

Without SAC:                  With SAC:
[C1][C2][C3]                  [Active][Standby][Standby]
  |   |   |                      |         (backup)
 Msg1 Msg2 Msg3              Msg1 Msg2 Msg3
(Round-robin)                (Only active receives)

Benefits

✅ Message Ordering: Ensure messages are processed in order
✅ Exclusive Access: Only one consumer processes at a time
✅ Automatic Failover: Standby consumers take over if active fails

Use Cases

// Ordered processing required
easyrmq.NewWorkerBuilder(easyrmq.ExchangeKindDirect).
    Queue("payment.process").
    SingleActiveConsumer(true).
    Build(processPayment)

// Stateful operations
easyrmq.NewWorkerBuilder(easyrmq.ExchangeKindDirect).
    Queue("inventory.update").
    SingleActiveConsumer(true).
    Build(updateInventory)

// Rate-limited external API
easyrmq.NewWorkerBuilder(easyrmq.ExchangeKindDirect).
    Queue("external.api").
    SingleActiveConsumer(true).
    Build(callExternalAPI)

Best Practices

1. Use when ordering matters: Enable for sequential processing requirements
2. Combine with retry: SAC works well with retry mechanisms
3. Monitor active consumer: Track which consumer is active
4. Handle failover: Ensure standby consumers can take over seamlessly