pubsub.md

Pub/Sub

StackExchange.Redis.Extensions wraps Redis Pub/Sub with typed serialization and error handling.

Subscribe to Messages

await redis.SubscribeAsync<OrderEvent>("orders:new", async order =>
{
    Console.WriteLine($"New order #{order.Id} for {order.Total:C}");
    await ProcessOrderAsync(order);
});

The handler receives a deserialized object. If the handler throws an exception, it is logged (not silently swallowed) and the subscription continues processing subsequent messages.

Publish Messages

var subscriberCount = await redis.PublishAsync("orders:new", new OrderEvent
{
    Id = 42,
    Total = 99.99m,
});
Console.WriteLine($"Message sent to {subscriberCount} subscribers");

Unsubscribe

// Unsubscribe a specific handler
await redis.UnsubscribeAsync<OrderEvent>("orders:new", myHandler);

// Unsubscribe all handlers on all channels
await redis.UnsubscribeAllAsync();

How KeyPrefix Affects Channels

When KeyPrefix is configured, it is automatically applied to both keys and Pub/Sub channels via StackExchange.Redis's ChannelPrefix mechanism:

// Config: KeyPrefix = "myapp:"
await redis.PublishAsync("orders", message);
// Actual Redis channel: "myapp:orders"

You should NOT manually add the prefix to channel names.

Error Handling

Exceptions in subscription handlers are logged via ILogger and do not crash the process or drop the subscription:

sequenceDiagram
    participant Redis
    participant Handler as SubscribeAsync Handler
    participant Logger as ILogger

    Redis->>Handler: Message 1
    Handler->>Handler: throw Exception
    Handler->>Logger: LogError(exception, "Error processing...")
    Redis->>Handler: Message 2
    Handler->>Handler: Process successfully

Loading

Note: For the logger to work in production, ensure RedisConfiguration.LoggerFactory is set (it is automatically wired when using AddStackExchangeRedisExtensions with ASP.NET Core DI).