Publisher Channel Events

Publishers expose RabbitMQ channel-level events through the common IAsyncBrokerClient contract.

This is useful when you want to observe broker/channel behavior while the publisher is running.

---

Enable Channel Events

Channel events are enabled through the publisher descriptor.

var descriptor = new PublisherBoundDescriptor
{
    EnableChannelEvents = true,

    Exchanges =
    {
        new ExchangeBoundDescriptor
        {
            Name = "orders",
            Type = ExchangeTypes.Direct,
            Durable = true
        }
    }
};

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Register Event Handlers

A publisher exposes:

IDelegateHandler<ChannelEventArgs> OnChannelEventFired { get; }

You can register one or more handlers.

publisher.OnChannelEventFired.Add(
    async (sender, args) =>
    {
        var eventText = args.ToString();

        Console.WriteLine(
            $"channel event: {DateTime.UtcNow:u}, {eventText}");

        await Task.CompletedTask;
    });

---

EventTag

ChannelEventArgs.EventTag identifies the channel event raised by the RabbitMQ client.

Common event tags include:

EventTag	Description
FlowControl	RabbitMQ changed the channel flow-control state.
CallbackException	RabbitMQ raised a callback exception on the channel.
ModelShutdown	The channel/model was shut down.

---

Multiple Handlers

Multiple handlers can be registered.

publisher.OnChannelEventFired.Add(
    async (sender, args) =>
    {
        Console.WriteLine(args.EventTag);

        await Task.CompletedTask;
    });

publisher.OnChannelEventFired.Add(
    async (sender, args) =>
    {
        // Send the event to telemetry or monitoring.

        await Task.CompletedTask;
    });

---

Handler Errors

If a channel event handler throws an exception, the exception belongs to the handler logic.

Keep handlers lightweight and resilient.

publisher.OnChannelEventFired.Add(
    async (sender, args) =>
    {
        try
        {
            Console.WriteLine(args.ToString());
        }
        catch (Exception exception)
        {
            Console.WriteLine(exception.Message);
        }

        await Task.CompletedTask;
    });

---

When To Use

Publisher channel events are useful for:

• diagnostics;
• observability;
• broker troubleshooting;
• monitoring flow-control events;
• detecting channel shutdowns.

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Difference From Delivery Confirmation

Channel events are not the same as publisher confirmations.

Feature	Purpose
Delivery confirmation	Confirms whether RabbitMQ accepted a published message.
Channel events	Exposes channel-level events raised by RabbitMQ.Client.

Use delivery confirmation for publish reliability.

Use channel events for observability and diagnostics.