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Channel Events

Channel events provide visibility into RabbitMQ channel activity.

They are useful when diagnosing connection, publishing and consuming issues.

Enable Channel Events

Channel events must be enabled explicitly.

Example:

EnableChannelEvents = true;

Publisher Diagnostics

Publishers expose:

OnChannelEventFired

Example:

publisher.OnChannelEventFired.Add(
    async (sender, args) =>
    {
        Console.WriteLine(
            $"{DateTime.UtcNow:u} {args}");

        await Task.CompletedTask;
    });

Subscriber Diagnostics

Subscribers expose:

OnChannelEventFired

Example:

subscriber.OnChannelEventFired.Add(
    async (sender, args) =>
    {
        Console.WriteLine(
            $"{DateTime.UtcNow:u} {args}");

        await Task.CompletedTask;
    });

ChannelEventArgs

Handlers receive:

ChannelEventArgs

This object contains information about the RabbitMQ event that occurred.

One of the most useful properties is:

EventTag

which identifies the event category generated by the broker client.

Typical Diagnostic Scenarios

Channel events are useful for:

  • connection failures;
  • channel shutdowns;
  • publisher confirmations;
  • consumer lifecycle events;
  • topology creation failures;
  • unexpected broker behavior.

Event Handler Failures

Avoid throwing exceptions from event handlers.

Bad example:

publisher.OnChannelEventFired.Add(
    (sender, args) =>
    {
        throw new InvalidOperationException();
    });

Prefer logging and diagnostics.

Use channel events as a diagnostic and observability mechanism.

graph LR

    RabbitMQ

    Channel

    ChannelEventArgs

    Handler

    RabbitMQ --> Channel

    Channel --> ChannelEventArgs

    ChannelEventArgs --> Handler

Diagnostic Checklist

Verify:

  • channel events enabled;
  • handlers registered;
  • event handler exceptions;
  • channel lifecycle;
  • connection lifecycle.