What causes "Invalid queue type: {_queueType}." in microsoft/autogen?

Construct the queue grain only with MessageRegistryGrain.QueueType.DeadLetterQueue or .EventBuffer.

microsoft/autogen · error · ArgumentException

Invalid queue type: {_queueType}.

Error message

Invalid queue type: {_queueType}.

What it means

ArgumentException thrown by MessageRegistryQueue.GetQueue() when the grain's _queueType is neither QueueType.DeadLetterQueue nor QueueType.EventBuffer. The queue grain is constructed per queue type and switches on that value to pick the right state bucket; any other value (including an uncast int or an out-of-range enum) is rejected.

Source

Thrown at dotnet/src/Microsoft.AutoGen/RuntimeGateway.Grpc/Services/Orleans/MessageRegistryQueue.cs:130

    }

    private async Task AddOrUpdate(string topic, CloudEvent message)
    {
        var queue = GetQueue();
        var list = queue.GetOrAdd(topic, _ => new());
        list.Add(message);
        queue.AddOrUpdate(topic, list, (_, _) => list);
        await _stateManager.WriteStateAsync().ConfigureAwait(true);
        _timestamps.Add(DateTime.UtcNow, topic);
    }

    private ConcurrentDictionary<string, List<CloudEvent>> GetQueue()
    {
        return _queueType switch
        {
            MessageRegistryGrain.QueueType.DeadLetterQueue => _state.State.DeadLetterQueue,
            MessageRegistryGrain.QueueType.EventBuffer => _state.State.EventBuffer,
            _ => throw new ArgumentException($"Invalid queue type: {_queueType}.")
        };
    }

    public async Task RemoveMessageAfterDelayAsync(string topic, CloudEvent message, int delay)
    {
        await Task.Delay(delay);
        await RemoveMessageAsync(topic, message);
        _currentSize -= message.CalculateSize();
    }
}

View on GitHub (pinned to 027ecf0a37)

Solutions

Construct the queue grain only with MessageRegistryGrain.QueueType.DeadLetterQueue or .EventBuffer.
If you add a new queue type, extend the switch in GetQueue() to map it to a state bucket (or throw a descriptive error naming the value).
Validate the enum at construction: if (!Enum.IsDefined(typeof(QueueType), value)) throw ... with the actual value.

Example fix

// before
var queue = new MessageRegistryQueue((MessageRegistryGrain.QueueType)7, state, stateManager);

// after
var queue = new MessageRegistryQueue(MessageRegistryGrain.QueueType.DeadLetterQueue, state, stateManager);

Defensive patterns

Strategy: validation

Validate before calling

if (!Enum.IsDefined(typeof(MessageRegistryGrain.QueueType), queueType)
    || queueType == (MessageRegistryGrain.QueueType)(-1))
{
    throw new ArgumentOutOfRangeException(nameof(queueType), queueType, "QueueType must be DeadLetterQueue or EventBuffer");
}

Type guard

static bool IsKnownQueueType(MessageRegistryGrain.QueueType t) =>
    t is MessageRegistryGrain.QueueType.DeadLetterQueue
       or MessageRegistryGrain.QueueType.EventBuffer;

Try / catch

try { var queue = GetQueue(); }
catch (ArgumentException ex) when (ex.Message.Contains("Invalid queue type"))
{
    _logger.LogError("MessageRegistryQueue misconfigured with queue type {Type}.", _queueType);
    throw;
}

Prevention

Only construct the grain with the two defined enum members.
When adding queue types, update GetQueue's switch in the same commit.
Validate enum values at construction boundaries in tests.

When it happens

Trigger: Instantiating MessageRegistryQueue with an int cast to MessageRegistryGrain.QueueType that is not 0 or 1 (e.g. (QueueType)42); new queue kinds added to the enum without extending GetQueue's switch; deserialized grain state producing an unexpected enum value.

Common situations: Direct unit tests of the grain that pass arbitrary enum values; refactors that introduce a third queue type but forget this switch expression; enum reordering between serialized versions shifting numeric meanings.

Related errors

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/e8c6c418b99591d6. Report an issue: GitHub.