abpframework
"Collection was modified; enumeration operation may not execute." error on EventBusBase
Is there an existing issue for this?
- [X] I have searched the existing issues
Description
The same error occurs in https://github.com/aspnetboilerplate/aspnetboilerplate/pull/6805
to https://github.com/abpframework/abp/blob/ac792033d78a7b7644835c866acc2d6a55e5990c/framework/src/Volo.Abp.EventBus/Volo/Abp/EventBus/EventBusBase.cs#L139
Reproduction Steps
No response
Expected behavior
No response
Actual behavior
No response
Regression?
No response
Known Workarounds
No response
Version
6.0.3
User Interface
MVC
Database Provider
EF Core (Default)
Tiered or separate authentication server
None (Default)
Operation System
Windows (Default)
Other information
no
I am also facing this as well @maliming
this is because of this line
https://github.com/abpframework/abp/blob/5d0a6e01ca22b1797e61cdf087a161ec4d4e8d25/framework/src/Volo.Abp.EventBus/Volo/Abp/EventBus/EventBusBase.cs#L140
this is a race condition that can happen when you subscribe to an event WHILE publishing another event this is a common pattern in async APIs when you publish an event and wait for another event as a response.
e.g.
class SomeAppService(IDistributedEventBus distributedEventBus)
{
[UnitOfWork]
public async Task DoSomething()
{
// create a unique identifier for the request.
var requestId = Guid.NewGuid();
// create a completer to catch the reply.
var completer = new TaskCompletionSource<ReplyEto>();
// start listening for the reply.
var disp = distributedEventBus.Subscribe<ReplyEto>(
(eventData) =>
{
// listen for a reply with the same request id.
if (eventData.RequestId == requestId)
{
// set the result when the reply is received.
completer.TrySetResult(eventData);
}
return Task.CompletedTask;
}
);
await distributedEventBus.PublishAsync(
new RequestEto
{
RequestId = requestId,
// other request data ...
},
// event needs to be published NOW.
onUnitOfWorkComplete: false
);
// Wait for the reply.
var replyEto = await completer.Task;
// stop listening after getting the reply.
disp.Dispose();
}
}
here is a workaround implementation until this is fixed:
[Dependency(ReplaceServices = true)]
[ExposeServices(
typeof(IDistributedEventBus),
typeof(RabbitMqDistributedEventBus),
typeof(FixedRabbitMqDistributedEventBus)
)]
public class FixedRabbitMqDistributedEventBus(
IOptions<AbpRabbitMqEventBusOptions> options,
IConnectionPool connectionPool,
IRabbitMqSerializer serializer,
IServiceScopeFactory serviceScopeFactory,
IOptions<AbpDistributedEventBusOptions> distributedEventBusOptions,
IRabbitMqMessageConsumerFactory messageConsumerFactory,
ICurrentTenant currentTenant,
IUnitOfWorkManager unitOfWorkManager,
IGuidGenerator guidGenerator,
IClock clock,
IEventHandlerInvoker eventHandlerInvoker,
ILocalEventBus localEventBus,
ICorrelationIdProvider correlationIdProvider
)
: RabbitMqDistributedEventBus(
options,
connectionPool,
serializer,
serviceScopeFactory,
distributedEventBusOptions,
messageConsumerFactory,
currentTenant,
unitOfWorkManager,
guidGenerator,
clock,
eventHandlerInvoker,
localEventBus,
correlationIdProvider
)
{
protected override async Task TriggerHandlersAsync(
Type eventType,
object eventData,
List<Exception> exceptions,
InboxConfig? inboxConfig = null
)
{
await new SynchronizationContextRemover();
foreach (var handlerFactories in GetHandlerFactories(eventType))
{
// important part:
foreach (var handlerFactory in handlerFactories.EventHandlerFactories.ToList())
{
await TriggerHandlerAsync(
handlerFactory,
handlerFactories.EventType,
eventData,
exceptions,
inboxConfig
);
}
}
//Implements generic argument inheritance. See IEventDataWithInheritableGenericArgument
if (
eventType.GetTypeInfo().IsGenericType
&& eventType.GetGenericArguments().Length == 1
&& typeof(IEventDataWithInheritableGenericArgument).IsAssignableFrom(eventType)
)
{
var genericArg = eventType.GetGenericArguments()[0];
var baseArg = genericArg.GetTypeInfo().BaseType;
if (baseArg != null)
{
var baseEventType = eventType.GetGenericTypeDefinition().MakeGenericType(baseArg);
var constructorArgs = (
(IEventDataWithInheritableGenericArgument)eventData
).GetConstructorArgs();
var baseEventData = Activator.CreateInstance(baseEventType, constructorArgs)!;
await PublishToEventBusAsync(baseEventType, baseEventData);
}
}
}
}
