As a follow-up to Axon Event Published Multiple Times Over Eventbus, when using an EmbeddedEventStore and publishing a command that will attempt to create an instance of an aggregate that already exists, Axon is not throwing an exception indicating the instance exists (or constraint violation), as is on the contrary, when using Axon's JPA event store. Is this the expected behavior? If so, why?
Recently our community filed a similar issue to our repo that I am going refer here.
Essentially the JPA or JDBC implementation are responsible for catching this kind of exceptions and translating them to something the Framework understands.
If that occurs, you should see an AggregateStreamCreationException dispatched, indicating that it failed and why it failed. If this is not happening I recommend you looking into your PersistenceExceptionResolver.
If you still see this happening after checking what I shared, this is likely a bug and in this case, feel free to open it on our repo as such.
Related
We are using axon framework version 3.4.2 and found a bug inside our code. The bug relates to a missing event which was not published. The solution is to fix the code but this would not fix the event store and views.
My question is how would one fix this? We thought of appending the events to the event store (we use a JDBC event store), but without the correct data, the new events would not be processed. The best would be to do it in the application by publishing the event in axon and let axon handle all the details, but this is a once-off, correcting action.
Is there any way of "injecting" a once-off event into axon?
The comment which Matt shared is conceptually what you should do.
Thus, to resolve the issue you unintendedly introduced, you should produce a compensation action, aka a command. This command will be handled in your command model, will validate the model's state and publish the desired event.
Added, I am assuming this event of your should originate from an Aggregate, correct?
In Axon terms, that means you want to publish a domain event rather than a regular event.
Although you can publish events on the EventBus or store in the EventStore directly, it is rather complicated to make those domain events through that process.
Thus, as I started off with and what Matt Freeman commented on your question, a compensating action would be the way to go, with or without Axon.
Last note, know that Axon 4.2 is already out for some time now. Although Axon 3 will still under go bug fixes, none of these have occurred in the last year. Simply put, there is no active development on Axon 3. Migrating to a more recent version would thus be beneficial for your project.
I am using Axon 3.1.1 and wanted to know,
How can I get a list of eventprocessor in my configuration file,
I went through the springAmQPmessageSource file but still not sure how to exactly do it.
So that I can pass my event to appropriate eventhandler on Query side.
List<Consumer<List<? extends EventMessage<?>>>> eventProcessors = new CopyOnWriteArrayList<>();
Updated
I was retrieving message from kafka topic and wanted to wire them to specific eventhandler but since I am not able to get evenprocessors, I am not able to do that.
Can you please tell me how to do it, if I am using Axon 3.0.5
If you're using the SpringAmqpMessageSource, you will not need to retrieve the list of eventProcessors you've shared, as Axon will automatically subscribe all the event handling components to it for you.
Subsequently, the events the Message Source receives will automatically be pushed to all the listeners in your query side.
As this is all covered as Axon infrastructure under the hood, there is no one-off way to pull them out of it for your own use (other than potentially wiring them yourself).
Hence, you shouldn't have to do this yourself.
But, maybe I'm missing an obvious point here.
Could you elaborate a little more why you need the list of handlers in the first place?
Is there a way to execute the DbContext.SaveChanges() without invoke its internal auto transaction handling?
I'm working to handle the transaction (DbTransaction) myself, but when I invoking it's Commit, I getting error "SqlConnection does not support parallel transactions"
I believe this is due to SaveChanges is doing its own internal transaction work, which I want to suppress it.
.NET 4.5, EntityFramework.dll ver 5.
googling shows few approaches, but the code are not compatible.
Some showing SaveChanges can accept a Boolean, which it is not in this ver. and then invoking AcceptAllChanges() which method also not exist.
While some is using System.Transaction.TransactionScope, but its different with this System.Data.Common.DbTransaction.
after many PITA efforts digging over the EF thing. the only way I found out to have proper transaction control over it is best to use ObjectContext, instead of DbContext.
http://sqlanywhere-forum.sap.com/questions/11320/entity-framework-savechanges-closes-connection
this hinted the ObjectContext
DbContext codebase is genereated if your EDMX code generation strategy is set to None.
link: Is ObjectContext deprecated in .NET 4.5?
by changing it to Default, you will get ObjectContext code base gen.
the diff of them so far of what I found out, using DbContext, whenever you invoke its SaveChanges(), it will AUTO close the underneath connection, and your next db task will have a new connection, which basically break the transaction control of what I seek.
you need to run the whole db tasks without the conx being close or recreate within the transaction.
by using ObjectContext, SaveChanges() will not auto close the connection if I setup the transaction and connection codes properly before it.
I recently upgraded an application from .net 3.5 to 4.0. Since I did that, with debug settings to break on all exceptions enabled, I've been getting a few of these exceptions each time I start a section of the application that connects to a database using the EF. The exact number is variable; sometimes I only get one, others several in rapid succession.
ReleaseHandleFailed was detected Message: A SafeHandle or
CriticalHandle of type
'Microsoft.Win32.SafeHandles.SafeCapiHashHandle' failed to properly
release the handle with value 0x06AD3D08. This usually indicates that
the handle was released incorrectly via another means (such as
extracting the handle using DangerousGetHandle and closing it directly
or building another SafeHandle around it.)
I never got exceptions like this when targeting 3.5. These exceptions don't have any meaningful call stack attached, all I get is [External Code], denying any easy way to localize where they're coming from. The reason I suspect EntityFramework is somehow involved is that one section of the app uses nHiberate instead doesn't generate any of these messages.
To run down other dependencies that might be involved: In all cases, the ORM is talking to an Sql Compact database MS Sync Framework 2.1 is being used to update the local DB from SqlServer. The Entity framework models have been regenerated with the 4.0 framework, and I upgraded the cache DB to v4.0 as well.
Since there's no call stack I'm not sure if these messages fall into the category of "harmless" errors automatically cleaned up internal to the framework; or if there's an exception eater catching them elsewhere in the application.
This is not an exception, it is a Managed Debugging Assistant warning. You might have gone over-board a bit when you changed the settings to "break on all exceptions enabled". Debug + Exceptions, Managed Debugging Assistants node, untick the "ReleaseHandleFailed" warning. It is off by default.
The MDA catches an old bug that's gone undetected for a while in the AesCryptoServiceProvider class. Backgrounder is here.
Judging from your comment, you are about to make a drastic mistake. You do not solve this by avoiding encryption or compromising your dbase connection security. You accidentally turned on an MDA that's normally off. MDAs in general tend to produce false warnings and many of them are turned off by default. The warning is in fact bogus, releasing the handle failed because it was already released. This happens in the finalizer thread, that's why you don't get a stack trace. And thus can't easily find out what code uses the class in the first place.
The proper way to fix it is to use the Debug + Exceptions dialog properly. Fix the problem you created by clicking the Reset All button. Then click only the Thrown checkbox for Common Language Runtime exceptions. That's what you are trying to debug.
Getting into CQRS and I understand that you have commands (app layer) and events (from the domain).
In the simple case where events are to update the read model, do read model updates fail? If there is no "bug" then I cannot see them failing and as I am using EventStore, I know there is a commit flag which will retry failures.
So my question is do I have to do anything in addition to EventStore to handle failures?
Coming from a world where you do everything in one transaction and now things are done separately is worrying me.
Of course there may be cases where a published event will fail in the read models.
You have to make sure you can detect that and solve it.
The nice thing is that you can replay all the events again and again so you have the chance not only to fix the error. You can also test the fix by replaying every single event if you want.
I use NServiceBus as my publishing mechanism which allows me to use an error queue. Using my other logging tools together with the error queue I can easily determine what happened since I have the error log and the actual message that caused the error in the first place.