I use Nservicebus 5 with RabbitMQ, and I want to send different messages to different queues under the same uow. Is it possible ?
using (_NsbunitOfWork)
{
_NsbunitOfWork.Begin();
_busSms.Send(smsmessage);
_busOffer.Send(offermessage);
_busTrnx.Send(Trnxmessage);
_NsbunitOfWork.Commit();
}
I'm not sure what you're trying to accomplish? I'm assuming you want to send messages to different queues, so that different applications can process these messages? In the documentation these are usually called endpoints.
If you read the routing documentation, you'll notice that the sender code should not be aware of where the message should be sent. This is what routing takes care of. So you could do multiple calls to context.Send() and NServiceBus would figure out where to send the message to.
Does that make sense? You could also try https://discuss.particular.net/ which is more suited for NServiceBus related discussions with multiple replies, or try support#particular.net
Related
I was just reading about Enterprise Service Bus and trying to figure out how to implement it. However, the more I read about it, my conclusion was that it is just a glorified message queue.
I read about it here: What is an ESB and what is it good for?
We use RabbitMQ in our architecture quite a lot and what I was having hard time understanding was that there any many similarities between both concepts:
Both are basically post and forget
You can post a message of any format in both queues
My question is that what is it that an ESB does and RabbitMQ is not able to do?
I have not used RabbitMQ so I wont be able to comment on it. I have used ESB and currently using it.
ESB: It provides you multiple ways of subscribing to your message.Its mostly useful in Publisher-Subscriber model in which topics and subscription is used. You can publish your message payload in topics(similar to queues). Unlike a queue,topic provides us with capability to have more than one subscription for a single topic. This subscription can be divided based on your business need and you can define some kind of filter expression on those topic (also called channel)and with the specified filter a proper subscriber will pull the message from bus. Also one single message can be subscribed by multiple subscriber at a time. If no filtering is used on topics then it means all subscriber for that topic will pull the message from the channel.
This is asynchronous mechanism as you mentioned, post and forget. There is a retry mechanism in ESB where you can try subscribing the message for some number of times I think its 10 times(max) after which its sent in dead queue.
So if your requirement is to connect multiple enterprise system with loosely couple architecture then ESB is a good option.
I hope this was helpful to know about ESB
I have a situation where the Maxtries in my MSMQ is 5. After 5 times nservicebus sends the message to the Error que that I have defined. Now I want to perfomr some further action when this happens (I have to update status of some processes to Error)
Is it possible to write a handler in my Saga class to read these error queues?
Thanks in Advance
Haris
If your are using 2.x you may want to consider writing a separate endpoint where the error queue is its input queue. The downside to this is that the messages will come off the queue. Assuming you still want to store them, you'll have to push them off to a database or some other type of storage.
You could also write a Saga that polls the error queue to check for messages and updates the appropriate status. After each time you check the queue, you would need to request another Timeout.
In 3.0, you have more control over the exceptions, and can implement your own way to handle the errors. If you implement the interface IManageMessageFailures, you can do your work there.
As an alternative to the solutions provided by Adam, you can subscribe to events raised by ServiceControl which are raisesd when a messages is sent to the errorqueue. See the official documentation about this here: http://docs.particular.net/servicecontrol/contracts
Another approach would be the notification API as described here: http://docs.particular.net/nservicebus/errors/subscribing-to-error-notifications. It allows you to subscribe to certain events (not event messages) like "MessageSentToErrorQueue" directly on the endpoint, so you wouldn't need to consume the error queue.
My team are looking for ways to separate the various components of our system to decoupled services. What we'd like to achieve is an event-driven pattern where services subscribe to receive information sent when events occur in other systems.
Since we're already using WCF for our request-reply messaging, we'd like to continue using it for this particular pattern. Ideally, the messages would be managed via MSMQ to enable us to use reliable messaging to give us fault tolerance in the event of a service failure.
We're not looking for anything complicated like transactional support across service boundaries. Really, we just need a simple subscription-based message dispatch system. Are there any simple frameworks or services which can help us work to this pattern?
Probably the easiest is NServiceBus (http://www.nservicebus.com/PubSub.aspx) but this does not use WCF.
However from a integration perspective sending and receiving messages is far simpler than the messaging semantics on web services, so you don't need WCF to abstract that away.
Edit: In order to enable this using NetMsmqBinding you will have to implement the subscription infrastructure yourself. It would also be fairly easy to do.
Your publisher would need to have a database to store the subscriptions. When your subscribers start up, the first thing they do is send a subscription message to the publisher, who logs the subscription in it's subscription db.
The subscription messages should contain:
The message types I am interested in
My queue address
Then when your publisher wants to publish a message it retrieves the subscriptions and evaluates each one to see if the message matches the subscription and to retrieve the address to send to. Then it just sends the messages.
This is a standard pattern for implementing pub sub.
Let's say I have a ClientRequestMessage message that contains a request for a specific Client. A web application will generate these requests and they need to be sent to the correct Client for handling. I can think of a few options for this.
I could have a single queue that all messages go to and specific client handlers check a property (like ClientId) to decide whether they care about it. This feels wrong on many levels to me though.
I could publish a message to all of the clients and they could decide whether or not they care about it during handling. This seems like too much traffic and wastes each client's time handling messages they shouldn't care about in the first place though.
I could have client specific queues that these messages get routed too. This one feels the best to me, but I am unsure of how to do it. I'd like to keep it simple and avoid client specific message types, but I am not sure how to tell NServiceBus "for client A send it to client A's queue and for client B send it to client B's queue".
So my question is, what is the best (most efficient? easiest to manage?) way to set this up? I am pretty sure I need to use the distributor, but not positive so thought I would ask.
BONUS QUESTION:
Let's say each client has multiple handlers. How can I make sure only one of them handles a given message? Would I need a distributor per client?
If what you really want is the solution that allows you to have just a single message where you can place a specific filter on the message based on clientId and only route the message to the client when it relates to them then I would use PServiceBus(pservicebus.codeplex.com). It will make it easier for you specific a set of subscriptions for each of your client where their messages are all filtered by clientId into a specific queue or what transport you have available. The below example shows filtering a ChatTopic by the UserName Property and the subscriber only receives the message at the specified transport when the message been published UserName property is not TJ. You are also allowed to use complex filter where you do thing such as GreaterThan("MyComplexProperty.Blah.ID", 5)
Subscriber.New("MyUserName").Durable(false)
.SubscribeTo(Topic.Select<ChatTopic>().NotEqual("UserName", "TJ"))
.AddTransport("Tcp",
Transport.New<TcpTransport>(
transport => {
transport.Format = TransportFormat.Json;
transport.IPAddress = "127.0.0.1";
transport.Port = port;
}), "ChatTopic")
.Save();
You can tell NSB where to put messages by using the MessageEndpointMappings configuration section. You can map a specific message type or a whole assembly to a queue. If you don't want to create specific message types and map them, then I would recommend the publish approach. The overhead of removing a message from the queue is pretty minimal.
If your "client" has many instances of NSB to pick up messages then you will need to use a Distributor. Check out the distributed Pub/Sub documentation.
It's a really common pattern and I'm finding it a nightmare to implement!
--
The WcfIntegration sample is almost what I'm looking for in that it receives messages via a WCF endpoint. However, it receives messages back on itself. I want a separate subscriber.
So what I'm trying to do is merge the WcfIntegration and pub/sub samples.
The real need is for a website to call a class library, which then calls the WCF endpoint of the publisher.
A subscriber then picks receives a message that the publisher publishes, and does whatever with it.
--
Rob
You shouldn't need the interface IEventMessageService; NSB handles that for you.
In my local example, I mapped the messages to myself. For you this would be:
<UnicastBusConfig><MessageEndpointMappings>
<add Messages="MyMessages" Endpoint="MyPublisherInputQueue"/>
</MessageEndpointMappings></UnicastBusConfig>
You also need to move your Publish to the actual handler. Right now, it is only happening once (at startup):
public void Handle(EventMessage message)
{
bus.Publish(message);
bus.Return((int)ErrorCodes.None);
}
Make sure your infrastructure is primed, i.e. the queue is transactional, and MSDTC is running.
I'm willing to bet that since there is no mapping, once the service is called, it doesn't know where to put the messages (it calls Bus.Send() internally). I didn't look at the subscribers since that didn't seem to be the issue.
I've finally got it to work here:-
http://code.google.com/p/nservicebus-wcf-pubsub/downloads/list
Anyone is welcome to improve the code.