Is it recommended to use NServiceBus (or any service bus library) solely for the purpose of publishing messages on the client side?
I've been looking at a handful of sample open source projects and they all seem to have one thing in common. All projects are publishing messages and getting consumers to handle the specific message (or command).
Essentially, I'm looking to decouple my actions by sending out messages and have a handler take care of it. This would all be done locally on the client.
I think NServiceBus and equivalent tools are too heavy on the client side and often requires extensive configuration.
Related
I would like to find a solution to create a pub/sub medium for 2 microservices to talk to each other,
I am aware i can use some third parties E.g Redis, RabbitMQ
Implementing event-based communication between microservices (integration events)
The challenge lies on the client is unable to allow install any third parties tool due to security reason.
The messageQueue server in Windows won't be allowed to use too.
I can only use the applications that is only existed in the server.
Therefore i am asking if there is anyway that i can create one simple app using windows service.
It is a one-to-many relationship. I have one service that will be dealing with data, once if there is any update, it will publish to those services that is subsribed to it.
It seems my problem could be similar with
.NET Scalable Pub/Sub service implementation
WCF Pub/Sub with subscriber caching(link is dead on the WCF pub-sub)
but i dont see any critical solutions.
I was thinking to use data notifications that MSSQL offers as last alternatives, but seems like it could cause a bottle neck when the applications get scale up.
The internet is so much flooded with articles using third parties tool.
Thanks
Check out Rebus library, that allows using different transport methods to send end receive messages in just a line of code (so in the future you can change it without effort).
You could use SQL Server or try to develop your own transport method
Domain Driven Design Passing Events to separate Bounded Contexts
A user action in MVC should generate an Event which is passed to a remote (same LAN) Event handler.
What I've tested:
MVC: fire and forget service call (asynchronous) ->
(IIS hosted) WCF which gathers data and populates a message ->
Sent via EasyNetQ/RabbitMQ ServiceBus ->
The event is consumed by a Subscriber (using a DI container initialized from a WCF service endpoint) which handles the event & it's data.
I did some testing to see how it works if the service is called fairly quickly by looping in the MVC side
for (int i = 0; i < 200; i++)
{
...
client.MyServiceMethod(someId, startDate);
...
}
The MessageQueue part is quick, based on the timestamps it is sent to the queue and received by the subscriber within the same second. Looping through the WCF service calls is very slow. It takes many seconds to loop through them. I tried switching from wsHttpBinding to netTcpBinding, and playing with the serviceThrottling in WCF.
WCF isn't compulsory, but it seems like a separate event handling project (on the publisher end) would be beneficial and could be physically located elsewhere from the MVC app (load reduction etc.). Is WCF plausible for a situation like this, or should I try using Windows services or some other self-hosted e.g. console app etc, or potentially using a thread in MVC to generate the event data, or are there better scenarios? What are the best practices in this type of Event handling system? Basically it seems like it would be beneficial to have something generating the Event data since it has to be handled somewhere while not slowing down the UI that the end user is using.
Instead of trying to roll your own infrastructure like this, I think you would do well to employ a tool like NServiceBus (not free) or MassTransit (free). (I would consider this best practice.)
I can't speak for MassTransit, but my experience with NServiceBus has been very good. You only need to specify which messages go to which queue. You can use several different queueing technologies, but I would recommend starting with the default MSMQ implementation. No WCF configuration nightmares necessary. ;)
All of your message handlers will also be automatically wrapped in a distributed transaction so that if a DB interaction fails, the entire message will be rolled back and you'll be able to try the message again in the future.
If I undertood well, your event creation process is "heavy" and you want to avoid to be created in the MVC process. I guess you are sending some information to the WCF service in order to let him prepare the event.
You could think of a 2 consumers scenario avoiding the WCF step:
Your MVC application creates and publish a "light" event with all data required in order to create the "heavy" event (basically with the input data you would pass to WCF)
An EventCreator subscriber consumes this message and prepares the heavy event
Your already existing consumer will then consume the heavy event
EasyNetQ already provides simple functions to publish and consume the message.
Most of the tutorials you find online suggest using TopShelf for hosting your consumers in a console application (debug) or windows service (production). EasyNetQ has an example here: EasyNetQ with TopShelf
If you want to "hide" the EasyNetQ dependecy on your MVC project, you could wrap the EasyNetQ IBus to a custom Bus and use an IoC container in order to inject a specific implementation of your bus. The example provided above uses Castle.Windsor as IoC container
I have three wcf services A,B and C respectively ,since i wanted it to be SOA(Service Oriented Architecture) the way my setup works is when i send a request from client to server.
All the services are self hosted windows services.
Client sends request to service A (client has no clue about the other services B and C);
Service A eventually sends that request to Service B and Service C.
Service B and C sends response back to Service A which would be sent back to the client by service A.
Issue i m facing :If i make any changes in the code of Service B and rebuild and restart the service ,i am having issue getting the response back but when i restart all the remaining services then it works fine.
In other words my client doesn't get the response back unless i restart all the services(A,B and C) even though i just changed the code in only one service and rebuilt it.I know the thing works if i restart all the three services but i want to know is this the problem in my way of designing or it is something i have to deal with self hosted windows services.And all the services(A,B,C) are independent as none depends on each other.
Did some one ever see such things happened in SOA.I would be glad if some one can guide me to appropriate solution ?
Replace WCF between services with any sort of queue (one service publishes something, other can read when they are ready). Can be anything. Can be a simple table where you read from if there is something new. Can be RabbitMQ, NServiceBus, etc, whatever works for you.
Define messages you put into the queue: commands and events. Both are simple classes with properties, no logic there. Commands represent what the system is asked to do (RegisterUser, PlaceOrder, ect), events represent what the system has done (UserRegistered, OrderApproved, PaymentReceived, etc). Be explicit about actions, Don't do something like "I have changed all the properties of a user on the client, now I call SaveUser(user)". Your service supposes to know how to change objects, clients should only command what to do.
Never break your contract. It is easy, easier than it sounds: you can add things to your message contracts, but cannot remove. In other word you just keep your contract backwards compatible.
Now you have a much better design: services communicate only through messages in queues, messages are backward compatible. This means that you can stop any of the services at any time without impacting others: they will continue sending messages into queues, and when the stopped service comes back again it will catch up processing all the stuff from the queue.
Then, if you want, you can use the same approach with client interactions: if instead of calling WCF clients would only put their commands in some sort of a queue then service upgrades or other downtime would not impact user experience.
Example: if I use WCF to place an order or to put an item into a shopping card then if there is a problem or a service is down for maintenance I will not be able to do it. I would click a button and have a nasty error. More importantly my order will not make into the system.
In contrast, if there is a queue in the middle, I only put my command into the queue. Now even if my service is down at the moment, or experience a high load (and therefore slow) then my user experience is still the same and does not degrade. It is just my command will be processed a bit later, but as a client I don't really care. And my order will not be lost in this scenario. The system became fault-tolerate and self-balanced.
There are all sorts of fantastic tricks you can do if you simply put a queue in the middle instead of experiencing problems with spatial and temporal coupling that comes with WCF :)
And what I described is just the beginning... :)
You may want to consider using a service bus such as NServiceBus to help you accomplish your functionality.
The first issue it will help you address is the decoupling of your services via publish/subscribe messaging pattern. Rather than invoking web services in one or the other service, publish events that notify the respective services when something has occurred. In your case this would look something like this:
Client invokes web service in Service A.
Service A publishes a message "Client Command Received" which Service B and C subscribe to.
Service B and C handle this event and then publish events of their own.
Service A subscribes to both events and replies to the client.
The first and immediate benefit of using something NServiceBus is reliability. On top of that you are able to easily version your message without affecting your client or your respective services. NServiceBus has full WCF integration so your client can continue to send messages to your service as before.
One of the things that makes your scenario interesting is that you can't guarantee when Service B and C send their responses back to you. Do you keep the connection to the client open until Service has received their responses? Do you need both responses before you can send a the client its response? What happens if either or one of the service crash? What if there is a time limit to how long you can wait before a response is received by Service A? All of these questions and more can be answered with a feature in NServiceBus called Sagas. Check it out.
If using NServiceBus is not possible then things become more difficult. WCF doesn't support publish/subscribe out of the box so you will have to bake your own. At a minimum I would recommend using this to decouple your services. How you manage state and temporal coupling in your services is another matter. Save yourself the trouble.
There are other frameworks out there but if you want a developer centric, cost effective way to create a .NET based solution then recommend using NServiceBus.
I have been playing around with pubsub and so far it looks good for what I need (a basic game experiment).
From a Javascript perspective and mobile (via Appcelerator's Titanium) I can really see the value of using pubsub.
However, I need to write a server app in c#/.NET (although open to other ideas) to listen to the subscriber queue I have, and process the messages.. which involves some decision making etc, and then possibly writing another message to the publish queue for example.
So far I have played with RX (Reactive Extensions) for C# which listen on my subscribe channel. So far so good, I see the messages come in, although for now I just wrote a C# console app to test.
My question is would the best way to wait and listen for pubsub subscriber messages be to write a windows service app? or is there another technique more appropriate? obviously at some possible point I might have to scale the server to 2-3 servers, however given the nature of pubsub queue/messaging, I don't see a problem if I had some load-balancing etc.
Any ideas welcome!
Use Service Bus. When cloud is good for you, than Azure Service Bus. When not then nServiceBus. Take a look also for RabbitMQ, it's AMQP framework and is able to do more then pubsub. Also rabbit has multiple clients on multiple platorms. For example one of approaches purely for JavaScript is RabitMQ + Node.js + WebSockets.
All clients and devtools, and articles about RabbitMQ for different platforms and languages are here.
There is also special RabbitMQ binding for .NET, find it here.
NServiceBus PubSub explanation is here. It's .NET service bus, but is not such free as RabbitMQ. Anyway RabbitMQ is platform agnostic.
Any of service buses implementations already has PubSub, that is the reason they exist. Therefore there is no reason to implement, what is already implemented
Suppose, I want to scale out (add more boxes) some WCF service. This looks pretty easy, set up load balancer that calls WCF services on multiple boxes using for example round robin algorithm.
However how to deal with situation when a WCF service have callback contract. When a client connects to some particular box, it receives events only raised by this computer WCF service instance. And I want client to receive events that were raised by any WCF service instance in group (cluster).
What is the best way to make WCF service know about events raised by other WCF service instances?
Some ideas: Multicast, broadcast, WCF NetPeerTcpBinding, Single server that subscribes to all WCF services in cluster (acting as event aggregate).
UPDATE: I have managed to create test system, using NetPeerTCPBinding as a mechanism to share events across servers. I haven't made a benchmark yet, but I feel that WCF P2P is to heavy for this tusk, I'm gonna implement UDP broadcast based event sharing system.
I would implement this by setting up a MSMQ queue that each server can subscribe to, and when an event occurs that the other servers need to know about, the service can publish it.
I use a library called NServiceBus to make this entire process simple. NServiceBus is a full-featured library that uses MSMQ (among other transports) to create pub/sub messaging buses, which would exactly solve your problem. It is easy to use and has a fluent interface for configuration, subscription, and publishing.
I will come back and edit this post later with an example, but the NServiceBus website has plenty of documentation to get you started until then.
Have you considered messaging? Sounds ideal.