What is the required IOC instance lifecycle I need to use in conjuction with a NServiceBus message handler if I want an instance per message handled.
PerRequest won't work, since given the numerous constructor dependenices and dependency graph I have, it gives me many instances when I require only one per Handle(MessageX msg) call. I can't or don't want to inject it directly into the message handler since it is required further down the object graph. E.g. inject IPersonService, depends on IPersonRepository, they can be per request (Default), but IPersonDBContext need to be per message call.
PerThread won't work since NServiceBus uses the same worker threads over and over.
Singleton, HttpContext, etc.. are obviously not applicable.
Has anyone came across this with either StructureMap or Castle?
I might be missing something here, but PerRequest will give you a new instance for each MessageHandler ( the messagehandlers are them selves registered as PerRequest). I have just committed a fix for a bug that caused messagehandlers to fire multiple times for each message. I wonder if that bug has been misleading you (try to get the lastest 2.0 build from CI and see if that does it for you)
http://teamcity.codebetter.com/viewLog.html?buildId=7087&tab=artifacts&buildTypeId=bt96
Hope this helps!
Related
I have been successfully evaluating Spring Cloud DataFlow with a typically simple flow: source | processor | sink.
For deployment there will be multiple sources feeding into this pipeline which I can do using data flow labels. All well and good.
Each source is a different rabbitmq instance and because the processor needs to know where the message came from (because it has to call back to the source system to get further information), the strategy I'd thought of was to enrich each message with header details about the source system which is then transparently passed along to the processor.
Now, I'm well-versed in Spring, Spring Boot and Spring Integration but I cannot find out how to enrich each message in a dataflow source component.
The source component is bound to an org.springframework.cloud.stream.app.rabbit.source.RabbitSourceConfiguration. The source uses the default Source.OUTPUT channel. How do I get hold of each message in the source to enrich it?
My processor component uses some Spring Integration DSL to do some of what it needs to do but then this processor component has both an INPUT and OUTPUT channel by definition. Not so with the RabbitSourceConfiguration source.
So, can this be done?
I think you need a custom MessageListener on the MessageListenerContainer in RabbitSourceConfiguration.
In the RabbitSourceConfiguration you can set a custom ChannelAwareMessageListener (You can possibly extend from MessagingMessageListenerAdapter as well) on the MessageListenerContainer that does what you incline to do.
In the end what worked was subclassing org.springframework.cloud.stream.app.rabbit.source.RabbitSourceConfiguration to:
override public SimpleMessageListenerContainer container() so that I could insert a custom health check before calling super.container(). My business logic enriches each message (see next bullet) with details of where the message came from (note, this is the publisher of the messages and not the rabbit queue). There's a health check needed to validate the additional enriching information (which is provided via configuration) to ensure that messages aren't consumed from the queue and enriched with the wrong information. If the validation fails, the source component fails to start and hence no messages are consumed.
override the creation of the AmqpInboundChannelAdapter bean so that a custom subclass of DefaultAmqpHeaderMapper can be set on the adapter. This custom mapper adds the enriched headers in public Map toHeadersFromRequest(final MessageProperties source).
For me, the inability of stream/dataflow to intercept and modify messages in Source components is problematic. I really shouldn't have to fiddle around with the underlying message broker API in the ways I did. I should be able to do it with e.g. Spring Integration. Indeed I can register a global message interceptor but I cannot change the headers of the message.
This ability would go on my WIBNI (wouldn't it be nice if) list. Perhaps I'll raise a request for this.
I building multitenancy into the unit of work for a set of services. I want to keep the tenancy question out of the way of day-to-day business domain work, and I do not want to touch every existing consumer in the system (I am retrofitting the multitenancy onto a system without any prior concept of a tenant).
Most messages in the system will be contexted by a tenant. However, there will be some infrastructure messages which will not be, particularly for the purpose of automating tenant creation. I need a way of determining whether to use a tenant-contexted unit of work, or a infrastructure unit of work uncontexted by a tenant because the way I interact with the database is different depending on whether I have tenant context. The unit of work is built in the process of spinning up the dependencies of the consumer.
As such I need a way of peeking at the message or its metadata before consuming it, and specifically, I need to be able to peek at it during the dependency building. I was intended to have a tag interface to mark tenant management messages out from normal business domain messages, but any form of identifying the difference could work. If I am in a unit of work resulting from an HTTP request, I can look at WebApi's HttpContext.Current and see the headers of the current request, etc. How do I do something analogous to this if I am in a unit of work resulting from messaging?
I see there is a way to intercept messages with BeforeConsumingMessage() but I need a way of correlating it to the current unit of work I am spinning up and I'm not seeing how that would work for me. Pseudocode for what I am trying to do:
if MessageContext.Message.GetType() = typeof<ITenantInfrastructureMessage>:
database = new Database(...)
else:
tenantId = MessageContext.Headers.TenantId;
database = new TenantDatabase(..., tenantId)
I am working in C#/.NET using MassTransit with RabbitMQ and Autofac with MassTransit's built-in support for both.
Your best option is to override at the IConsumerFactory<T> extension point, and extract the tenant from the message (either via a message header, or some message property) and register that in the container child lifetime scope so that subsequent resolutions from the actual consumer class (and it's dependencies) are properly matched to the tenant in the message.
In our systems, we have a TenantContext that is registered in a newly created LifetimeScope (we're using Autofac), after which we resolve the consume from the child scope, and the dependencies that use the tenant context get the proper value since it's registered as part of building the child container for the message scope.
It works extremely well, we even built up extension methods to make it easy for developers registering consumers to specify "tenant context providers" that go from a message type to the proper tenant id, which is used to build the TenantContext.
You can do similar things with activity factories in Courier routing slips (which are a specialization of a consumer).
I'm planning to build a quite large application (large in term of concurrent user / number of request, not in term of features).
Basically, I'll have a service somewhere, that is waiting for commands execute them, and acknowledge the completion later. This service will use a service bus to communicate, making the execution eventual, before a acknowledge message is issued.
The consumers of this service can be any kind of application (WPF, SL, ...) but my main (and first) client will be an asp.net MVC application + WebApi (.Net 4.5) or MVC only (.Net 4.0) with ajax controller actions.
The web application will be relying on Ajax call to keep a user friendly responsive application.
I'm quite new to such full blown async architecture, and I'm having some questions to avoid future headache :
my web api calls can take some amount of times. How should I design properly the api to support long running operations (some kind of async?). I've read about the new async keyword, but for the sake of knowledge, I'd like to understand what's behind.
My calls to the service will consist is publishing a message and wait for the ack message. If I wrap this in a single method, how should I write this method? Should I "block" until the ack is received (I suppose I shouldn't)? Should I return a Task object and let the consumer decide?
I'm also wondering if SignalR can help me. With signalR, I think I can use a real "fire and forget" command issuing, and route up to the client to ack message.
Am I completely out of subject, and should I take another approach?
In term of implementation details / framework, I think I'll use :
Rabbitmq as messaging system
Masstransit to abstract the messaging system
asp.MVC 4 to build the UI
Webapi to isolate command issuing out of UI controllers, and to allow other kind of client to issue commands
my web api calls can take some amount of times.
How should I design properly the api to support long
running operations (some kind of async?).
I'm not 100% sure where you're going. You ask questions about Async but also mention message queuing, by throwing in RabbitMQ and MassTransit. Message queuing is asynchronous by default.
You also mention executing commands. If you're referring to CQRS, you seperate commands and queries. But what I'm not 100% about is what you're referring to when mentioning "long running processes".
When you query data, the data should already be present. Preferably in a way that is needed for the question at hand.
When you query data, no long-running-process should be started
When you execute commands, a long-running-processes can be started. But that's why you should use message queuing. Specify a task to start the long running process, create a message for it, throw it onto the queue, forget about it altogether. Some other process in the background will pick it up.
When the command is executed, the long-running-process can be started.
When the command is executed, a database can be updated with data
This data can be used by the API if someone requests data
When using this model, it doesn't matter that the long-running-process might take up to 10 minutes to complete. I won't go into detail on actually having a single thread take up to 10 minutes to complete, including locks on database, but I hope you get the point. Your API will be free almost instantly after throwing a message onto the queue. No need for Async there.
My calls to the service will consist is publishing a message and wait for the ack message.
I don't get this. The .NET Framework and your queuing platform take care of this for you. Why would you wait on an ack?
In MassTransit
Bus.Instance.Publish(new YourMessage{Text = "Hi"});
In NServiceBus
Bus.Publish(new YourMessage{Text = "Hi"});
I'm also wondering if SignalR can help me.
I should think so! Because of the asynchronous nature of messaging, the user has to 'wait' for updates. If you can provide this data by 'pushing' updates via SignalR to the user, all the better.
Am I completely out of subject, and should I take another approach?
Perhaps, I'm still not sure where you're going.
Perhaps read up on the following resources.
Resources:
http://www.udidahan.com/2013/04/28/queries-patterns-and-search-food-for-thought/
http://www.udidahan.com/2011/10/02/why-you-should-be-using-cqrs-almost-everywhere%E2%80%A6/
http://www.udidahan.com/2011/04/22/when-to-avoid-cqrs/
http://www.udidahan.com/2012/12/10/service-oriented-api-implementations/
http://bloggingabout.net/blogs/dennis/archive/2012/04/25/what-is-messaging.aspx
http://bloggingabout.net/blogs/dennis/archive/2013/07/30/partitioning-data-through-events.aspx
http://bloggingabout.net/blogs/dennis/archive/2013/01/04/databases-and-coupling.aspx
my web api calls can take some amount of times. How should I design
properly the api to support long running operations (some kind of
async?). I've read about the new async keyword, but for the sake of
knowledge, I'd like to understand what's behind.
Regarding Async, I saw this link being recommended on another question on stackoverflow:
http://msdn.microsoft.com/en-us/library/ee728598(v=vs.100).aspx
It says that when a request is made to an ASP .NET application, a thread is assigned to process the request from a limited thread pool.
An asynchronous controller action releases the thread back to the thread pool so that it is ready to accept addtitional requests. Within the action the operation which needs to be executed asynchronously is assigned to a callback controller action.
The asynchronous controller action is named using Async as the suffix and the callback action has a Completed suffix.
public void NewsAsync(string city) {}
public ActionResult NewsCompleted(string[] headlines) {}
Regarding when to use Async:
In general, use asynchronous pipelines when the following conditions
are true:
The operations are network-bound or I/O-bound instead of CPU-bound.
Testing shows that the blocking operations are a bottleneck in site performance and that IIS can service more requests by using
asynchronous action methods for these blocking calls.
Parallelism is more important than simplicity of code.
You want to provide a mechanism that lets users cancel a long-running request.
I think developing your service using ASP .NET MVC with Web API and using Async controllers where needed would be a good approach to developing a highly available web service.
Using a message based service framework like ServiceStack looks good too:
http://www.servicestack.net/
Additional resources:
http://msdn.microsoft.com/en-us/magazine/cc163725.aspx
http://www.codethinked.com/net-40-and-systemthreadingtasks
http://dotnet.dzone.com/news/net-zone-evolution
http://www.aaronstannard.com/post/2011/01/06/asynchonrous-controllers-ASPNET-mvc.aspx
http://channel9.msdn.com/Events/TechDays/Techdays-2012-the-Netherlands/2287
http://www.dotnetcurry.com/ShowArticle.aspx?ID=948 // also shows setup of performance tests
http://www.asp.net/mvc/tutorials/mvc-4/using-asynchronous-methods-in-aspnet-mvc-4
http://visualstudiomagazine.com/articles/2013/07/23/async-actions-in-aspnet-mvc-4.aspx
http://hanselminutes.com/327/everything-net-programmers-know-about-asynchronous-programming-is-wrong
http://www.hanselman.com/blog/TheMagicOfUsingAsynchronousMethodsInASPNET45PlusAnImportantGotcha.aspx
I've just run into a problem with a Quartz job that I'm invoking through Spring. My ExecuteInternal method had a [Transaction] attribute (because it does a load of DB calls) but when it runs, I get the 'No NHibernate session bound to thread' error.
Just wondering if that's because Spring.NET doesn't support the [Transaction] attribute in Quartz objects?
If not, that's fine... I can start a transaction manually, but wanted to check that it was the case, and not a silly error in my config somewhere.
[Update]
I figured it out actually. In the API docs, it says the preferable way to do this is use transactions on the service layer. My job was using DAOs to do its work, but my transactions are on my service layer, so I just called service methods from my job instead to do the same work (saving, updating records etc) since they already existed.
It also suggests that if you give the SchedulerFactoryObject a DbProvider, you can use transactions in the job itself, but when I did that it seemed to want to find my triggers configured in a special table in the DB (which I haven't set up since my triggers are all in XML) but that's possibly another way to do it.
Calling service methods works fine for me though.
The transaction attribute works using aop. Spring.NET creates an aop proxy for the decorated object. This proxy creates the session and starts the transaction.
In the ExecuteInternal method, you don't call the method on a proxy, but on the target itself. Therefore spring cannot intercept the call and do its transaction magic.
Your services are injected and therefore the transaction attribute works for them.
There's a good explanation in the spring docs on this subject: http://www.springframework.net/doc-latest/reference/html/transaction.html#tx-understandingimpl
I am trying to build a sample application using ICEfaces 2.0 , glassfish 3.0.1, JMS.
I have created a JMS Topic publisher which is a desktop application and publishes some data to the TOPIC, on the other end I have a web application where a user subscribes to this TOPIC to receive messages from the it. In order to apply the page updates asynchronously I am using ICEFaces PushRenderer. PushRenderer works in the scenario where PushRenderer.render() is being called by the managed Bean instance, but fails when being called from the onMessage() function which is a listener for the JMS messages.The push rendering fails, saying "The current thread does not have FacesContext associated with it. Now in order to make this work, is how can I execute the call to PushRenderer.render from the managed bean instance thread OR is there another way to make the PushRenderer.render work when onMessage() is being called by the TOPIC publisher.?
Please help regarding this. I am looking for other ways to make this work. Also the same procedure works with ICEFaces 1.8.2 SessionRenderer.render but it fails with PushRenderer.render as mentioned above.
You may try the ondemand renderer, something like:
renderManager.getOnDemandRenderer(identifier).requestRender();