We have a Kafka listener consuming messages from topic. We want to make this bean as functional so we can spin up multiple instances of function using server less architecture when there is heavy load. Can anyone show me a right direction
Take a look at Spring Cloud Stream Function support. You can use it with a Kafka binder.
In the previous post, I tried to provide justification for our shift to a functional programming model in Spring Cloud Stream (SCSt). It’s less code, less configuration. Most importantly, though, your code is completely decoupled and independent from the internals of SCSt.
In this post, I’ll dig a little deeper and summarize the core features of our functional support, specifically around its reactive features.
Related
We have 5 microservices (more on the way) that communicate with each other asynchronously. 3 of these microservices do not have any API. Those consume data from a message queue, do some processing, and write data into another queue. 2 of these microservices do have APIs, and those also consume data from the queues but send the response back to the caller.
Given that, for testing the service interactions, correctness of contracts, and end-to-end flow:
what would be the best way to test the asynchronous services that read from and write to queues?
would consumer-contract test be applicable anywhere?
I feel end-to-end production testing is possible, but can something more granular and effective be done?
First, let's correct one thing - you do have APIs. The messages that the "API-less" services read must have some defined content or format. That's an API. You should be testing it, both positive and negative.
Before you get to whole-system testing (in a test or staging environment that mimics your production environment) your testing should probably be in layers, much as in any other system.
Unit tests to test the behavior of each class. In your message-handling classes, for example, call each with messages that prompt specific actions and test that it works correctly. These can usually be run very quickly so it's easy to run them often while developing code.
Integration tests to make sure your interaction with next-level external systems works. You can use, for example, testcontainers to run isolated instances of the queueing system that your services interact with.
Exactly what form these tests take depends on what languages and frameworks your system is built with. I briefly looked at the Pact tool you referenced and it is taking a similar approach.
Looks like with Pact it is possible to do message-based contract testing. I think I have a path forward with this.
We are building a platform based on microservices. The platform will provide a number of basic functions that will be used in various independent projects.
We need to come up with such an architecture that will allow us to extend the basic functionality and interact with existing services. The main task is to ensure that the code of the main services remains unchanged, and custom solutions based on the platform can be easily reused.
We are considering several options. For example, there is a certain service "foo" which provides the functions foo1 and foo2. To extend the functions, we can create an independent "foobar" service and put it in front of the foo service, accept API requests, execute custom functions, and then redirect the request to foo. It turns out a kind of intermediary service, which acts as the main link in the implementation of the functions specific to a given project and the main platform. The advantage of this approach can be attributed to complete independence from the code base of basic services. And the main disadvantage is the complexity of implementation and the need to greatly fragment the functions of the main service.
The second option under consideration is similar to the approach that is often used in monolithic applications - the hook system, which allows you to override the behavior of the system. For example, you can create an independent service that will connect events and subscribers.
This approach is more flexible, but at the same time it is still quite difficult to implement. The main disadvantage of this approach is synchronous blocking network calls.
The third option that we are considering is the construction of the microservices themselves in such a way that additional modules can be added to them so that services can be customized at the build stage. The main code remains unchanged, but inside the process, the already mentioned scheme of hooks and events is implemented (at the code level of individual services). Benefit is ease of implementation. Of the cons, it is very difficult to implement customizations in the case multiple services are involved.
Perhaps we are trying to invent a bicycle and there are exist good solution(s) for the problem. If you know such, or you have a good idea about possible ways to solve this problem, please share.
I don't think there is an answer to this generic problem. The third solution seems pretty good. You might take advantage of chain-of-responsabilities or request-response pipelines paradigm to implement the open/closed principle pretty easily. This should ensure that you can add/modify features into your foo service without touching the existing code.
If you are looking for something to tackle to whole architecture rather than a single microservice, you might want to give a look at the Event-Driven microservices design.
This design approach is similar to your option 2, with the difference that it uses a message broker and async communication to let the microservices communicate.
There are a lot of advantages, like more resiliency and decoupling of the services.
I have inherited supporting and making BizTalk applications as part of my development role.
I'm a general C# developer so I was pleased to see I can create Classes and call the Methods from the Expression shape of an Orchestration.
This means I can do all the data manipulation using code I am familiar and faster with rather than learn the BizTalk ways.
At this point I am not concerned with if it's a good idea or not.
Are there any purely technical reasons I should not do this?
You would have to make sure that whatever external methods you are calling is muli-threading capable and can handle high throughput.
If you don't achieve the above then you will either get some very strange issues (caused by cross thread contamination) or you will cause a bottle neck in BizTalk which will reduce message throughput.
You also need to make sure that errors are handled, retried and propagated back correctly to the calling Orchestration on failure. I came across one solution where the developer for some reason had decided to call a web service using an external class. Every so often this web service would throw an error, but the class would just pass the error message as it was back to the Orchestration as if it was a valid response message. This would cause a failure later on in the Orchestration when it tried to use the message and it did not match the expected message. When I got allocated budget I replaced this class with a properly configured send port, which also automatically retried the message when it encountered the web service error and then it successfully processed.
Technically you are adding deployment and maintaining complexity with the externals assemblies, for example any change in some contract will require changes in the assembly and the orchestration.
And you're losing all the advantages of the BizTalk mapping engine for data transformation which is in general an easy part to learn.
I say this, it's very important for future maintainability to develop BizTalk apps in the "BizTalk Way".
For example, if you did message manipulation in an external class that should have been done in a Map or with XPath, I would fail that in Code Review and you'd have to refactor.
The reason is because whoever might take this over from you should expect a BizTalk app. I've seen situations such as you describe and it does make it harder to upgrade, enhance, support new business requirements because now the developer has to accommodate the BizTalk and external processes.
Technically using .NET classes does not break anything in the BizTalk. Lots of BizTalk components are based of .NET framework such as Adapters, pipeline components etc. In my view, use the best of both BizTalk and .NET depending on the scenarios. e.g. if you need to map an inbound XML to outbound XML use BizTalk maps as they are lot easier and quicker to implement, in this scenario using a .NET class is more tedious then using map. I don't think there is a big learning curve in using BizTalk features such as Maps, orchestrations, pipeline components.
I am very new to remoting in flex. I am using flex 4.5 and talking to a web application built by someone else on the team using AMF. They have used Zend_AMF to serialize and unserialize the data.
One of the main issues I am facing at the moment is that I will need to talk to a lot of services (about 60 or so).
From examples on remoting I have seen online and from adobe, it seems that I need to define a remoting object for EACH service:
<mx:RemoteObject id="testservice" fault="testservice_faultHandler(event)" showBusyCursor="true" destination="account"/>
With so many services, I think I might have to define about 60 of those, which I don't think is very elegant.
At the same time, I have been playing with Pinta to test out the AMF endpoint. Pinta seems to be able to allow one to define an arbitary amount of services, methods and parameters without any of these limitations. Digging through the source, I find that they have actually drilled down deep into the remoting and are handling a lot of low level stuff.
So, the question is, is there a way to approach this problem without having to define loads or remoteobjects and without having to go down too deep and start having to handling low level remoting events ourselves?
Cheers
It seems unusual for an application to require that many RemoteObjects. I've worked on extremely large applications, and we typically end up with no more than ~6-10 RemoteObject declarations.
Although you don't give a lot of specifics in your post about the variations of RemoteObjects, I suspect you may be confusing RemoteObject with Operation.
You typically declare a RemoteObject instance for every end-point in your application. However, that endpoint can (and normally does) expose many different methods to be invoked. Each of these server-side methods gets results in a client-side Operation.
You can explicitly declare these if you wish, however the RemoteObject builds Operations for you if you don't declare them:
var remoteObject:RemoteObject;
// creates an operation for the saveAccount RPC call, and invokes it,
// returning the AsyncToken
var token:AsyncToken = remoteObject.saveAccount(account);
token.addResponder(this);
//... etc
If you're interacting with a single server layer, you can often get away with a single RemoteObject, pointing to a single destination on the API, which exposes many methods. This is approach is often referred to as an API Façade, and can be very useful, if backed with a solid dependency injection discipline on the API.
Another common approach is to segregate your API methods by logical business area, eg., AccountService, ShoppingCartService, etc. This has the benefit of being able to mix & match protocols between services (eg., AccountService may run over HTTPS).
How you choose to split up these RemoteObjects is up to you. However, 60 in a single applications sounds a bit suspect to me.
I started to use silverlight/flex and immediately bumped into the asynchronous service calling. I'm used to solving the data access problems in an OO-way with one server fetch mechanism or another.
I have the following trivial code example:
public double ComputeOrderTotal(Order order)
{
double total = 0;
// OrderLines are lazy loaded
foreach (Orderline line in order.Orderlines)
{
// Article,customer are lazy loaded
total = total + line.Article.Price - order.Customer.discount;
}
return total;
}
If I understand correctly, this code is impossible in Flex/Silverlight. The lazy loading forces you to work with callbacks. IMO the simple expample above will be a BIG mess.
Can anyone give me a structured way to implement the above ?
Edit:
The problem is the same for Flex/Silverlight, pseudo code would
do fine
Its not really ORM related but most orms use lazy loading so i'll remove
that tag
The problem is lazy loading in the model
The above example would be very doable of all data was in memory but
we assume some has to be fetched from
the server
Closueres dont help since sometimes data is already loaded and no asynchronous fetch is needed
Yes I must agree that O/R mapping is usually done on the server-side of your application.
In SilverLight asynchronous way of execution is the desired pattern to use when working with services. Why services? Because as I said before there is no O/R mapping tool at the moment that could be used on the client-side (SilverLight). The best approach is to have your O/R mapped data exposed by a service that can be consumed by a SilverLight application. The best way at the moment is to use Ado.Net DataServices to transport the data, and on the client-side to manage the data using LINQ to Services. What is really interesting about ADS (former Astoria project) is that it is designed to be used with Entity Framework, but the good folks also implemented support for IQueriable so basically you can hook up any data provider that support LINQ. To name few you can consider Linq To Sql, Telerik OpenAccess, LLBLGen, etc. To push the updates back to the server the data source is required to support the ADS IUpdateable.
You can look just exactly how this could be done in a series of blogposts that I have prepared here: Getting Started with ADO.NET Data Services and Telerik Open Access
I can't speak to Silverlight but Flex is a web browser client technology and does not have any database driver embedded in the Flash runtime. You can do HTTP protocol interactions to a web server instead. It is there in the middle-tier web server where you will do any ORM with respect to a database connection, such as Java JDBC. Hibernate ORM and iBATIS are two popular choices in the Java middle-tier space.
Also, because of this:
Fallacies of Distributed Computing
You do not do synchronous interactions from a Flex client to its middle-tier services. Synchronous network operations have become verboten these days and are the hallmark signature of a poorly designed application - as due to reasons enumerated at the above link, the app can (and often will) exhibit a very bad user experience.
You instead make async calls to retrieve data, load the data into your client app's model object(s), and proceed to implement operations on the model. With Flex and BlazeDS you can also have the middle-tier push data to the client and update the client's model objects asynchronously. (Data binding is one way to respond to data being updated in an event driven manner.)
All this probably seems very far afield from the nature of inquiry in your posting - but your posting indicates you're off on an entirely incorrect footing as to how to understand client-side technologies that have asynchronous and event-driven programming baked into their fundamental architecture. These RIA client technologies are designed this way completely on purpose. So you will need to learn their mode of thinking if you want to have a good and productive experience using them.
I go into this in more detail, and with a Flex perspective, in this article:
Flex Async I/O vs Java and C# Explicit Threading
In my direct experience with Flex, I think this discussion is getting too complicated.
Your conceptual OO view is no different between sync and asynch. The only difference is that you use event handlers to deal with the host conversation in the DAL, rather than something returned from a method call. And that often happens entirely on the host side, and has nothing to do with Flex or Silverlight. (If you are using AIR for a workstation app, then it might be in client code, but the same applies. As well if you are using prolonged AJAX. Silverlight, of course, has no AIR equivalent.)
I've been able to design everything I need without any other changes required to accomodate asynch.
Flex has a single-threaded model. If you make a synchronous call to the web server, you'd block the entire GUI of the application. The user would have a frozen application until the call completes (or times out on a network error condition, etc.).
Of course real RIA programs aren't written that way. Their GUI remains accessible and responsive to the user via use of async calls. It also makes it possible to have real progress indicators that offer cancel buttons and such if the nature of the interaction warrants such.
Old, bad user experience web 1.0 applications exhibited the synchronous behaviour in their interactions with the web tier.
As my linked article points out, the async single-threaded model coupled with ActionScript3 closures is a good thing because it's a much simpler programming model than the alternative - writing multi-thread apps. Multi-threading was the approach of writing client-server Java Swing or C# .NET WinForm applications in order to achieve a similarly responsive, fluid-at-all-times user experience in the GUI.
Here's another article that delves into this whole subject matter of asynchronous, messaging/event-driven distributed app architecture:
Building Effective Enterprise Distributed Software Systems
data-driven communication vs behavior-driven communication
Silverlight is a client technology and the Object - Relational mapping happens completely in the server. So you have to forgot about the ORM in Silverlight.
Following your example what you have to do is to create a webservice (SOAP, REST...) that can give your silverlight client the complete "Order" object.
Once you have the object you can work with it with no communication with the server in a normal - synchronous way.
Speaking about Silverlight, you should definitely check RIA services.
Simply, it brings the DataContext from the server to the client from where you can asynchronously query it (there is no need to write WCF services by hand, it's all done by RIA).
C# 5
async / await construct will almost exactly what I want..
watch presentation by anders hejlsberg