Thursday, 14 December 2017
First steps with Vert.x and Infinispan PUSH API (Part 2)
Welcome to the second in a multi-part series of blog posts about creating Eclipse Vert.x applications with Infinispan. In the previous blog post we have seen how to create a REST API. The purpose of this tutorial is to showcase how to create a PUSH API implemented with Vert.x and using Infinispan as a server.
All the code of this tutorial is available in this GitHub repository. The backend is a Java project using Maven, so all the needed dependencies can be found in the pom.xml. The front is a super simple react application.
PUSH API
Creating a REST API is very straightforward. But today, even if we are heavily using REST, we don’t always want to use request/response or polling, but instead we want to push directly from the server to the client. In this example, we are going to create an API that pushes every new value inserted in the default cache of Infinispan. These values are cute names, as we did in the REST API example.
We are using two features here :
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Infinispan client listeners
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Vert.x bridge between the Event Bus and the browser
Infinispan Listeners provide a way to the client get notified when something happens in a cache.
The Event Bus Bridge that connects to the browser, uses SockJS. SockJS is a JavaScript library that provides a WebSocket API, but it can be used with browsers that don’t support web-sockets (see the website of the project for more detailed information). Vert.x supports this library and creates a bridge between your browser and your back-end easily through the Event Bus.
Creating an Event Bus bridge
Vert.x is a reactive framework, which means that uses RxJava too, and provides a fancy API on top of it.
First, we are going to create a new verticle called SendCuteNamesAPI. This verticle extends the CacheAccessVerticle we created in the previous blog post. CacheAccessVerticle initialises the connection with Infinispan using the Hot Rod protocol.
Now we need to create a SocketJSHandler. This handler has a method called bridge, where we configure some BridgeOptions. Obviously we don’t want the client to be able to read everything traveling on the event bus, and this won’t happen. We configure an address, 'cute-names', and we add the permission to read and write to this address.
This handler is passed to the event bus route, where the path is /eventbus/*.
Finally, we create a http server as we did in the REST API example. The difference is that instead of calling listen method, we call rxListen and subscribe.
Getting notified and publishing
Using Infinispan listeners is very easy.
First, we are going to create a class that has the @ClientListener annotation. The client listener has to be added to the cache client configuration. We add a protected method called addConfigToCache that will be called just after the initialisation of the defaultCache in the abstract CacheAccessVerticle. Verticles extending the abstract class can now add custom configuration to the client.
We want to be notified when a new entry is created. In this case, our listener has to contain a method with the @ClientCacheEntryCreated annotation on it. The signature of the method has to include a ClientCacheEntryCreatedEvent<String> parameter. This parameter will hold the 'key' of the entry that has been created.
Finally, we use the key to retrieve the name using the getAsync method and then publish the value in the Vert.x event bus to the address where the socket listener is permitted to read : cute-names.
Now we can run the main method and whenever we post a new name, we will see in the logs that the client listener is notified!
Client code
We are going to create a super simple react application that will just display hello. React community is huge, so there are lot’s of tutorials out there to create a hello world client application. This application has a single component that displays "Hello".
The react application runs calling npm install and npm start in http://localhost:9000/.
Now we need to connect the client to the backend with SockJS. Vert.x provides a JavaScript library for that: vertx3-eventbus-client, built on top of SockJS. We create an EventBus object that will connect to http://localhost:8082/eventbus as we configured in the SendCuteNamesAPI. We register a handler on the 'cute-names' address. The body of the message will contain the new cute name published in the event bus. Every time the handler is called, we update the component’s state, and it will be rendered.
Wrap up
We have learned how to create PUSH APIs with Vert.x, powered by Infinispan. The repository has some unit tests. Feedback is more than welcome to improve the code and the provided examples. I hope you enjoyed this tutorial ! On the next tutorials we will talk about Infinispan as the cluster manager for Vert.x. Stay tuned !
Tags: reactive listeners vert.x push api react
Tuesday, 12 December 2017
First steps with Vert.x and Infinispan REST API (Part 1)
Welcome to the first in a multi-part series of blog posts about creating Eclipse Vert.x applications with Infinispan. The purpose of this first tutorial is to showcase how to create a REST API.
All the code of this tutorial is available in this GitHub repository. The backend is a Java project using Maven, so all the needed dependencies can be found in the pom.xml.
==
What is Vert.x ?
Vert.x is a tool-kit for building reactive applications on the JVM. It’s an event driven and non blocking tool-kit. It is based on the Reactor Pattern, like Node.js, but unlike Node it can easily use all the cores of your machine so you can create highly concurrent and performant applications. Code examples can be found in this repository.
==
REST API
Let’s start creating a simple endpoint that will display a welcome message on '/'. In Vert.x this is done by creating a Verticle. A verticle is a unit of deployment and processes incoming events over an event-loop. Event-loops are used in asynchronous programming models. I won’t spend more time here explaining these concepts as this is very well done in this Devoxx Vert.x talk or in the documentation available here.
We need to override the start method, create a 'router' so '/' requests can be handled, and finally create a http server.
The most important thing to remember about vert.x, is that we can NEVER EVER call blocking code (we will see how to deal with blocking API’s just after). If we do so, we will block the event loop and we won’t be able to serve incoming requests properly.
Run the main method, go to your browser to http://localhost:8081/ and we see the welcome message !
Connecting with Infinispan
Now we are going to create a REST API that uses Infinispan. The purpose here is to post and get names by id. We are going to use the default cache in Infinispan for this example, and we will connect to it remotely. To do that, we are going to use the Infinispan hotrod protocol, which is the recommended way to do it (but we could use REST or Memcached protocol too)
Start Infinispan locally
The first thing we are going to do is to run an Infinispan Server locally. We download the Infinispan Server from here, unzip the downloaded file and run ./bin/standalone.sh.
If you are using Docker on Linux, you can use the Ihttps://hub.docker.com/r/jboss/infinispan-server/[nfinispan Docker Image Available] easily. If you are using Docker for Mac, at the time of this writing there is an issue with internal IP addresses and they can’t be called externally. Different workarounds exist to solve the problem, but the easiest thing for this example is simply downloading and running the standalone server locally. We will see how to use the docker image in Openshift just after.
The hotrod server is listening in localhost:11222.
Connect the client to the server
The code we need to connect with Infinispan from our java application is the following :
This code is blocking. As I said before, we can’t block the event loop and this will happen if we directly call these API’s from a verticle. The code must be called using vertx.executeBlocking method, and passing a Handler. The code in the handler will be executed from a worker thread pool and will pass the result back asynchronously. Instead of overriding the start method, we are going to override start(Future<Void> startFuture). This way, we are going to be able to handle errors.
To stop the client, the API supplies a non blocking method that can be called when the verticle is stopped, so we are safe on that.
We are going to create an abstract CacheAccessVerticle where we will initialise the manager and get default cache. When everything is correct and the defautCache variable is initialised, we will log a message and execute the initSuccess abstract method.
REST API to create names
We are going to add 3 new endpoints.
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GET /api displays the API name
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POST /api/cutenames creates a new name
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GET /api/cutenames/id displays a name by id
CuteNamesRestAPI verticle can now extend this class and override the initSuccess method instead of the start method.
POST
Our goal is to use a curl to create a name like this :
curl -X POST \ -H "Content-Type: application/json" \ -d '\{"name":"Oihana"}' "http://localhost:8081/api/cutenames"
For those that are not familiar with basques names, Oihana means 'rainforest' and is a super cute name. Those who know me will confirm that I’m absolutely not biased making this statement.
To read the body content, we need to add a body handler to the route, otherwise the body won’t be parsed. This is done by calling router.route().handler(BodyHandler.create()).
The handler that will handle the post method in '/api/cutenames' is a RoutingContext handler. We want to create a new name in the default cache. For that, we will call putAsync method from the defaultCache.
The server responds 201 when the name is correctly created, and 400 when the request is not correct.
GET by id
To create a get endpoint by id, we need to declare a route that will take a parameter :id. In the route handler, we are going to call getAsync method.
If we run the main, we can POST and GET names using curl !
curl -X POST -H "Content-Type: application/json" \ -d '\{"id":"42", "name":"Oihana"}' \ "http://localhost:8081/api/cutenames"
Cute name added
curl -X GET -H "Content-Type: application/json" \ "http://localhost:8081/api/cutenames/42" * \{"name":"Oihana"}*
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Wrap up
We have learned how to create a REST API with Vert.x, powered by Infinispan. The repository has some unit tests using the web client. Feedback is more than welcome to improve the code and the provided examples. I hope you enjoyed this tutorial ! On the next tutorial you will learn how to create a PUSH API.
Tags: vert.x rest API
Wednesday, 22 November 2017
Infinispan and Vert.x coming to Codemotion Spain and Madrid JUG
I’m happy to announce that Infinispan and Eclipse Vert.x team members are in Madrid (Spain) this week!
The 23th of November, Galder (Infinispan) and Thomas (Vert.x) will be presenting at Madrid Java User Group two talks about Infinispan and Ver.x. From my side, I’ve been invited to give a talk about programming career path to Computer Science and Engineering students in the Universidad San Pablo CEU.
The following days, 24th and 25th of November, Codemotion Spain will take place in Madrid. Codemotion is the biggest developer centric conference in Spain. More than 1.500 people will be attending this year. The conference does not focus on any particular technical stack. You can learn about mobile, web, front-end, back-end, devops and there are some inspirational tracks too during the two days of the conference.
https://www.blogger.com/[#goog_607202257]
On Friday, Galder will be presenting a talk about Streaming and BigData architecture. Thomas will be presenting "Better performance on server side with HTTP/2" and I will join a debate around Enterprise Culture, where I will give my insights about RedHat’s Culture. On Saturday we will run our Streaming Data Workshop: a hands on lab that showcases a simplified streaming architecture built on top of Infinispan and Vert.x and running on OpenShift. If you cannot attend any of these events, you can always do the workshop at your self peace.
We hope to see you in Madrid, or anywhere else in 2018!!
Cheers, Katia
Tags: conference JUGs codemotion vert.x
