I've been looking at the event driven architecture and it's seems it might be the right architecture for a project I'm working on.
But there is one thing I don't really get yet, what is the best practice/common pattern when your micro services are being consumed by front-end applications?
For my project, I have a web app and an iOS and Android app.
Let's take a simple case of a feature letting users create their profile.
Let's say I send the profile data via REST/GraphQL to the api endpoint which triggers microservices (running behind Kafka or Pulsar).
How can I get the result of the profile creation and then maybe use it on the next screen?
Cheers
websocket calls to Pulsar will do most of what you want https://pulsar.apache.org/docs/en/client-libraries-websocket/
You could also call Apache Pulsar via MQTT which is not too uncommon from cell phones.
Or use a REST gateway or microservice between the app and Pulsar services. I use Apache NiFi for that.
Need to develop a rest API which can read published messages from kafka cluster to a dataware house application.
Materials available over internet say use POST/GET commands , but i don't think this is for production use rather useful for testing purposes.
How to implement it in scala/ Java Programming?
Materials available over internet say use POST/GET commands , but i don't think this is for production use rather useful for testing purposes
Please link to where you read this... All production web-services operate over (more than) these two HTTP methods, hundreds of thousands times a day...
If you want to really use Kafka for throughput, though, you wouldn't "hide it" behind a REST interface, though. You would distribute SSL certs plus usernames+passwords, to remote clients, for example.
Need to develop a rest API which can read publish messages from kafka
REST is not meant to keep an open connection, primarily because it is stateless (it shouldn't maintain where you are reading from in Kafka)... It would make more sense to forward a websocket from a Kafka consumer, which is different from a REST API.
how to implement it in scala/ Java Programming
The Confluent REST Proxy is already written in Java, and it is open-source (and used in Production at several companies, I believe). If you need inspiration, then you can start there. Otherwise, you can find examples of Spring and Vert.x, for example, with their Kafka integrations in their respective documentations, but you'll be re-implementing a lot of the existing functionality.
In a "computer system" there are two web servers that manage independent applications, both using JSP technology. There is a necessity to have access from server A to information stored in server B. In case of interconnection with:
Invocation of a data access service with GET/POST of an URL.
Definition and use of Web services.
Direct integration in Java, with Java RMI.
Which would be the best solution? Why? What are the advantages and disadvantages of each of them?
A solution would be to use REST API on the server from where you need to invoke the information. You might want to use an ajax call or just include contact via iframe.
Get call will be simple and quick to develop and maintain however if it is low latency and high throughput application then you might want to go with Java RMI.
I like the APIs of the Retrofit and OkHttp rest/http libraries from Square. I am evaluating options for writing a server-side rest client. For each request to my SOAP-based web service, I have to consume another, restful web service, thus my need for a rest client.
My question is, are Retrofit and OkHttp suitable for server-side use in a highly concurrent web app, or are there likely to be issues, known or otherwise, stemming from these APIs having been designed for use primarily outside of the server-side?
Reading the documentation and perusing the code, nothing jumped out at me to indicate that these libraries would not be suitable. But I don't want to be a guinea pig either. Has anyone experienced any issues with server-side use under high load/concurrency? Had success? Anyone from the dev teams for those libraries care to comment? ;)
We use OkHttp on the Square Cash server and we haven't had problems.
Some of the default settings are not suitable for server side usage, for example, the maximum number of concurrent requests per host defaults to 5.
There is some discussion on this at https://github.com/square/okhttp/issues/4354.
In the microservices architecture world (using Spring Framework), Retrofit/Okhttp may not be a good fit as a REST client for inter-service communication. Using WebClient/RestTemplate will have at least the below advantages over using retrofit for the same purpose:
RestTemplate/WebClient can be easily configured to make use of client-side load balancing (Ribbon), thereby requests can be rotated among various instances or another microservice.
Hystrix can be easily configured with RestTemplate, thereby increasing the fault tolerance (circuit breaker pattern) of the overall system w.r.t inter-service communication.
Service discovery can be easily configured using Eureka or Consul, thereby the client need not know the host/port/protocol of the target web service. All we need is to enable the discovery client.
Alternatively, you can also explore Feign, which is a declarative web service client similar to retrofit, but with all the advantages of RestTemplate.
You can also have a loot at the following article:
https://www.javacodemonk.com/retrofit-vs-feignclient-on-server-side-with-spring-cloud-d7f199c4
I have heard a lot of people talking recently about middleware, but what is the exact definition of middleware? When I look into middleware, I find a lot of information and some definitions, but while reading these information and definitions, it seems that mostly all 'wares' are in the middle of something. So, are all things middleware?
Or do you have an example of a ware that isn't middleware?
Lets say your company makes 4 different products, your client has another 3 different products from another 3 different companies.
Someday the client thought, why don't we integrate all our systems into one huge system. Ten minutes later their IT department said that will take 2 years.
You (the wise developer) said, why don't we just integrate all the different systems and make them work together? The client manager staring at you... You continued, we will use a Middleware, we will study the Inputs/Outputs of all different systems, the resources they use and then choose an appropriate Middleware framework.
Still explaining to the non tech manager
With Middleware framework in the middle, the first system will produce X stuff, the system Y and Z would consume those outputs and so on.
Middleware is a terribly nebulous term. What is "middleware" in one case won't be in another. In general, you can expect something classed as middleware to have the following characteristics:
Primarily (usually exclusively) software; usually doesn't need any specialized hardware.
If it weren't there, applications that depend on it would have to incorporate it as part of their application and would experience a lot of duplication.
Almost certainly connects two applications and passes data between them.
You'll notice that this is pretty much the same definition as an operating system. So, for instance, a TCP/IP stack or caching could be considered middleware. But your OS could provide the same features, too. Indeed, middleware can be thought of like a special extension to an operating system, specific to a set of applications that depend on it. It just provides a higher-level service.
Some examples of middleware:
distributed cache
message queue
transaction monitor
packet rewriter
automated backup system
Wikipedia has a quite good explanation: http://en.wikipedia.org/wiki/Middleware
It starts with
Middleware is computer software that connects software components or applications. The software consists of a set of services that allows multiple processes running on one or more machines to interact.
What is Middleware gives a few examples.
There are (at least) three different definitions I'm aware of
in business computing, middleware is messaging and integration software between applications and services
in gaming, middleware is pretty well anything that is provided by a third-party
in (some) embedded software systems, middleware provides services that applications use, which are composed out of the functions provided by the hardware abstraction layer - it sits between the application layer and the hardware abstraction layer.
Simply put Middleware is a software component which provides services to integrate disparate systems together.
In an complex enterprise environment, there are a number of challenges when you need to integrate two or more enterprise systems together to talk to each other. Normally these systems do not understand each others language as they are developed on different platforms using different languages (like C++, Java, Cobol, etc.).
So here comes middleware software in picture which provides services like
transformation of messages formats from one app to other,
routing and enriching messages besides taking care of security,
encryption,
validation and
applying different business rules to these messages.
A typical example of middleware is an ESB products like IBM message broker (WMB/IIB), WESB, Datapower XI50, Oracle Fusion, Mule and many others.
Therefore, middleware sits mostly in between the service consuming apps and services provider apps and help these apps to talk to each other.
Middleware is about how our application responds to incoming requests. Middlewares look into the incoming request, and make decisions based on this request. We can build entire applications only using middlewares. For e.g. ASP.NET is a web framework comprising of following chief HTTP middleware components.
Exception/error handling
Static file server
Authentication
MVC
As shown in the above diagram, there are various middleware components in ASP.NET which receive the incoming request, and redirect it to a C# class (in this case a controller class).
Middleware is a general term for software that serves to "glue together" separate, often complex and already existing, programs. Some software components that are frequently connected with middleware include enterprise applications and Web services.
There is a common definition in web application development which is (and I'm making this wording up but it seems to fit): A component which is designed to modify an HTTP request and/or response but does not (usually) serve the response in its entirety, designed to be chained together to form a pipeline of behavioral changes during request processing.
Examples of tasks that are commonly implemented by middleware:
Gzip response compression
HTTP authentication
Request logging
The key point here is that none of these is fully responsible for responding to the client. Instead each changes the behavior in some way as part of the pipeline, leaving the actual response to come from something later in the sequence (pipeline).
Usually, the middlewares are run before some sort of "router", which examines the request (often the path) and calls the appropriate code to generate the response.
Personally, I hate the term "middleware" for its genericity but it is in common use.
Here is an additional explanation specifically applicable to Ruby on Rails.
Middleware stands between web applications and web services that natively can't communicate and often are written in different languages/frameworks.
One such example is OWIN middleware for .NET environment, before owin people were forced to host web apps in a microsoft hosting software called IIS. After owin was developed, it has added capacity to host both in IIS and self host, in IIS was just added support for Owin which acted as an interface. Also it become possible to host .NET web apps on Linux via Mono, which again added support for Owin.
It also added capacity to create Single Page Applications, Owin handling Http request/response context, so on top of owin you can add authentication/authorization logic via OAuth2 for example, you can configure middleware to register a class which contains logic of user authentification (for ex. OAuth2 implementation) or class which contains logic of how to manage http request/response messages, that way you can make one application communicate with other applications/services via different data format (like json, xml, etc if you are targeting web).
Some examples of middleware: CORBA, Remote Method Invocation (RMI),...
The examples mentioned above are all pieces of software allowing you to take care of communication between different processes (either running on the same machine or distributed over e.g. the internet).
From my own experience with webwork, a middleware was stuff between users (the web browser) and the backend database. It was the software that took stuff that users put in (example: orders for iPads, did some magical business logic, i.e. check if there are enough iPads available to fill the order) and updated the backend database to reflect those changes.
It is just a piece of software or a tool on which your application executes and rapplication capabilities with respect to high availability,scalability,integrating with other softwares or systems without you bothering about your application level code changes .
For example : The operating system on which your application runs requires an I.P change , you do not have to worry about it in your code , it is the middleware stack on which you can simple update the configuration.
Example 2 : You experience problems with your runtime memory allocation and feel that the your application usage has increased , you do not have to much about it unless you have a bug or bottleneck in your code , it is easily achievable by tuning middleware software configuration on which your application runs.
Example 3 : You have multiple disparate software and you need them to talk to each other or send data in a common format which is understandable by all the systems then this is where middleware systems comes handy.
Hope the information provided helps.
it is a software layer between the operating system
and applications on each side of a distributed computing system in a network. In fact it connects heterogeneous network and software systems.
If I am not wrong, in software application framework, based on the context, you can consider middleware for the following roles that can be combined in order to perform certain activities in between the user request and the application response.
Adapter
Sanitizer
Validator
I always thought of it as the oldest software I have had to install. The total app used a web server, a database server, and an application server. The web server being the middleware between the data and the app.