I am a newbie in Microservices, having theoretical knowledge. I want to make a small application in Microservices. Can anyone please help me with the idea of how to implement microservices?
Thanks in Advance!!
You can create something like a currency conversion app with three microservices like these:
Limit service;
Exchange service;
Currency conversion service.
Limit service and currency conversion service can communicate with the database for retrieving the values of the limits and currencies conversion.
For more info check github.com/in28minutes and look after a microservice repository.
No matter how perfect the code of your microservice is, you may face issues with support and development if the microservice architecture doesn’t work according to certain
rules.
The following rules can help you with microservices a lot:
You have to do everything by yourself because you do not have any Rails and architecture out of the box that can be started by one command. Your microservice should load libraries, establish client connections, and be able to release resources if it stops working for any reason.
It means that being in the microservice folder and having made the 'ruby server.rb' command (a file for starting a microservice) we should make the microservice do the following:
Load used gems, vendor libraries (if used), and our own libraries
Use the configuration (depend on the environment) for adapters or classes of client connections
Establish client connections (permanent connections are meant here). As your microservice should be ready for any shutdowns, you should take care of closing these client connections at such moments. EventMachine and its callback mechanism helps a lot with this.
After that your microservice should be loaded and ready for work.
Incapsulate your communication with the services into abstractly named adapters. We name these adapters based on their role (PubSub, SMSMessenger, Mailer, etc.). This way, we can always change the inner implementation of these adapters by replacing the service if the names of our classes are service agnostic.
For example, we almost always use Redis in our application from the very beginning, thus it is also possible to use it as a message bus, so that we don’t have to integrate any other services. However, with the application growth we should think about solutions like RabbitMQ which are more appropriate for cases like ours.
If your code is designed in such a way that your classes are coupled with each other, do it according to the dependency inversion principle. This will help your code to avoid issues with lib booting.
Learn more here
You can try splitting an existing Monolithic application to gain perspective on microservice architecture.
I wrote this article, which talks about splitting a Django App into microservices. Hope it helps.
Related
I am developing web application backend with Spring where client and server talk through Restful APIs. There is a specific API where I assume the hit will be much. Is there any way to scale this specific API?( Like, assigning more threads)
In this application everything is interdependent. So, microservice wont be best approach I guess.
There are two possible ways, i can think of
Use Load Balancer, this will help you to add multiple application instances of Rest API. This is classical approach in such cases.
This depends upon existing implementation, API can be refactor to just receive the message and decouple the processing thread.
The your suggested way of increasing thread has limitation and more fine tuning require. If the use case is just to support limited user, following configure can be use. tomcat thread pool.
Just have multiple instances of the same service. REST has a statelessness constraint, so it is easy to do it.
I am exploring to put rate limiting functionality on rest API which are developed using spring boot.
After going through many articles, I came to know that the best way to put rate limiting functionality is with application code, rather then putting it on web servers.
My question is how do you decide that which functionality should go where. Since, its monitoring your incoming calls and nothing to do with business logic, the ideal place should be a web server.
My question is how do you decide that which functionality should go
where. Since, its monitoring your incoming calls and nothing to do
with business logic, the ideal place should be a web server.
Technically the web server could do the job but in the facts, a web server doesn't have necessarily all needed information, it is not specialized for API consuming and it may also make the testability of this feature much harder.
Some practical reasons why the webserver side could be a bad choice :
the developers don't have necessarily the configuration of the HTTP web server in local.
you want to write unit and integration test to check that the rate limitations are applied as specified. Creating a configuration for automated testing is much simpler in the scope of your Java application than with a configuration file defined on a web server.
web servers reasons in terms of HTTP request-response, not in terms of service.
Rate limitations may be applied according to the IP but not only, the username, the user roles, the type of service may influence the limitations. Not sure that you could get all of these easily from an HTTP server.
For example roles are stored on the server side or in a database.
A better option is setting these mechanisms by adding specific and specialized classes or configuration files, which simplifies their reading, their maintenance and their testability.
As you mention Spring Boot in your tags, that and that should interest you.
I recommend spring-cloud-gateway's rate limiter
you could separate this functionality from your business logic by using Filters.
https://www.baeldung.com/spring-boot-add-filter
we are currently facing some tough architectural questions about integrating multiple Web Components with individual backend services in a composite web UI to one smooth web application.
There are some constraints an (negotiable) design decisions:
A MicroService should serve it's own frontend (WebComponent), we would like to use HTML Imports to allow including such a WebComponent to the composite UI
A frontend WebComponent needs to be able to recieve live updates/events from it's backend MicroService
The page (sum of Web Components used in the composite UI) shall only use one connection/permanent occupied port to communicate with the backend
I made a sketch representing our abstract / non-technical requirements for further discussion:
As of my understanding, the problem could be rephrased to: How do we
a) concentrate communication on entering
b) distribute communication on exiting
the single transport path on both ends.
This two tasks need to be solved on both sides of the transport path, eg. the backend and the frontend.
For the backend, I am quite hopefull that adopting the BFF pattern as not only described by Sam Newman could serve our needs. The right half (backend) side of the above sketch could then look similar to this:
The transport path might be best served using standardized web technologies, eg. https and websocket (wss) for the most times needed, bidirectional communication. I'm keen to learn about alternatives with an equivalent high adoption rate in the web technology sector.
For the frontend we are currently lacking ideas and knowledge about previously described patterns or frameworks.
The tricky thing is, that multiple basically independent WebComponents need to find together for using the ONE central communication path. If the frontend would be realized by implementing one (big) Angular application for example, we would implement and inject a "BackendConnectorService" (Name to be discussed) and inject in to our various components.
But since we would like to use decoupled Web Components, none such background layer for shared business logic and dependency injection exists. Should we write a proprietary JS-library, which will be loaded to the window-context if not present yet from every of our components, and will be used (by convention) to communicate with the backend?
This would roughly integrate to the sketch like below:
Are we thinking/designing our application wrong?
I'm thankful for every reasonable idea or hint for a proven pattern/framework.
Also your view on the problem and the architecture might be helpful to circumnavigate the issues we are facing right now.
I would go with same approach you are using on the backend for the frontend.
Create an HTTP or WS gateway, that frontend components will poll with requests. It will connect to backend BFF and there you solved all your problems. Anytime you want to swap your components, transfer or architecture, one is not dependent on the other.
How can I share database connection aong in spring cloud module microservices. If there are many microservices how can i use same db connection or should i use db connection per microservices?
In my opinion, the thing that you've asked for is impossible only because each microservice is a dedicated process and it runs inside its own JVM (probably in more than one server). When you create a connection to the database (assuming you use connection pool) its always at the level of a single JVM.
I understand that the chances are that you meant something different but I had to put it on because it directly answers your question
Now, you can share the same database between microservices (the same schema, tables, etc) so that each JVM will have a set of connections opened (in accordance with connection pool definitions).
However, this is a really bad practice - you don't want to share the databases between microservice. The reason is the cost of change: if you (as a maintainer of microservice A) decide to, say, alter one of the tables, now all microservices will have to support this, and this is not a trivial thing to do.
So, a better approach is to have a service that has a "sole responsibility" for your data in some domain. Now, all the services could contact this service and ask for the required data through well-established APIs that should never be broken. In this approach, the cost of change is much "cheaper" since only this "data service" should be changed in a way that it doesn't break existing APIs.
Now regarding the database connection thing: you usually will have more than one JVM that runs the same microservice (like data microservice) so, it's not that you share connections between them, but rather you share the same way of working with database (because after all its the same code).
When dealing with a mircoservice architecture it is usually the case that you have a distributed system.
Most microservices that communicate with each other are not on the same machine, instance or container. Communication between them is most commonly done via http, though there are many other ways.
I would suggest designing mircoservices around a single concern of your application. For example, in your case, you could have a "persistence microservice" that would be responsible for dealing with data persistence operations on a single or multiple types data-stores. It could possibly deal with relational DBs, noSQL, file storage etc. Then, via REST endpoints, you can expose any persistence functionality to the mircoservices that deal with business logic.
A very easy way to build a REST service like this would be with the help of Spring Data REST project.
To answer your actual question, I'm not aware of any way to share actual connections between processes. Beyond that, having many microservices running on the same instance is not a good practice most of the time.
Mircoservices are very popular these days and everybody is trying to transition to them. My advice would be to make sure you don't "over-engineer" your project.
Hope I didn't misunderstand your question, but to be fair it is a little vague. If you could provide a longer more detailed description of your architecture and use case I can suggest more tools/frameworks you can use to achieve your cloudy goals.
First and most important - your microservice should be responsible for handling all data in a given business domain/bounded context. So the question is - 'Why do you need to share database connection between microservices and isn't this a sign you went too far with slicing your system?' Microservice is a tool and word 'micro' may be misleading a bit :)
For more reading I would suggest e.g. https://learn.microsoft.com/en-us/dotnet/standard/microservices-architecture/architect-microservice-container-applications/identify-microservice-domain-model-boundaries (don' t worry, it's general enough to be applicable also to Spring).
I try to work with go-kit (gokit.io) and to build real-work application with it.
I look through examples. These examples are great. But I do not understand how to do services to service communications / data transfers in go-kit framework.
I can see "real-world" shipping app, but I do not understand how it could be "real world" micro-services. I can see in sources that, for example, they build the booking service just passing foreign repositories into service
type service struct {
cargoRepository cargo.Repository
locationRepository location.Repository
routingService routing.Service
handlingEventRepository cargo.HandlingEventRepository
}
and later they get data from repositories (this repository belongs to foreign micro-service) just calling the method:
locationRepository.Find(...)
Could someone please explain me:
how to build micro-service to micro-service communications in go-kit framework? Just show me the way / pattern, please. I do not understand it at all.
I see it as they just share direct access to data. But in real world micro-services, I expected that micro-services will communicate to each other to get needed data. And I do not understand how to do it in go-kit framework.
I'm the author of the shipping example. Sorry for not seeing your question earlier.
This particular example needs a bit of explanation. It is an example based on tactical patterns from Domain Driven Design, which means that we need to understand what we are talking about when we're referring to a service.
There are application services that deal with the use cases offered by the application, e.g. booking.Service. There are domain services that reside in the domain layer and provides your domain with concepts that aren't necessarily bound to a domain object. In the shipping example, routing.Service is a domain service whose implementation actually queries another application, in this case it talks to this routing service.
Application and domain services are merely ways of organizing our code. Putting it differently, these services communicate within a process, while microservices typically communicate over a network using some form of common transport, e.g. JSON, gRPC and so on.
Coming back to your question, what I believe you are looking for is the implementation of the routing.Service which you can find here.
The proxy service used here is explained under Client-side endpoints on this page, and is used to make requests from your application to another.
If you want more detail, I wrote a blog post on the subject a while ago.