Can Eureka be used by outside world to discover my service? Below is the flow:
Public client( developed in any technology and not using Eureka) --> Eureka server (hosted on my organization server, exposed to outside world) --> My Eureka aware services.
I am trying to understand how Netfilx Eureka works from overall architecture point of view.
Basically Load Balancer and discovery service are two completely different things.
Discovery service = a registry of currently available services
Load Balancer = a routing of requests based on various rules
So, Eureka, as a discovery service, cannot be used a Load Balancer by itself.
However Eureka, being an application by itself, exposes an HTTP REST API
So if you want to build a load balancer by yourself based on the information provided by eureka, you can call rest APIs like this.
For example, Ribbon, being a client side load balancer, calls these APIs internally.
Having said that, its not unclear why to use the tool for the purpose for which is not intended to be...
Related
I am using "Spring Cloud Gateway" in my microservices application
Ex:
spring.cloud.gateway.routes[0].id=mydemoservice
spring.cloud.gateway.routes[0].uri=http://localhost:8100/
spring.cloud.gateway.routes[0].predicates[0]=Path=/mydemoservice/**
In this case if the request is coming from client like : http://localhost:8100/mydemoservice/api/getdetails
in this case "Spring Cloud Gateway" will route the request to respective service.
But why is Eureka Server required here ? I am not really understanding Eureka Server use here can some please explain.
Best I could find is this medium article which depicts the problems and solutions Eureka provides.
https://medium.com/javarevisited/how-to-use-spring-cloud-gateway-to-dynamically-discover-microservices-194c0c3869c6
This comes to shine when you deploy services with horizontal auto scalability (such as kubernetes). At certain moments, based on the equation you configure (recourse usage, client connections, etc.) the orchestration can and will scale your services (e.g. mydemoservice). It can scale your service instance up to:
the configured max number of instances
until the service usage limit is reached
either way, all of them will have different IP addresses.
Eureka is a discovery/registry service which provides to your gateway information of which cluster/load balancer (IP address) will it pass the request based on Round Robins and such algorithms. The gateway needs to configure all of the services but it will use aliases provided by the Eureka server depicted as such:
https://github.com/rubykv/code-examples/blob/master/gateway/src/main/resources/application.yml
In this example, we see the gateways are configured for services: subject, student, and eureka.
Eureka has a dashboard:
https://miro.medium.com/max/1400/1*KgT1_hnuXvX6xldyiJJuaQ.png
and will display all eureka clients. To display a service as a eureka client one must implement:
https://github.com/rubykv/code-examples/blob/master/student/pom.xml (netflix eureka and open feign)
annotate application with #EnableFeignClients https://github.com/rubykv/code-examples/blob/master/student/src/main/java/com/example/demo/StudentApplication.java
There are lots of tutorials and articles on medium, I hope this helps for your further investigation.
I am following a course about microservice architecture using spring, covering netflix's eureka.
The clientui serves webpages and calls the 3 microservices when needed.
The config-server serves configuration for the 3 microservices from a git repo.
Of course the 3 microservices are registered as eureka clients.
My questions are :
should the config server and also be registered as an eureka client, or is there no benefit in doing so?
what about the clientui (which is the web entry point) ? can it be registered as an eureka client in order to benefit from load balancing system and if yes, how then should the app be accessed by clients?
About your first question :- Yes you can register config server as eureka client. Benefit of this will be that in terms of service management it will give you a single point of visibility of all the services. Also later if you try to expand your app in terms of distributed architecture and say you implement an api gateway like zuul, it will be easy for you to setup a fallback config server say if one config server goes down requests can be routed to other config server and so on.
About your second question :- Honestly speaking , I didn't understand it very well in first place. I have never seen any ui service registering to eureka so I am not very sure about this. Still if you have more doubts about it , you can let me know like is it a angular ui or is it a http based client or what.
So I have a very small micro service architecture built using Eureka service discovery. The problem I am facing right now is that I only want my service endpoints to accept request from my api gateway, as it is right now you can just make a request straight to the service and hit that service endpoint. Is this a problem Kubernetes would solve? Or Is there a more practical way of doing this?
You should be using network policies to control the traffic between the services.
In kubernetes the services you want to expose internally use service type ClusterIP. This is default anyway which means services are accessible within cluster only. your api gateway is exposed as load balancer service type which then takes traffic from external world and talks to services internally. Depending on your cloud provider you can use firewall in front of load balancer since you can compromise security by simply exposing load balancer. e.g. azure kubernetes you could use application gateway. You can also replace the api gateway with ingress controller. it's very powerful reverse proxy controller which you can expose directly to traffic and that would talk to your services internally.
You really need to understand concepts so i would recommend following links
https://kubernetes.io/docs/concepts/services-networking/service/
https://blog.getambassador.io/kubernetes-ingress-nodeport-load-balancers-and-ingress-controllers-6e29f1c44f2d
i have created two java spring-boot micro services they are
1) producer
2) consumer
and i have used spring eureka server for service registration and discovery . it worked fine . then what is the use of Netflix Zuul.
Let's suppose you have 20 services to which user can interact to, and of course we are not going to expose each and every services publicly because that will be madness (because all services will have different ports and context), so the best approach will be to use an API gateway which will act as single entry point access to our application (developed in micro service pattern) and that is where Zuul comes into picture. Zuul act as a reverse proxy to all your micro-services running behind it and is capable of following
Authentication
Dynamic Routing
Service Migration
Load Shedding
Security
Static Response handling
Active/Active traffic management
You can go through documentation here
If you have enough experience in the domain, you could look at zuul as an API gateway like Apigee. It is very feature rich and touches up on a lot of different concerns like routing, monitoring and most importantly, security. And eureka as a service discovery platform that allows you to load balance (in Linux terms the nginx or haproxy) and fail over between your service instances.
Typically the backend services that perform the server side business operations (i.e. core) are not exposed publicly due to many reasons. They are shielded by some Gateway layer that also serves as reverse-proxy. Netflix Zuul serves as this gateway layer which easily gives you the capabilities as mentioned by #Apollo and here
I am new to spring cloud and going through some examples and material available online to make myself comfortable. However, while reading about ZUUL, some sites configured the routes in ZUUL's application.yml and some other sites mentioned that the requests will be forwarded to the respective microservice and no need to explicitly configure the routes. I was bit confused. For ex, in the below scenario what is the approach, to configure routes or to let zuul route automatically?
Let's say i have few micro services running and all of them along with ZUUL are registered to Eureka.
I have a front end which is running on a different port on the same server and needs to interact with the above micro services.
I also have few other applications (Running entirely on different servers) which need to interact with the above micro services for fetching the data.
TIA..
Did you use Zuul (which know microservices address through Eureka) to forward request between your micro-services ? if it's the case, you are using Server-Side Load Balancing pattern.
If you use a discovery service (Eureka in your case), i think the best approach it's to use Client-Side load balancing pattern for all inter-services requests (inside your system). (you can use Ribbon or RestTemplate for that).
You can use Zuul as a unified front door to your system, which allows a browser, mobile app or other user interface to consume services from multiple hosts without managing cross-origin resource sharing (CORS) and authentication for each one.
For example : a client (mobile app) request for all picture comments. The client dont need to know the Comments-service address. Only proxy address needed and Zuul will forward the request to the right service. You can do this in application.yml/.properties by
zuul.routes.comments.path=/comments/**
zuul.routes.comments.service-id=comments
The request will be GET www.myproxy.mycompany.com/comments. Dont forget the service name in your application.yml/.properties is very important (spring.application.name). It's the service-id in Zuul routes (which the same identifier in Eureka).
For some reason, your system need to request external services (as you mentionned in the 3th note). In this case, your external services are not a discovery client, Zuul can't look for the service-id from Eureka. you use routes as
zuul.routes.currencyprovider.path=/currencies/**
zuul.routes.currencyprovider.url=https://currencies.net/
with this route, all /currencies/** requests from your services THROUGH Zuul will be done.
with this approach you have one door for all your system. This is API Gateway pattern.
Sometimes your system need to aggregate multiple results from different services to response to client request. You can do this in Proxy (Zuul in your case).