If I have multiple Spring Boot embedded tomcat containers and each can have service endpoints like
http://localhost:8080/employeeSelfService/getDetails
http://localhost:8081/employeeSelfService/getDetails
How can do load balancing using 2 micro services such that clients can hit any of the URL's mentioned based on some load balancing startegy
One option thats come to my mind is to use NetFlix Curator (or) have a apache webserver acting as reverse proxy but with apache, when you create new instances of your services, you will have have an entry of that service as a member in httpd.conf
Does Spring Boot provides any service discovery and load balancing mechanism ?
Spring Boot does not provide this feature, as it is already usually provided by a reverse proxy such as apache/nginx running in front of the Spring Boot server.
See here for an example here how the commercial version of nginx provides the functionality of dynamically scaling and reducing the upstream nodes.
So in this case it's for the dynamic instance, in this case the Spring Boot process to signal it's presence/unregister itself to the upstream server at initialization/shutdown.
See here how to do so in the case of nginx, this procedure will be different from server to server.
Arguably it's not really an application's role to manage its own load-balancing, and Spring Boot focuses on the implementation of an application (or service, equivalently). We have been thinking about whether we could provide features in Spring (Boot or otherwise) to make it easy to write your own load-balancer, or service registry app, but even then I don't think that was what the question was really about (or was it?).
If I interpret the question, and the example use case, literally, I would say that the most natural answer is an out-of-the-box reverse proxy solution (as the other answers pointed out). I also note that such a reverse proxy is an essential and natural part of a PaaS solution, so if you need it to "just work" and don't want to know about the details, PaaS would be a natural path (e.g. see cloudfoundry as an example of such a solution that I happen to have worked on).
Indeed Spring Boot has not inherit support for load-balancing. Just to add to the list of available solutions for load-balancing, here are the instructions to configure an Apache for load-balancing.
Related
Was wondering the recommended way of starting a spring boot app if the Spring cloud config server is temporarily down or unavailable. What would be the approach? I know of the retry configurations, but I am wondering if there is a way to have a 'replica' config server and use that as a failover (or something along those lines).
Sure, why not?
After all, spring-cloud-config server exposes rest API and all the interaction with spring boot microservices is done over HTTP.
From this point of view, you can scale out the spring cloud config server by providing more than one instance of it all are up-and-running and mapping them to one virtual IP.
If you're running in some kind of orchestrated environment (like kubernetes) it is a very easy thing to do.
I am building a middle tier which will consume information from multiple downstream systems. The ask is to talk to them over 1 way SSL. I looked up samples but this concept is a bit if a mystery to me. Please help.
The question is too vague IMHO, I'll try to provide general insights
The answer may vary depending on the actual requirements in your organization security department and your actual spring boot configuration.
Spring Boot is a Java framework that usually allows the deployment architecture with an embedded tomcat, jetty or undertow servers that serve Http endpoints exposed by Spring MVC or without an embedded server at all (usually for legacy deployments)
If you in a "legacy" mode (build a WAR) - then HTTPs configuration should be done on the actual server and not in spring boot application.
If you use an embedded server, then the actual technical solution can actually depend on the server you use underneath, at least to some extent.
Indeed like Steffen Ullrich has stated in the comment section, there are many examples of doing this.
For example, take a look at This one
If you want to redirect HTTP requests to HTTPs you should configure your server to do so, and this solution is Tomcat specific.
Another thing to consider is whether you want to use SSL at the level of spring boot at all. Maybe you're running under the gateway / some kind of proxy. In this case, it can make sense to use https for accessing the proxy from outside, but from a proxy to java application you could use HTTP.
I know I'm just speculating about this solution, I've just decided to mention it because in my experience there are many organizations that work like this.
In addition, since spring boot is used for microservice development, the chances are that you have many spring boot artifacts that somehow "talk" to each other, so maybe running HTTPs between them is redundant.
I am learning building microservices using spring boot, Spring Cloud(netflix OSS Components). I have used netflix Eureka for service discovery, zuul for api gateway, ribbon, feign while running in my local machine.
Netflix eureka, zuul, ribbon, feign spring cloud config are not useful when we deploy to PCF?(if yes what are the alternatives available in pcf and how to configure them?)
As who are building microservices follows CI/CD approach, how developer verify working of their micro services before pushing code as we don't use eureka, zuul,ribbon,feign in production pcf. (how to simulate pcf environment in developer machine?).
I'd suggest to read below content before implementing if you have any doubt regarding usage of Eureka and Zuul, you will get all answers yourself.
https://github.com/Netflix/eureka/wiki/Eureka-at-a-glance
https://github.com/Netflix/zuul/wiki
As who are building microservices follows CI/CD approach, how developer verify working of their micro services before pushing code as we don't use eureka, zuul,ribbon,feign in production pcf.
Answer to this question is: You must be aware of JUnit test cases, so you can run you test cases using deployment pipelines to make sure all your functionalities are working as expected or you can use Test Automation for the same.
(how to simulate pcf environment in developer machine?).
Answer to this one:
You can use eclipse plugin you are using eclipse/STS IDE. Or you can connect all PCF services from you local machine using CloudFactory
#Bean
public Cloud cloud() {
return new CloudFactory().getCloud();
}
https://docs.pivotal.io/pivotalcf/2-1/buildpacks/java/sts.html
Here are some thoughts:
Eureka Service discovery: in my opinion this is not strictly necessary when running on PCF. When you push an app on PCF usually a route is assigned to your app, and you can use this Route as a poor man's service discovery. Eureka would allow you to use client-side load balancing in the case of container-to-container networking, but usually you wouldn't need this.
Zuul: Can be very useful also on CloudFoundry in case you are doing things like writing frontend-for-backend services, providing frontends for different devices (mobiles, desktops, i-pads) that use the same backend services. Might also be useful for an authentication/authorization layer or rate-limiting. One native CloudFoundry alternative would be to use route-services for tasks such as rate limiting, authentication/authorization.
spring-cloud-config: makes sense if you want your configuration to be under version control for different environments. This is useful no matter if you are running on CloudFoundry or not. I don't know of any alternatives on plain CloudFoundry.
spring-cloud-feign: makes sense if you want use annotations such as #RequestMapping with your Feign client interfaces. This is independent on if you are running on CloudFoundry or not. AFAIK there are no alternatives for this in case you want to use Spring MVC annotations with Feign.
ribbon: makes sense if you want to use client side load balancing as opposed to let the CloudFoundry router to do the load balancing for you.
How developers can check locally if this works for them:
In general, I don't believe developers should need to check locally if their app is working fine together with zuul, cloud-config-service, and eureka.
They could check this in a dev or test space or environment though.
If they really want to check this on their local machine, they could download PCFDev and run these infrastructure components there.
Hope this helps.
I am trying to build a simple application with microservices architecture.
Below are the details about 3 microservices I have created.
1] Customer.
database: mongodb
server : embeded tomcat server.
port : 8081
2] vendor.
database: mongodb
server : embeded tomcat server.
port : 8082
3] product.
database: mongodb
server : embeded tomcat server.
port : 8083
All the 3 micros runs on an embeded tomcat server.
Now I want to create a common gateway for all these micros [API gateway].
which help me to route my request based on the request I get for example:-
for example if I get a request of http://hostname:port_of_gateway/customer.
on reading this I need to route the request tom my customer micro and fetch its response and send it back to client.
Which of the spring tool I can use to achieve this?
Because your requirements are quite simple you can implement such a gateway by yourself. Here's an example.
But if you really want to use some Spring solution you can try to use Spring Cloud Netflix which is a part of Spring Cloud umbrella project. It includes router and filter features which in turn based on Netflix Zuul gateway service.
Note that this is not a complete standalone application but a library. Therefore you still should create another microservice that would act as API gateway in your application. To make it a gateway you should just add #EnableZuulProxy annotation to the same class that has #SrpingBootApplication annotation. You can find a very good example here.
Please also note that you should somehow inform the gateway about your microservices' addresses for redirection. It can be done in two general ways:
By statically defining the addresses in gateway microservice's configuration;
By applying service discovery pattern in conjunction with e.g. Netflix Eureka service registry.
The 1st approach is easy and straightforward but is not very well for large number of microservices and/or when microservices' locations can change dynamically (e.g. due to auto-scaling).
The 2nd approach requires additional component - service registry - and needs modification of other microservices (to let them register themselves in the registry). This is quite more complicated approach but is the only possible in case of complex architecture. Simple yet expressive example can be found in the same article.
UPDATE (January'19)
As of December 2018 the Spring Cloud team announced that almost all Netflix components in Spring Cloud (except Eureka) entered maintenance mode. It means that for the next year they won't receive any feature updates (only bugs and security fixes).
There are replacements for all the affected components, including Netflix Zuul aforementioned above. So please consider using Spring Cloud Gateway instead of it in new projects.
Is Spring cloud config server an example of sidecar application for microservices?
Do you mean if the Spring Cloud Config Server itself is what the Spring Cloud documentation labels as Sidecar? Then no, as far as I know it is just a plain, regular Spring Boot app.
A Sidecar as referred to in Polyglot support with Sidecar is a Spring Boot application that acts as a bridge between your service infrastructure and a service that is not written in a JVM language. Apps written in Python, Go, Ruby, C#, NodeJS, Erlang or really any other language that can bind something to a port come to mind.
The benefits of the Sidecar are, that your Non-JVM apps
service discovery become automatically discoverable through Eureka, which means that JVM services can resolve the host:port/<service-id> of the Non-JVM apps as well as the other way around,
monitoring are monitorable through the same health-endpoints-infrastructure that is available in Spring Boot (Actuator), i.e. by manually providing the health endpoint in the Non-JVM app Eureka knows when the Non-JVM service is down
routing/proxying query the services by either manually looking up their hosts/ports or proxying these requests through Zuul, which in turn resolves their current addresses through Eureka
balancing be load balanced by Ribbon and
configuration may consume configuration properties provided via Spring Cloud Config.
I hope this answer addresses your question, if not (or someone finds it to be inaccurate or misleading) just let me know and I delete it to make room for something more suitable. ;-)