My application is simple 3-tier Spring Boot rest web-service with usual synchronous endpoints.
But since the period of getting response from downstream system where my service sends requests is quite long (kind of 60 seconds), I need to add support of asynchronous REST calls to my service to save upstream systems from a response awaiting. In other words, if a response to a downstream system is going to take more than 60 seconds (timeout), then the upstream system break the connection with my service and keeps its doing...
But when the response come, my service using "reply-to" header from the upstream system will send the response to the upstream system.
All the things above are kind of call back or webhook.
But I didn't find any examples of implementation.
How to implement this mechanism?
How can I find more information?
Does Spring Boot have something to implement it out-of-box?
Thank you for attention!
You can use the #Async annotation from Spring. You will also need to enable in your application this by setting #EnableAsync.
An important note is that your method with the #Async annotation should be on a different class from where it is being called. This will let the Spring proxy intercept the call and effectively do it asynchronous.
Please find here the official tutorial.
Related
I am working on the micro-service developed using Spring Boot . I have implemented following layers:
Controller layer: Invoked when user sends API request
Service layer: Processes the request. Either sends request to third-part service or sends request to database
Repository layer: Used to interact with the
database
.
Methods in all of above layers returns the CompletableFuture. I have following questions related to this setup:
Is it good practice to return Completable future from all methods across all layers?
Is it always recommended to use #Async annotation when using CompletableFuture? what happens when I use default fork-join pool to process the requests?
How can I configure the threads for above methods? Will it be a good idea to configure the thread pool per layer? what are other configurations I can consider here?
Which metrics I should focus while optimizing performance for this micro-service?
If the work your application is doing can be done on the request thread without too much latency, I would recommend it. You can always move to an async model if you find that your web server is running out of worker threads.
The #Async annotation is basically helping with scheduling. If you can, use it - it can keep the code free of the references to the thread pool on which the work will be scheduled. As for what thread actually does your async work, that's really up to you. If you can, use your own pool. That will make sure you can add instrumentation and expose configuration options that you may need once your service is running.
Technically you will have two pools in play. One that Spring will use to consume the result of your future, and another that you will use to do the async work. If I recall correctly, Spring Boot will configure its pool if you don't already have one, and will log a warning if you didn't explicitly configure one. As for your worker threads, start simple. Consider using Spring's ThreadPoolTaskExecutor.
Regarding which metrics to monitor, start first by choosing how you will monitor. Using something like Spring Sleuth coupled with Spring Actuator will give you a lot of information out of the box. There are a lot of services that can collect all the metrics actuator generates into time-based databases that you can then use to analyze performance and get some ideas on what to tweak.
One final recommendation is that Spring's Web Flux is designed from the start to be async. It has a learning curve for sure since reactive code is very different from the usual MVC stuff. However, that framework is also thinking about all the questions you are asking so it might be better suited for your application, specially if you want to make everything async by default.
I have an spring boot application that pulls message from an cloud message queue and put it back to a cloud db. I realize that my program is single thread(I am not using request mapping, just pull,process,put to db). I want Spring handle concurrency things. So can I make a dispatcher function, which calls controller in the application with #RequestMapping?
#RestController
#RequestMapping("/test")
public class GatewayController {
#RequestMapping("/service")
public void InvokeService(...) {...}
}
I need mutithread to call other service for response, which I don't want it to block others. If I recieve 10 messages, I want it to call /test/service... which have 10 threads processing them.
My question is:
Will Spring make the controller multithread?
How to call its own controller? Send request to the url? (I don't need response from controller, just let controller call a service to put response in a db on could)
RequestMapping is MVC thing - intended to issue http requests. And yes, it uses tomcat under the hood.
If you'll inject RestController into your class it won't issue any HTTP requests, you'll only call the controller as a regular bean. If you consume messages in one thread, it won't become multithreaded to answer your first question.
You can, of course, create HTTP request but frankly it's just wrong. So don't do it. This answers your second question to some extent :)
Now, there is nothing wrong conceptually if your microservice acts as a consumer and producer and deals with queues, not all microservices have to be accessible via HTTP.
In order to work in a multi threaded environment:
Check whether you can consume messages in a multi-threaded manner. Maybe the client of your "cloud message queue" offers multi-threaded configuration (thread pool or something).
If it's not possible, create a thread pool executor by yourself and upon each message submit the processing task to this thread pool. This will make the processing logic multithreaded with a parallelism level confined by the thread pool size and thread pool configurations.
I am a newbie in reactive programming. I did some research but could not find any satisfactory answer. My requirement is to correlate request and response using reactive programming (using spring boot) in a asynchronous set up.
In detail - My organization application architecture has front end, middleware and legacy backend. Front end makes a call to middleware which talks to legacy backend over MQ. At the moment call to backend is synchronous over MQ. We are trying to uplift the experience by making the backend call asynchronous. So in this setup front end will make a call over http/rest to middleware which puts the message over MQ to be consumed by legacy systems. Once legacy system is done with processing, it will put the message back on to another queue which will in turn be picked up by middleware again and send back to front end systems. In this set up my job is to correlate the request/response in the middle layer. We have one option to use DB but I want to see whether it is possible to use reactive java for the same.
Any help in this regard would be appreciated.
There are a lot of tutorials and articles (including official site) promoting spring boot as a good tool for building microservices.
Let's say we have some rest api endpoint (User profile) which aggregates data from multiple services (User service, Stat service, Friends service).
To achieve this, user profile endpoint makes 3 http calls to those services.
But in Spring, requests are blocking and as I see, the server will quickly run out of available resources (threads) to serve request in such system.
So to me, it as quite inefficient way to build such systems (compared to non-blocking frameworks, like play! framework or node.js)
Do I miss something?
P.S.: I do not mean here spring 5 with its new webflux framework.
No one prevents you from building an asynchronous microservice architecture with Spring Boot :).
Something along these lines:
Instead of one service calling another synchronously, a service can put events to a queue (e.g. RabbitMQ). The events are delivered to services that subscribe to those events.
Using RabbitMQ and its "exchange" concept, the event producing service doesn't even need to the consumers of its events.
A blog post detailing this with Spring Boot code can be found here: https://reflectoring.io/event-messaging-with-spring-boot-and-rabbitmq/
This is not a limitation of Spring rather it is more to do with the Application Architecture.
For instance, the scenario that you have is commonly solved using Aggregate Design Pattern
While this solution is quite prevalent,it has the limitation of being synchronous, and thus blocking. Asynchronous behaviour in such scenarios should be implemented in an application specific way.
Having said that if you have to call other services in order to be able to serve a response to a request from a client(outside), this is typically an architectural problem. It really doesn’t matter if you are using HTTP or asynchronous message passing (with a request-reply pattern), the overall response time for the outside client will be bad
Also, I have seen quite a few applications which uses synchronous REST calls for external clients, but when communication is needed between internal MicroServices, it should always be asynchronous. You can read an interesting paper on this topic here MicroServices Messaging Patterns
I have requirement something like this:
once the request is received by my service, i need to send it 2-3 third party servers at a time and get the response from all server and return the response.
How can I achieve that?.
My thought : I can create separate threads for different servers and send the request to all servers parallely, but here the issue is, how I will come to know the threads are finished and consolidate the response from all servers and return to caller.
Is there any other way to do in spring boot(micro service)?.
You can leverage asyn feature supported by Spring Framework. Let's see the folllowing example which issue multiple calls in Async style from Spring's official guides:Async Method
Another possible solution for internal communications between Microserives is to use the message queue.
You didn't specify what type of services are you consuming. If they are HTTP, you may want to use some Enterprise Integrations abstractions (most popular are Spring Integration and Apache Camel).
If you don't want to introduce message bus solution into your microservice, you may want to take a look at AsyncRestTemplate