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FeignRetryableException When Service is down

I am using OpenFeign client in Spring Boot without using Ribbon or Eureka. I created a custom error decoder which handles response errors as intended but connection refused errors seem to bypass my custom decoder.
P.S. When my remote service is up, I can make requests and receive responses.
I am new to Java and Spring and I am wondering if I need to wrap all my calls with try catch, or adding my custom error handler should be catching the error since it seems cleaner to handle all errors in one place
public class FeignErrorDecoder implements ErrorDecoder {
private final ErrorDecoder defaultErrorDecoder = new Default();
#Override
public Exception decode(String methodKey, Response response) {
if (response.status() >= 400 && response.status() <= 499) {
//handle with custom exception
}
if (response.status() >=500) {
//handle with custom exception
}
return defaultErrorDecoder.decode(methodKey, response);
}
}
#Configuration
public class FeignConfig {
//other beans here
#Bean
public ErrorDecoder feignErrorDecoder() {
return new FeignErrorDecoder();
}
}

How to check HTTP request header for certain endpoints in Spring Framework

I have a simple Spring Boot REST service for the IFTTT platform. Each authorized request will contain a header IFTTT-Service-Key with my account's service key and I will use that to either process the request or return a 401 (Unauthorized). However, I only want to do this for select endpoints -- and specifically not for ANY of the Spring actuator endpoints.
I have looked into Spring Security, using filters, using HandlerInterceptors, but none seem to fit what I am trying to do exactly. Spring security seems to come with a lot of extra stuff (especially the default user login), filters don't really seem to match the use case, and the handler interceptor works fine but I would have to code logic in to watch specific URLs and ignore others.
What is the best way to achieve what I am trying to do?
For reference, this is the code I have now:
public class ServiceKeyValidator implements HandlerInterceptor {
private final String myIftttServiceKey;
public ServiceKeyValidator(#Value("${ifttt.service-key}") String myIftttServiceKey) {
this.myIftttServiceKey = myIftttServiceKey;
}
#Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
// TODO will have to put logic in to skip this when actuator endpoints are added
String serviceKeyHeader = request.getHeader("IFTTT-Service-Key");
if (!myIftttServiceKey.equals(serviceKeyHeader)) {
var error = new Error("Incorrect value for IFTTT-Service-Key");
var errorResponse = new ErrorResponse(Collections.singletonList(error));
throw new UnauthorizedException(errorResponse);
}
return HandlerInterceptor.super.preHandle(request, response, handler);
}
}

You need to add filtering for the required endpoints in the place where you register your HandlerInterceptor.
For example:
#EnableWebMvc
#Configuration
public class AppConfig implements WebMvcConfigurer {
#Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(
new ServiceKeyValidator())
.addPathPatterns("/ifttt/**")
.excludePathPatterns("/actuator/**");
}
}
You can use different URLs path matchers to filter which URL endpoints must be handled by your interceptor and which are not. As the method addPathPatterns returns InterceptorRegistration object that configures this.

How to implement "load balancer" using spring boot?

Depends on request body content I need to redirect http requests to URL_1 or URL_2.
I started controller implementation:
#RestController
public class RouteController {
#Autowired
private RestTemplate restTemplate;
#RequestMapping(value = "/**")
public HttpServletResponse route(HttpServletRequest request) {
String body = IOUtils.toString(request.getReader());
if(isFirstServer(body)) {
//send request to URL_1 and get response
} else {
//send request to URL_2 and get response
}
}
}
Request might be GET or POST ot PUT or PATCH etc.
Could you help me to write that code?

I've asked a somehow similar question a while ago. Plea see Server side redirect for REST call for more context.
The best way (to my current understanding) you could achieve this is by manually invoking the desired endpoints from your initial endpoint.
#RestController
public class RouteController {
#Value("${firstUrl}")
private String firstUrl;
#Value("${secondUrl}")
private String secondUrl;
#Autowired
private RestTemplate restTemplate;
#RequestMapping(value = "/**")
public void route(HttpServletRequest request) {
String body = IOUtils.toString(request.getReader());
if(isFirstServer(body)) {
restTemplate.exchange(firstUrl,
getHttpMethod(request),
getHttpEntity(request),
getResponseClass(request),
getParams(params));
} else {
restTemplate.exchange(secondUrl,
getHttpMethod(request),
getHttpEntity(request),
getResponseClass(request),
getParams(params))
}
}
}
Example implementation for getHttpMethod:
public HttpMethod getHttpMethod(HttpServletRequest request) {
return HttpMethod.valueOf(request.getMethod());
}
Similar implementations for getHttpEntity, getResponseClass and getParams. They are used for converting the data from the HttpServletRequest request to the types required by the exchange method.
There seem to be a lot of better ways of doing this for a Spring MVC app, but I guess that it does not apply to your context.
Another way you could achieve this would be defining your own REST client and adding the routing logic there.

Micronaut security fails to "secure"

I have a simple Micronaut- based "hello world" service that has a simple security built in (for the sake of testing and illustrating the Micronaut security). The controller code in the service that implements the hello service is provided below:
#Controller("/hello")
public class HelloController
{
public HelloController()
{
// Might put some stuff in in the future
}
#Get("/")
#Produces(MediaType.TEXT_PLAIN)
public String index()
{
return("Hello to the World of Micronaut!!!");
}
}
In order to test the security mechanism, I have followed the Micronaut tutorial instructions and created a security service class:
#Singleton
public class SecurityService
{
public SecurityService()
{
// Might put in some stuff in the future
}
Flowable<Boolean> checkAuthorization(HttpRequest<?> theReq)
{
Flowable<Boolean> flow = Flowable.fromCallable(()->{
System.out.println("Security Engaged!");
return(false); <== The tutorial says return true
}).subscribeOn(Schedulers.io());
return(flow);
}
}
It should be noted that, in a departure from the tutorial, the flowable.fromCallable() lambda returns false. In the tutorial, it returns true. I had assumed that a security check would fail if a false is returned, and that a failure would cause the hello service to fail to respond.
According to the tutorials, in ordeer to begin using the Security object, it is necessary to have a filter. The filter I created is shown below:
#Filter("/**")
public class HelloFilter implements HttpServerFilter
{
private final SecurityService secService;
public HelloFilter(SecurityService aSec)
{
System.out.println("Filter Created!");
secService = aSec;
}
#Override
public Publisher<MutableHttpResponse<?>> doFilter(HttpRequest<?> theReq, ServerFilterChain theChain)
{
System.out.println("Filtering!");
Publisher<MutableHttpResponse<?>> resp = secService.checkAuthorization(theReq)
.doOnNext(res->{
System.out.println("Responding!");
});
return(resp);
}
}
The problem occurs when I run the microservice and access the Helo world URL. (http://localhost:8080/hello) I cannot cause the access to the service to fail. The filter catches all requests, and the security object is engaged, but it does not seem to prevent access to the hello service. I do not know what it takes to make the access fail.
Can someone help on this matter? Thank you.

You need to change request in your filter when you no have access to resource or process request as usual. Your HelloFilter looks like this:
#Override
public Publisher<MutableHttpResponse<?>> doFilter(HttpRequest<?> theReq, ServerFilterChain theChain) {
System.out.println("Filtering!");
Publisher<MutableHttpResponse<?>> resp = secService.checkAuthorization(theReq)
.switchMap((authResult) -> { // authResult - is you result from SecurityService
if (!authResult) {
return Publishers.just(HttpResponse.status(HttpStatus.FORBIDDEN)); // reject request
} else {
return theChain.proceed(theReq); // process request as usual
}
})
.doOnNext(res -> {
System.out.println("Responding!");
});
return (resp);
}
And in the last - micronaut has security module with SecurityFilter, you can use #Secured annotations or write access rules in configuration files more examples in the doc

Spring Cloud Feign Interceptor

I have created a ClientHttpRequestInterceptor that I use to intercept all outgoing RestTemplate requests and responses. I would like to add the interceptor to all outgoing Feign requests/responses. Is there a way to do this?
I know that there is a feign.RequestInterceptor but with this I can only intercept the request and not the response.
There is a class FeignConfiguration that I found in Github that has the ability to add interceptors but I don't know in which maven dependency version it is.

A practical example of how to intercept the response in a Spring Cloud OpenFeign.
Create a custom Client by extending Client.Default as shown below:
public class CustomFeignClient extends Client.Default {
public CustomFeignClient(SSLSocketFactory sslContextFactory, HostnameVerifier hostnameVerifier) {
super(sslContextFactory, hostnameVerifier);
}
#Override
public Response execute(Request request, Request.Options options) throws IOException {
Response response = super.execute(request, options);
InputStream bodyStream = response.body().asInputStream();
String responseBody = StreamUtils.copyToString(bodyStream, StandardCharsets.UTF_8);
//TODO do whatever you want with the responseBody - parse and modify it
return response.toBuilder().body(responseBody, StandardCharsets.UTF_8).build();
}
}
Then use the custom Client in a configuration class:
public class FeignClientConfig {
public FeignClientConfig() { }
#Bean
public Client client() {
return new CustomFeignClient(null, null);
}
}
Finally, use the configuration class in a FeignClient:
#FeignClient(name = "api-client", url = "${api.base-url}", configuration = FeignClientConfig.class)
public interface ApiClient {
}
Good luck

If you want to use feign from spring cloud, use org.springframework.cloud:spring-cloud-starter-feign as your dependency coordinates. Currently the only way to modify the response is to implement your own feign.Client.