Rest Template Exchange not working inside docker container but working outside

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I have the following java code:

  ResponseEntity<FAQResolver.FAQResponse[]> responseEntity = restTemplate.exchange(SUGGESTION_URL, HttpMethod.POST,
                    requestEntity, FAQResolver.FAQResponse[].class);

Now if I try to run the java application inside docker through docker-compose, I get

org.springframework.web.client.ResourceAccessException: I/O error on POST request for "http://localhost:8888/search": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
searchbot_1      |
searchbot_1      | org.springframework.web.client.ResourceAccessException: I/O error on POST request for "http://localhost:8888/search": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
searchbot_1      |      at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:744)
searchbot_1      |      at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:670)
searchbot_1      |      at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:579)
searchbot_1      |      at com.globant.fluentlab.searchbot.search.api.SearchController.suggest(SearchController.java:106)
searchbot_1      |      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
searchbot_1      |      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
searchbot_1      |      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
searchbot_1      |      at java.lang.reflect.Method.invoke(Method.java:498)
searchbot_1      |      at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
searchbot_1      |      at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
searchbot_1      |      at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
searchbot_1      |      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892)
searchbot_1      |      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797)
searchbot_1      |      at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
searchbot_1      |      at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1039)
searchbot_1      |      at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
searchbot_1      |      at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
searchbot_1      |      at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897)
searchbot_1      |      at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
searchbot_1      |      at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
searchbot_1      |      at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
searchbot_1      |      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
searchbot_1      |      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
searchbot_1      |      at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
searchbot_1      |      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
searchbot_1      |      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
searchbot_1      |      at org.springframework.boot.actuate.web.trace.servlet.HttpTraceFilter.doFilterInternal(HttpTraceFilter.java:90)
searchbot_1      |      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
searchbot_1      |      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

However if I stop the java application running in docker an use Intellij's debu g mode I get: Same code works locally without docker

To be quite honest I don't know why. I was wondering if docker-compose is restricting communication between containers or something. Any help will be much appreciated.

resttemplate spring-boot docker java
4 Answers
I/O error on POST request for "http://localhost:8888/search": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)

This means that restTemplate can not reach SUGGESTION_URL

Is SUGGESTION_URL already available under an other service?

If yes then are both of those services (your spring boot app and SUGGESTION_URL) defined in the same docker-compose as services? If they are under the same docker-compose then they shouldn't have any problem communicating. In that case I would check the SUGGESTION_URL to be sure it is correct , port numb , ip ...etc

user_72378840

Well, my boss just came back from holidays and answered this. Basically when you have several services running using docker-compose they can't find each other using localhost. Instead you must use the name of the service you want to connect to. This means SUGGESTION_URL = http://faqserver:8888/search. That did the trick for me. Hope this helps anyone if they get stuck like me.

user_26468360

this happens due to the fact that you are using localhost to reach out the service. I provide you an example below:

version: '3.7'

services:

  currency-exchange:
    image: chaklader/mmv2-currency-exchange-service:0.0.1-SNAPSHOT
    mem_limit: 700m
    ports:
      - "8000:8000"
    networks:
      - currency-network  
    depends_on:
      - naming-server 
    environment:
      EUREKA.CLIENT.SERVICEURL.DEFAULTZONE: http://naming-server:8761/eureka  
  
  naming-server:
    image: chaklader/mmv2-naming-server:0.0.1-SNAPSHOT
    mem_limit: 700m
    ports:
      - "8761:8761"
    networks:
      - currency-network

If you are running locally, the Eureka will be available in localhost, but, in the container environments, you will need to reference like below:

http://naming-server:8761/eureka
user_27461100

Or you can reference the localhost of the machine, which runs the docker-compose by using host.docker.internal instead.

So your restTemplate call would look like this instead:

restTemplate.exchange(
        SUGGESTION_URL.replace("localhost", "host.docker.internal"), 
        HttpMethod.POST,
        requestEntity,
        FAQResolver.FAQResponse[].class);
user_70829560
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