I am implementing an elastic pool for my spring boot project also I am using spring boot 2.1.4 and elastic search 7.3.0. I am stuck at this. When any API trying to query it gives `java.net.ConnectException: Connection refused`. I want to use configuration with `customizeHttpClient` with a setting thread count. So It makes only one connection when application will start and querying to the database using that one connection only till bean will destroy.  

I tried with this **Elastic Configuration**: 

```java
    import java.io.IOException;

    import org.apache.http.HttpHost;
    import org.apache.http.auth.AuthScope;
    import org.apache.http.auth.UsernamePasswordCredentials;
    import org.apache.http.client.CredentialsProvider;
    import org.apache.http.impl.client.BasicCredentialsProvider;
    import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
    import org.apache.http.impl.nio.reactor.IOReactorConfig;
    import org.elasticsearch.client.RestClient;
    import org.elasticsearch.client.RestClientBuilder;
    import org.elasticsearch.client.RestClientBuilder.HttpClientConfigCallback;
    import org.elasticsearch.client.RestHighLevelClient;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.beans.factory.config.ConfigurableBeanFactory;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Scope;
    import org.springframework.stereotype.Component;

    @Component
    public class ElasticConfig{

        public static String host;

        private static String port;

        private static String protocol;

        private static String username;

        private static String password;

        private RestHighLevelClient client;

        @Value("${dselastic.host}")
        public void setHost(String value) {
            host = value;
        }

        @Value("${dselastic.port}")
        public void setPort(String value) {
            port = value;
        }

        @Value("${dselastic.protocol}")
        public void setProtocol(String value) {
            protocol = value;
        }

        @Value("${dselastic.username}")
        public void setUsername(String value) {
            username = value;
        }

        @Value("${dselastic.password}")
        public void setPassword(String value) {
            password = value;
        }

        @Bean(destroyMethod = "cleanUp")
        @Scope(value = ConfigurableBeanFactory.SCOPE_SINGLETON)
        public void prepareConnection() {
            RestClientBuilder restBuilder = RestClient.builder(new HttpHost(host, Integer.valueOf(port), protocol));
            if (username != null & password != null) {
                final CredentialsProvider creadential = new BasicCredentialsProvider();
                creadential.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(username, password));
                restBuilder.setHttpClientConfigCallback(new HttpClientConfigCallback() {
                    @Override
                    public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {

                        return httpClientBuilder.setDefaultCredentialsProvider(creadential)
                                .setDefaultIOReactorConfig(IOReactorConfig.custom().setIoThreadCount(1).build());
                    }
                });
                restBuilder.setRequestConfigCallback(requestConfigBuilder -> 
                requestConfigBuilder.setConnectTimeout(10000) // time until a connection with the server is established.
                        .setSocketTimeout(60000) // time of inactivity to wait for packets[data] to receive.
                        .setConnectionRequestTimeout(0)); // time to fetch a connection from the connection pool 0 for infinite.
                client = new RestHighLevelClient(restBuilder);
            }
        }

        public void cleanUp() {
            try {
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

```

I also tried by implementing `DisposableBean` interface and it's `destroy` method but I got same exception.  

This is my API where I am trying to querying a document:

```java
    public class IndexNameController {

        @Autowired
        RestHighLevelClient client;

        @GetMapping(value = "/listAllNames")
        public ArrayList<Object> listAllNames(HttpSession session) {
            ArrayList<Object> results = new ArrayList<>();
            try {
                SearchRequest searchRequest = new SearchRequest();
                SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
                searchRequest.indices("indexname");
                String[] fields = { "name", "id" };
                searchSourceBuilder.fetchSource(fields, new String[] {});
                searchSourceBuilder.query(QueryBuilders.matchAllQuery()).size(10000);
                searchSourceBuilder = searchSourceBuilder.sort(new FieldSortBuilder("createdTime").order(SortOrder.DESC));
                searchRequest.source(searchSourceBuilder);
                SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
                SearchHit[] searchHits = searchResponse.getHits().getHits();
                for (SearchHit searchHit : searchHits) {
                    Map<String, Object> map = new HashMap<>();
                    map.put("value", searchHit.getSourceAsMap().get("id"));
                    map.put("name", searchHit.getSourceAsMap().get("name"));
                    results.add(map);
                }
                return results;
            } catch (Exception e) {
                e.printStackTrace();
            }
            return new ArrayList<>();
        }
    }   

```

When it's trying to query it gives exception at `client.search()`. This is the **Stack Trace**: 

```java
    java.net.ConnectException: Connection refused
        at org.elasticsearch.client.RestClient.extractAndWrapCause(RestClient.java:788)
        at org.elasticsearch.client.RestClient.performRequest(RestClient.java:218)
        at org.elasticsearch.client.RestClient.performRequest(RestClient.java:205)
        at org.elasticsearch.client.RestHighLevelClient.internalPerformRequest(RestHighLevelClient.java:1454)
        at org.elasticsearch.client.RestHighLevelClient.performRequest(RestHighLevelClient.java:1424)
        at org.elasticsearch.client.RestHighLevelClient.performRequestAndParseEntity(RestHighLevelClient.java:1394)
        at org.elasticsearch.client.RestHighLevelClient.search(RestHighLevelClient.java:930)
        at com.incident.response.controller.IncidentController.listAllIncidents(IncidentController.java:569)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:189)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
        at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
        at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
        at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415)
        at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:748)
    Caused by: java.net.ConnectException: Connection refused
        at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
        at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
        at org.apache.http.impl.nio.reactor.DefaultConnectingIOReactor.processEvent(DefaultConnectingIOReactor.java:171)
        at org.apache.http.impl.nio.reactor.DefaultConnectingIOReactor.processEvents(DefaultConnectingIOReactor.java:145)
        at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor.execute(AbstractMultiworkerIOReactor.java:351)
        at org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager.execute(PoolingNHttpClientConnectionManager.java:221)
        at org.apache.http.impl.nio.client.CloseableHttpAsyncClientBase$1.run(CloseableHttpAsyncClientBase.java:64)
        ... 1 more

```

Please help me to get rid from this. All help and suggestions will be appriciate.