It seems I'm having the same problem as described in this post, except I'm using the SolrJ client. Since that question remains unanswered, I'm posting my own here.
I get intermittent SolrServerExceptions (Connection refused caused by a Connection timed out) on an otherwise well-running setup. The SolrJ client and Solr server are both running on AWS EC2 instances (Bitnami Ubuntu AMIs) that are talking to each other just fine. It's just that every once in a while (several times a day) I see these errors in the tomcat logs (on the client side only! There is no evidence on the server log that anything went wrong). I can't tell for sure, but the timeouts seem to be getting logged about 30s after the query is issued.
This is a new system with two cores, each with < 1000 indexed documents running as a single instance (no zookeeper). Traffic volume is very low at this point.
Here is the complete stacktrace:
org.apache.solr.client.solrj.SolrServerException: Server refused connection at: http://xx.xxx.xx.xx/solr/vehicles
at org.apache.solr.client.solrj.impl.HttpSolrServer.request(HttpSolrServer.java:496)
at org.apache.solr.client.solrj.impl.HttpSolrServer.request(HttpSolrServer.java:197)
at org.apache.solr.client.solrj.request.QueryRequest.process(QueryRequest.java:90)
at org.apache.solr.client.solrj.SolrServer.query(SolrServer.java:301)
at com.autoap.api.service.search.VehicleSearchServiceImpl.search(VehicleSearchServiceImpl.java:141)
at sun.reflect.GeneratedMethodAccessor147.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:198)
at com.sun.proxy.$Proxy108.search(Unknown Source)
at com.autoap.api.resources.search.SearchResource.searchVehicles(SearchResource.java:92)
at sun.reflect.GeneratedMethodAccessor146.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:151)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:171)
at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$ResponseOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:152)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:104)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:402)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:349)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:106)
at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:259)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:318)
at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:236)
at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1010)
at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:373)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:382)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:345)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:220)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.autoap.api.spring.security.ServletFilter.doFilter(ServletFilter.java:38)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:186)
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.ajp.AjpAprProcessor.process(AjpAprProcessor.java:190)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.AprEndpoint$SocketWithOptionsProcessor.run(AprEndpoint.java:2378)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.http.conn.HttpHostConnectException: Connection to http://54.214.14.50 refused
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:190)
at org.apache.http.impl.conn.ManagedClientConnectionImpl.open(ManagedClientConnectionImpl.java:294)
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:643)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:479)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:906)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:805)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:784)
at org.apache.solr.client.solrj.impl.HttpSolrServer.request(HttpSolrServer.java:393)
... 65 more
Caused by: java.net.ConnectException: Connection timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:127)
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180)
... 72 more
UPDATE: SolrJ is version 4.6.0, the Solr server is 4.7.1. I think we've narrowed it down to a problem with SolrJ client connections and/or network issues. I came to this conclusion by looking at the logs for Apache that sits in front of Solr, and there are no errors or entries in the access logs for the failed connections. If Apache isn't even getting the requests, then the Solr server can be eliminated as the problem.
Does SolrJ use any type of HTTP connection pooling? Perhaps I'm hitting a stale or orphaned connection.
