HTTP ERROR 500
Problem accessing /proxy/application_1538120222810_0072/. Reason:

    Connection refused (Connection refused)
Caused by:
java.net.ConnectException: Connection refused (Connection refused)
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:120)
    at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:179)
    at org.apache.http.impl.conn.ManagedClientConnectionImpl.open(ManagedClientConnectionImpl.java:328)
    at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:612)
    at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:447)
    at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:884)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:107)
    at org.apache.hadoop.yarn.server.webproxy.WebAppProxyServlet.proxyLink(WebAppProxyServlet.java:252)
    at org.apache.hadoop.yarn.server.webproxy.WebAppProxyServlet.methodAction(WebAppProxyServlet.java:462)
    at org.apache.hadoop.yarn.server.webproxy.WebAppProxyServlet.doGet(WebAppProxyServlet.java:300)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1221)
    at com.google.inject.servlet.FilterChainInvocation.doFilter(FilterChainInvocation.java:66)
    at com.sun.jersey.spi.container.servlet.ServletContainer.doFilter(ServletContainer.java:900)
    at com.sun.jersey.spi.container.servlet.ServletContainer.doFilter(ServletContainer.java:834)
    at org.apache.hadoop.yarn.server.resourcemanager.webapp.RMWebAppFilter.doFilter(RMWebAppFilter.java:178)
    at com.sun.jersey.spi.container.servlet.ServletContainer.doFilter(ServletContainer.java:795)
    at com.google.inject.servlet.FilterDefinition.doFilter(FilterDefinition.java:163)
    at com.google.inject.servlet.FilterChainInvocation.doFilter(FilterChainInvocation.java:58)
    at com.google.inject.servlet.ManagedFilterPipeline.dispatch(ManagedFilterPipeline.java:118)
    at com.google.inject.servlet.GuiceFilter.doFilter(GuiceFilter.java:113)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
    at org.apache.hadoop.security.http.XFrameOptionsFilter.doFilter(XFrameOptionsFilter.java:57)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
    at org.apache.hadoop.http.lib.StaticUserWebFilter$StaticUserFilter.doFilter(StaticUserWebFilter.java:110)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
    at org.apache.hadoop.security.authentication.server.AuthenticationFilter.doFilter(AuthenticationFilter.java:644)
    at org.apache.hadoop.security.token.delegation.web.DelegationTokenAuthenticationFilter.doFilter(DelegationTokenAuthenticationFilter.java:304)
    at org.apache.hadoop.security.authentication.server.AuthenticationFilter.doFilter(AuthenticationFilter.java:592)
    at org.apache.hadoop.yarn.server.security.http.RMAuthenticationFilter.doFilter(RMAuthenticationFilter.java:82)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
    at org.apache.hadoop.http.HttpServer2$QuotingInputFilter.doFilter(HttpServer2.java:1440)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
    at org.apache.hadoop.http.NoCacheFilter.doFilter(NoCacheFilter.java:45)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
    at org.apache.hadoop.http.NoCacheFilter.doFilter(NoCacheFilter.java:45)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:399)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
    at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
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解决方案
在Active ResourceManager和Standby ResourceManager及所有NodeManager上的yarn-site.xml上添加yarn.resourcemanager.webapp.address属性, 并重启相应的ResourceManager及NodeManager

如果是client模式，本地配置文件调整即可cover。无需重启集群