YARN-4092. Fixed UI redirection to print useful messages when both RMs are in standby mode. Contributed by Xuan Gong

(cherry picked from commit a3fd2ccc869dfc1f04d1cf0a8678d4d90a43a80f)
(cherry picked from commit 48f5161cd5d4c2f4e385b253a5bea066b2e23b9e)

hadoop-yarn-project/CHANGES.txt

@@ -17,6 +17,9 @@ Release 2.7.2 - UNRELEASED
     YARN-3978. Configurably turn off the saving of container info in Generic AHS
     (Eric Payne via jeagles)
 
+    YARN-4092. Fixed UI redirection to print useful messages when both RMs are
+    in standby mode. (Xuan Gong via jianhe)
+
   OPTIMIZATIONS
 
   BUG FIXES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-client/src/test/java/org/apache/hadoop/yarn/client/TestRMFailover.java

@@ -27,6 +27,7 @@ import static org.junit.Assert.fail;
 import java.io.IOException;
 import java.net.HttpURLConnection;
 import java.net.URL;
+
 import javax.servlet.http.HttpServletResponse;
 
 import org.apache.commons.logging.Log;
@@ -45,6 +46,7 @@ import org.apache.hadoop.yarn.server.MiniYARNCluster;
 import org.apache.hadoop.yarn.server.resourcemanager.AdminService;
 import org.apache.hadoop.yarn.server.resourcemanager.ResourceManager;
 import org.apache.hadoop.yarn.server.webproxy.WebAppProxyServer;
+import org.apache.hadoop.yarn.webapp.YarnWebParams;
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
@@ -285,6 +287,7 @@ public class TestRMFailover extends ClientBaseWithFixes {
     getAdminService(0).transitionToActive(req);
     String rm1Url = "http://0.0.0.0:18088";
     String rm2Url = "http://0.0.0.0:28088";
+
     String redirectURL = getRedirectURL(rm2Url);
     // if uri is null, RMWebAppFilter will append a slash at the trail of the redirection url
     assertEquals(redirectURL,rm1Url+"/");
@@ -324,6 +327,17 @@ public class TestRMFailover extends ClientBaseWithFixes {
 
     redirectURL = getRedirectURL(rm2Url + "/proxy/" + fakeAppId);
     assertNull(redirectURL);
+
+    // transit the active RM to standby
+    // Both of RMs are in standby mode
+    getAdminService(0).transitionToStandby(req);
+    // RM2 is expected to send the httpRequest to itself.
+    // The Header Field: Refresh is expected to be set.
+    redirectURL = getRefreshURL(rm2Url);
+    assertTrue(redirectURL != null
+        && redirectURL.contains(YarnWebParams.NEXT_REFRESH_INTERVAL)
+        && redirectURL.contains(rm2Url));
+
   }
 
   // set up http connection with the given url and get the redirection url from the response
@@ -343,4 +357,17 @@ public class TestRMFailover extends ClientBaseWithFixes {
     return redirectUrl;
   }
 
+  static String getRefreshURL(String url) {
+    String redirectUrl = null;
+    try {
+      HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();
+      // do not automatically follow the redirection
+      // otherwise we get too many redirections exception
+      conn.setInstanceFollowRedirects(false);
+      redirectUrl = conn.getHeaderField("Refresh");
+    } catch (Exception e) {
+      // throw new RuntimeException(e);
+    }
+    return redirectUrl;
+  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/webapp/YarnWebParams.java

@@ -37,4 +37,5 @@ public interface YarnWebParams {
   String NODE_STATE = "node.state";
   String NODE_LABEL = "node.label";
   String WEB_UI_TYPE = "web.ui.type";
+  String NEXT_REFRESH_INTERVAL = "next.fresh.interval";
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/RMWebAppFilter.java

@@ -20,6 +20,10 @@ package org.apache.hadoop.yarn.server.resourcemanager.webapp;
 
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.Random;
 import java.util.Set;
 
 import javax.inject.Inject;
@@ -29,8 +33,11 @@ import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.http.HtmlQuoting;
+import org.apache.hadoop.yarn.conf.YarnConfiguration;
 import org.apache.hadoop.yarn.server.webproxy.ProxyUriUtils;
+import org.apache.hadoop.yarn.webapp.YarnWebParams;
 
 import com.google.common.collect.Sets;
 import com.google.inject.Injector;
@@ -48,11 +55,26 @@ public class RMWebAppFilter extends GuiceContainer {
   // define a set of URIs which do not need to do redirection
   private static final Set<String> NON_REDIRECTED_URIS = Sets.newHashSet(
       "/conf", "/stacks", "/logLevel", "/logs");
+  private String path;
+  private static final int BASIC_SLEEP_TIME = 5;
+  private static final int MAX_SLEEP_TIME = 5 * 60;
 
   @Inject
-  public RMWebAppFilter(Injector injector) {
+  public RMWebAppFilter(Injector injector, Configuration conf) {
     super(injector);
     this.injector=injector;
+    InetSocketAddress sock = YarnConfiguration.useHttps(conf)
+        ? conf.getSocketAddr(YarnConfiguration.RM_WEBAPP_HTTPS_ADDRESS,
+            YarnConfiguration.DEFAULT_RM_WEBAPP_HTTPS_ADDRESS,
+            YarnConfiguration.DEFAULT_RM_WEBAPP_HTTPS_PORT)
+        : conf.getSocketAddr(YarnConfiguration.RM_WEBAPP_ADDRESS,
+            YarnConfiguration.DEFAULT_RM_WEBAPP_ADDRESS,
+            YarnConfiguration.DEFAULT_RM_WEBAPP_PORT);
+
+    path = sock.getHostName() + ":" + Integer.toString(sock.getPort());
+    path = YarnConfiguration.useHttps(conf)
+        ? "https://" + path
+        : "http://" + path;
   }
 
   @Override
@@ -69,9 +91,11 @@ public class RMWebAppFilter extends GuiceContainer {
     rmWebApp.checkIfStandbyRM();
     if (rmWebApp.isStandby()
         && shouldRedirect(rmWebApp, uri)) {
-      String redirectPath = rmWebApp.getRedirectPath() + uri;
+
+      String redirectPath = rmWebApp.getRedirectPath();
 
       if (redirectPath != null && !redirectPath.isEmpty()) {
+        redirectPath += uri;
         String redirectMsg =
             "This is standby RM. The redirect url is: " + redirectPath;
         PrintWriter out = response.getWriter();
@@ -79,11 +103,40 @@ public class RMWebAppFilter extends GuiceContainer {
         response.setHeader("Location", redirectPath);
         response.setStatus(HttpServletResponse.SC_TEMPORARY_REDIRECT);
         return;
+      } else {
+        boolean doRetry = true;
+        String retryIntervalStr =
+            request.getParameter(YarnWebParams.NEXT_REFRESH_INTERVAL);
+        int retryInterval = 0;
+        if (retryIntervalStr != null) {
+          try {
+            retryInterval = Integer.parseInt(retryIntervalStr.trim());
+          } catch (NumberFormatException ex) {
+            doRetry = false;
+          }
+        }
+        int next = calculateExponentialTime(retryInterval);
+
+        String redirectUrl =
+            appendOrReplaceParamter(path + uri,
+              YarnWebParams.NEXT_REFRESH_INTERVAL + "=" + (retryInterval + 1));
+        if (redirectUrl == null || next > MAX_SLEEP_TIME) {
+          doRetry = false;
+        }
+        String redirectMsg =
+            doRetry ? "Can not find any active RM. Will retry in next " + next
+                + " seconds." : "There is no active RM right now.";
+        PrintWriter out = response.getWriter();
+        out.println(redirectMsg);
+        if (doRetry) {
+          response.setHeader("Refresh", next + ";url=" + redirectUrl);
+          response.setStatus(HttpServletResponse.SC_TEMPORARY_REDIRECT);
+        }
       }
+      return;
     }
 
     super.doFilter(request, response, chain);
-
   }
 
   private boolean shouldRedirect(RMWebApp rmWebApp, String uri) {
@@ -92,4 +145,33 @@ public class RMWebAppFilter extends GuiceContainer {
         && !uri.startsWith(ProxyUriUtils.PROXY_BASE)
         && !NON_REDIRECTED_URIS.contains(uri);
   }
-}
+
+  private String appendOrReplaceParamter(String uri, String newQuery) {
+    if (uri.contains(YarnWebParams.NEXT_REFRESH_INTERVAL + "=")) {
+      return uri.replaceAll(YarnWebParams.NEXT_REFRESH_INTERVAL + "=[^&]+",
+        newQuery);
+    }
+    try {
+      URI oldUri = new URI(uri);
+      String appendQuery = oldUri.getQuery();
+      if (appendQuery == null) {
+        appendQuery = newQuery;
+      } else {
+        appendQuery += "&" + newQuery;
+      }
+
+      URI newUri =
+          new URI(oldUri.getScheme(), oldUri.getAuthority(), oldUri.getPath(),
+            appendQuery, oldUri.getFragment());
+
+      return newUri.toString();
+    } catch (URISyntaxException e) {
+      return null;
+    }
+  }
+
+  private static int calculateExponentialTime(int retries) {
+    long baseTime = BASIC_SLEEP_TIME * (1L << retries);
+    return (int) (baseTime * ((new Random()).nextDouble() + 0.5));
+  }
+}