fix:NoNamenodesAvailableException long time when ns failover

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/resolver/ActiveNamenodeResolver.java

@@ -146,4 +146,14 @@ List<? extends FederationNamenodeContext> getNamenodesForNameserviceId(
    * @param routerId Unique string identifier for the router.
    */
   void setRouterId(String routerId);
+
+  /**
+   * Rotate cache, make the current namenode have the lowest priority,
+   * to ensure that the current namenode will not be accessed first next time.
+   *
+   * @param nsId name service id
+   * @param namenode namenode contexts
+   * @param listObserversFirst Observer read case, observer NN will be ranked first
+   */
+  void rotateCache(String nsId, FederationNamenodeContext namenode, boolean listObserversFirst);
 }

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/resolver/MembershipNamenodeResolver.java

@@ -478,4 +478,45 @@ private List<MembershipState> getRecentRegistrationForQuery(
   public void setRouterId(String router) {
     this.routerId = router;
   }
+
+  /**
+   * Rotate cache, make the current namenode have the lowest priority,
+   * to ensure that the current namenode will not be accessed first next time.
+   *
+   * @param nsId name service id
+   * @param namenode namenode contexts
+   * @param listObserversFirst Observer read case, observer NN will be ranked first
+   */
+  @Override
+  public void rotateCache(
+      String nsId, FederationNamenodeContext namenode, boolean listObserversFirst) {
+    cacheNS.compute(Pair.of(nsId, listObserversFirst), (ns, namenodeContexts) -> {
+      if (namenodeContexts == null || namenodeContexts.size() <= 1) {
+        return namenodeContexts;
+      }
+      FederationNamenodeContext firstNamenodeContext = namenodeContexts.get(0);
+      /*
+       * If the first nn in the cache is active, the active nn priority cannot be lowered.
+       * This happens when other threads have already updated the cache.
+       */
+      if (firstNamenodeContext.getState().equals(ACTIVE)) {
+        return namenodeContexts;
+      }
+      /*
+       * If the first nn in the cache at this time is not the nn
+       * that needs to be lowered in priority, there is no need to rotate.
+       * This happens when other threads have already rotated the cache.
+       */
+      if (firstNamenodeContext.getRpcAddress().equals(namenode.getRpcAddress())) {
+        List<FederationNamenodeContext> rotatedNnContexts = new ArrayList<>(namenodeContexts);
+        Collections.rotate(rotatedNnContexts, -1);
+        String firstNamenodeId = namenodeContexts.get(0).getNamenodeId();
+        LOG.info("Rotate cache of pair <ns: {}, observer first: {}>, put namenode: {} in the " +
+            "first position of the cache and namenode: {} in the last position of the cache",
+            nsId, listObserversFirst, firstNamenodeId, namenode.getNamenodeId());
+        return rotatedNnContexts;
+      }
+      return namenodeContexts;
+    });
+  }
 }

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcClient.java

@@ -599,6 +599,8 @@ public Object invokeMethod(
           }
           LOG.error("Cannot get available namenode for {} {} error: {}",
               nsId, rpcAddress, ioe.getMessage());
+          // Rotate cache so that client can retry the next namenode in the cache
+          this.namenodeResolver.rotateCache(nsId, namenode, shouldUseObserver);
           // Throw RetriableException so that client can retry
           throw new RetriableException(ioe);
         } else {

hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/MiniRouterDFSCluster.java

@@ -1202,4 +1202,13 @@ public void waitClusterUp() throws IOException {
       throw new IOException("Cannot wait for the namenodes", e);
     }
   }
+
+  /**
+   * Get cache flush interval in milliseconds.
+   *
+   * @return Cache flush interval in milliseconds.
+   */
+  public long getCacheFlushInterval() {
+    return cacheFlushInterval;
+  }
 }

hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/MockResolver.java

@@ -397,6 +397,11 @@ public List<String> getMountPoints(String path) throws IOException {
   public void setRouterId(String router) {
   }
 
+  @Override
+  public void rotateCache(
+      String nsId, FederationNamenodeContext namenode, boolean listObserversFirst) {
+  }
+
   /**
    * Mocks the availability of default namespace.
    * @param b if true default namespace is unset.

hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterClientRejectOverload.java

@@ -17,6 +17,8 @@
  */
 package org.apache.hadoop.hdfs.server.federation.router;
 
+import static org.apache.hadoop.ha.HAServiceProtocol.HAServiceState.ACTIVE;
+import static org.apache.hadoop.ha.HAServiceProtocol.HAServiceState.STANDBY;
 import static org.apache.hadoop.hdfs.server.federation.FederationTestUtils.simulateSlowNamenode;
 import static org.apache.hadoop.hdfs.server.federation.FederationTestUtils.simulateThrowExceptionRouterRpcServer;
 import static org.apache.hadoop.hdfs.server.federation.FederationTestUtils.transitionClusterNSToStandby;
@@ -42,16 +44,19 @@
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
+import org.apache.hadoop.hdfs.server.federation.MiniRouterDFSCluster;
 import org.apache.hadoop.hdfs.server.federation.MiniRouterDFSCluster.RouterContext;
 import org.apache.hadoop.hdfs.server.federation.RouterConfigBuilder;
 import org.apache.hadoop.hdfs.server.federation.StateStoreDFSCluster;
 import org.apache.hadoop.hdfs.server.federation.metrics.FederationRPCMetrics;
+import org.apache.hadoop.hdfs.server.federation.resolver.FederationNamenodeContext;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.ipc.RemoteException;
 import org.apache.hadoop.ipc.StandbyException;
 import org.apache.hadoop.test.GenericTestUtils;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.hadoop.util.Time;
 import org.junit.After;
 import org.junit.Rule;
 import org.junit.Test;
@@ -357,6 +362,82 @@ public void testNoNamenodesAvailable() throws Exception{
     assertEquals(originalRouter0Failures, rpcMetrics0.getProxyOpNoNamenodes());
   }
 
+  /**
+   * When failover occurs, the router may record that the ns has no active namenode.
+   * Only when the router updates the cache next time can the memory status be updated,
+   * causing the router to report NoNamenodesAvailableException for a long time.
+   */
+  @Test
+  public void testNoNamenodesAvailableLongTimeWhenNsFailover() throws Exception {
+    setupCluster(false, true);
+    transitionClusterNSToStandby(cluster);
+    for (RouterContext routerContext : cluster.getRouters()) {
+      // Manually trigger the heartbeat
+      Collection<NamenodeHeartbeatService> heartbeatServices = routerContext
+              .getRouter().getNamenodeHeartbeatServices();
+      for (NamenodeHeartbeatService service : heartbeatServices) {
+        service.periodicInvoke();
+      }
+      // Update service cache
+      routerContext.getRouter().getStateStore().refreshCaches(true);
+    }
+    // Record the time after the router first updated the cache
+    long firstLoadTime = Time.now();
+    List<MiniRouterDFSCluster.NamenodeContext> namenodes = cluster.getNamenodes();
+
+    // Make sure all namenodes are in standby state
+    for (MiniRouterDFSCluster.NamenodeContext namenodeContext : namenodes) {
+      assertEquals(STANDBY.ordinal(), namenodeContext.getNamenode().getNameNodeState());
+    }
+
+    Configuration conf = cluster.getRouterClientConf();
+    // Set dfs.client.failover.random.order false, to pick 1st router at first
+    conf.setBoolean("dfs.client.failover.random.order", false);
+
+    DFSClient routerClient = new DFSClient(new URI("hdfs://fed"), conf);
+
+    for (RouterContext routerContext : cluster.getRouters()) {
+      // Get the second namenode in the router cache and make it active
+      List<? extends FederationNamenodeContext> ns0 = routerContext.getRouter()
+              .getNamenodeResolver()
+              .getNamenodesForNameserviceId("ns0", false);
+
+      String nsId = ns0.get(1).getNamenodeId();
+      cluster.switchToActive("ns0", nsId);
+      // Manually trigger the heartbeat, but the router does not manually load the cache
+      Collection<NamenodeHeartbeatService> heartbeatServices = routerContext
+              .getRouter().getNamenodeHeartbeatServices();
+      for (NamenodeHeartbeatService service : heartbeatServices) {
+        service.periodicInvoke();
+      }
+      assertEquals(ACTIVE.ordinal(),
+              cluster.getNamenode("ns0", nsId).getNamenode().getNameNodeState());
+    }
+
+    // Get router0 metrics
+    FederationRPCMetrics rpcMetrics0 = cluster.getRouters().get(0)
+            .getRouter().getRpcServer().getRPCMetrics();
+    // Original failures
+    long originalRouter0Failures = rpcMetrics0.getProxyOpNoNamenodes();
+
+    /*
+     * At this time, the router has recorded 2 standby namenodes in memory,
+     * and the first accessed namenode is indeed standby,
+     * then an NoNamenodesAvailableException will be reported for the first access,
+     * and the next access will be successful.
+     */
+    routerClient.getFileInfo("/");
+    long successReadTime = Time.now();
+    assertEquals(originalRouter0Failures + 1, rpcMetrics0.getProxyOpNoNamenodes());
+
+    /*
+     * access the active namenode without waiting for the router to update the cache,
+     * even if there are 2 standby states recorded in the router memory.
+     */
+    assertTrue(successReadTime - firstLoadTime < cluster.getCacheFlushInterval());
+  }
+
+
   @Test
   public void testAsyncCallerPoolMetrics() throws Exception {
     setupCluster(true, false);