[HBASE-24956] ConnectionManager#locateRegionInMeta waits for user region lock indefinitely. (#2415)

Signed-off-by: Bharath Vissapragada <bharathv@apache.org>
Signed-off-by: Viraj Jasani <vjasani@apache.org>

hbase-client/src/main/java/org/apache/hadoop/hbase/client/ConnectionManager.java

@@ -72,6 +72,7 @@ import org.apache.hadoop.hbase.client.backoff.ClientBackoffPolicy;
 import org.apache.hadoop.hbase.client.backoff.ClientBackoffPolicyFactory;
 import org.apache.hadoop.hbase.client.coprocessor.Batch;
 import org.apache.hadoop.hbase.exceptions.ClientExceptionsUtil;
+import org.apache.hadoop.hbase.exceptions.LockTimeoutException;
 import org.apache.hadoop.hbase.exceptions.RegionMovedException;
 import org.apache.hadoop.hbase.ipc.RpcClient;
 import org.apache.hadoop.hbase.ipc.RpcClientFactory;
@@ -1316,13 +1317,15 @@ class ConnectionManager {
 
         // Query the meta region
         long pauseBase = this.pause;
-        userRegionLock.lock();
+        takeUserRegionLock();
         try {
-          if (useCache) {// re-check cache after get lock
+          // We don't need to check if useCache is enabled or not. Even if useCache is false
-            RegionLocations locations = getCachedLocation(tableName, row);
+          // we already cleared the cache for this row before acquiring userRegion lock so if this
-            if (locations != null && locations.getRegionLocation(replicaId) != null) {
+          // row is present in cache that means some other thread has populated it while we were
-              return locations;
+          // waiting to acquire user region lock.
-            }
+          RegionLocations locations = getCachedLocation(tableName, row);
+          if (locations != null && locations.getRegionLocation(replicaId) != null) {
+            return locations;
           }
           Result regionInfoRow = null;
           s.resetMvccReadPoint();
@@ -1339,7 +1342,7 @@ class ConnectionManager {
           }
 
           // convert the row result into the HRegionLocation we need!
-          RegionLocations locations = MetaTableAccessor.getRegionLocations(regionInfoRow);
+          locations = MetaTableAccessor.getRegionLocations(regionInfoRow);
           if (locations == null || locations.getRegionLocation(replicaId) == null) {
             throw new IOException("HRegionInfo was null in " +
               tableName + ", row=" + regionInfoRow);
@@ -1423,6 +1426,19 @@ class ConnectionManager {
       }
     }
 
+    void takeUserRegionLock() throws IOException {
+      try {
+        long waitTime = connectionConfig.getMetaOperationTimeout();
+        if (!userRegionLock.tryLock(waitTime, TimeUnit.MILLISECONDS)) {
+          throw new LockTimeoutException("Failed to get user region lock in"
+            + waitTime + " ms. " + " for accessing meta region server.");
+        }
+      } catch (InterruptedException ie) {
+        LOG.error("Interrupted while waiting for a lock", ie);
+        throw ExceptionUtil.asInterrupt(ie);
+      }
+    }
+
     /**
      * Put a newly discovered HRegionLocation into the cache.
      * @param tableName The table name.

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestMetaCache.java

@@ -23,6 +23,7 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.*;
 
 import org.apache.hadoop.hbase.exceptions.ClientExceptionsUtil;
+import org.apache.hadoop.hbase.exceptions.LockTimeoutException;
 import org.apache.hadoop.hbase.exceptions.RegionOpeningException;
 import org.apache.hadoop.hbase.protobuf.generated.ClientProtos;
 import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.GetResponse;
@@ -42,6 +43,8 @@ import org.junit.experimental.categories.Category;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import static junit.framework.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
@@ -57,6 +60,7 @@ public class TestMetaCache {
   private static final byte[] QUALIFIER = Bytes.toBytes("qual");
 
   private static HRegionServer badRS;
+  private static final Logger LOG = LoggerFactory.getLogger(TestMetaCache.class);
 
   /**
    * @throws java.lang.Exception
@@ -356,4 +360,77 @@ public class TestMetaCache {
         throws ServiceException {
     }
   }
-}
+
+  @Test
+  public void testUserRegionLockThrowsException() throws IOException, InterruptedException {
+    ((FakeRSRpcServices)badRS.getRSRpcServices()).setExceptionInjector(new LockSleepInjector());
+    Configuration conf = new Configuration(TEST_UTIL.getConfiguration());
+    conf.setInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, 1);
+    conf.setLong(HConstants.HBASE_CLIENT_META_OPERATION_TIMEOUT, 2000);
+    conf.setLong(HConstants.HBASE_CLIENT_SCANNER_TIMEOUT_PERIOD, 2000);
+
+    try (ConnectionManager.HConnectionImplementation conn =
+           (ConnectionManager.HConnectionImplementation) ConnectionFactory.createConnection(conf)) {
+      ClientThread client1 = new ClientThread(conn);
+      ClientThread client2 = new ClientThread(conn);
+      client1.start();
+      client2.start();
+      client1.join();
+      client2.join();
+      // One thread will get the lock but will sleep in  LockExceptionInjector#throwOnScan and
+      // eventually fail since the sleep time is more than hbase client scanner timeout period.
+      // Other thread will wait to acquire userRegionLock.
+      // Have no idea which thread will be scheduled first. So need to check both threads.
+
+      // Both the threads will throw exception. One thread will throw exception since after
+      // acquiring user region lock, it is sleeping for 5 seconds when the scanner time out period
+      // is 2 seconds.
+      // Other thread will throw exception since it was not able to get hold of user region lock
+      // within meta operation timeout period.
+      assertNotNull(client1.getException());
+      assertNotNull(client2.getException());
+
+      assertTrue(client1.getException() instanceof LockTimeoutException
+        ^ client2.getException() instanceof LockTimeoutException);
+    }
+  }
+
+  private final class ClientThread extends Thread {
+    private Exception exception;
+    private ConnectionManager.HConnectionImplementation connection;
+
+    private ClientThread(ConnectionManager.HConnectionImplementation connection) {
+      this.connection = connection;
+    }
+    @Override
+    public void run() {
+      byte[] currentKey = HConstants.EMPTY_START_ROW;
+      try {
+        connection.getRegionLocation(TABLE_NAME, currentKey, true);
+      } catch (IOException e) {
+        LOG.error("Thread id: " + this.getId() + "  exception: ", e);
+        this.exception = e;
+      }
+    }
+    public Exception getException() {
+      return exception;
+    }
+  }
+
+  public static class LockSleepInjector extends ExceptionInjector {
+    @Override
+    public void throwOnScan(FakeRSRpcServices rpcServices, ClientProtos.ScanRequest request) {
+      try {
+        Thread.sleep(5000);
+      } catch (InterruptedException e) {
+        LOG.info("Interrupted exception", e);
+      }
+    }
+
+    @Override
+    public void throwOnGet(FakeRSRpcServices rpcServices, ClientProtos.GetRequest request) { }
+
+    @Override
+    public void throwOnMutate(FakeRSRpcServices rpcServices, ClientProtos.MutateRequest request) { }
+  }
+}