HDFS-12318. Fix IOException condition for openInfo in DFSInputStream. Contributed by legend.

(cherry picked from commit 3123895db0518552eb357093fddf0e8ff1a6cadf)

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java

@@ -270,6 +270,11 @@ public class DFSInputStream extends FSInputStream
     openInfo(false);
   }
 
+  @VisibleForTesting
+  public long getlastBlockBeingWrittenLengthForTesting() {
+    return lastBlockBeingWrittenLength;
+  }
+
   /**
    * Grab the open-file info from namenode
    * @param refreshLocatedBlocks whether to re-fetch locatedblocks
@@ -297,7 +302,8 @@ public class DFSInputStream extends FSInputStream
         }
         retriesForLastBlockLength--;
       }
-      if (retriesForLastBlockLength == 0) {
+      if (lastBlockBeingWrittenLength == -1
+          && retriesForLastBlockLength == 0) {
         throw new IOException("Could not obtain the last block locations.");
       }
     }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDFSInputStream.java

@@ -33,6 +33,9 @@ import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.net.unix.DomainSocket;
 import org.apache.hadoop.net.unix.TemporarySocketDirectory;
+import org.apache.hadoop.hdfs.client.impl.DfsClientConf;
+import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.Retry;
+
 import org.junit.Assume;
 import org.junit.Test;
 
@@ -136,4 +139,42 @@ public class TestDFSInputStream {
       cluster.shutdown();
     }
   }
+
+  @Test(timeout=60000)
+  public void testOpenInfo() throws IOException {
+    Configuration conf = new Configuration();
+    conf.setInt(Retry.TIMES_GET_LAST_BLOCK_LENGTH_KEY, 0);
+    MiniDFSCluster cluster =
+            new MiniDFSCluster.Builder(conf).build();
+    cluster.waitActive();
+    try {
+      DistributedFileSystem fs = cluster.getFileSystem();
+
+      int chunkSize = 512;
+      Random r = new Random(12345L);
+      byte[] data = new byte[chunkSize];
+      r.nextBytes(data);
+
+      Path file = new Path("/testfile");
+      try(FSDataOutputStream fout = fs.create(file)) {
+        fout.write(data);
+      }
+
+      DfsClientConf dcconf = new DfsClientConf(conf);
+      int retryTimesForGetLastBlockLength =
+              dcconf.getRetryTimesForGetLastBlockLength();
+      assertEquals(0, retryTimesForGetLastBlockLength);
+
+      try(DFSInputStream fin = fs.dfs.open("/testfile")) {
+        long flen = fin.getFileLength();
+        assertEquals(chunkSize, flen);
+
+        long lastBlockBeingWrittenLength =
+                fin.getlastBlockBeingWrittenLengthForTesting();
+        assertEquals(0, lastBlockBeingWrittenLength);
+      }
+    } finally {
+      cluster.shutdown();
+    }
+  }
 }