HADOOP-15870. S3AInputStream.remainingInFile should use nextReadPos.

Contributed by lqjacklee.

Change-Id: I32bb00a683102e7ff8ff8ce0b8d9c3195ca7381c

hadoop-common-project/hadoop-common/src/site/markdown/filesystem/fsdatainputstream.md

@@ -119,6 +119,59 @@ Return the data at the current position.
     else
         result = -1
 
+### <a name="InputStream.available"></a> `InputStream.available()`
+
+Returns the number of bytes "estimated" to be readable on a stream before `read()`
+blocks on any IO (i.e. the thread is potentially suspended for some time).
+
+That is: for all values `v` returned by `available()`, `read(buffer, 0, v)`
+is should not block.
+
+#### Postconditions
+
+```python
+if len(data) == 0:
+  result = 0
+
+elif pos >= len(data):
+  result = 0
+
+else:
+  d = "the amount of data known to be already buffered/cached locally"
+  result = min(1, d)  # optional but recommended: see below.
+```
+
+As `0` is a number which is always meets this condition, it is nominally
+possible for an implementation to simply return `0`. However, this is not
+considered useful, and some applications/libraries expect a positive number.
+
+#### The GZip problem.
+
+[JDK-7036144](http://bugs.java.com/bugdatabase/view_bug.do?bug_id=7036144),
+"GZIPInputStream readTrailer uses faulty available() test for end-of-stream"
+discusses how the JDK's GZip code it uses `available()` to detect an EOF,
+in a loop similar to the the following
+
+```java
+while(instream.available()) {
+  process(instream.read());
+}
+```
+
+The correct loop would have been:
+
+```java
+int r;
+while((r=instream.read()) >= 0) {
+  process(r);
+}
+```
+
+If `available()` ever returns 0, then the gzip loop halts prematurely.
+
+For this reason, implementations *should* return a value &gt;=1, even
+if it breaks that requirement of `available()` returning the amount guaranteed
+not to block on reads.
 
 ### <a name="InputStream.read.buffer[]"></a> `InputStream.read(buffer[], offset, length)`
 

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/contract/AbstractContractSeekTest.java

@@ -32,6 +32,7 @@
 import java.io.IOException;
 import java.util.Random;
 
+import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_KEY;
 import static org.apache.hadoop.fs.contract.ContractTestUtils.createFile;
 import static org.apache.hadoop.fs.contract.ContractTestUtils.dataset;
 import static org.apache.hadoop.fs.contract.ContractTestUtils.skip;
@@ -99,14 +100,18 @@ public void testSeekZeroByteFile() throws Throwable {
     describe("seek and read a 0 byte file");
     instream = getFileSystem().open(zeroByteFile);
     assertEquals(0, instream.getPos());
+    assertAvailableIsZero(instream);
     //expect initial read to fai;
     int result = instream.read();
     assertMinusOne("initial byte read", result);
+    assertAvailableIsZero(instream);
     byte[] buffer = new byte[1];
     //expect that seek to 0 works
     instream.seek(0);
+    assertAvailableIsZero(instream);
     //reread, expect same exception
     result = instream.read();
+    assertAvailableIsZero(instream);
     assertMinusOne("post-seek byte read", result);
     result = instream.read(buffer, 0, 1);
     assertMinusOne("post-seek buffer read", result);
@@ -132,8 +137,8 @@ public void testBlockReadZeroByteFile() throws Throwable {
   @Test
   public void testSeekReadClosedFile() throws Throwable {
     instream = getFileSystem().open(smallSeekFile);
-    getLogger().debug(
-      "Stream is of type " + instream.getClass().getCanonicalName());
+    getLogger().debug("Stream is of type {}",
+        instream.getClass().getCanonicalName());
     instream.close();
     try {
       instream.seek(0);
@@ -168,10 +173,26 @@ public void testSeekReadClosedFile() throws Throwable {
     try {
       long offset = instream.getPos();
     } catch (IOException e) {
-      // its valid to raise error here; but the test is applied to make
+      // it is valid to raise error here; but the test is applied to make
       // sure there's no other exception like an NPE.
 
     }
+    // a closed stream should either fail or return 0 bytes.
+    try {
+      int a = instream.available();
+      LOG.info("available() returns a value on a closed file: {}", a);
+      assertAvailableIsZero(instream);
+    } catch (IOException | IllegalStateException expected) {
+      // expected
+    }
+    // a closed stream should either fail or return 0 bytes.
+    try {
+      int a = instream.available();
+      LOG.info("available() returns a value on a closed file: {}", a);
+      assertAvailableIsZero(instream);
+    } catch (IOException | IllegalStateException expected) {
+      // expected
+    }
     //and close again
     instream.close();
   }
@@ -205,6 +226,7 @@ public void testSeekFile() throws Throwable {
     //expect that seek to 0 works
     instream.seek(0);
     int result = instream.read();
+    assertAvailableIsPositive(instream);
     assertEquals(0, result);
     assertEquals(1, instream.read());
     assertEquals(2, instream.getPos());
@@ -226,13 +248,24 @@ public void testSeekAndReadPastEndOfFile() throws Throwable {
     //go just before the end
     instream.seek(TEST_FILE_LEN - 2);
     assertTrue("Premature EOF", instream.read() != -1);
+    assertAvailableIsPositive(instream);
     assertTrue("Premature EOF", instream.read() != -1);
+    checkAvailabilityAtEOF();
     assertMinusOne("read past end of file", instream.read());
   }
 
+  /**
+   * This can be overridden if a filesystem always returns 01
+   * @throws IOException
+   */
+  protected void checkAvailabilityAtEOF() throws IOException {
+    assertAvailableIsZero(instream);
+  }
+
   @Test
   public void testSeekPastEndOfFileThenReseekAndRead() throws Throwable {
-    describe("do a seek past the EOF, then verify the stream recovers");
+    describe("do a seek past the EOF, " +
+            "then verify the stream recovers");
     instream = getFileSystem().open(smallSeekFile);
     //go just before the end. This may or may not fail; it may be delayed until the
     //read
@@ -261,6 +294,7 @@ public void testSeekPastEndOfFileThenReseekAndRead() throws Throwable {
     //now go back and try to read from a valid point in the file
     instream.seek(1);
     assertTrue("Premature EOF", instream.read() != -1);
+    assertAvailableIsPositive(instream);
   }
 
   /**
@@ -278,6 +312,7 @@ public void testSeekBigFile() throws Throwable {
     //expect that seek to 0 works
     instream.seek(0);
     int result = instream.read();
+    assertAvailableIsPositive(instream);
     assertEquals(0, result);
     assertEquals(1, instream.read());
     assertEquals(2, instream.read());
@@ -296,6 +331,7 @@ public void testSeekBigFile() throws Throwable {
     instream.seek(0);
     assertEquals(0, instream.getPos());
     instream.read();
+    assertAvailableIsPositive(instream);
     assertEquals(1, instream.getPos());
     byte[] buf = new byte[80 * 1024];
     instream.readFully(1, buf, 0, buf.length);
@@ -314,7 +350,7 @@ public void testPositionedBulkReadDoesntChangePosition() throws Throwable {
     instream.seek(39999);
     assertTrue(-1 != instream.read());
     assertEquals(40000, instream.getPos());
-
+    assertAvailableIsPositive(instream);
     int v = 256;
     byte[] readBuffer = new byte[v];
     assertEquals(v, instream.read(128, readBuffer, 0, v));
@@ -322,6 +358,7 @@ public void testPositionedBulkReadDoesntChangePosition() throws Throwable {
     assertEquals(40000, instream.getPos());
     //content is the same too
     assertEquals("@40000", block[40000], (byte) instream.read());
+    assertAvailableIsPositive(instream);
     //now verify the picked up data
     for (int i = 0; i < 256; i++) {
       assertEquals("@" + i, block[i + 128], readBuffer[i]);
@@ -376,6 +413,7 @@ public void testReadFullyZeroByteFile() throws Throwable {
     assertEquals(0, instream.getPos());
     byte[] buffer = new byte[1];
     instream.readFully(0, buffer, 0, 0);
+    assertAvailableIsZero(instream);
     assertEquals(0, instream.getPos());
     // seek to 0 read 0 bytes from it
     instream.seek(0);
@@ -551,7 +589,9 @@ public void testReadSmallFile() throws Throwable {
       fail("Expected an exception, got " + r);
     } catch (EOFException e) {
       handleExpectedException(e);
-    } catch (IOException | IllegalArgumentException | IndexOutOfBoundsException e) {
+    } catch (IOException
+        | IllegalArgumentException
+        | IndexOutOfBoundsException e) {
       handleRelaxedException("read() with a negative position ",
           "EOFException",
           e);
@@ -587,6 +627,29 @@ public void testReadAtExactEOF() throws Throwable {
     instream = getFileSystem().open(smallSeekFile);
     instream.seek(TEST_FILE_LEN -1);
     assertTrue("read at last byte", instream.read() > 0);
+    assertAvailableIsZero(instream);
     assertEquals("read just past EOF", -1, instream.read());
   }
+
+  /**
+   * Assert that the number of bytes available is zero.
+   * @param in input stream
+   */
+  protected static void assertAvailableIsZero(FSDataInputStream in)
+      throws IOException {
+    assertEquals("stream.available() should be zero",
+        0, in.available());
+  }
+
+  /**
+   * Assert that the number of bytes available is greater than zero.
+   * @param in input stream
+   */
+  protected static void assertAvailableIsPositive(FSDataInputStream in)
+      throws IOException {
+    int available = in.available();
+    assertTrue("stream.available() should be positive but is "
+        + available,
+        available > 0);
+  }
 }

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AInputStream.java

@@ -218,7 +218,7 @@ private synchronized void reopen(String reason, long targetPos, long length,
   }
 
   @Override
-  public synchronized long getPos() throws IOException {
+  public synchronized long getPos() {
     return (nextReadPos < 0) ? 0 : nextReadPos;
   }
 
@@ -620,15 +620,26 @@ public synchronized boolean resetConnection() throws IOException {
     return isObjectStreamOpen();
   }
 
+  /**
+   * Return the number of bytes available.
+   * If the inner stream is closed, the value is 1 for consistency
+   * with S3ObjectStream -and so address the GZip bug
+   * http://bugs.java.com/bugdatabase/view_bug.do?bug_id=7036144 .
+   * If the stream is open, then it is the amount returned by the
+   * wrapped stream.
+   * @return a value greater than or equal to zero.
+   * @throws IOException IO failure.
+   */
   @Override
   public synchronized int available() throws IOException {
     checkNotClosed();
-
-    long remaining = remainingInFile();
-    if (remaining > Integer.MAX_VALUE) {
-      return Integer.MAX_VALUE;
+    if (contentLength == 0 || (nextReadPos >= contentLength)) {
+      return 0;
     }
-    return (int)remaining;
+
+    return wrappedStream == null
+        ? 1
+        : wrappedStream.available();
   }
 
   /**
@@ -637,8 +648,8 @@ public synchronized int available() throws IOException {
    */
   @InterfaceAudience.Private
   @InterfaceStability.Unstable
-  public synchronized long remainingInFile() {
-    return this.contentLength - this.pos;
+  public synchronized long remainingInFile() throws IOException {
+    return contentLength - getPos();
   }
 
   /**
@@ -649,7 +660,7 @@ public synchronized long remainingInFile() {
   @InterfaceAudience.Private
   @InterfaceStability.Unstable
   public synchronized long remainingInCurrentRequest() {
-    return this.contentRangeFinish - this.pos;
+    return contentRangeFinish - getPos();
   }
 
   @InterfaceAudience.Private

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/contract/s3a/ITestS3AContractSeek.java

@@ -80,7 +80,7 @@ public class ITestS3AContractSeek extends AbstractContractSeekTest {
    * which S3A Supports.
    * @return a list of seek policies to test.
    */
-  @Parameterized.Parameters
+  @Parameterized.Parameters(name = "{0}-{1}")
   public static Collection<Object[]> params() {
     return Arrays.asList(new Object[][]{
         {INPUT_FADV_SEQUENTIAL, Default_JSSE},