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Revert "HADOOP-15870. S3AInputStream.remainingInFile should use nextReadPos." 

This reverts commit 7a4b3d42c4.

The patch broke TestRouterWebHDFSContractSeek as it turns out that
WebHDFSInputStream.available() is always 0.
This commit is contained in:
Steve Loughran 2019-10-14 16:56:50 +01:00
parent 5cc7873a47
commit dee9e97075
4 changed files with 16 additions and 143 deletions
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53
hadoop-common-project/hadoop-common/src/site/markdown/filesystem/fsdatainputstream.md
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@ -119,59 +119,6 @@ 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)`

75
hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/contract/AbstractContractSeekTest.java
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@ -32,7 +32,6 @@ import java.io.EOFException;
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;
@ -100,18 +99,14 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
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);
@ -137,8 +132,8 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
@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);
@ -173,26 +168,10 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
try {
long offset = instream.getPos();
} catch (IOException e) {
// it is valid to raise error here; but the test is applied to make
// its 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();
}
@ -226,7 +205,6 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
//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());
@ -248,24 +226,13 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
//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
@ -294,7 +261,6 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
//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);
}
/**
@ -312,7 +278,6 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
//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());
@ -331,7 +296,6 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
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);
@ -350,7 +314,7 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
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));
@ -358,7 +322,6 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
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]);
@ -413,7 +376,6 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
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);
@ -589,9 +551,7 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
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);
@ -627,29 +587,6 @@ public abstract class AbstractContractSeekTest extends AbstractFSContractTestBas
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);
}
}

29
hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AInputStream.java
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@ -218,7 +218,7 @@ public class S3AInputStream extends FSInputStream implements CanSetReadahead,
}
@Override
public synchronized long getPos() {
public synchronized long getPos() throws IOException {
return (nextReadPos < 0) ? 0 : nextReadPos;
}
@ -620,26 +620,15 @@ public class S3AInputStream extends FSInputStream implements CanSetReadahead,
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();
if (contentLength == 0 || (nextReadPos >= contentLength)) {
return 0;
}
return wrappedStream == null
? 1
: wrappedStream.available();
long remaining = remainingInFile();
if (remaining > Integer.MAX_VALUE) {
return Integer.MAX_VALUE;
}
return (int)remaining;
}
/**
@ -648,8 +637,8 @@ public class S3AInputStream extends FSInputStream implements CanSetReadahead,
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public synchronized long remainingInFile() throws IOException {
return contentLength - getPos();
public synchronized long remainingInFile() {
return this.contentLength - this.pos;
}
/**
@ -660,7 +649,7 @@ public class S3AInputStream extends FSInputStream implements CanSetReadahead,
@InterfaceAudience.Private
@InterfaceStability.Unstable
public synchronized long remainingInCurrentRequest() {
return contentRangeFinish - getPos();
return this.contentRangeFinish - this.pos;
}
@InterfaceAudience.Private

2
hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/contract/s3a/ITestS3AContractSeek.java
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@ -80,7 +80,7 @@ public class ITestS3AContractSeek extends AbstractContractSeekTest {
* which S3A Supports.
* @return a list of seek policies to test.
*/
@Parameterized.Parameters(name = "{0}-{1}")
@Parameterized.Parameters
public static Collection<Object[]> params() {
return Arrays.asList(new Object[][]{
{INPUT_FADV_SEQUENTIAL, Default_JSSE},