hbase-server/src/main/java/org/apache/hadoop/hbase/io/FSDataInputStreamWrapper.java - hbase - Git at Google

 /**
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership.  The ASF licenses this file
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package org.apache.hadoop.hbase.io;

 import java.io.IOException;

 import org.apache.hadoop.fs.FSDataInputStream;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.fs.HFileSystem;

 import com.google.common.annotations.VisibleForTesting;

 /**
  * Wrapper for input stream(s) that takes care of the interaction of FS and HBase checksums,
  * as well as closing streams. Initialization is not thread-safe, but normal operation is;
  * see method comments.
  */
 public class FSDataInputStreamWrapper {
   private final HFileSystem hfs;
   private final Path path;
   private final FileLink link;
   private final boolean doCloseStreams;

   /** Two stream handles, one with and one without FS-level checksum.
    * HDFS checksum setting is on FS level, not single read level, so you have to keep two
    * FS objects and two handles open to interleave different reads freely, which is very sad.
    * This is what we do:
    * 1) First, we need to read the trailer of HFile to determine checksum parameters.
    *  We always use FS checksum to do that, so ctor opens {@link #stream}.
    * 2.1) After that, if HBase checksum is not used, we'd just always use {@link #stream};
    * 2.2) If HBase checksum can be used, we'll open {@link #streamNoFsChecksum},
    *  and close {@link #stream}. User MUST call prepareForBlockReader for that to happen;
    *  if they don't, (2.1) will be the default.
    * 3) The users can call {@link #shouldUseHBaseChecksum()}, and pass its result to
    *  {@link #getStream(boolean)} to get stream (if Java had out/pointer params we could
    *  return both in one call). This stream is guaranteed to be set.
    * 4) The first time HBase checksum fails, one would call {@link #fallbackToFsChecksum(int)}.
    * That will take lock, and open {@link #stream}. While this is going on, others will
    * continue to use the old stream; if they also want to fall back, they'll also call
    * {@link #fallbackToFsChecksum(int)}, and block until {@link #stream} is set.
    * 5) After some number of checksumOk() calls, we will go back to using HBase checksum.
    * We will have 2 handles; however we presume checksums fail so rarely that we don't care.
    */
   private volatile FSDataInputStream stream = null;
   private volatile FSDataInputStream streamNoFsChecksum = null;
   private Object streamNoFsChecksumFirstCreateLock = new Object();

   // The configuration states that we should validate hbase checksums
   private boolean useHBaseChecksumConfigured;

   // Record the current state of this reader with respect to
   // validating checkums in HBase. This is originally set the same
   // value as useHBaseChecksumConfigured, but can change state as and when
   // we encounter checksum verification failures.
   private volatile boolean useHBaseChecksum;

   // In the case of a checksum failure, do these many succeeding
   // reads without hbase checksum verification.
   private volatile int hbaseChecksumOffCount = -1;

   public FSDataInputStreamWrapper(FileSystem fs, Path path) throws IOException {
     this(fs, null, path, false);
   }

   public FSDataInputStreamWrapper(FileSystem fs, Path path, boolean dropBehind) throws IOException {
     this(fs, null, path, dropBehind);
   }

   public FSDataInputStreamWrapper(FileSystem fs, FileLink link) throws IOException {
     this(fs, link, null, false);
   }
   public FSDataInputStreamWrapper(FileSystem fs, FileLink link,
                                   boolean dropBehind) throws IOException {
     this(fs, link, null, dropBehind);
   }

   private FSDataInputStreamWrapper(FileSystem fs, FileLink link,
                                    Path path, boolean dropBehind) throws IOException {
     assert (path == null) != (link == null);
     this.path = path;
     this.link = link;
     this.doCloseStreams = true;
     // If the fs is not an instance of HFileSystem, then create an instance of HFileSystem
     // that wraps over the specified fs. In this case, we will not be able to avoid
     // checksumming inside the filesystem.
     this.hfs = (fs instanceof HFileSystem) ? (HFileSystem)fs : new HFileSystem(fs);

     // Initially we are going to read the tail block. Open the reader w/FS checksum.
     this.useHBaseChecksumConfigured = this.useHBaseChecksum = false;
     this.stream = (link != null) ? link.open(hfs) : hfs.open(path);
     try {
       this.stream.setDropBehind(dropBehind);
     } catch (Exception e) {
       // Skipped.
     }
   }


   /**
    * Prepares the streams for block reader. NOT THREAD SAFE. Must be called once, after any
    * reads finish and before any other reads start (what happens in reality is we read the
    * tail, then call this based on what's in the tail, then read blocks).
    * @param forceNoHBaseChecksum Force not using HBase checksum.
    */
   public void prepareForBlockReader(boolean forceNoHBaseChecksum) throws IOException {
     if (hfs == null) return;
     assert this.stream != null && !this.useHBaseChecksumConfigured;
     boolean useHBaseChecksum =
         !forceNoHBaseChecksum && hfs.useHBaseChecksum() && (hfs.getNoChecksumFs() != hfs);

     if (useHBaseChecksum) {
       FileSystem fsNc = hfs.getNoChecksumFs();
       this.streamNoFsChecksum = (link != null) ? link.open(fsNc) : fsNc.open(path);
       this.useHBaseChecksumConfigured = this.useHBaseChecksum = useHBaseChecksum;
       // Close the checksum stream; we will reopen it if we get an HBase checksum failure.
       this.stream.close();
       this.stream = null;
     }
   }

   /** For use in tests. */
   @VisibleForTesting
   public FSDataInputStreamWrapper(FSDataInputStream fsdis) {
     this(fsdis, fsdis);
   }

   /** For use in tests. */
   @VisibleForTesting
   public FSDataInputStreamWrapper(FSDataInputStream fsdis, FSDataInputStream noChecksum) {
     doCloseStreams = false;
     stream = fsdis;
     streamNoFsChecksum = noChecksum;
     path = null;
     link = null;
     hfs = null;
     useHBaseChecksumConfigured = useHBaseChecksum = false;
   }

   /**
    * @return Whether we are presently using HBase checksum.
    */
   public boolean shouldUseHBaseChecksum() {
     return this.useHBaseChecksum;
   }

   /**
    * Get the stream to use. Thread-safe.
    * @param useHBaseChecksum must be the value that shouldUseHBaseChecksum has returned
    *  at some point in the past, otherwise the result is undefined.
    */
   public FSDataInputStream getStream(boolean useHBaseChecksum) {
     return useHBaseChecksum ? this.streamNoFsChecksum : this.stream;
   }

   /**
    * Read from non-checksum stream failed, fall back to FS checksum. Thread-safe.
    * @param offCount For how many checksumOk calls to turn off the HBase checksum.
    */
   public FSDataInputStream fallbackToFsChecksum(int offCount) throws IOException {
     // checksumOffCount is speculative, but let's try to reset it less.
     boolean partOfConvoy = false;
     if (this.stream == null) {
       synchronized (streamNoFsChecksumFirstCreateLock) {
         partOfConvoy = (this.stream != null);
         if (!partOfConvoy) {
           this.stream = (link != null) ? link.open(hfs) : hfs.open(path);
         }
       }
     }
     if (!partOfConvoy) {
       this.useHBaseChecksum = false;
       this.hbaseChecksumOffCount = offCount;
     }
     return this.stream;
   }

   /** Report that checksum was ok, so we may ponder going back to HBase checksum. */
   public void checksumOk() {
     if (this.useHBaseChecksumConfigured && !this.useHBaseChecksum
         && (this.hbaseChecksumOffCount-- < 0)) {
       // The stream we need is already open (because we were using HBase checksum in the past).
       assert this.streamNoFsChecksum != null;
       this.useHBaseChecksum = true;
     }
   }

   /** Close stream(s) if necessary. */
   public void close() throws IOException {
     if (!doCloseStreams) return;
     try {
       if (stream != streamNoFsChecksum && streamNoFsChecksum != null) {
         streamNoFsChecksum.close();
         streamNoFsChecksum = null;
       }
     } finally {
       if (stream != null) {
         stream.close();
         stream = null;
       }
     }
   }

   public HFileSystem getHfs() {
     return this.hfs;
   }
 }
	/**
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you under the Apache License, Version 2.0 (the
	* "License"); you may not use this file except in compliance
	* with the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package org.apache.hadoop.hbase.io;

	import java.io.IOException;

	import org.apache.hadoop.fs.FSDataInputStream;
	import org.apache.hadoop.fs.FileSystem;
	import org.apache.hadoop.fs.Path;
	import org.apache.hadoop.hbase.fs.HFileSystem;

	import com.google.common.annotations.VisibleForTesting;

	/**
	* Wrapper for input stream(s) that takes care of the interaction of FS and HBase checksums,
	* as well as closing streams. Initialization is not thread-safe, but normal operation is;
	* see method comments.
	*/
	public class FSDataInputStreamWrapper {
	private final HFileSystem hfs;
	private final Path path;
	private final FileLink link;
	private final boolean doCloseStreams;

	/** Two stream handles, one with and one without FS-level checksum.
	* HDFS checksum setting is on FS level, not single read level, so you have to keep two
	* FS objects and two handles open to interleave different reads freely, which is very sad.
	* This is what we do:
	* 1) First, we need to read the trailer of HFile to determine checksum parameters.
	* We always use FS checksum to do that, so ctor opens {@link #stream}.
	* 2.1) After that, if HBase checksum is not used, we'd just always use {@link #stream};
	* 2.2) If HBase checksum can be used, we'll open {@link #streamNoFsChecksum},
	* and close {@link #stream}. User MUST call prepareForBlockReader for that to happen;
	* if they don't, (2.1) will be the default.
	* 3) The users can call {@link #shouldUseHBaseChecksum()}, and pass its result to
	* {@link #getStream(boolean)} to get stream (if Java had out/pointer params we could
	* return both in one call). This stream is guaranteed to be set.
	* 4) The first time HBase checksum fails, one would call {@link #fallbackToFsChecksum(int)}.
	* That will take lock, and open {@link #stream}. While this is going on, others will
	* continue to use the old stream; if they also want to fall back, they'll also call
	* {@link #fallbackToFsChecksum(int)}, and block until {@link #stream} is set.
	* 5) After some number of checksumOk() calls, we will go back to using HBase checksum.
	* We will have 2 handles; however we presume checksums fail so rarely that we don't care.
	*/
	private volatile FSDataInputStream stream = null;
	private volatile FSDataInputStream streamNoFsChecksum = null;
	private Object streamNoFsChecksumFirstCreateLock = new Object();

	// The configuration states that we should validate hbase checksums
	private boolean useHBaseChecksumConfigured;

	// Record the current state of this reader with respect to
	// validating checkums in HBase. This is originally set the same
	// value as useHBaseChecksumConfigured, but can change state as and when
	// we encounter checksum verification failures.
	private volatile boolean useHBaseChecksum;

	// In the case of a checksum failure, do these many succeeding
	// reads without hbase checksum verification.
	private volatile int hbaseChecksumOffCount = -1;

	public FSDataInputStreamWrapper(FileSystem fs, Path path) throws IOException {
	this(fs, null, path, false);
	}

	public FSDataInputStreamWrapper(FileSystem fs, Path path, boolean dropBehind) throws IOException {
	this(fs, null, path, dropBehind);
	}

	public FSDataInputStreamWrapper(FileSystem fs, FileLink link) throws IOException {
	this(fs, link, null, false);
	}
	public FSDataInputStreamWrapper(FileSystem fs, FileLink link,
	boolean dropBehind) throws IOException {
	this(fs, link, null, dropBehind);
	}

	private FSDataInputStreamWrapper(FileSystem fs, FileLink link,
	Path path, boolean dropBehind) throws IOException {
	assert (path == null) != (link == null);
	this.path = path;
	this.link = link;
	this.doCloseStreams = true;
	// If the fs is not an instance of HFileSystem, then create an instance of HFileSystem
	// that wraps over the specified fs. In this case, we will not be able to avoid
	// checksumming inside the filesystem.
	this.hfs = (fs instanceof HFileSystem) ? (HFileSystem)fs : new HFileSystem(fs);

	// Initially we are going to read the tail block. Open the reader w/FS checksum.
	this.useHBaseChecksumConfigured = this.useHBaseChecksum = false;
	this.stream = (link != null) ? link.open(hfs) : hfs.open(path);
	try {
	this.stream.setDropBehind(dropBehind);
	} catch (Exception e) {
	// Skipped.
	}
	}


	/**
	* Prepares the streams for block reader. NOT THREAD SAFE. Must be called once, after any
	* reads finish and before any other reads start (what happens in reality is we read the
	* tail, then call this based on what's in the tail, then read blocks).
	* @param forceNoHBaseChecksum Force not using HBase checksum.
	*/
	public void prepareForBlockReader(boolean forceNoHBaseChecksum) throws IOException {
	if (hfs == null) return;
	assert this.stream != null && !this.useHBaseChecksumConfigured;
	boolean useHBaseChecksum =
	!forceNoHBaseChecksum && hfs.useHBaseChecksum() && (hfs.getNoChecksumFs() != hfs);

	if (useHBaseChecksum) {
	FileSystem fsNc = hfs.getNoChecksumFs();
	this.streamNoFsChecksum = (link != null) ? link.open(fsNc) : fsNc.open(path);
	this.useHBaseChecksumConfigured = this.useHBaseChecksum = useHBaseChecksum;
	// Close the checksum stream; we will reopen it if we get an HBase checksum failure.
	this.stream.close();
	this.stream = null;
	}
	}

	/** For use in tests. */
	@VisibleForTesting
	public FSDataInputStreamWrapper(FSDataInputStream fsdis) {
	this(fsdis, fsdis);
	}

	/** For use in tests. */
	@VisibleForTesting
	public FSDataInputStreamWrapper(FSDataInputStream fsdis, FSDataInputStream noChecksum) {
	doCloseStreams = false;
	stream = fsdis;
	streamNoFsChecksum = noChecksum;
	path = null;
	link = null;
	hfs = null;
	useHBaseChecksumConfigured = useHBaseChecksum = false;
	}

	/**
	* @return Whether we are presently using HBase checksum.
	*/
	public boolean shouldUseHBaseChecksum() {
	return this.useHBaseChecksum;
	}

	/**
	* Get the stream to use. Thread-safe.
	* @param useHBaseChecksum must be the value that shouldUseHBaseChecksum has returned
	* at some point in the past, otherwise the result is undefined.
	*/
	public FSDataInputStream getStream(boolean useHBaseChecksum) {
	return useHBaseChecksum ? this.streamNoFsChecksum : this.stream;
	}

	/**
	* Read from non-checksum stream failed, fall back to FS checksum. Thread-safe.
	* @param offCount For how many checksumOk calls to turn off the HBase checksum.
	*/
	public FSDataInputStream fallbackToFsChecksum(int offCount) throws IOException {
	// checksumOffCount is speculative, but let's try to reset it less.
	boolean partOfConvoy = false;
	if (this.stream == null) {
	synchronized (streamNoFsChecksumFirstCreateLock) {
	partOfConvoy = (this.stream != null);
	if (!partOfConvoy) {
	this.stream = (link != null) ? link.open(hfs) : hfs.open(path);
	}
	}
	}
	if (!partOfConvoy) {
	this.useHBaseChecksum = false;
	this.hbaseChecksumOffCount = offCount;
	}
	return this.stream;
	}

	/** Report that checksum was ok, so we may ponder going back to HBase checksum. */
	public void checksumOk() {
	if (this.useHBaseChecksumConfigured && !this.useHBaseChecksum
	&& (this.hbaseChecksumOffCount-- < 0)) {
	// The stream we need is already open (because we were using HBase checksum in the past).
	assert this.streamNoFsChecksum != null;
	this.useHBaseChecksum = true;
	}
	}

	/** Close stream(s) if necessary. */
	public void close() throws IOException {
	if (!doCloseStreams) return;
	try {
	if (stream != streamNoFsChecksum && streamNoFsChecksum != null) {
	streamNoFsChecksum.close();
	streamNoFsChecksum = null;
	}
	} finally {
	if (stream != null) {
	stream.close();
	stream = null;
	}
	}
	}

	public HFileSystem getHfs() {
	return this.hfs;
	}
	}