sdks/java/core/src/main/java/org/apache/beam/sdk/io/range/OffsetRangeTracker.java - beam - 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.beam.sdk.io.range;

 import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkState;

 import org.apache.beam.sdk.io.BoundedSource.BoundedReader;
 import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.annotations.VisibleForTesting;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 /**
  * A {@link RangeTracker} for non-negative positions of type {@code long}.
  *
  * <p>Not to be confused with {@link
  * org.apache.beam.sdk.transforms.splittabledofn.OffsetRangeTracker}.
  */
 public class OffsetRangeTracker implements RangeTracker<Long> {
   private static final Logger LOG = LoggerFactory.getLogger(OffsetRangeTracker.class);

   private long startOffset;
   private long stopOffset;
   private long lastRecordStart = -1L;
   private long offsetOfLastSplitPoint = -1L;
   private long splitPointsSeen = 0L;
   private boolean done = false;

   /**
    * Offset corresponding to infinity. This can only be used as the upper-bound of a range, and
    * indicates reading all of the records until the end without specifying exactly what the end is.
    *
    * <p>Infinite ranges cannot be split because it is impossible to estimate progress within them.
    */
   public static final long OFFSET_INFINITY = Long.MAX_VALUE;

   /** Creates an {@code OffsetRangeTracker} for the specified range. */
   public OffsetRangeTracker(long startOffset, long stopOffset) {
     this.startOffset = startOffset;
     this.stopOffset = stopOffset;
   }

   private OffsetRangeTracker() {}

   public synchronized boolean isStarted() {
     // done => started: handles the case when the reader was empty.
     return (offsetOfLastSplitPoint != -1) || done;
   }

   public synchronized boolean isDone() {
     return done;
   }

   @Override
   public synchronized Long getStartPosition() {
     return startOffset;
   }

   @Override
   public synchronized Long getStopPosition() {
     return stopOffset;
   }

   @Override
   public boolean tryReturnRecordAt(boolean isAtSplitPoint, Long recordStart) {
     return tryReturnRecordAt(isAtSplitPoint, recordStart.longValue());
   }

   public synchronized boolean tryReturnRecordAt(boolean isAtSplitPoint, long recordStart) {
     if (!isStarted() && !isAtSplitPoint) {
       throw new IllegalStateException(
           String.format("The first record [starting at %d] must be at a split point", recordStart));
     }
     if (recordStart < startOffset) {
       throw new IllegalStateException(
           String.format(
               "Trying to return record [starting at %d] which is before the start offset [%d]",
               recordStart, startOffset));
     }
     if (recordStart < lastRecordStart) {
       throw new IllegalStateException(
           String.format(
               "Trying to return record [starting at %d] "
                   + "which is before the last-returned record [starting at %d]",
               recordStart, lastRecordStart));
     }

     if (lastRecordStart == -1) {
       startOffset = recordStart;
     }
     lastRecordStart = recordStart;

     if (isAtSplitPoint) {
       if (recordStart == offsetOfLastSplitPoint) {
         throw new IllegalStateException(
             String.format(
                 "Record at a split point has same offset as the previous split point: "
                     + "previous split point at %d, current record starts at %d",
                 offsetOfLastSplitPoint, recordStart));
       }
       if (recordStart >= stopOffset) {
         done = true;
         return false;
       }
       offsetOfLastSplitPoint = recordStart;
       ++splitPointsSeen;
     }

     return true;
   }

   @Override
   public boolean trySplitAtPosition(Long splitOffset) {
     return trySplitAtPosition(splitOffset.longValue());
   }

   public synchronized boolean trySplitAtPosition(long splitOffset) {
     if (stopOffset == OFFSET_INFINITY) {
       LOG.debug("Refusing to split {} at {}: stop position unspecified", this, splitOffset);
       return false;
     }
     if (!isStarted()) {
       LOG.debug("Refusing to split {} at {}: unstarted", this, splitOffset);
       return false;
     }

     // Note: technically it is correct to split at any position after the last returned
     // split point, not just the last returned record.
     // TODO: Investigate whether in practice this is useful or, rather, confusing.
     if (splitOffset <= lastRecordStart) {
       LOG.debug(
           "Refusing to split {} at {}: already past proposed split position", this, splitOffset);
       return false;
     }
     if (splitOffset < startOffset || splitOffset >= stopOffset) {
       LOG.debug(
           "Refusing to split {} at {}: proposed split position out of range", this, splitOffset);
       return false;
     }
     LOG.debug("Agreeing to split {} at {}", this, splitOffset);
     this.stopOffset = splitOffset;
     return true;
   }

   /**
    * Returns a position {@code P} such that the range {@code [start, P)} represents approximately
    * the given fraction of the range {@code [start, end)}. Assumes that the density of records in
    * the range is approximately uniform.
    */
   public synchronized long getPositionForFractionConsumed(double fraction) {
     if (stopOffset == OFFSET_INFINITY) {
       throw new IllegalArgumentException(
           "getPositionForFractionConsumed is not applicable to an unbounded range: " + this);
     }
     return (long) Math.floor(startOffset + fraction * (stopOffset - startOffset));
   }

   @Override
   public synchronized double getFractionConsumed() {
     if (!isStarted()) {
       return 0.0;
     } else if (isDone()) {
       return 1.0;
     } else if (stopOffset == OFFSET_INFINITY) {
       return 0.0;
     } else if (lastRecordStart >= stopOffset) {
       return 1.0;
     } else {
       // E.g., when reading [3, 6) and lastRecordStart is 4, that means we consumed 3 of 3,4,5
       // which is (4 - 3) / (6 - 3) = 33%.
       // Also, clamp to at most 1.0 because the last consumed position can extend past the
       // stop position.
       return Math.min(1.0, 1.0 * (lastRecordStart - startOffset) / (stopOffset - startOffset));
     }
   }

   /**
    * Returns the total number of split points that have been processed.
    *
    * <p>A split point at a particular offset has been seen if there has been a corresponding call to
    * {@link #tryReturnRecordAt(boolean, long)} with {@code isAtSplitPoint} true. It has been
    * processed if there has been a <em>subsequent</em> call to {@link #tryReturnRecordAt(boolean,
    * long)} with {@code isAtSplitPoint} true and at a larger offset.
    *
    * <p>Note that for correctness when implementing {@link BoundedReader#getSplitPointsConsumed()},
    * if a reader finishes before {@link #tryReturnRecordAt(boolean, long)} returns false, the reader
    * should add an additional call to {@link #markDone()}. This will indicate that processing for
    * the last seen split point has been finished.
    *
    * @see org.apache.beam.sdk.io.OffsetBasedSource for a {@link BoundedReader} implemented using
    *     {@link OffsetRangeTracker}.
    */
   public synchronized long getSplitPointsProcessed() {
     if (!isStarted()) {
       return 0;
     } else if (isDone()) {
       return splitPointsSeen;
     } else {
       // There is a current split point, and it has not finished processing.
       checkState(
           splitPointsSeen > 0,
           "A started rangeTracker should have seen > 0 split points (is %s)",
           splitPointsSeen);
       return splitPointsSeen - 1;
     }
   }

   /**
    * Marks this range tracker as being done. Specifically, this will mark the current split point,
    * if one exists, as being finished.
    *
    * <p>Always returns false, so that it can be used in an implementation of {@link
    * BoundedReader#start()} or {@link BoundedReader#advance()} as follows:
    *
    * <pre>{@code
    * public boolean start() {
    *   return startImpl() && rangeTracker.tryReturnRecordAt(isAtSplitPoint, position)
    *       || rangeTracker.markDone();
    * }
    * }</pre>
    */
   public synchronized boolean markDone() {
     done = true;
     return false;
   }

   @Override
   public synchronized String toString() {
     String stopString = (stopOffset == OFFSET_INFINITY) ? "infinity" : String.valueOf(stopOffset);
     if (lastRecordStart >= 0) {
       return String.format(
           "<at [starting at %d] of offset range [%d, %s)>",
           lastRecordStart, startOffset, stopString);
     } else {
       return String.format("<unstarted in offset range [%d, %s)>", startOffset, stopString);
     }
   }

   /**
    * Returns a copy of this tracker for testing purposes (to simplify testing methods with side
    * effects).
    */
   @VisibleForTesting
   OffsetRangeTracker copy() {
     synchronized (this) {
       OffsetRangeTracker res = new OffsetRangeTracker();
       // This synchronized is not really necessary, because there's no concurrent access to "res",
       // however it is necessary to prevent findbugs from complaining about unsynchronized access.
       synchronized (res) {
         res.startOffset = this.startOffset;
         res.stopOffset = this.stopOffset;
         res.offsetOfLastSplitPoint = this.offsetOfLastSplitPoint;
         res.lastRecordStart = this.lastRecordStart;
         res.done = this.done;
         res.splitPointsSeen = this.splitPointsSeen;
       }
       return res;
     }
   }
 }
	/*
	* 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.beam.sdk.io.range;

	import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkState;

	import org.apache.beam.sdk.io.BoundedSource.BoundedReader;
	import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.annotations.VisibleForTesting;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;

	/**
	* A {@link RangeTracker} for non-negative positions of type {@code long}.
	*
	* <p>Not to be confused with {@link
	* org.apache.beam.sdk.transforms.splittabledofn.OffsetRangeTracker}.
	*/
	public class OffsetRangeTracker implements RangeTracker<Long> {
	private static final Logger LOG = LoggerFactory.getLogger(OffsetRangeTracker.class);

	private long startOffset;
	private long stopOffset;
	private long lastRecordStart = -1L;
	private long offsetOfLastSplitPoint = -1L;
	private long splitPointsSeen = 0L;
	private boolean done = false;

	/**
	* Offset corresponding to infinity. This can only be used as the upper-bound of a range, and
	* indicates reading all of the records until the end without specifying exactly what the end is.
	*
	* <p>Infinite ranges cannot be split because it is impossible to estimate progress within them.
	*/
	public static final long OFFSET_INFINITY = Long.MAX_VALUE;

	/** Creates an {@code OffsetRangeTracker} for the specified range. */
	public OffsetRangeTracker(long startOffset, long stopOffset) {
	this.startOffset = startOffset;
	this.stopOffset = stopOffset;
	}

	private OffsetRangeTracker() {}

	public synchronized boolean isStarted() {
	// done => started: handles the case when the reader was empty.
	return (offsetOfLastSplitPoint != -1) \|\| done;
	}

	public synchronized boolean isDone() {
	return done;
	}

	@Override
	public synchronized Long getStartPosition() {
	return startOffset;
	}

	@Override
	public synchronized Long getStopPosition() {
	return stopOffset;
	}

	@Override
	public boolean tryReturnRecordAt(boolean isAtSplitPoint, Long recordStart) {
	return tryReturnRecordAt(isAtSplitPoint, recordStart.longValue());
	}

	public synchronized boolean tryReturnRecordAt(boolean isAtSplitPoint, long recordStart) {
	if (!isStarted() && !isAtSplitPoint) {
	throw new IllegalStateException(
	String.format("The first record [starting at %d] must be at a split point", recordStart));
	}
	if (recordStart < startOffset) {
	throw new IllegalStateException(
	String.format(
	"Trying to return record [starting at %d] which is before the start offset [%d]",
	recordStart, startOffset));
	}
	if (recordStart < lastRecordStart) {
	throw new IllegalStateException(
	String.format(
	"Trying to return record [starting at %d] "
	+ "which is before the last-returned record [starting at %d]",
	recordStart, lastRecordStart));
	}

	if (lastRecordStart == -1) {
	startOffset = recordStart;
	}
	lastRecordStart = recordStart;

	if (isAtSplitPoint) {
	if (recordStart == offsetOfLastSplitPoint) {
	throw new IllegalStateException(
	String.format(
	"Record at a split point has same offset as the previous split point: "
	+ "previous split point at %d, current record starts at %d",
	offsetOfLastSplitPoint, recordStart));
	}
	if (recordStart >= stopOffset) {
	done = true;
	return false;
	}
	offsetOfLastSplitPoint = recordStart;
	++splitPointsSeen;
	}

	return true;
	}

	@Override
	public boolean trySplitAtPosition(Long splitOffset) {
	return trySplitAtPosition(splitOffset.longValue());
	}

	public synchronized boolean trySplitAtPosition(long splitOffset) {
	if (stopOffset == OFFSET_INFINITY) {
	LOG.debug("Refusing to split {} at {}: stop position unspecified", this, splitOffset);
	return false;
	}
	if (!isStarted()) {
	LOG.debug("Refusing to split {} at {}: unstarted", this, splitOffset);
	return false;
	}

	// Note: technically it is correct to split at any position after the last returned
	// split point, not just the last returned record.
	// TODO: Investigate whether in practice this is useful or, rather, confusing.
	if (splitOffset <= lastRecordStart) {
	LOG.debug(
	"Refusing to split {} at {}: already past proposed split position", this, splitOffset);
	return false;
	}
	if (splitOffset < startOffset \|\| splitOffset >= stopOffset) {
	LOG.debug(
	"Refusing to split {} at {}: proposed split position out of range", this, splitOffset);
	return false;
	}
	LOG.debug("Agreeing to split {} at {}", this, splitOffset);
	this.stopOffset = splitOffset;
	return true;
	}

	/**
	* Returns a position {@code P} such that the range {@code [start, P)} represents approximately
	* the given fraction of the range {@code [start, end)}. Assumes that the density of records in
	* the range is approximately uniform.
	*/
	public synchronized long getPositionForFractionConsumed(double fraction) {
	if (stopOffset == OFFSET_INFINITY) {
	throw new IllegalArgumentException(
	"getPositionForFractionConsumed is not applicable to an unbounded range: " + this);
	}
	return (long) Math.floor(startOffset + fraction * (stopOffset - startOffset));
	}

	@Override
	public synchronized double getFractionConsumed() {
	if (!isStarted()) {
	return 0.0;
	} else if (isDone()) {
	return 1.0;
	} else if (stopOffset == OFFSET_INFINITY) {
	return 0.0;
	} else if (lastRecordStart >= stopOffset) {
	return 1.0;
	} else {
	// E.g., when reading [3, 6) and lastRecordStart is 4, that means we consumed 3 of 3,4,5
	// which is (4 - 3) / (6 - 3) = 33%.
	// Also, clamp to at most 1.0 because the last consumed position can extend past the
	// stop position.
	return Math.min(1.0, 1.0 * (lastRecordStart - startOffset) / (stopOffset - startOffset));
	}
	}

	/**
	* Returns the total number of split points that have been processed.
	*
	* <p>A split point at a particular offset has been seen if there has been a corresponding call to
	* {@link #tryReturnRecordAt(boolean, long)} with {@code isAtSplitPoint} true. It has been
	* processed if there has been a <em>subsequent</em> call to {@link #tryReturnRecordAt(boolean,
	* long)} with {@code isAtSplitPoint} true and at a larger offset.
	*
	* <p>Note that for correctness when implementing {@link BoundedReader#getSplitPointsConsumed()},
	* if a reader finishes before {@link #tryReturnRecordAt(boolean, long)} returns false, the reader
	* should add an additional call to {@link #markDone()}. This will indicate that processing for
	* the last seen split point has been finished.
	*
	* @see org.apache.beam.sdk.io.OffsetBasedSource for a {@link BoundedReader} implemented using
	* {@link OffsetRangeTracker}.
	*/
	public synchronized long getSplitPointsProcessed() {
	if (!isStarted()) {
	return 0;
	} else if (isDone()) {
	return splitPointsSeen;
	} else {
	// There is a current split point, and it has not finished processing.
	checkState(
	splitPointsSeen > 0,
	"A started rangeTracker should have seen > 0 split points (is %s)",
	splitPointsSeen);
	return splitPointsSeen - 1;
	}
	}

	/**
	* Marks this range tracker as being done. Specifically, this will mark the current split point,
	* if one exists, as being finished.
	*
	* <p>Always returns false, so that it can be used in an implementation of {@link
	* BoundedReader#start()} or {@link BoundedReader#advance()} as follows:
	*
	* <pre>{@code
	* public boolean start() {
	* return startImpl() && rangeTracker.tryReturnRecordAt(isAtSplitPoint, position)
	* \|\| rangeTracker.markDone();
	* }
	* }</pre>
	*/
	public synchronized boolean markDone() {
	done = true;
	return false;
	}

	@Override
	public synchronized String toString() {
	String stopString = (stopOffset == OFFSET_INFINITY) ? "infinity" : String.valueOf(stopOffset);
	if (lastRecordStart >= 0) {
	return String.format(
	"<at [starting at %d] of offset range [%d, %s)>",
	lastRecordStart, startOffset, stopString);
	} else {
	return String.format("<unstarted in offset range [%d, %s)>", startOffset, stopString);
	}
	}

	/**
	* Returns a copy of this tracker for testing purposes (to simplify testing methods with side
	* effects).
	*/
	@VisibleForTesting
	OffsetRangeTracker copy() {
	synchronized (this) {
	OffsetRangeTracker res = new OffsetRangeTracker();
	// This synchronized is not really necessary, because there's no concurrent access to "res",
	// however it is necessary to prevent findbugs from complaining about unsynchronized access.
	synchronized (res) {
	res.startOffset = this.startOffset;
	res.stopOffset = this.stopOffset;
	res.offsetOfLastSplitPoint = this.offsetOfLastSplitPoint;
	res.lastRecordStart = this.lastRecordStart;
	res.done = this.done;
	res.splitPointsSeen = this.splitPointsSeen;
	}
	return res;
	}
	}
	}