[BEAM-86] Add CountingInput as a PTransform #10
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| /* | ||
| * Copyright (C) 2016 Google Inc. | ||
| * | ||
| * Licensed 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. | ||
| */ | ||
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| package com.google.cloud.dataflow.sdk.io; | ||
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| import static com.google.common.base.Preconditions.checkArgument; | ||
| import static com.google.common.base.Preconditions.checkNotNull; | ||
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| import com.google.cloud.dataflow.sdk.io.CountingSource.NowTimestampFn; | ||
| import com.google.cloud.dataflow.sdk.io.Read.Unbounded; | ||
| import com.google.cloud.dataflow.sdk.transforms.PTransform; | ||
| import com.google.cloud.dataflow.sdk.transforms.SerializableFunction; | ||
| import com.google.cloud.dataflow.sdk.values.PBegin; | ||
| import com.google.cloud.dataflow.sdk.values.PCollection; | ||
| import com.google.cloud.dataflow.sdk.values.PCollection.IsBounded; | ||
| import com.google.common.base.Optional; | ||
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| import org.joda.time.Duration; | ||
| import org.joda.time.Instant; | ||
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| /** | ||
| * A {@link PTransform} that produces longs. When used to produce a | ||
| * {@link IsBounded#BOUNDED bounded} {@link PCollection}, {@link CountingInput} starts at {@code 0} | ||
| * and counts up to a specified maximum. When used to produce an | ||
| * {@link IsBounded#UNBOUNDED unbounded} {@link PCollection}, it counts up to {@link Long#MAX_VALUE} | ||
| * and then never produces more output. (In practice, this limit should never be reached.) | ||
| * | ||
| * <p>The bounded {@link CountingInput} is implemented based on {@link OffsetBasedSource} and | ||
| * {@link OffsetBasedSource.OffsetBasedReader}, so it performs efficient initial splitting and it | ||
| * supports dynamic work rebalancing. | ||
| * | ||
| * <p>To produce a bounded {@code PCollection<Long>}, use {@link CountingInput#upTo(long)}: | ||
| * | ||
| * <pre>{@code | ||
| * Pipeline p = ... | ||
| * PTransform<PBegin, PCollection<Long>> producer = CountingInput.upTo(1000); | ||
| * PCollection<Long> bounded = p.apply(producer); | ||
| * }</pre> | ||
| * | ||
| * <p>To produce an unbounded {@code PCollection<Long>}, use {@link CountingInput#unbounded()}, | ||
| * calling {@link UnboundedCountingInput#withTimestampFn(SerializableFunction)} to provide values | ||
| * with timestamps other than {@link Instant#now}. | ||
| * | ||
| * <pre>{@code | ||
| * Pipeline p = ... | ||
| * | ||
| * // To create an unbounded producer that uses processing time as the element timestamp. | ||
| * PCollection<Long> unbounded = p.apply(CountingInput.unbounded()); | ||
| * // Or, to create an unbounded source that uses a provided function to set the element timestamp. | ||
| * PCollection<Long> unboundedWithTimestamps = | ||
| * p.apply(CountingInput.unbounded().withTimestampFn(someFn)); | ||
| * }</pre> | ||
| */ | ||
| public class CountingInput { | ||
| /** | ||
| * Creates a {@link BoundedCountingInput} that will produce the specified number of elements, | ||
| * from {@code 0} to {@code numElements - 1}. | ||
| */ | ||
| public static BoundedCountingInput upTo(long numElements) { | ||
| checkArgument(numElements > 0, "numElements (%s) must be greater than 0", numElements); | ||
| return new BoundedCountingInput(numElements); | ||
| } | ||
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| /** | ||
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| * Creates an {@link UnboundedCountingInput} that will produce numbers starting from {@code 0} up | ||
| * to {@link Long#MAX_VALUE}. | ||
| * | ||
| * <p>After {@link Long#MAX_VALUE}, the transform never produces more output. (In practice, this | ||
| * limit should never be reached.) | ||
| * | ||
| * <p>Elements in the resulting {@link PCollection PCollection<Long>} will by default have | ||
| * timestamps corresponding to processing time at element generation, provided by | ||
| * {@link Instant#now}. Use the transform returned by | ||
| * {@link UnboundedCountingInput#withTimestampFn(SerializableFunction)} to control the output | ||
| * timestamps. | ||
| */ | ||
| public static UnboundedCountingInput unbounded() { | ||
| return new UnboundedCountingInput( | ||
| new NowTimestampFn(), Optional.<Long>absent(), Optional.<Duration>absent()); | ||
| } | ||
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| /** | ||
| * A {@link PTransform} that will produce a specified number of {@link Long Longs} starting from | ||
| * 0. | ||
| */ | ||
| public static class BoundedCountingInput extends PTransform<PBegin, PCollection<Long>> { | ||
| private final long numElements; | ||
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| private BoundedCountingInput(long numElements) { | ||
| this.numElements = numElements; | ||
| } | ||
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| @SuppressWarnings("deprecation") | ||
| @Override | ||
| public PCollection<Long> apply(PBegin begin) { | ||
| return begin.apply(Read.from(CountingSource.upTo(numElements))); | ||
| } | ||
| } | ||
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| /** | ||
| * A {@link PTransform} that will produce numbers starting from {@code 0} up to | ||
| * {@link Long#MAX_VALUE}. | ||
| * | ||
| * <p>After {@link Long#MAX_VALUE}, the transform never produces more output. (In practice, this | ||
| * limit should never be reached.) | ||
| * | ||
| * <p>Elements in the resulting {@link PCollection PCollection<Long>} will by default have | ||
| * timestamps corresponding to processing time at element generation, provided by | ||
| * {@link Instant#now}. Use the transform returned by | ||
| * {@link UnboundedCountingInput#withTimestampFn(SerializableFunction)} to control the output | ||
| * timestamps. | ||
| */ | ||
| public static class UnboundedCountingInput extends PTransform<PBegin, PCollection<Long>> { | ||
| private final SerializableFunction<Long, Instant> timestampFn; | ||
| private final Optional<Long> maxNumRecords; | ||
| private final Optional<Duration> maxReadTime; | ||
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| private UnboundedCountingInput( | ||
| SerializableFunction<Long, Instant> timestampFn, | ||
| Optional<Long> maxNumRecords, | ||
| Optional<Duration> maxReadTime) { | ||
| this.timestampFn = timestampFn; | ||
| this.maxNumRecords = maxNumRecords; | ||
| this.maxReadTime = maxReadTime; | ||
| } | ||
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| /** | ||
| * Returns an {@link UnboundedCountingInput} like this one, but where output elements have the | ||
| * timestamp specified by the timestampFn. | ||
| * | ||
| * <p>Note that the timestamps produced by {@code timestampFn} may not decrease. | ||
| */ | ||
| public UnboundedCountingInput withTimestampFn(SerializableFunction<Long, Instant> timestampFn) { | ||
| return new UnboundedCountingInput(timestampFn, maxNumRecords, maxReadTime); | ||
| } | ||
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| /** | ||
| * Returns an {@link UnboundedCountingInput} like this one, but that will read at most the | ||
| * specified number of elements. | ||
| * | ||
| * <p>A bounded amount of elements will be produced by the result transform, and the result | ||
| * {@link PCollection} will be {@link IsBounded#BOUNDED bounded}. | ||
| */ | ||
| public UnboundedCountingInput withMaxNumRecords(long maxRecords) { | ||
| checkArgument( | ||
| maxRecords > 0, "MaxRecords must be a positive (nonzero) value. Got %s", maxRecords); | ||
| return new UnboundedCountingInput(timestampFn, Optional.of(maxRecords), maxReadTime); | ||
| } | ||
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| /** | ||
| * Returns an {@link UnboundedCountingInput} like this one, but that will read for at most the | ||
| * specified amount of time. | ||
| * | ||
| * <p>A bounded amount of elements will be produced by the result transform, and the result | ||
| * {@link PCollection} will be {@link IsBounded#BOUNDED bounded}. | ||
| */ | ||
| public UnboundedCountingInput withMaxReadTime(Duration readTime) { | ||
| checkNotNull(readTime, "ReadTime cannot be null"); | ||
| return new UnboundedCountingInput(timestampFn, maxNumRecords, Optional.of(readTime)); | ||
| } | ||
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| @SuppressWarnings("deprecation") | ||
| @Override | ||
| public PCollection<Long> apply(PBegin begin) { | ||
| Unbounded<Long> read = Read.from(CountingSource.unboundedWithTimestampFn(timestampFn)); | ||
| if (!maxNumRecords.isPresent() && !maxReadTime.isPresent()) { | ||
| return begin.apply(read); | ||
| } else if (maxNumRecords.isPresent() && !maxReadTime.isPresent()) { | ||
| return begin.apply(read.withMaxNumRecords(maxNumRecords.get())); | ||
| } else if (!maxNumRecords.isPresent() && maxReadTime.isPresent()) { | ||
| return begin.apply(read.withMaxReadTime(maxReadTime.get())); | ||
| } else { | ||
| return begin.apply( | ||
| read.withMaxReadTime(maxReadTime.get()).withMaxNumRecords(maxNumRecords.get())); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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class-level javadoc mimicking the CountingSource javadoc.