add key reshuffler, takes key and outputs autoshardable key

sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/AutoshardedKeyReshuffle.java

@@ -0,0 +1,136 @@
+/*
+ * 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.transforms;
+
+import org.apache.beam.sdk.transforms.WithKeys;
+import java.util.concurrent.ThreadLocalRandom;
+import org.apache.beam.sdk.annotations.Internal;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.apache.beam.sdk.transforms.windowing.ReshuffleTrigger;
+import org.apache.beam.sdk.transforms.windowing.TimestampCombiner;
+import org.apache.beam.sdk.transforms.windowing.Window;
+import org.apache.beam.sdk.util.IdentityWindowFn;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.TimestampedValue;
+import org.apache.beam.sdk.values.WindowingStrategy;
+import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.primitives.UnsignedInteger;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Duration;
+import org.apache.beam.sdk.util.ShardedKey;
+import java.io.Serializable;
+import java.nio.ByteBuffer;
+import java.util.UUID;
+
+/**
+ * <b>For internal use only; no backwards compatibility guarantees.</b>
+ *
+ * <p>A {@link PTransform} that returns a {@link PCollection} equivalent to its input but
+ * operationally provides some of the side effects of a {@link GroupByKey}, in particular
+ * checkpointing, and preventing fusion of the surrounding transforms.
+ *
+ * <p>Performs a {@link GroupByKey} so that the data is key-partitioned. Configures the {@link
+ * WindowingStrategy} so that no data is dropped, but doesn't affect the need for the user to
+ * specify allowed lateness and accumulation mode before a user-inserted GroupByKey.
+ *
+ * @param <K> The type of key being reshuffled on.
+ * @param <V> The type of value being reshuffled.
+ */
+public class AutoshardedKeyReshuffle<K, V> extends PTransform<
+    PCollection<KV<ShardedKey<K>, V>>, PCollection<KV<ShardedKey<K>, V>>> {
+
+  private AutoshardedKeyReshuffle() {}
+
+  public static <K, V>  AutoshardedKeyReshuffle<K, V>  of() {
+    return new AutoshardedKeyReshuffle<>();
+  }
+
+  /**
+   * Encapsulates the sequence "take keyed value, return the same as autosharded key with single autoshardable key, apply {@link Reshuffle#of}, DONT drop the
+   * key" commonly used to break fusion.
+   */
+  public static <K, V> ViaRandomKey <K, V> viaRandomKey() {
+    return new ViaRandomKey<>();
+  }
+
+  @Override
+  public PCollection<KV<ShardedKey<K>, V>>  expand(PCollection<KV<ShardedKey<K>, V>> input) {
+    WindowingStrategy<?, ?> originalStrategy = input.getWindowingStrategy();
+    // If the input has already had its windows merged, then the GBK that performed the merge
+    // will have set originalStrategy.getWindowFn() to InvalidWindows, causing the GBK contained
+    // here to fail. Instead, we install a valid WindowFn that leaves all windows unchanged.
+    // The TimestampCombiner is set to ensure the GroupByKey does not shift elements forwards in
+    // time.
+    // Because this outputs as fast as possible, this should not hold the watermark.
+    Window<KV<ShardedKey<K>, V>> rewindow =
+        Window.<KV<ShardedKey<K>, V>>into(new IdentityWindowFn<>(originalStrategy.getWindowFn().windowCoder()))
+            .triggering(new ReshuffleTrigger<>()) // can this be reused?
+            .discardingFiredPanes()
+            .withTimestampCombiner(TimestampCombiner.EARLIEST)
+            .withAllowedLateness(Duration.millis(BoundedWindow.TIMESTAMP_MAX_VALUE.getMillis()));
+
+    return input
+        .apply(rewindow)
+        .apply("ReifyOriginalTimestamps", Reify.timestampsInValue())
+        .apply(GroupByKey.create())
+        // Set the windowing strategy directly, so that it doesn't get counted as the user having
+        // set allowed lateness.
+        .setWindowingStrategyInternal(originalStrategy)
+        .apply(
+            "ExpandIterable",
+            ParDo.of(
+                new DoFn<KV<ShardedKey<K>, Iterable<TimestampedValue<V>>>, KV<ShardedKey<K>, TimestampedValue<V>>>() {
+                  @ProcessElement
+                  public void processElement(
+                      @Element KV<ShardedKey<K>, Iterable<TimestampedValue<V>>> element,
+                      OutputReceiver<KV<ShardedKey<K>, TimestampedValue<V>>> r) {
+                    ShardedKey<K> key = element.getKey();
+                    for (TimestampedValue<V> value : element.getValue()) {
+                      r.output(KV.of(key, value));
+                    }
+                  }
+                }))
+        .apply("RestoreOriginalTimestamps", ReifyTimestamps.extractFromValues());
+  }
+
+  /** Implementation of {@link #viaRandomKey()}. */
+  public static class ViaRandomKey<K, V> extends PTransform<PCollection<KV<K, V>>, PCollection<KV<ShardedKey<K>, V>>> {
+    public ViaRandomKey() {}
+
+    @Override
+    public PCollection<KV<ShardedKey<K>, V>>  expand(PCollection<KV<K, V>> input) {
+      return input
+          .apply("Pair element with a single autoshardable key", ParDo.of(new AssignShardFn<>())) // assign a single autoshardable key 
+          .apply(AutoshardedKeyReshuffle.of()); // takes autosharded keyed input, ensures windows are correctly handled 
+    }
+  }
+
+public static class AssignShardFn<K, V> extends DoFn<KV<K, V>, KV<ShardedKey<K>, V>> {
+    private static final UUID workerUuid = UUID.randomUUID();
+
+    @ProcessElement
+    public void processElement(@Element KV<K, V> element, OutputReceiver<KV<ShardedKey<K>, V>> r) {
+      long shard = Thread.currentThread().getId();
+        ByteBuffer buffer = ByteBuffer.allocate(3 * Long.BYTES);
+        buffer.putLong(workerUuid.getMostSignificantBits());
+        buffer.putLong(workerUuid.getLeastSignificantBits());
+        buffer.putLong(shard);
+      r.output(KV.of(ShardedKey.of(element.getKey(), buffer.array()), element.getValue()));
+    }
+  }
+}