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Beam IO for Google Cloud Pub/Sub Lite

There is a newer version: 0.23.0

/*
 * Copyright 2020 Google LLC
 *
 * 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.
 */

package com.google.cloud.pubsublite.beam;

import com.google.cloud.pubsublite.proto.AttributeValues;
import com.google.cloud.pubsublite.proto.PubSubMessage;
import org.apache.beam.sdk.transforms.MapElements;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.Reshuffle;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.TypeDescriptor;

/** A transform to add UUIDs to each message to be written to Pub/Sub Lite. */
class AddUuidsTransform extends PTransform, PCollection> {
  private static PubSubMessage addUuid(PubSubMessage message) {
    PubSubMessage.Builder builder = message.toBuilder();
    builder.putAttributes(
        Uuid.DEFAULT_ATTRIBUTE,
        AttributeValues.newBuilder().addValues(Uuid.random().value()).build());
    return builder.build();
  }

  @Override
  public PCollection expand(PCollection input) {
    PCollection withUuids =
        input.apply(
            "AddUuids",
            MapElements.into(new TypeDescriptor() {})
                .via(AddUuidsTransform::addUuid));
    // Reshuffle into 1000 buckets to avoid having unit-sized bundles under high throughput.
    return withUuids.apply(
        "ShuffleToPersist", Reshuffle.viaRandomKey().withNumBuckets(1000));
  }
}