ahmedabu98 commented on code in PR #33504: URL: https://github.com/apache/beam/pull/33504#discussion_r1987807578
########## sdks/java/io/iceberg/src/main/java/org/apache/beam/sdk/io/iceberg/WatchForSnapshots.java: ########## @@ -0,0 +1,117 @@ +/* + * 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.iceberg; + +import static org.apache.beam.sdk.transforms.Watch.Growth.PollResult; + +import java.util.ArrayList; +import java.util.List; +import org.apache.beam.sdk.coders.ListCoder; +import org.apache.beam.sdk.metrics.Gauge; +import org.apache.beam.sdk.metrics.Metrics; +import org.apache.beam.sdk.transforms.Create; +import org.apache.beam.sdk.transforms.PTransform; +import org.apache.beam.sdk.transforms.Watch; +import org.apache.beam.sdk.transforms.windowing.BoundedWindow; +import org.apache.beam.sdk.values.KV; +import org.apache.beam.sdk.values.PBegin; +import org.apache.beam.sdk.values.PCollection; +import org.apache.beam.sdk.values.TimestampedValue; +import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.MoreObjects; +import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Objects; +import org.apache.iceberg.Snapshot; +import org.apache.iceberg.Table; +import org.checkerframework.checker.nullness.qual.Nullable; +import org.joda.time.Duration; + +/** + * Keeps watch over an Iceberg table and continuously outputs a range of snapshots, at the specified + * interval. + * + * <p>A downstream transform will create a list of read tasks for each range. + */ +class WatchForSnapshots extends PTransform<PBegin, PCollection<KV<String, List<SnapshotInfo>>>> { + private final Duration pollInterval; + private final IcebergScanConfig scanConfig; + + WatchForSnapshots(IcebergScanConfig scanConfig, Duration pollInterval) { + this.pollInterval = pollInterval; + this.scanConfig = scanConfig; + } + + @Override + public PCollection<KV<String, List<SnapshotInfo>>> expand(PBegin input) { + return input + .apply(Create.of(scanConfig.getTableIdentifier())) + .apply( + "Watch for Snapshots", + Watch.growthOf(new SnapshotPollFn(scanConfig)) + .withPollInterval(pollInterval) + .withOutputCoder(ListCoder.of(SnapshotInfo.getCoder()))); + } + + private static class SnapshotPollFn extends Watch.Growth.PollFn<String, List<SnapshotInfo>> { + private final Gauge latestSnapshot = Metrics.gauge(SnapshotPollFn.class, "latestSnapshot"); + private final IcebergScanConfig scanConfig; + private @Nullable Long fromSnapshotId; + + SnapshotPollFn(IcebergScanConfig scanConfig) { + this.scanConfig = scanConfig; + } + + @Override + public PollResult<List<SnapshotInfo>> apply(String tableIdentifier, Context c) { + // fetch a fresh table to catch updated snapshots + Table table = + TableCache.getRefreshed(tableIdentifier, scanConfig.getCatalogConfig().catalog()); + @Nullable Long userSpecifiedToSnapshot = ReadUtils.getToSnapshot(table, scanConfig); + boolean isComplete = userSpecifiedToSnapshot != null; + if (fromSnapshotId == null) { + fromSnapshotId = ReadUtils.getFromSnapshotExclusive(table, scanConfig); + } + + Snapshot currentSnapshot = table.currentSnapshot(); + if (currentSnapshot == null || Objects.equal(currentSnapshot.snapshotId(), fromSnapshotId)) { + // no new snapshots since last poll. return empty result. + return getPollResult(null, isComplete); + } + Long currentSnapshotId = currentSnapshot.snapshotId(); + + // if no upper bound is specified, we poll up to the current snapshot + long toSnapshotId = MoreObjects.firstNonNull(userSpecifiedToSnapshot, currentSnapshotId); + latestSnapshot.set(toSnapshotId); + + List<SnapshotInfo> snapshots = + ReadUtils.snapshotsBetween(table, tableIdentifier, fromSnapshotId, toSnapshotId); + return getPollResult(snapshots, isComplete); + } + + /** Returns an appropriate PollResult based on the requested boundedness. */ + private PollResult<List<SnapshotInfo>> getPollResult( + @Nullable List<SnapshotInfo> snapshots, boolean isComplete) { + List<TimestampedValue<List<SnapshotInfo>>> timestampedSnapshots = new ArrayList<>(1); + if (snapshots != null) { + timestampedSnapshots.add(TimestampedValue.of(snapshots, BoundedWindow.TIMESTAMP_MIN_VALUE)); + } + + return isComplete + ? PollResult.complete(timestampedSnapshots) // stop at specified snapshot + : PollResult.incomplete(timestampedSnapshots); // continue forever Review Comment: Added watermark to the TimestampedValue above, as well as to individual read tasks outputted by CreateReadTasksDofn ########## sdks/java/io/iceberg/src/main/java/org/apache/beam/sdk/io/iceberg/IcebergIO.java: ########## @@ -310,7 +409,155 @@ * </tr> * </table> * - * <p>For internal use only; no backwards compatibility guarantees + * <br> + * <br> + * + * <h2>Reading from Tables</h2> + * + * With the following configuration, + * + * <pre>{@code + * Map<String, Object> config = Map.of( + * "table", table, + * "catalog_name", name, + * "catalog_properties", Map.of(...), + * "config_properties", Map.of(...)); + * }</pre> + * + * Example of a simple batch read: + * + * <pre>{@code + * PCollection<Row> rows = pipeline + * .apply(Managed.read(ICEBERG).withConfig(config)) + * .getSinglePCollection(); + * }</pre> + * + * Example of a simple CDC read: + * + * <pre>{@code + * PCollection<Row> output = pipeline + * .apply(Managed.read(ICEBERG_CDC).withConfig(config)) + * .getSinglePCollection(); + * + * PCollection<Row> rows = output + * .apply(ReadUtils.extractRecords()); + * }</pre> + * + * <p><b>Note</b>: This reads <b>append-only</b> snapshots. Full CDC is not supported yet. + * + * <p>The CDC <b>streaming</b> source (enabled with {@code streaming=true}) continuously polls the Review Comment: Done (although note that this is automatically true if there's an unbounded PCollection) -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
