[HUDI-2685] Support scheduling online compaction plan when there are no commit data (#3928)

Co-authored-by: yuzhaojing <yuzhaojing@bytedance.com>

hudi-client/hudi-client-common/src/main/java/org/apache/hudi/table/action/compact/ScheduleCompactionActionExecutor.java

@@ -123,13 +123,13 @@ public class ScheduleCompactionActionExecutor<T extends HoodieRecordPayload, I,
     return new HoodieCompactionPlan();
   }
 
-  private Pair<Integer, String> getLatestDeltaCommitInfo(CompactionTriggerStrategy compactionTriggerStrategy) {
+  private Pair<Integer, String> getLatestDeltaCommitInfo() {
     Option<HoodieInstant> lastCompaction = table.getActiveTimeline().getCommitTimeline()
         .filterCompletedInstants().lastInstant();
     HoodieTimeline deltaCommits = table.getActiveTimeline().getDeltaCommitTimeline();
 
     String latestInstantTs;
-    int deltaCommitsSinceLastCompaction = 0;
+    final int deltaCommitsSinceLastCompaction;
     if (lastCompaction.isPresent()) {
       latestInstantTs = lastCompaction.get().getTimestamp();
       deltaCommitsSinceLastCompaction = deltaCommits.findInstantsAfter(latestInstantTs, Integer.MAX_VALUE).countInstants();
@@ -143,7 +143,7 @@ public class ScheduleCompactionActionExecutor<T extends HoodieRecordPayload, I,
   private boolean needCompact(CompactionTriggerStrategy compactionTriggerStrategy) {
     boolean compactable;
     // get deltaCommitsSinceLastCompaction and lastCompactionTs
-    Pair<Integer, String> latestDeltaCommitInfo = getLatestDeltaCommitInfo(compactionTriggerStrategy);
+    Pair<Integer, String> latestDeltaCommitInfo = getLatestDeltaCommitInfo();
     int inlineCompactDeltaCommitMax = config.getInlineCompactDeltaCommitMax();
     int inlineCompactDeltaSecondsMax = config.getInlineCompactDeltaSecondsMax();
     switch (compactionTriggerStrategy) {

hudi-flink/src/main/java/org/apache/hudi/configuration/OptionsResolver.java

@@ -84,4 +84,12 @@ public class OptionsResolver {
     final String preCombineField = conf.getString(FlinkOptions.PRECOMBINE_FIELD);
     return preCombineField.equals(FlinkOptions.NO_PRE_COMBINE) ? null : preCombineField;
   }
+
+  /**
+   * Returns whether the compaction strategy is based on elapsed delta time.
+   */
+  public static boolean isDeltaTimeCompaction(Configuration conf) {
+    final String strategy = conf.getString(FlinkOptions.COMPACTION_TRIGGER_STRATEGY).toLowerCase(Locale.ROOT);
+    return FlinkOptions.TIME_ELAPSED.equals(strategy) || FlinkOptions.NUM_OR_TIME.equals(strategy);
+  }
 }

hudi-flink/src/main/java/org/apache/hudi/sink/StreamWriteOperatorCoordinator.java

@@ -29,11 +29,13 @@ import org.apache.hudi.common.util.CommitUtils;
 import org.apache.hudi.common.util.Option;
 import org.apache.hudi.common.util.ValidationUtils;
 import org.apache.hudi.configuration.FlinkOptions;
+import org.apache.hudi.configuration.OptionsResolver;
 import org.apache.hudi.exception.HoodieException;
 import org.apache.hudi.sink.event.CommitAckEvent;
 import org.apache.hudi.sink.event.WriteMetadataEvent;
 import org.apache.hudi.sink.utils.HiveSyncContext;
 import org.apache.hudi.sink.utils.NonThrownExecutor;
+import org.apache.hudi.util.CompactionUtil;
 import org.apache.hudi.util.StreamerUtil;
 
 import org.apache.flink.annotation.VisibleForTesting;
@@ -221,11 +223,13 @@ public class StreamWriteOperatorCoordinator
           // the stream write task snapshot and flush the data buffer synchronously in sequence,
           // so a successful checkpoint subsumes the old one(follows the checkpoint subsuming contract)
           final boolean committed = commitInstant(this.instant, checkpointId);
+
+          if (tableState.scheduleCompaction) {
+            // if async compaction is on, schedule the compaction
+            CompactionUtil.scheduleCompaction(metaClient, writeClient, tableState.isDeltaTimeCompaction, committed);
+          }
+
           if (committed) {
-            if (tableState.scheduleCompaction) {
-              // if async compaction is on, schedule the compaction
-              writeClient.scheduleCompaction(Option.empty());
-            }
             // start new instant.
             startInstant();
             // sync Hive if is enabled
@@ -557,6 +561,7 @@ public class StreamWriteOperatorCoordinator
     final boolean scheduleCompaction;
     final boolean syncHive;
     final boolean syncMetadata;
+    final boolean isDeltaTimeCompaction;
 
     private TableState(Configuration conf) {
       this.operationType = WriteOperationType.fromValue(conf.getString(FlinkOptions.OPERATION));
@@ -566,6 +571,7 @@ public class StreamWriteOperatorCoordinator
       this.scheduleCompaction = StreamerUtil.needsScheduleCompaction(conf);
       this.syncHive = conf.getBoolean(FlinkOptions.HIVE_SYNC_ENABLED);
       this.syncMetadata = conf.getBoolean(FlinkOptions.METADATA_ENABLED);
+      this.isDeltaTimeCompaction = OptionsResolver.isDeltaTimeCompaction(conf);
     }
 
     public static TableState create(Configuration conf) {

hudi-flink/src/main/java/org/apache/hudi/sink/compact/HoodieFlinkCompactor.java

@@ -75,14 +75,16 @@ public class HoodieFlinkCompactor {
     // judge whether have operation
     // to compute the compaction instant time and do compaction.
     if (cfg.schedule) {
-      String compactionInstantTime = CompactionUtil.getCompactionInstantTime(metaClient);
+      Option<String> compactionInstantTimeOption = CompactionUtil.getCompactionInstantTime(metaClient);
-      boolean scheduled = writeClient.scheduleCompactionAtInstant(compactionInstantTime, Option.empty());
+      if (compactionInstantTimeOption.isPresent()) {
-      if (!scheduled) {
+        boolean scheduled = writeClient.scheduleCompactionAtInstant(compactionInstantTimeOption.get(), Option.empty());
-        // do nothing.
+        if (!scheduled) {
-        LOG.info("No compaction plan for this job ");
+          // do nothing.
-        return;
+          LOG.info("No compaction plan for this job ");
+          return;
+        }
+        table.getMetaClient().reloadActiveTimeline();
       }
-      table.getMetaClient().reloadActiveTimeline();
     }
 
     // fetch the instant based on the configured execution sequence

hudi-flink/src/main/java/org/apache/hudi/util/CompactionUtil.java

@@ -18,6 +18,7 @@
 
 package org.apache.hudi.util;
 
+import org.apache.hudi.client.HoodieFlinkWriteClient;
 import org.apache.hudi.common.model.HoodieRecord;
 import org.apache.hudi.common.table.HoodieTableMetaClient;
 import org.apache.hudi.common.table.TableSchemaResolver;
@@ -46,10 +47,36 @@ public class CompactionUtil {
 
   private static final Logger LOG = LoggerFactory.getLogger(CompactionUtil.class);
 
+  /**
+   * Schedules a new compaction instant.
+   *
+   * @param metaClient The metadata client
+   * @param writeClient The write client
+   * @param deltaTimeCompaction Whether the compaction is trigger by elapsed delta time
+   * @param committed Whether the last instant was committed successfully
+   */
+  public static void scheduleCompaction(
+      HoodieTableMetaClient metaClient,
+      HoodieFlinkWriteClient<?> writeClient,
+      boolean deltaTimeCompaction,
+      boolean committed) {
+    if (committed) {
+      writeClient.scheduleCompaction(Option.empty());
+    } else if (deltaTimeCompaction) {
+      // if there are no new commits and the compaction trigger strategy is based on elapsed delta time,
+      // schedules the compaction anyway.
+      metaClient.reloadActiveTimeline();
+      Option<String> compactionInstantTime = CompactionUtil.getCompactionInstantTime(metaClient);
+      if (compactionInstantTime.isPresent()) {
+        writeClient.scheduleCompactionAtInstant(compactionInstantTime.get(), Option.empty());
+      }
+    }
+  }
+
   /**
    * Gets compaction Instant time.
    */
-  public static String getCompactionInstantTime(HoodieTableMetaClient metaClient) {
+  public static Option<String> getCompactionInstantTime(HoodieTableMetaClient metaClient) {
     Option<HoodieInstant> firstPendingInstant = metaClient.getCommitsTimeline()
         .filterPendingExcludingCompaction().firstInstant();
     Option<HoodieInstant> lastCompleteInstant = metaClient.getActiveTimeline().getWriteTimeline()
@@ -59,8 +86,11 @@ public class CompactionUtil {
       String lastCompleteTimestamp = lastCompleteInstant.get().getTimestamp();
       // Committed and pending compaction instants should have strictly lower timestamps
       return StreamerUtil.medianInstantTime(firstPendingTimestamp, lastCompleteTimestamp);
+    } else if (!lastCompleteInstant.isPresent()) {
+      LOG.info("No instants to schedule the compaction plan");
+      return Option.empty();
     } else {
-      return HoodieActiveTimeline.createNewInstantTime();
+      return Option.of(HoodieActiveTimeline.createNewInstantTime());
     }
   }
 

hudi-flink/src/main/java/org/apache/hudi/util/StreamerUtil.java

@@ -407,14 +407,14 @@ public class StreamerUtil {
   /**
    * Returns the median instant time between the given two instant time.
    */
-  public static String medianInstantTime(String highVal, String lowVal) {
+  public static Option<String> medianInstantTime(String highVal, String lowVal) {
     try {
       long high = HoodieActiveTimeline.parseInstantTime(highVal).getTime();
       long low = HoodieActiveTimeline.parseInstantTime(lowVal).getTime();
       ValidationUtils.checkArgument(high > low,
           "Instant [" + highVal + "] should have newer timestamp than instant [" + lowVal + "]");
       long median = low + (high - low) / 2;
-      return HoodieActiveTimeline.formatInstantTime(new Date(median));
+      return low >= median ? Option.empty() : Option.of(HoodieActiveTimeline.formatInstantTime(new Date(median)));
     } catch (ParseException e) {
       throw new HoodieException("Get median instant time with interval [" + lowVal + ", " + highVal + "] error", e);
     }

hudi-flink/src/test/java/org/apache/hudi/sink/compact/ITTestHoodieFlinkCompactor.java

@@ -109,11 +109,17 @@ public class ITTestHoodieFlinkCompactor {
     // infer changelog mode
     CompactionUtil.inferChangelogMode(conf, metaClient);
 
+    HoodieFlinkWriteClient writeClient = StreamerUtil.createWriteClient(conf);
+
+    boolean scheduled = false;
     // judge whether have operation
     // To compute the compaction instant time and do compaction.
-    String compactionInstantTime = CompactionUtil.getCompactionInstantTime(metaClient);
+    Option<String> compactionInstantTimeOption = CompactionUtil.getCompactionInstantTime(metaClient);
-    HoodieFlinkWriteClient writeClient = StreamerUtil.createWriteClient(conf);
+    if (compactionInstantTimeOption.isPresent()) {
-    boolean scheduled = writeClient.scheduleCompactionAtInstant(compactionInstantTime, Option.empty());
+      scheduled = writeClient.scheduleCompactionAtInstant(compactionInstantTimeOption.get(), Option.empty());
+    }
+
+    String compactionInstantTime = compactionInstantTimeOption.get();
 
     assertTrue(scheduled, "The compaction plan should be scheduled");
 

hudi-flink/src/test/java/org/apache/hudi/sink/utils/StreamWriteFunctionWrapper.java

@@ -223,6 +223,10 @@ public class StreamWriteFunctionWrapper<I> implements TestFunctionWrapper<I> {
     stateInitializationContext.getOperatorStateStore().checkpointBegin(checkpointId);
   }
 
+  public void endInput() {
+    writeFunction.endInput();
+  }
+
   public void checkpointComplete(long checkpointId) {
     stateInitializationContext.getOperatorStateStore().checkpointSuccess(checkpointId);
     coordinator.notifyCheckpointComplete(checkpointId);
@@ -248,6 +252,11 @@ public class StreamWriteFunctionWrapper<I> implements TestFunctionWrapper<I> {
   public void close() throws Exception {
     coordinator.close();
     ioManager.close();
+    bucketAssignerFunction.close();
+    writeFunction.close();
+    if (compactFunctionWrapper != null) {
+      compactFunctionWrapper.close();
+    }
   }
 
   public StreamWriteOperatorCoordinator getCoordinator() {

hudi-flink/src/test/java/org/apache/hudi/utils/TestCompactionUtil.java

@@ -20,11 +20,13 @@ package org.apache.hudi.utils;
 
 import org.apache.hudi.avro.model.HoodieCompactionOperation;
 import org.apache.hudi.avro.model.HoodieCompactionPlan;
+import org.apache.hudi.client.HoodieFlinkWriteClient;
 import org.apache.hudi.common.table.HoodieTableMetaClient;
 import org.apache.hudi.common.table.timeline.HoodieActiveTimeline;
 import org.apache.hudi.common.table.timeline.HoodieInstant;
 import org.apache.hudi.common.table.timeline.HoodieTimeline;
 import org.apache.hudi.common.table.timeline.TimelineMetadataUtils;
+import org.apache.hudi.common.util.Option;
 import org.apache.hudi.configuration.FlinkOptions;
 import org.apache.hudi.exception.HoodieIOException;
 import org.apache.hudi.table.HoodieFlinkTable;
@@ -33,14 +35,16 @@ import org.apache.hudi.util.FlinkTables;
 import org.apache.hudi.util.StreamerUtil;
 
 import org.apache.flink.configuration.Configuration;
-import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 
 import java.io.File;
 import java.io.IOException;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
@@ -60,16 +64,24 @@ public class TestCompactionUtil {
   @TempDir
   File tempFile;
 
-  @BeforeEach
   void beforeEach() throws IOException {
+    beforeEach(Collections.emptyMap());
+  }
+
+  void beforeEach(Map<String, String> options) throws IOException {
     this.conf = TestConfigurations.getDefaultConf(tempFile.getAbsolutePath());
+    conf.setString(FlinkOptions.TABLE_TYPE, FlinkOptions.TABLE_TYPE_MERGE_ON_READ);
+    options.forEach((k, v) -> conf.setString(k, v));
+
     StreamerUtil.initTableIfNotExists(conf);
+
     this.table = FlinkTables.createTable(conf);
     this.metaClient = table.getMetaClient();
   }
 
   @Test
-  void rollbackCompaction() {
+  void rollbackCompaction() throws Exception {
+    beforeEach();
     List<String> oriInstants = IntStream.range(0, 3)
         .mapToObj(i -> generateCompactionPlan()).collect(Collectors.toList());
     List<HoodieInstant> instants = metaClient.getActiveTimeline()
@@ -88,7 +100,8 @@ public class TestCompactionUtil {
   }
 
   @Test
-  void rollbackEarliestCompaction() {
+  void rollbackEarliestCompaction() throws Exception {
+    beforeEach();
     conf.setInteger(FlinkOptions.COMPACTION_TIMEOUT_SECONDS, 0);
     List<String> oriInstants = IntStream.range(0, 3)
         .mapToObj(i -> generateCompactionPlan()).collect(Collectors.toList());
@@ -109,6 +122,33 @@ public class TestCompactionUtil {
     assertThat(instantTime, is(oriInstants.get(0)));
   }
 
+  @Test
+  void testScheduleCompaction() throws Exception {
+    Map<String, String> options = new HashMap<>();
+    options.put(FlinkOptions.COMPACTION_SCHEDULE_ENABLED.key(), "false");
+    options.put(FlinkOptions.COMPACTION_TRIGGER_STRATEGY.key(), FlinkOptions.TIME_ELAPSED);
+    options.put(FlinkOptions.COMPACTION_DELTA_SECONDS.key(), "0");
+    beforeEach(options);
+
+    // write a commit with data first
+    TestData.writeDataAsBatch(TestData.DATA_SET_SINGLE_INSERT, conf);
+
+    HoodieFlinkWriteClient<?> writeClient = StreamerUtil.createWriteClient(conf);
+    CompactionUtil.scheduleCompaction(metaClient, writeClient, true, true);
+
+    Option<HoodieInstant> pendingCompactionInstant = metaClient.reloadActiveTimeline().filterPendingCompactionTimeline().lastInstant();
+    assertTrue(pendingCompactionInstant.isPresent(), "A compaction plan expects to be scheduled");
+
+    // write another commit with data and start a new instant
+    TestData.writeDataAsBatch(TestData.DATA_SET_INSERT, conf);
+    TimeUnit.SECONDS.sleep(3); // in case the instant time interval is too close
+    writeClient.startCommit();
+
+    CompactionUtil.scheduleCompaction(metaClient, writeClient, true, false);
+    int numCompactionCommits = metaClient.reloadActiveTimeline().filterPendingCompactionTimeline().countInstants();
+    assertThat("Two compaction plan expects to be scheduled", numCompactionCommits, is(2));
+  }
+
   /**
    * Generates a compaction plan on the timeline and returns its instant time.
    */

hudi-flink/src/test/java/org/apache/hudi/utils/TestData.java

@@ -343,6 +343,37 @@ public class TestData {
     funcWrapper.close();
   }
 
+  /**
+   * Write a list of row data with Hoodie format base on the given configuration.
+   *
+   * <p>The difference with {@link #writeData} is that it flush data using #endInput, and it
+   * does not generate inflight instant.
+   *
+   * @param dataBuffer The data buffer to write
+   * @param conf       The flink configuration
+   * @throws Exception if error occurs
+   */
+  public static void writeDataAsBatch(
+      List<RowData> dataBuffer,
+      Configuration conf) throws Exception {
+    StreamWriteFunctionWrapper<RowData> funcWrapper = new StreamWriteFunctionWrapper<>(
+        conf.getString(FlinkOptions.PATH),
+        conf);
+    funcWrapper.openFunction();
+
+    for (RowData rowData : dataBuffer) {
+      funcWrapper.invoke(rowData);
+    }
+
+    // this triggers the data write and event send
+    funcWrapper.endInput();
+
+    final OperatorEvent nextEvent = funcWrapper.getNextEvent();
+    funcWrapper.getCoordinator().handleEventFromOperator(0, nextEvent);
+
+    funcWrapper.close();
+  }
+
   private static String toStringSafely(Object obj) {
     return obj == null ? "null" : obj.toString();
   }

hudi-flink/src/test/java/org/apache/hudi/utils/TestStreamerUtil.java

@@ -80,7 +80,7 @@ public class TestStreamerUtil {
   void testMedianInstantTime() {
     String higher = "20210705125921";
     String lower = "20210705125806";
-    String median1 = StreamerUtil.medianInstantTime(higher, lower);
+    String median1 = StreamerUtil.medianInstantTime(higher, lower).get();
     assertThat(median1, is("20210705125843"));
     // test symmetry
     assertThrows(IllegalArgumentException.class,