add wiring for creating checkpoints of responsive kv stores

kafka-client/build.gradle.kts

@@ -137,6 +137,7 @@ dependencies {
     implementation("dev.responsive:controller-api:0.16.0")
     implementation(libs.bundles.scylla)
     implementation(libs.bundles.commons)
+    implementation(libs.jackson)
     implementation(libs.mongodb.driver.sync)
     implementation(libs.bundles.otel)
     implementation(libs.bundles.grpc)

kafka-client/src/main/java/dev/responsive/kafka/internal/clients/StoreCommitListener.java

@@ -41,14 +41,14 @@ private void onCommit(
       final TopicPartition p = e.getKey().getPartition();
       for (final ResponsiveStoreRegistration storeRegistration
           : storeRegistry.getRegisteredStoresForChangelog(p, threadId)) {
-        storeRegistration.onCommit().accept(e.getValue());
+        storeRegistration.callbacks().notifyCommit(e.getValue());
       }
     }
     for (final var e : writtenOffsets.entrySet()) {
       final TopicPartition p = e.getKey();
       for (final ResponsiveStoreRegistration storeRegistration
           : storeRegistry.getRegisteredStoresForChangelog(p, threadId)) {
-        storeRegistration.onCommit().accept(e.getValue());
+        storeRegistration.callbacks().notifyCommit(e.getValue());
       }
     }
   }

kafka-client/src/main/java/dev/responsive/kafka/internal/db/RemoteKVTable.java

@@ -94,4 +94,8 @@ <PS extends Serializer<P>, P> KeyValueIterator<Bytes, byte[]> prefix(
    * @return the approximate number of entries for this kafka partition
    */
   long approximateNumEntries(int kafkaPartition);
+
+  default byte[] checkpoint() {
+    throw new UnsupportedOperationException("checkpoints not supported for this store type");
+  }
 }

kafka-client/src/main/java/dev/responsive/kafka/internal/db/rs3/RS3KVTable.java

@@ -18,6 +18,7 @@
 import dev.responsive.kafka.internal.db.rs3.client.LssId;
 import dev.responsive.kafka.internal.db.rs3.client.LssMetadata;
 import dev.responsive.kafka.internal.db.rs3.client.MeteredRS3Client;
+import dev.responsive.kafka.internal.db.rs3.client.PssCheckpoint;
 import dev.responsive.kafka.internal.db.rs3.client.Put;
 import dev.responsive.kafka.internal.db.rs3.client.RS3Client;
 import dev.responsive.kafka.internal.db.rs3.client.RS3ClientUtil;
@@ -30,6 +31,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.UUID;
 import org.apache.kafka.common.serialization.Serializer;
 import org.apache.kafka.common.utils.Bytes;
@@ -97,6 +99,7 @@ public KVFlushManager init(final int kafkaPartition) {
 
   @Override
   public byte[] get(final int kafkaPartition, final Bytes key, final long minValidTs) {
+    checkInitialized();
     final int pssId = pssPartitioner.pss(key.get(), this.lssId);
     return rs3Client.get(
         storeId,
@@ -114,6 +117,7 @@ public KeyValueIterator<Bytes, byte[]> range(
       final Bytes to,
       final long streamTimeMs
   ) {
+    checkInitialized();
     final var range = new Range<>(RangeBound.inclusive(from), RangeBound.exclusive(to));
     final List<KeyValueIterator<Bytes, byte[]>> pssIters = new ArrayList<>();
 
@@ -181,4 +185,31 @@ public WalEntry delete(final int kafkaPartition, final Bytes key) {
   public long lastWrittenOffset(final int kafkaPartition) {
     return fetchOffset;
   }
+
+  @Override
+  public byte[] checkpoint() {
+    checkInitialized();
+    final List<TableCheckpoint.TablePssCheckpoint> checkpoints = new ArrayList<>();
+    for (final int pss : pssPartitioner.pssForLss(this.lssId)) {
+      final Optional<Long> writtenOffset = flushManager.writtenOffset(pss);
+      final PssCheckpoint rs3Checkpoint = rs3Client.createCheckpoint(
+          storeId,
+          lssId,
+          pss,
+          writtenOffset
+      );
+      checkpoints.add(new TableCheckpoint.TablePssCheckpoint(
+          writtenOffset,
+          rs3Checkpoint
+      ));
+    }
+    final TableCheckpoint checkpoint = new TableCheckpoint(checkpoints);
+    return TableCheckpoint.serialize(checkpoint);
+  }
+
+  private void checkInitialized() {
+    if (this.lssId == null) {
+      throw new IllegalStateException("table not initialized");
+    }
+  }
 }

kafka-client/src/main/java/dev/responsive/kafka/internal/db/rs3/TableCheckpoint.java

@@ -0,0 +1,114 @@
+package dev.responsive.kafka.internal.db.rs3;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
+import dev.responsive.kafka.internal.db.rs3.client.PssCheckpoint;
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+
+public class TableCheckpoint {
+  private static final ObjectMapper MAPPER = new ObjectMapper();
+
+  static {
+    MAPPER.registerModule(new Jdk8Module());
+  }
+
+  final List<TablePssCheckpoint> pssCheckpoints;
+
+  @JsonCreator
+  public TableCheckpoint(
+      @JsonProperty("pssCheckpoints") final List<TablePssCheckpoint> pssCheckpoints
+  ) {
+    this.pssCheckpoints = List.copyOf(Objects.requireNonNull(pssCheckpoints));
+  }
+
+  @JsonProperty("pssCheckpoints")
+  public List<TablePssCheckpoint> pssCheckpoints() {
+    return pssCheckpoints;
+  }
+
+  @Override
+  public boolean equals(final Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (!(o instanceof TableCheckpoint)) {
+      return false;
+    }
+    final TableCheckpoint that = (TableCheckpoint) o;
+    return Objects.equals(pssCheckpoints, that.pssCheckpoints);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hashCode(pssCheckpoints);
+  }
+
+  public static class TablePssCheckpoint {
+    final Optional<Long> writtenOffset;
+    final PssCheckpoint checkpoint;
+
+    @JsonCreator
+    public TablePssCheckpoint(
+        @JsonProperty("writtenOffset") final Optional<Long> writtenOffset,
+        @JsonProperty("checkpoint") final PssCheckpoint checkpoint
+    ) {
+      this.writtenOffset = Objects.requireNonNull(writtenOffset);
+      this.checkpoint = Objects.requireNonNull(checkpoint);
+    }
+
+    @JsonProperty("writtenOffset")
+    public Optional<Long> writtenOffset() {
+      return writtenOffset;
+    }
+
+    @JsonProperty("checkpoint")
+    public PssCheckpoint checkpoint() {
+      return checkpoint;
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+      if (this == o) {
+        return true;
+      }
+      if (!(o instanceof TablePssCheckpoint)) {
+        return false;
+      }
+      final TablePssCheckpoint that = (TablePssCheckpoint) o;
+      return Objects.equals(writtenOffset, that.writtenOffset)
+          && Objects.equals(checkpoint, that.checkpoint);
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(writtenOffset, checkpoint);
+    }
+  }
+
+  @Override
+  public String toString() {
+    return new String(TableCheckpoint.serialize(this), Charset.defaultCharset());
+  }
+
+  public static byte[] serialize(TableCheckpoint tableCheckpoint) {
+    try {
+      return MAPPER.writeValueAsBytes(tableCheckpoint);
+    } catch (final IOException e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  public static TableCheckpoint deserialize(byte[] serialized) {
+    try {
+      return MAPPER.readValue(serialized, TableCheckpoint.class);
+    } catch (final IOException e) {
+      throw new RuntimeException(e);
+    }
+  }
+}

kafka-client/src/main/java/dev/responsive/kafka/internal/db/rs3/client/LssId.java

@@ -41,4 +41,9 @@ public boolean equals(final Object o) {
   public int hashCode() {
     return Objects.hashCode(id);
   }
+
+  @Override
+  public String toString() {
+    return "LssId{" + "id=" + id + '}';
+  }
 }

kafka-client/src/main/java/dev/responsive/kafka/internal/db/rs3/client/MeteredRS3Client.java

@@ -168,6 +168,15 @@ public CreateStoreResult createStore(
     return delegate.createStore(storeName, options);
   }
 
+  @Override
+  public PssCheckpoint createCheckpoint(
+      final UUID storeId,
+      final LssId lssId,
+      final int pssId,
+      final Optional<Long> expectedWrittenOffset) {
+    return delegate.createCheckpoint(storeId, lssId, pssId, expectedWrittenOffset);
+  }
+
   public void close() {
     this.metrics.removeSensor(GET_SENSOR_NAME);
   }