[GitHub] [beam] aromanenko-dev commented on a diff in pull request #17828: [BEAM-14378] [CdapIO] SparkReceiverIO Read via SDF

[GitBox <gi...@apache.org>]

aromanenko-dev commented on code in PR #17828:
URL: https://github.com/apache/beam/pull/17828#discussion_r948150634


##########
sdks/java/io/sparkreceiver/src/main/java/org/apache/beam/sdk/io/sparkreceiver/SparkReceiverIO.java:
##########
@@ -0,0 +1,142 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+
+import com.google.auto.value.AutoValue;
+import org.apache.beam.sdk.annotations.Experimental;
+import org.apache.beam.sdk.transforms.Impulse;
+import org.apache.beam.sdk.transforms.PTransform;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.values.PBegin;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.spark.streaming.receiver.Receiver;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Instant;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/** Streaming sources for Spark {@link Receiver}. */

Review Comment:
   Please, add more details about this connector and examples of how to use it.



##########
sdks/java/io/sparkreceiver/src/test/java/org/apache/beam/sdk/io/sparkreceiver/SparkReceiverIOTest.java:
##########
@@ -0,0 +1,125 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import java.util.List;
+import org.apache.beam.runners.direct.DirectOptions;
+import org.apache.beam.runners.direct.DirectRunner;
+import org.apache.beam.sdk.Pipeline;
+import org.apache.beam.sdk.coders.StringUtf8Coder;
+import org.apache.beam.sdk.options.PipelineOptionsFactory;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.joda.time.Duration;
+import org.joda.time.Instant;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Test class for {@link SparkReceiverIO}. */
+@RunWith(JUnit4.class)
+public class SparkReceiverIOTest {
+
+  @Test
+  public void testReadBuildsCorrectly() {
+    ReceiverBuilder<String, CustomReceiverWithOffset> receiverBuilder =
+        new ReceiverBuilder<>(CustomReceiverWithOffset.class).withConstructorArgs();
+    SerializableFunction<String, Long> offsetFn = Long::valueOf;
+    SerializableFunction<String, Instant> watermarkFn = Instant::parse;
+
+    SparkReceiverIO.Read<String> read =
+        SparkReceiverIO.<String>read()
+            .withValueClass(String.class)
+            .withGetOffsetFn(offsetFn)
+            .withWatermarkFn(watermarkFn)
+            .withSparkReceiverBuilder(receiverBuilder);
+
+    assertEquals(offsetFn, read.getGetOffsetFn());
+    assertEquals(receiverBuilder, read.getSparkReceiverBuilder());
+    assertEquals(String.class, read.getValueClass());
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfReceiverBuilderIsNull() {
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> SparkReceiverIO.<String>read().withSparkReceiverBuilder(null));
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfGetOffsetFnIsNull() {
+    assertThrows(
+        IllegalArgumentException.class, () -> SparkReceiverIO.<String>read().withGetOffsetFn(null));
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfWatermarkFnIsNull() {
+    assertThrows(
+        IllegalArgumentException.class, () -> SparkReceiverIO.<String>read().withWatermarkFn(null));
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfValueClassIsNull() {
+    assertThrows(
+        IllegalArgumentException.class, () -> SparkReceiverIO.<String>read().withValueClass(null));
+  }
+
+  @Test
+  public void testReadValidationFailsMissingReceiverBuilder() {
+    SparkReceiverIO.Read<String> read = SparkReceiverIO.read();
+    assertThrows(IllegalStateException.class, read::validateTransform);
+  }
+
+  @Test
+  public void testReadValidationFailsMissingSparkConsumer() {
+    ReceiverBuilder<String, CustomReceiverWithOffset> receiverBuilder =
+        new ReceiverBuilder<>(CustomReceiverWithOffset.class).withConstructorArgs();
+    SparkReceiverIO.Read<String> read =
+        SparkReceiverIO.<String>read().withSparkReceiverBuilder(receiverBuilder);
+    assertThrows(IllegalStateException.class, read::validateTransform);
+  }
+
+  @Test
+  public void testReadFromCustomReceiverWithOffset() {
+    DirectOptions options = PipelineOptionsFactory.as(DirectOptions.class);
+    options.setBlockOnRun(false);
+    options.setRunner(DirectRunner.class);

Review Comment:
   No need to specify a runner - unit tests are running by default on DirectRunner



##########
sdks/java/io/sparkreceiver/src/test/java/org/apache/beam/sdk/io/sparkreceiver/SparkReceiverIOTest.java:
##########
@@ -0,0 +1,125 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import java.util.List;
+import org.apache.beam.runners.direct.DirectOptions;
+import org.apache.beam.runners.direct.DirectRunner;
+import org.apache.beam.sdk.Pipeline;
+import org.apache.beam.sdk.coders.StringUtf8Coder;
+import org.apache.beam.sdk.options.PipelineOptionsFactory;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.joda.time.Duration;
+import org.joda.time.Instant;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Test class for {@link SparkReceiverIO}. */
+@RunWith(JUnit4.class)
+public class SparkReceiverIOTest {
+
+  @Test
+  public void testReadBuildsCorrectly() {
+    ReceiverBuilder<String, CustomReceiverWithOffset> receiverBuilder =
+        new ReceiverBuilder<>(CustomReceiverWithOffset.class).withConstructorArgs();
+    SerializableFunction<String, Long> offsetFn = Long::valueOf;
+    SerializableFunction<String, Instant> watermarkFn = Instant::parse;
+
+    SparkReceiverIO.Read<String> read =
+        SparkReceiverIO.<String>read()
+            .withValueClass(String.class)
+            .withGetOffsetFn(offsetFn)
+            .withWatermarkFn(watermarkFn)
+            .withSparkReceiverBuilder(receiverBuilder);
+
+    assertEquals(offsetFn, read.getGetOffsetFn());
+    assertEquals(receiverBuilder, read.getSparkReceiverBuilder());
+    assertEquals(String.class, read.getValueClass());
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfReceiverBuilderIsNull() {
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> SparkReceiverIO.<String>read().withSparkReceiverBuilder(null));
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfGetOffsetFnIsNull() {
+    assertThrows(
+        IllegalArgumentException.class, () -> SparkReceiverIO.<String>read().withGetOffsetFn(null));
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfWatermarkFnIsNull() {
+    assertThrows(
+        IllegalArgumentException.class, () -> SparkReceiverIO.<String>read().withWatermarkFn(null));
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfValueClassIsNull() {
+    assertThrows(
+        IllegalArgumentException.class, () -> SparkReceiverIO.<String>read().withValueClass(null));
+  }
+
+  @Test
+  public void testReadValidationFailsMissingReceiverBuilder() {
+    SparkReceiverIO.Read<String> read = SparkReceiverIO.read();
+    assertThrows(IllegalStateException.class, read::validateTransform);
+  }
+
+  @Test
+  public void testReadValidationFailsMissingSparkConsumer() {
+    ReceiverBuilder<String, CustomReceiverWithOffset> receiverBuilder =
+        new ReceiverBuilder<>(CustomReceiverWithOffset.class).withConstructorArgs();
+    SparkReceiverIO.Read<String> read =
+        SparkReceiverIO.<String>read().withSparkReceiverBuilder(receiverBuilder);
+    assertThrows(IllegalStateException.class, read::validateTransform);
+  }
+
+  @Test
+  public void testReadFromCustomReceiverWithOffset() {
+    DirectOptions options = PipelineOptionsFactory.as(DirectOptions.class);
+    options.setBlockOnRun(false);
+    options.setRunner(DirectRunner.class);
+    Pipeline p = Pipeline.create(options);

Review Comment:
   Use `TestPipeline` for tests (see examples for other IO connectors).



##########
sdks/java/io/sparkreceiver/src/main/java/org/apache/beam/sdk/io/sparkreceiver/SparkReceiverIO.java:
##########
@@ -0,0 +1,142 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+
+import com.google.auto.value.AutoValue;
+import org.apache.beam.sdk.annotations.Experimental;
+import org.apache.beam.sdk.transforms.Impulse;
+import org.apache.beam.sdk.transforms.PTransform;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.values.PBegin;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.spark.streaming.receiver.Receiver;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Instant;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/** Streaming sources for Spark {@link Receiver}. */
+public class SparkReceiverIO {
+
+  private static final Logger LOG = LoggerFactory.getLogger(SparkReceiverIO.class);
+
+  public static <V> Read<V> read() {
+    return new AutoValue_SparkReceiverIO_Read.Builder<V>().build();
+  }
+
+  /** A {@link PTransform} to read from Spark {@link Receiver}. */
+  @AutoValue
+  @AutoValue.CopyAnnotations
+  public abstract static class Read<V> extends PTransform<PBegin, PCollection<V>> {
+
+    abstract @Nullable ReceiverBuilder<V, ? extends Receiver<V>> getSparkReceiverBuilder();
+
+    abstract @Nullable Class<V> getValueClass();
+
+    abstract @Nullable SerializableFunction<V, Long> getGetOffsetFn();
+
+    abstract @Nullable SerializableFunction<V, Instant> getWatermarkFn();
+
+    abstract Builder<V> toBuilder();
+
+    @Experimental(Experimental.Kind.PORTABILITY)

Review Comment:
   Does this connector support portability?



##########
sdks/java/io/sparkreceiver/src/test/java/org/apache/beam/sdk/io/sparkreceiver/SparkReceiverIOTest.java:
##########
@@ -0,0 +1,125 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import java.util.List;
+import org.apache.beam.runners.direct.DirectOptions;
+import org.apache.beam.runners.direct.DirectRunner;
+import org.apache.beam.sdk.Pipeline;
+import org.apache.beam.sdk.coders.StringUtf8Coder;
+import org.apache.beam.sdk.options.PipelineOptionsFactory;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.joda.time.Duration;
+import org.joda.time.Instant;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Test class for {@link SparkReceiverIO}. */
+@RunWith(JUnit4.class)
+public class SparkReceiverIOTest {
+
+  @Test
+  public void testReadBuildsCorrectly() {
+    ReceiverBuilder<String, CustomReceiverWithOffset> receiverBuilder =
+        new ReceiverBuilder<>(CustomReceiverWithOffset.class).withConstructorArgs();
+    SerializableFunction<String, Long> offsetFn = Long::valueOf;
+    SerializableFunction<String, Instant> watermarkFn = Instant::parse;
+
+    SparkReceiverIO.Read<String> read =
+        SparkReceiverIO.<String>read()
+            .withValueClass(String.class)
+            .withGetOffsetFn(offsetFn)
+            .withWatermarkFn(watermarkFn)
+            .withSparkReceiverBuilder(receiverBuilder);
+
+    assertEquals(offsetFn, read.getGetOffsetFn());
+    assertEquals(receiverBuilder, read.getSparkReceiverBuilder());
+    assertEquals(String.class, read.getValueClass());
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfReceiverBuilderIsNull() {
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> SparkReceiverIO.<String>read().withSparkReceiverBuilder(null));
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfGetOffsetFnIsNull() {
+    assertThrows(
+        IllegalArgumentException.class, () -> SparkReceiverIO.<String>read().withGetOffsetFn(null));
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfWatermarkFnIsNull() {
+    assertThrows(
+        IllegalArgumentException.class, () -> SparkReceiverIO.<String>read().withWatermarkFn(null));
+  }
+
+  @Test
+  public void testReadObjectCreationFailsIfValueClassIsNull() {
+    assertThrows(
+        IllegalArgumentException.class, () -> SparkReceiverIO.<String>read().withValueClass(null));
+  }
+
+  @Test
+  public void testReadValidationFailsMissingReceiverBuilder() {
+    SparkReceiverIO.Read<String> read = SparkReceiverIO.read();
+    assertThrows(IllegalStateException.class, read::validateTransform);
+  }
+
+  @Test
+  public void testReadValidationFailsMissingSparkConsumer() {
+    ReceiverBuilder<String, CustomReceiverWithOffset> receiverBuilder =
+        new ReceiverBuilder<>(CustomReceiverWithOffset.class).withConstructorArgs();
+    SparkReceiverIO.Read<String> read =
+        SparkReceiverIO.<String>read().withSparkReceiverBuilder(receiverBuilder);
+    assertThrows(IllegalStateException.class, read::validateTransform);
+  }
+
+  @Test
+  public void testReadFromCustomReceiverWithOffset() {
+    DirectOptions options = PipelineOptionsFactory.as(DirectOptions.class);
+    options.setBlockOnRun(false);
+    options.setRunner(DirectRunner.class);
+    Pipeline p = Pipeline.create(options);
+
+    ReceiverBuilder<String, CustomReceiverWithOffset> receiverBuilder =
+        new ReceiverBuilder<>(CustomReceiverWithOffset.class).withConstructorArgs();
+    SparkReceiverIO.Read<String> reader =
+        SparkReceiverIO.<String>read()
+            .withValueClass(String.class)
+            .withGetOffsetFn(Long::valueOf)
+            .withWatermarkFn(Instant::parse)
+            .withSparkReceiverBuilder(receiverBuilder);
+
+    List<String> storedRecords = CustomReceiverWithOffset.getStoredRecords();
+    List<String> outputRecords = TestOutputDoFn.getRecords();
+    outputRecords.clear();
+
+    p.apply(reader).setCoder(StringUtf8Coder.of()).apply(ParDo.of(new TestOutputDoFn()));
+    p.run().waitUntilFinish(Duration.standardSeconds(15));
+
+    assertEquals(outputRecords, storedRecords);

Review Comment:
   Use 
   ```
   PCollection<String> output = p.apply(...)...
   
   PAssert.that(output).containsInAnyOrder(expectedRecords);
   ```



##########
sdks/java/io/sparkreceiver/src/main/java/org/apache/beam/sdk/io/sparkreceiver/ReadFromSparkReceiverWithOffsetDoFn.java:
##########
@@ -0,0 +1,224 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull;
+
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.TimeUnit;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.io.range.OffsetRange;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.DoFn.UnboundedPerElement;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.transforms.splittabledofn.ManualWatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.OffsetRangeTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimators;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.apache.spark.SparkConf;
+import org.apache.spark.streaming.receiver.Receiver;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Instant;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A SplittableDoFn which reads from {@link Receiver} that implements {@link HasOffset}. By default,
+ * a {@link WatermarkEstimators.Manual} watermark estimator is used to track watermark.
+ *
+ * <p>Initial range The initial range is {@code [0, Long.MAX_VALUE)}
+ *
+ * <p>Resume Processing Every time the sparkConsumer.hasRecords() returns false, {@link
+ * ReadFromSparkReceiverWithOffsetDoFn} will move to process the next element.
+ */
+@UnboundedPerElement
+public class ReadFromSparkReceiverWithOffsetDoFn<V> extends DoFn<byte[], V> {
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(ReadFromSparkReceiverWithOffsetDoFn.class);
+
+  /** Constant waiting time after the {@link Receiver} starts. Required to prepare for polling */
+  private static final int START_POLL_TIMEOUT_MS = 1000;
+
+  private final SerializableFunction<Instant, WatermarkEstimator<Instant>>
+      createWatermarkEstimatorFn;
+  private final SerializableFunction<V, Long> getOffsetFn;
+  private final SerializableFunction<V, Instant> getWatermarkFn;
+  private final ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder;
+
+  public ReadFromSparkReceiverWithOffsetDoFn(SparkReceiverIO.Read<V> transform) {
+    createWatermarkEstimatorFn = WatermarkEstimators.Manual::new;
+
+    ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder =
+        transform.getSparkReceiverBuilder();
+    checkStateNotNull(sparkReceiverBuilder, "Spark Receiver Builder can't be null!");
+    this.sparkReceiverBuilder = sparkReceiverBuilder;
+
+    SerializableFunction<V, Long> getOffsetFn = transform.getGetOffsetFn();
+    checkStateNotNull(getOffsetFn, "Get offset fn can't be null!");
+    this.getOffsetFn = getOffsetFn;
+
+    SerializableFunction<V, Instant> getWatermarkFn = transform.getWatermarkFn();
+    checkStateNotNull(getWatermarkFn, "Watermark fn can't be null!");
+    this.getWatermarkFn = getWatermarkFn;
+  }
+
+  @GetInitialRestriction
+  public OffsetRange initialRestriction(@Element byte[] element) {
+    return new OffsetRange(0, Long.MAX_VALUE);
+  }
+
+  @GetInitialWatermarkEstimatorState
+  public Instant getInitialWatermarkEstimatorState(@Timestamp Instant currentElementTimestamp) {
+    return currentElementTimestamp;
+  }
+
+  @NewWatermarkEstimator
+  public WatermarkEstimator<Instant> newWatermarkEstimator(
+      @WatermarkEstimatorState Instant watermarkEstimatorState) {
+    return createWatermarkEstimatorFn.apply(ensureTimestampWithinBounds(watermarkEstimatorState));
+  }
+
+  @GetSize
+  public double getSize(@Element byte[] element, @Restriction OffsetRange offsetRange) {
+    return restrictionTracker(element, offsetRange).getProgress().getWorkRemaining();
+    // Before processing elements, we don't have a good estimated size of records and offset gap.
+  }
+
+  @NewTracker
+  public OffsetRangeTracker restrictionTracker(
+      @Element byte[] element, @Restriction OffsetRange restriction) {
+    return new OffsetRangeTracker(restriction);
+  }
+
+  @GetRestrictionCoder
+  public Coder<OffsetRange> restrictionCoder() {
+    return new OffsetRange.Coder();
+  }
+
+  @Setup
+  public void setup() throws Exception {}

Review Comment:
   No need to specify the empty methods.



##########
sdks/java/io/sparkreceiver/src/main/java/org/apache/beam/sdk/io/sparkreceiver/SparkConsumer.java:
##########
@@ -0,0 +1,38 @@
+/*
+ * 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.sparkreceiver;
+
+import java.io.Serializable;
+import org.apache.spark.streaming.receiver.Receiver;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * Interface for start/stop reading from some Spark {@link Receiver} into some place and poll from
+ * it.
+ */
+public interface SparkConsumer<V> extends Serializable {

Review Comment:
   Do we need this `public`?



##########
sdks/java/io/sparkreceiver/src/main/java/org/apache/beam/sdk/io/sparkreceiver/ReadFromSparkReceiverWithOffsetDoFn.java:
##########
@@ -0,0 +1,224 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull;
+
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.TimeUnit;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.io.range.OffsetRange;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.DoFn.UnboundedPerElement;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.transforms.splittabledofn.ManualWatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.OffsetRangeTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimators;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.apache.spark.SparkConf;
+import org.apache.spark.streaming.receiver.Receiver;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Instant;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A SplittableDoFn which reads from {@link Receiver} that implements {@link HasOffset}. By default,
+ * a {@link WatermarkEstimators.Manual} watermark estimator is used to track watermark.
+ *
+ * <p>Initial range The initial range is {@code [0, Long.MAX_VALUE)}
+ *
+ * <p>Resume Processing Every time the sparkConsumer.hasRecords() returns false, {@link
+ * ReadFromSparkReceiverWithOffsetDoFn} will move to process the next element.
+ */
+@UnboundedPerElement
+public class ReadFromSparkReceiverWithOffsetDoFn<V> extends DoFn<byte[], V> {
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(ReadFromSparkReceiverWithOffsetDoFn.class);
+
+  /** Constant waiting time after the {@link Receiver} starts. Required to prepare for polling */
+  private static final int START_POLL_TIMEOUT_MS = 1000;
+
+  private final SerializableFunction<Instant, WatermarkEstimator<Instant>>
+      createWatermarkEstimatorFn;
+  private final SerializableFunction<V, Long> getOffsetFn;
+  private final SerializableFunction<V, Instant> getWatermarkFn;
+  private final ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder;
+
+  public ReadFromSparkReceiverWithOffsetDoFn(SparkReceiverIO.Read<V> transform) {
+    createWatermarkEstimatorFn = WatermarkEstimators.Manual::new;
+
+    ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder =
+        transform.getSparkReceiverBuilder();
+    checkStateNotNull(sparkReceiverBuilder, "Spark Receiver Builder can't be null!");
+    this.sparkReceiverBuilder = sparkReceiverBuilder;
+
+    SerializableFunction<V, Long> getOffsetFn = transform.getGetOffsetFn();
+    checkStateNotNull(getOffsetFn, "Get offset fn can't be null!");
+    this.getOffsetFn = getOffsetFn;
+
+    SerializableFunction<V, Instant> getWatermarkFn = transform.getWatermarkFn();
+    checkStateNotNull(getWatermarkFn, "Watermark fn can't be null!");
+    this.getWatermarkFn = getWatermarkFn;
+  }
+
+  @GetInitialRestriction
+  public OffsetRange initialRestriction(@Element byte[] element) {
+    return new OffsetRange(0, Long.MAX_VALUE);
+  }
+
+  @GetInitialWatermarkEstimatorState
+  public Instant getInitialWatermarkEstimatorState(@Timestamp Instant currentElementTimestamp) {
+    return currentElementTimestamp;
+  }
+
+  @NewWatermarkEstimator
+  public WatermarkEstimator<Instant> newWatermarkEstimator(
+      @WatermarkEstimatorState Instant watermarkEstimatorState) {
+    return createWatermarkEstimatorFn.apply(ensureTimestampWithinBounds(watermarkEstimatorState));
+  }
+
+  @GetSize
+  public double getSize(@Element byte[] element, @Restriction OffsetRange offsetRange) {
+    return restrictionTracker(element, offsetRange).getProgress().getWorkRemaining();
+    // Before processing elements, we don't have a good estimated size of records and offset gap.
+  }
+
+  @NewTracker
+  public OffsetRangeTracker restrictionTracker(
+      @Element byte[] element, @Restriction OffsetRange restriction) {
+    return new OffsetRangeTracker(restriction);
+  }
+
+  @GetRestrictionCoder
+  public Coder<OffsetRange> restrictionCoder() {
+    return new OffsetRange.Coder();
+  }
+
+  @Setup
+  public void setup() throws Exception {}
+
+  @Teardown
+  public void teardown() throws Exception {}
+
+  @SuppressWarnings("unchecked")

Review Comment:
   Better to avoid `@SuppressWarnings` if possible



##########
sdks/java/io/sparkreceiver/src/main/java/org/apache/beam/sdk/io/sparkreceiver/ReadFromSparkReceiverWithOffsetDoFn.java:
##########
@@ -0,0 +1,224 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull;
+
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.TimeUnit;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.io.range.OffsetRange;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.DoFn.UnboundedPerElement;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.transforms.splittabledofn.ManualWatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.OffsetRangeTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimators;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.apache.spark.SparkConf;
+import org.apache.spark.streaming.receiver.Receiver;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Instant;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A SplittableDoFn which reads from {@link Receiver} that implements {@link HasOffset}. By default,
+ * a {@link WatermarkEstimators.Manual} watermark estimator is used to track watermark.
+ *
+ * <p>Initial range The initial range is {@code [0, Long.MAX_VALUE)}
+ *
+ * <p>Resume Processing Every time the sparkConsumer.hasRecords() returns false, {@link
+ * ReadFromSparkReceiverWithOffsetDoFn} will move to process the next element.
+ */
+@UnboundedPerElement
+public class ReadFromSparkReceiverWithOffsetDoFn<V> extends DoFn<byte[], V> {
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(ReadFromSparkReceiverWithOffsetDoFn.class);
+
+  /** Constant waiting time after the {@link Receiver} starts. Required to prepare for polling */
+  private static final int START_POLL_TIMEOUT_MS = 1000;
+
+  private final SerializableFunction<Instant, WatermarkEstimator<Instant>>
+      createWatermarkEstimatorFn;
+  private final SerializableFunction<V, Long> getOffsetFn;
+  private final SerializableFunction<V, Instant> getWatermarkFn;
+  private final ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder;
+
+  public ReadFromSparkReceiverWithOffsetDoFn(SparkReceiverIO.Read<V> transform) {
+    createWatermarkEstimatorFn = WatermarkEstimators.Manual::new;
+
+    ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder =
+        transform.getSparkReceiverBuilder();
+    checkStateNotNull(sparkReceiverBuilder, "Spark Receiver Builder can't be null!");
+    this.sparkReceiverBuilder = sparkReceiverBuilder;
+
+    SerializableFunction<V, Long> getOffsetFn = transform.getGetOffsetFn();
+    checkStateNotNull(getOffsetFn, "Get offset fn can't be null!");
+    this.getOffsetFn = getOffsetFn;
+
+    SerializableFunction<V, Instant> getWatermarkFn = transform.getWatermarkFn();
+    checkStateNotNull(getWatermarkFn, "Watermark fn can't be null!");
+    this.getWatermarkFn = getWatermarkFn;
+  }
+
+  @GetInitialRestriction
+  public OffsetRange initialRestriction(@Element byte[] element) {
+    return new OffsetRange(0, Long.MAX_VALUE);
+  }
+
+  @GetInitialWatermarkEstimatorState
+  public Instant getInitialWatermarkEstimatorState(@Timestamp Instant currentElementTimestamp) {
+    return currentElementTimestamp;
+  }
+
+  @NewWatermarkEstimator
+  public WatermarkEstimator<Instant> newWatermarkEstimator(
+      @WatermarkEstimatorState Instant watermarkEstimatorState) {
+    return createWatermarkEstimatorFn.apply(ensureTimestampWithinBounds(watermarkEstimatorState));
+  }
+
+  @GetSize
+  public double getSize(@Element byte[] element, @Restriction OffsetRange offsetRange) {
+    return restrictionTracker(element, offsetRange).getProgress().getWorkRemaining();
+    // Before processing elements, we don't have a good estimated size of records and offset gap.
+  }
+
+  @NewTracker
+  public OffsetRangeTracker restrictionTracker(
+      @Element byte[] element, @Restriction OffsetRange restriction) {
+    return new OffsetRangeTracker(restriction);
+  }
+
+  @GetRestrictionCoder
+  public Coder<OffsetRange> restrictionCoder() {
+    return new OffsetRange.Coder();
+  }
+
+  @Setup
+  public void setup() throws Exception {}
+
+  @Teardown
+  public void teardown() throws Exception {}
+
+  @SuppressWarnings("unchecked")
+  private static class SparkConsumerWithOffset<V> implements SparkConsumer<V> {
+    private final Queue<V> recordsQueue;
+    private @Nullable Receiver<V> sparkReceiver;
+    private final Long startOffset;
+
+    public SparkConsumerWithOffset(Long startOffset) {
+      this.startOffset = startOffset;
+      this.recordsQueue = new ConcurrentLinkedQueue<>();
+    }
+
+    @Override
+    public boolean hasRecords() {
+      return !recordsQueue.isEmpty();
+    }
+
+    @Override
+    public @Nullable V poll() {
+      return recordsQueue.poll();
+    }
+
+    @Override
+    public void start(Receiver<V> sparkReceiver) {
+      this.sparkReceiver = sparkReceiver;
+      try {
+        new WrappedSupervisor(
+            sparkReceiver,
+            new SparkConf(),
+            objects -> {
+              V record = (V) objects[0];
+              recordsQueue.offer(record);
+              return null;
+            });
+      } catch (Exception e) {
+        LOG.error("Can not init Spark Receiver!", e);
+      }
+      ((HasOffset) sparkReceiver).setStartOffset(startOffset);
+      sparkReceiver.supervisor().startReceiver();
+      try {
+        TimeUnit.MILLISECONDS.sleep(START_POLL_TIMEOUT_MS);
+      } catch (InterruptedException e) {
+        LOG.error("Interrupted", e);
+      }
+    }
+
+    @Override
+    public void stop() {
+      if (sparkReceiver != null) {
+        sparkReceiver.stop("Stopped");

Review Comment:
   nit: `SparkReceiver is stopped.`



##########
sdks/java/io/sparkreceiver/src/main/java/org/apache/beam/sdk/io/sparkreceiver/ReadFromSparkReceiverWithOffsetDoFn.java:
##########
@@ -0,0 +1,224 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull;
+
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.TimeUnit;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.io.range.OffsetRange;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.DoFn.UnboundedPerElement;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.transforms.splittabledofn.ManualWatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.OffsetRangeTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimators;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.apache.spark.SparkConf;
+import org.apache.spark.streaming.receiver.Receiver;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Instant;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A SplittableDoFn which reads from {@link Receiver} that implements {@link HasOffset}. By default,
+ * a {@link WatermarkEstimators.Manual} watermark estimator is used to track watermark.
+ *
+ * <p>Initial range The initial range is {@code [0, Long.MAX_VALUE)}
+ *
+ * <p>Resume Processing Every time the sparkConsumer.hasRecords() returns false, {@link
+ * ReadFromSparkReceiverWithOffsetDoFn} will move to process the next element.
+ */
+@UnboundedPerElement
+public class ReadFromSparkReceiverWithOffsetDoFn<V> extends DoFn<byte[], V> {
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(ReadFromSparkReceiverWithOffsetDoFn.class);
+
+  /** Constant waiting time after the {@link Receiver} starts. Required to prepare for polling */
+  private static final int START_POLL_TIMEOUT_MS = 1000;
+
+  private final SerializableFunction<Instant, WatermarkEstimator<Instant>>
+      createWatermarkEstimatorFn;
+  private final SerializableFunction<V, Long> getOffsetFn;
+  private final SerializableFunction<V, Instant> getWatermarkFn;
+  private final ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder;
+
+  public ReadFromSparkReceiverWithOffsetDoFn(SparkReceiverIO.Read<V> transform) {
+    createWatermarkEstimatorFn = WatermarkEstimators.Manual::new;
+
+    ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder =
+        transform.getSparkReceiverBuilder();
+    checkStateNotNull(sparkReceiverBuilder, "Spark Receiver Builder can't be null!");
+    this.sparkReceiverBuilder = sparkReceiverBuilder;
+
+    SerializableFunction<V, Long> getOffsetFn = transform.getGetOffsetFn();
+    checkStateNotNull(getOffsetFn, "Get offset fn can't be null!");
+    this.getOffsetFn = getOffsetFn;
+
+    SerializableFunction<V, Instant> getWatermarkFn = transform.getWatermarkFn();
+    checkStateNotNull(getWatermarkFn, "Watermark fn can't be null!");
+    this.getWatermarkFn = getWatermarkFn;
+  }
+
+  @GetInitialRestriction
+  public OffsetRange initialRestriction(@Element byte[] element) {
+    return new OffsetRange(0, Long.MAX_VALUE);
+  }
+
+  @GetInitialWatermarkEstimatorState
+  public Instant getInitialWatermarkEstimatorState(@Timestamp Instant currentElementTimestamp) {
+    return currentElementTimestamp;
+  }
+
+  @NewWatermarkEstimator
+  public WatermarkEstimator<Instant> newWatermarkEstimator(
+      @WatermarkEstimatorState Instant watermarkEstimatorState) {
+    return createWatermarkEstimatorFn.apply(ensureTimestampWithinBounds(watermarkEstimatorState));
+  }
+
+  @GetSize
+  public double getSize(@Element byte[] element, @Restriction OffsetRange offsetRange) {
+    return restrictionTracker(element, offsetRange).getProgress().getWorkRemaining();
+    // Before processing elements, we don't have a good estimated size of records and offset gap.
+  }
+
+  @NewTracker
+  public OffsetRangeTracker restrictionTracker(
+      @Element byte[] element, @Restriction OffsetRange restriction) {
+    return new OffsetRangeTracker(restriction);
+  }
+
+  @GetRestrictionCoder
+  public Coder<OffsetRange> restrictionCoder() {
+    return new OffsetRange.Coder();
+  }
+
+  @Setup
+  public void setup() throws Exception {}
+
+  @Teardown
+  public void teardown() throws Exception {}
+
+  @SuppressWarnings("unchecked")
+  private static class SparkConsumerWithOffset<V> implements SparkConsumer<V> {
+    private final Queue<V> recordsQueue;
+    private @Nullable Receiver<V> sparkReceiver;
+    private final Long startOffset;
+
+    public SparkConsumerWithOffset(Long startOffset) {
+      this.startOffset = startOffset;
+      this.recordsQueue = new ConcurrentLinkedQueue<>();
+    }
+
+    @Override
+    public boolean hasRecords() {
+      return !recordsQueue.isEmpty();
+    }
+
+    @Override
+    public @Nullable V poll() {
+      return recordsQueue.poll();
+    }
+
+    @Override
+    public void start(Receiver<V> sparkReceiver) {
+      this.sparkReceiver = sparkReceiver;
+      try {
+        new WrappedSupervisor(
+            sparkReceiver,
+            new SparkConf(),
+            objects -> {
+              V record = (V) objects[0];
+              recordsQueue.offer(record);
+              return null;
+            });
+      } catch (Exception e) {
+        LOG.error("Can not init Spark Receiver!", e);
+      }
+      ((HasOffset) sparkReceiver).setStartOffset(startOffset);
+      sparkReceiver.supervisor().startReceiver();
+      try {
+        TimeUnit.MILLISECONDS.sleep(START_POLL_TIMEOUT_MS);
+      } catch (InterruptedException e) {
+        LOG.error("Interrupted", e);

Review Comment:
   Please, add more detailed error message, like `SparkReceiver was interrupted because of <>`.



##########
sdks/java/io/sparkreceiver/src/main/java/org/apache/beam/sdk/io/sparkreceiver/ReadFromSparkReceiverWithOffsetDoFn.java:
##########
@@ -0,0 +1,224 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull;
+
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.TimeUnit;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.io.range.OffsetRange;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.DoFn.UnboundedPerElement;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.transforms.splittabledofn.ManualWatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.OffsetRangeTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimators;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.apache.spark.SparkConf;
+import org.apache.spark.streaming.receiver.Receiver;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Instant;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A SplittableDoFn which reads from {@link Receiver} that implements {@link HasOffset}. By default,
+ * a {@link WatermarkEstimators.Manual} watermark estimator is used to track watermark.
+ *
+ * <p>Initial range The initial range is {@code [0, Long.MAX_VALUE)}
+ *
+ * <p>Resume Processing Every time the sparkConsumer.hasRecords() returns false, {@link
+ * ReadFromSparkReceiverWithOffsetDoFn} will move to process the next element.
+ */
+@UnboundedPerElement
+public class ReadFromSparkReceiverWithOffsetDoFn<V> extends DoFn<byte[], V> {

Review Comment:
   Do we need this  class and its methods be `public`?



##########
sdks/java/io/sparkreceiver/src/main/java/org/apache/beam/sdk/io/sparkreceiver/ReadFromSparkReceiverWithOffsetDoFn.java:
##########
@@ -0,0 +1,224 @@
+/*
+ * 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.sparkreceiver;
+
+import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull;
+
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.TimeUnit;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.io.range.OffsetRange;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.DoFn.UnboundedPerElement;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.transforms.splittabledofn.ManualWatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.OffsetRangeTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimator;
+import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimators;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.apache.spark.SparkConf;
+import org.apache.spark.streaming.receiver.Receiver;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Instant;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A SplittableDoFn which reads from {@link Receiver} that implements {@link HasOffset}. By default,
+ * a {@link WatermarkEstimators.Manual} watermark estimator is used to track watermark.
+ *
+ * <p>Initial range The initial range is {@code [0, Long.MAX_VALUE)}
+ *
+ * <p>Resume Processing Every time the sparkConsumer.hasRecords() returns false, {@link
+ * ReadFromSparkReceiverWithOffsetDoFn} will move to process the next element.
+ */
+@UnboundedPerElement
+public class ReadFromSparkReceiverWithOffsetDoFn<V> extends DoFn<byte[], V> {
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(ReadFromSparkReceiverWithOffsetDoFn.class);
+
+  /** Constant waiting time after the {@link Receiver} starts. Required to prepare for polling */
+  private static final int START_POLL_TIMEOUT_MS = 1000;
+
+  private final SerializableFunction<Instant, WatermarkEstimator<Instant>>
+      createWatermarkEstimatorFn;
+  private final SerializableFunction<V, Long> getOffsetFn;
+  private final SerializableFunction<V, Instant> getWatermarkFn;
+  private final ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder;
+
+  public ReadFromSparkReceiverWithOffsetDoFn(SparkReceiverIO.Read<V> transform) {
+    createWatermarkEstimatorFn = WatermarkEstimators.Manual::new;
+
+    ReceiverBuilder<V, ? extends Receiver<V>> sparkReceiverBuilder =
+        transform.getSparkReceiverBuilder();
+    checkStateNotNull(sparkReceiverBuilder, "Spark Receiver Builder can't be null!");
+    this.sparkReceiverBuilder = sparkReceiverBuilder;
+
+    SerializableFunction<V, Long> getOffsetFn = transform.getGetOffsetFn();
+    checkStateNotNull(getOffsetFn, "Get offset fn can't be null!");
+    this.getOffsetFn = getOffsetFn;
+
+    SerializableFunction<V, Instant> getWatermarkFn = transform.getWatermarkFn();
+    checkStateNotNull(getWatermarkFn, "Watermark fn can't be null!");
+    this.getWatermarkFn = getWatermarkFn;
+  }
+
+  @GetInitialRestriction
+  public OffsetRange initialRestriction(@Element byte[] element) {
+    return new OffsetRange(0, Long.MAX_VALUE);
+  }
+
+  @GetInitialWatermarkEstimatorState
+  public Instant getInitialWatermarkEstimatorState(@Timestamp Instant currentElementTimestamp) {
+    return currentElementTimestamp;
+  }
+
+  @NewWatermarkEstimator
+  public WatermarkEstimator<Instant> newWatermarkEstimator(
+      @WatermarkEstimatorState Instant watermarkEstimatorState) {
+    return createWatermarkEstimatorFn.apply(ensureTimestampWithinBounds(watermarkEstimatorState));
+  }
+
+  @GetSize
+  public double getSize(@Element byte[] element, @Restriction OffsetRange offsetRange) {
+    return restrictionTracker(element, offsetRange).getProgress().getWorkRemaining();
+    // Before processing elements, we don't have a good estimated size of records and offset gap.
+  }
+
+  @NewTracker
+  public OffsetRangeTracker restrictionTracker(
+      @Element byte[] element, @Restriction OffsetRange restriction) {
+    return new OffsetRangeTracker(restriction);
+  }
+
+  @GetRestrictionCoder
+  public Coder<OffsetRange> restrictionCoder() {
+    return new OffsetRange.Coder();
+  }
+
+  @Setup
+  public void setup() throws Exception {}
+
+  @Teardown
+  public void teardown() throws Exception {}
+
+  @SuppressWarnings("unchecked")
+  private static class SparkConsumerWithOffset<V> implements SparkConsumer<V> {
+    private final Queue<V> recordsQueue;
+    private @Nullable Receiver<V> sparkReceiver;
+    private final Long startOffset;
+
+    public SparkConsumerWithOffset(Long startOffset) {

Review Comment:
   Please, restrict methods visibility where it's possible.



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