[GitHub] [beam] scwhittle commented on a diff in pull request #22612: Reimplement Pub/Sub Lite's I/O using UnboundedSource.

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

scwhittle commented on code in PR #22612:
URL: https://github.com/apache/beam/pull/22612#discussion_r941358993


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsublite/internal/SubscribeTransform.java:
##########
@@ -101,6 +91,42 @@ private MemoryBufferedSubscriber newBufferedSubscriber(
         consumer -> newSubscriber(subscriptionPartition.partition(), startOffset, consumer));
   }
 
+  private MemoryBufferedSubscriber getCachedSubscriber(
+      SubscriptionPartition subscriptionPartition, Offset startOffset) {
+    Supplier<MemoryBufferedSubscriber> getOrCreate =
+        () ->
+            PerServerSubscriberCache.CACHE.get(
+                subscriptionPartition,
+                () -> newBufferedSubscriber(subscriptionPartition, startOffset));
+    while (true) {
+      MemoryBufferedSubscriber subscriber = getOrCreate.get();
+      Offset fetchOffset = subscriber.fetchOffset();
+      if (startOffset.equals(fetchOffset)) {
+        return subscriber;
+      }
+      LOG.info(
+          "Discarding subscriber due to mismatch, this should be rare. {}, start: {} fetch: {}",
+          subscriptionPartition,
+          startOffset,
+          fetchOffset);
+      try {
+        subscriber.stopAsync().awaitTerminated();

Review Comment:
   does the get above remove it from the cache? Or do you have to do so here so a new one is returned next time?



##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsublite/internal/SubscribeTransform.java:
##########
@@ -134,19 +160,28 @@ private TopicPath getTopicPath() {
     }
   }
 
-  @Override
-  public PCollection<SequencedMessage> expand(PBegin input) {
-    PCollection<SubscriptionPartition> subscriptionPartitions;
-    subscriptionPartitions =
+  @SuppressWarnings("unused")
+  private PCollection<SequencedMessage> expandSdf(PBegin input) {
+    PCollection<SubscriptionPartition> subscriptionPartitions =
         input.apply(new SubscriptionPartitionLoader(getTopicPath(), options.subscriptionPath()));
-
     return subscriptionPartitions.apply(
         ParDo.of(
             new PerSubscriptionPartitionSdf(
-                new ManagedBacklogReaderFactoryImpl(this::newBacklogReader),
+                new ManagedFactoryImpl<>(this::newBacklogReader),
+                new ManagedFactoryImpl<>(this::newCommitter),
                 this::newInitialOffsetReader,
                 this::newRestrictionTracker,
-                this::newPartitionProcessor,
-                this::newCommitter)));
+                this::newPartitionProcessor)));
+  }
+
+  private PCollection<SequencedMessage> expandSource(PBegin input) {
+    return input.apply(
+        Read.from(
+            new UnboundedSourceImpl(options, this::newBufferedSubscriber, this::newBacklogReader)));
+  }
+
+  @Override
+  public PCollection<SequencedMessage> expand(PBegin input) {
+    return expandSource(input);

Review Comment:
   option to use SDF or Source? Or can SDF be used elsewhere by configuration?



##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsublite/internal/ApiServices.java:
##########
@@ -0,0 +1,30 @@
+/*
+ * 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.gcp.pubsublite.internal;
+
+import com.google.api.core.ApiService;
+import java.util.concurrent.TimeUnit;
+
+class ApiServices {
+
+  private ApiServices() {}
+
+  static AutoCloseable asCloseable(ApiService service) {
+    return () -> service.stopAsync().awaitTerminated(1, TimeUnit.MINUTES);

Review Comment:
   Is exception thrown if this is timed out? Should 1 minute be adjustable?



##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsublite/internal/UnboundedReaderImpl.java:
##########
@@ -0,0 +1,139 @@
+/*
+ * 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.gcp.pubsublite.internal;
+
+import static org.apache.beam.sdk.io.gcp.pubsublite.internal.ApiServices.asCloseable;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkState;
+
+import com.google.api.core.ApiService.State;
+import com.google.cloud.pubsublite.Offset;
+import com.google.cloud.pubsublite.proto.SequencedMessage;
+import com.google.protobuf.util.Timestamps;
+import java.io.IOException;
+import java.util.NoSuchElementException;
+import java.util.Optional;
+import java.util.concurrent.TimeUnit;
+import org.apache.beam.sdk.io.UnboundedSource;
+import org.apache.beam.sdk.io.UnboundedSource.UnboundedReader;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.joda.time.Instant;
+
+public class UnboundedReaderImpl extends UnboundedReader<SequencedMessage> {
+
+  private final UnboundedSource<SequencedMessage, CheckpointMarkImpl> source;
+  private final MemoryBufferedSubscriber subscriber;
+  private final TopicBacklogReader backlogReader;
+  private final BlockingCommitter committer;
+
+  private Offset fetchOffset;
+  private Optional<Instant> lastMessageTimestamp = Optional.empty();
+  private boolean advanced = false;
+
+  UnboundedReaderImpl(
+      UnboundedSource<SequencedMessage, CheckpointMarkImpl> source,
+      MemoryBufferedSubscriber subscriber,
+      TopicBacklogReader backlogReader,
+      BlockingCommitter committer,
+      Offset initialOffset) {
+    checkArgument(initialOffset.equals(subscriber.fetchOffset()));
+    this.source = source;
+    this.subscriber = subscriber;
+    this.backlogReader = backlogReader;
+    this.committer = committer;
+    this.fetchOffset = initialOffset;
+  }
+
+  @Override
+  public SequencedMessage getCurrent() throws NoSuchElementException {
+    if (!advanced) {
+      throw new NoSuchElementException();
+    }
+    return subscriber.peek().get();
+  }
+
+  @Override
+  public Instant getCurrentTimestamp() throws NoSuchElementException {
+    return getTimestamp(getCurrent());
+  }
+
+  private static Instant getTimestamp(SequencedMessage message) {
+    return Instant.ofEpochMilli(Timestamps.toMillis(message.getPublishTime()));
+  }
+
+  @Override
+  public void close() throws IOException {
+    try (AutoCloseable c1 = backlogReader;
+        AutoCloseable c2 = committer;
+        AutoCloseable c3 = asCloseable(subscriber)) {
+    } catch (Exception e) {
+      throw new IOException(e);
+    }
+  }
+
+  @Override
+  public boolean start() throws IOException {
+    try {
+      subscriber.startAsync().awaitRunning(1, TimeUnit.MINUTES);
+    } catch (Exception e) {
+      throw new IOException(e);
+    }
+    return advance();
+  }
+
+  @Override
+  public boolean advance() throws IOException {
+    if (!subscriber.state().equals(State.RUNNING)) {
+      throw new IOException("Subscriber failed: ", subscriber.failureCause());
+    }
+    if (advanced) {
+      subscriber.pop();
+    }
+    Optional<SequencedMessage> next = subscriber.peek();
+    advanced = next.isPresent();
+    if (!advanced) {
+      return false;
+    }
+    Offset nextOffset = Offset.of(next.get().getCursor().getOffset() + 1);
+    checkState(nextOffset.value() > fetchOffset.value());
+    fetchOffset = nextOffset;
+    lastMessageTimestamp = Optional.of(getTimestamp(next.get()));
+    return true;
+  }
+
+  @Override
+  public Instant getWatermark() {
+    return lastMessageTimestamp.orElse(BoundedWindow.TIMESTAMP_MIN_VALUE);

Review Comment:
   are timestamps increasing in PubsubLite?  Or does this need to be based upon last messages and some controllable skew option etc



##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsublite/internal/BlockingCommitterImpl.java:
##########
@@ -0,0 +1,50 @@
+/*
+ * 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.gcp.pubsublite.internal;
+
+import static com.google.cloud.pubsublite.internal.ExtractStatus.toCanonical;
+
+import com.google.cloud.pubsublite.Offset;
+import com.google.cloud.pubsublite.internal.wire.Committer;
+import java.util.concurrent.TimeUnit;
+
+public class BlockingCommitterImpl implements BlockingCommitter {
+
+  private final Committer committer;
+
+  BlockingCommitterImpl(Committer committer) {
+    if (!committer.isRunning()) {
+      throw new RuntimeException(committer.failureCause());
+    }
+    this.committer = committer;
+  }
+
+  @Override
+  public void commitOffset(Offset offset) {
+    try {
+      committer.commitOffset(offset).get(1, TimeUnit.MINUTES);

Review Comment:
   ditto should this timeout come from option?



##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsublite/internal/UnboundedSourceImpl.java:
##########
@@ -0,0 +1,121 @@
+/*
+ * 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.gcp.pubsublite.internal;
+
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkState;
+
+import com.google.cloud.pubsublite.Offset;
+import com.google.cloud.pubsublite.Partition;
+import com.google.cloud.pubsublite.PartitionLookupUtils;
+import com.google.cloud.pubsublite.proto.SequencedMessage;
+import java.io.IOException;
+import java.io.Serializable;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.extensions.protobuf.ProtoCoder;
+import org.apache.beam.sdk.io.UnboundedSource;
+import org.apache.beam.sdk.io.gcp.pubsublite.SubscriberOptions;
+import org.apache.beam.sdk.options.PipelineOptions;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Optional;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public class UnboundedSourceImpl extends UnboundedSource<SequencedMessage, CheckpointMarkImpl> {
+
+  private final SubscriberOptions subscriberOptions;
+  private final SubscriberFactory subscriberFactory;
+  private final BacklogReaderFactory readerFactory;
+  private final Optional<Partition> partition;
+
+  interface SubscriberFactory extends Serializable {
+
+    MemoryBufferedSubscriber create(SubscriptionPartition subscriptionPartition, Offset offset);
+  }
+
+  interface BacklogReaderFactory extends Serializable {
+
+    TopicBacklogReader create(SubscriptionPartition subscriptionPartition);
+  }
+
+  UnboundedSourceImpl(
+      SubscriberOptions subscriberOptions,
+      SubscriberFactory subscriberFactory,
+      BacklogReaderFactory readerFactory) {
+    this.subscriberOptions = subscriberOptions;
+    this.subscriberFactory = subscriberFactory;
+    this.readerFactory = readerFactory;
+    this.partition = Optional.absent();
+  }
+
+  private UnboundedSourceImpl(
+      SubscriberOptions subscriberOptions,
+      SubscriberFactory subscriberFactory,
+      BacklogReaderFactory readerFactory,
+      Partition partition) {
+    this.subscriberOptions = subscriberOptions;
+    this.subscriberFactory = subscriberFactory;
+    this.readerFactory = readerFactory;
+    this.partition = Optional.of(partition);
+  }
+
+  @Override
+  public List<? extends UnboundedSource<SequencedMessage, CheckpointMarkImpl>> split(
+      int desiredNumSplits, PipelineOptions options) throws Exception {
+    checkState(!partition.isPresent());
+    int numPartitions = PartitionLookupUtils.numPartitions(subscriberOptions.subscriptionPath());

Review Comment:
   Is there ever a crazy # of partitions? Would we want multiple partitions to a single source shard.  I believe Kafka did this.  I think one concern is per-shard information building up in the graph submitted to dataflow.



##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsublite/internal/UnboundedReaderImpl.java:
##########
@@ -0,0 +1,139 @@
+/*
+ * 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.gcp.pubsublite.internal;
+
+import static org.apache.beam.sdk.io.gcp.pubsublite.internal.ApiServices.asCloseable;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkState;
+
+import com.google.api.core.ApiService.State;
+import com.google.cloud.pubsublite.Offset;
+import com.google.cloud.pubsublite.proto.SequencedMessage;
+import com.google.protobuf.util.Timestamps;
+import java.io.IOException;
+import java.util.NoSuchElementException;
+import java.util.Optional;
+import java.util.concurrent.TimeUnit;
+import org.apache.beam.sdk.io.UnboundedSource;
+import org.apache.beam.sdk.io.UnboundedSource.UnboundedReader;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.joda.time.Instant;
+
+public class UnboundedReaderImpl extends UnboundedReader<SequencedMessage> {
+
+  private final UnboundedSource<SequencedMessage, CheckpointMarkImpl> source;
+  private final MemoryBufferedSubscriber subscriber;
+  private final TopicBacklogReader backlogReader;
+  private final BlockingCommitter committer;
+
+  private Offset fetchOffset;
+  private Optional<Instant> lastMessageTimestamp = Optional.empty();
+  private boolean advanced = false;
+
+  UnboundedReaderImpl(
+      UnboundedSource<SequencedMessage, CheckpointMarkImpl> source,
+      MemoryBufferedSubscriber subscriber,
+      TopicBacklogReader backlogReader,
+      BlockingCommitter committer,
+      Offset initialOffset) {
+    checkArgument(initialOffset.equals(subscriber.fetchOffset()));
+    this.source = source;
+    this.subscriber = subscriber;
+    this.backlogReader = backlogReader;
+    this.committer = committer;
+    this.fetchOffset = initialOffset;
+  }
+
+  @Override
+  public SequencedMessage getCurrent() throws NoSuchElementException {
+    if (!advanced) {
+      throw new NoSuchElementException();
+    }
+    return subscriber.peek().get();
+  }
+
+  @Override
+  public Instant getCurrentTimestamp() throws NoSuchElementException {
+    return getTimestamp(getCurrent());
+  }
+
+  private static Instant getTimestamp(SequencedMessage message) {
+    return Instant.ofEpochMilli(Timestamps.toMillis(message.getPublishTime()));
+  }
+
+  @Override
+  public void close() throws IOException {
+    try (AutoCloseable c1 = backlogReader;
+        AutoCloseable c2 = committer;
+        AutoCloseable c3 = asCloseable(subscriber)) {
+    } catch (Exception e) {
+      throw new IOException(e);
+    }
+  }
+
+  @Override
+  public boolean start() throws IOException {
+    try {
+      subscriber.startAsync().awaitRunning(1, TimeUnit.MINUTES);
+    } catch (Exception e) {
+      throw new IOException(e);
+    }
+    return advance();
+  }
+
+  @Override
+  public boolean advance() throws IOException {
+    if (!subscriber.state().equals(State.RUNNING)) {
+      throw new IOException("Subscriber failed: ", subscriber.failureCause());
+    }
+    if (advanced) {
+      subscriber.pop();
+    }
+    Optional<SequencedMessage> next = subscriber.peek();
+    advanced = next.isPresent();
+    if (!advanced) {
+      return false;
+    }
+    Offset nextOffset = Offset.of(next.get().getCursor().getOffset() + 1);
+    checkState(nextOffset.value() > fetchOffset.value());
+    fetchOffset = nextOffset;
+    lastMessageTimestamp = Optional.of(getTimestamp(next.get()));
+    return true;
+  }
+
+  @Override
+  public Instant getWatermark() {
+    return lastMessageTimestamp.orElse(BoundedWindow.TIMESTAMP_MIN_VALUE);
+  }
+
+  @Override
+  public CheckpointMarkImpl getCheckpointMark() {
+    subscriber.rebuffer();

Review Comment:
   add comment on why you rebuffer here



##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsublite/internal/BlockingCommitterImpl.java:
##########
@@ -0,0 +1,50 @@
+/*
+ * 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.gcp.pubsublite.internal;
+
+import static com.google.cloud.pubsublite.internal.ExtractStatus.toCanonical;
+
+import com.google.cloud.pubsublite.Offset;
+import com.google.cloud.pubsublite.internal.wire.Committer;
+import java.util.concurrent.TimeUnit;
+
+public class BlockingCommitterImpl implements BlockingCommitter {
+
+  private final Committer committer;
+
+  BlockingCommitterImpl(Committer committer) {
+    if (!committer.isRunning()) {
+      throw new RuntimeException(committer.failureCause());

Review Comment:
   would it be easier to debug if the exception was wrapped?



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