feat: Supports topic partition increase.

src/main/java/com/google/cloud/pubsublite/spark/CachedPartitionCountReader.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * Licensed 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 com.google.cloud.pubsublite.spark;
+
+import com.google.cloud.pubsublite.AdminClient;
+import com.google.cloud.pubsublite.PartitionLookupUtils;
+import com.google.cloud.pubsublite.TopicPath;
+import com.google.common.base.Supplier;
+import com.google.common.base.Suppliers;
+import java.util.concurrent.TimeUnit;
+import javax.annotation.concurrent.ThreadSafe;
+
+@ThreadSafe
+public class CachedPartitionCountReader implements PartitionCountReader {
+  private final AdminClient adminClient;
+  private final Supplier<Integer> supplier;
+
+  public CachedPartitionCountReader(AdminClient adminClient, TopicPath topicPath) {
+    this.adminClient = adminClient;
+    this.supplier =
+        Suppliers.memoizeWithExpiration(
+            () -> PartitionLookupUtils.numPartitions(topicPath, adminClient), 10, TimeUnit.SECONDS);
+  }
+
+  @Override
+  public void close() {
+    adminClient.close();
+  }
+
+  public int getPartitionCount() {
+    return supplier.get();
+  }
+}

src/main/java/com/google/cloud/pubsublite/spark/LimitingHeadOffsetReader.java

@@ -27,6 +27,7 @@
 import com.google.cloud.pubsublite.internal.TopicStatsClient;
 import com.google.cloud.pubsublite.proto.Cursor;
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.flogger.GoogleLogger;
 import com.google.common.util.concurrent.MoreExecutors;
 import java.util.HashSet;
 import java.util.Map;
@@ -40,18 +41,22 @@
  * offsets for the topic at most once per minute.
  */
 public class LimitingHeadOffsetReader implements PerTopicHeadOffsetReader {
+  private static final GoogleLogger log = GoogleLogger.forEnclosingClass();
 
   private final TopicStatsClient topicStatsClient;
   private final TopicPath topic;
-  private final long topicPartitionCount;
+  private final PartitionCountReader partitionCountReader;
   private final AsyncLoadingCache<Partition, Offset> cachedHeadOffsets;
 
   @VisibleForTesting
   public LimitingHeadOffsetReader(
-      TopicStatsClient topicStatsClient, TopicPath topic, long topicPartitionCount, Ticker ticker) {
+      TopicStatsClient topicStatsClient,
+      TopicPath topic,
+      PartitionCountReader partitionCountReader,
+      Ticker ticker) {
     this.topicStatsClient = topicStatsClient;
     this.topic = topic;
-    this.topicPartitionCount = topicPartitionCount;
+    this.partitionCountReader = partitionCountReader;
     this.cachedHeadOffsets =
         Caffeine.newBuilder()
             .ticker(ticker)
@@ -82,7 +87,7 @@ public void onSuccess(Cursor c) {
   @Override
   public PslSourceOffset getHeadOffset() {
     Set<Partition> keySet = new HashSet<>();
-    for (int i = 0; i < topicPartitionCount; i++) {
+    for (int i = 0; i < partitionCountReader.getPartitionCount(); i++) {
       keySet.add(Partition.of(i));
     }
     CompletableFuture<Map<Partition, Offset>> future = cachedHeadOffsets.getAll(keySet);
@@ -95,6 +100,15 @@ public PslSourceOffset getHeadOffset() {
 
   @Override
   public void close() {
-    topicStatsClient.close();
+    try {
+      topicStatsClient.close();
+    } catch (Exception e) {
+      log.atWarning().withCause(e).log("Unable to close TopicStatsClient.");
+    }
+    try {
+      partitionCountReader.close();
+    } catch (Exception e) {
+      log.atWarning().withCause(e).log("Unable to close PartitionCountReader.");
+    }
   }
 }

src/main/java/com/google/cloud/pubsublite/spark/MultiPartitionCommitterImpl.java

@@ -25,30 +25,95 @@
 import com.google.common.flogger.GoogleLogger;
 import com.google.common.util.concurrent.MoreExecutors;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import javax.annotation.concurrent.GuardedBy;
 
+/**
+ * A {@link MultiPartitionCommitter} that lazily adjusts for partition changes when {@link
+ * MultiPartitionCommitter#commit(PslSourceOffset)} is called.
+ */
 public class MultiPartitionCommitterImpl implements MultiPartitionCommitter {
   private static final GoogleLogger log = GoogleLogger.forEnclosingClass();
 
+  private final CommitterFactory committerFactory;
+
+  @GuardedBy("this")
   private final Map<Partition, Committer> committerMap = new HashMap<>();
 
+  @GuardedBy("this")
+  private final Set<Partition> partitionsCleanUp = new HashSet<>();
+
+  public MultiPartitionCommitterImpl(long topicPartitionCount, CommitterFactory committerFactory) {
+    this(
+        topicPartitionCount,
+        committerFactory,
+        MoreExecutors.getExitingScheduledExecutorService(new ScheduledThreadPoolExecutor(1)));
+  }
+
   @VisibleForTesting
-  MultiPartitionCommitterImpl(long topicPartitionCount, CommitterFactory committerFactory) {
+  MultiPartitionCommitterImpl(
+      long topicPartitionCount,
+      CommitterFactory committerFactory,
+      ScheduledExecutorService executorService) {
+    this.committerFactory = committerFactory;
     for (int i = 0; i < topicPartitionCount; i++) {
       Partition p = Partition.of(i);
-      Committer committer = committerFactory.newCommitter(p);
-      committer.startAsync().awaitRunning();
-      committerMap.put(p, committer);
+      committerMap.put(p, createCommitter(p));
     }
+    executorService.scheduleWithFixedDelay(this::cleanUpCommitterMap, 10, 10, TimeUnit.MINUTES);
   }
 
   @Override
   public synchronized void close() {
     committerMap.values().forEach(c -> c.stopAsync().awaitTerminated());
   }
 
+  /** Adjust committerMap based on the partitions that needs to be committed. */
+  private synchronized void updateCommitterMap(PslSourceOffset offset) {
+    int currentPartitions = committerMap.size();
+    int newPartitions = offset.partitionOffsetMap().size();
+
+    if (currentPartitions == newPartitions) {
+      return;
+    }
+    if (currentPartitions < newPartitions) {
+      for (int i = currentPartitions; i < newPartitions; i++) {
+        Partition p = Partition.of(i);
+        if (!committerMap.containsKey(p)) {
+          committerMap.put(p, createCommitter(p));
+        }
+        partitionsCleanUp.remove(p);
+      }
+      return;
+    }
+    partitionsCleanUp.clear();
+    for (int i = newPartitions; i < currentPartitions; i++) {
+      partitionsCleanUp.add(Partition.of(i));
+    }
+  }
+
+  private synchronized Committer createCommitter(Partition p) {
+    Committer committer = committerFactory.newCommitter(p);
+    committer.startAsync().awaitRunning();
+    return committer;
+  }
+
+  private synchronized void cleanUpCommitterMap() {
+    for (Partition p : partitionsCleanUp) {
+      committerMap.get(p).stopAsync();
+      committerMap.remove(p);
+    }
+    partitionsCleanUp.clear();
+  }
+
   @Override
   public synchronized void commit(PslSourceOffset offset) {
+    updateCommitterMap(offset);
     offset
         .partitionOffsetMap()
         .forEach(

src/main/java/com/google/cloud/pubsublite/spark/PartitionCountReader.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * Licensed 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 com.google.cloud.pubsublite.spark;
+
+import java.io.Closeable;
+
+public interface PartitionCountReader extends Closeable {
+  int getPartitionCount();
+
+  @Override
+  void close();
+}

src/main/java/com/google/cloud/pubsublite/spark/PslContinuousReader.java

@@ -41,8 +41,9 @@ public class PslContinuousReader implements ContinuousReader {
   private final PartitionSubscriberFactory partitionSubscriberFactory;
   private final SubscriptionPath subscriptionPath;
   private final FlowControlSettings flowControlSettings;
-  private final long topicPartitionCount;
   private SparkSourceOffset startOffset;
+  private final PartitionCountReader partitionCountReader;
+  private final long topicPartitionCount;
 
   @VisibleForTesting
   public PslContinuousReader(
@@ -51,13 +52,14 @@ public PslContinuousReader(
       PartitionSubscriberFactory partitionSubscriberFactory,
       SubscriptionPath subscriptionPath,
       FlowControlSettings flowControlSettings,
-      long topicPartitionCount) {
+      PartitionCountReader partitionCountReader) {
     this.cursorClient = cursorClient;
     this.committer = committer;
     this.partitionSubscriberFactory = partitionSubscriberFactory;
     this.subscriptionPath = subscriptionPath;
     this.flowControlSettings = flowControlSettings;
-    this.topicPartitionCount = topicPartitionCount;
+    this.partitionCountReader = partitionCountReader;
+    this.topicPartitionCount = partitionCountReader.getPartitionCount();
   }
 
   @Override
@@ -126,4 +128,9 @@ public List<InputPartition<InternalRow>> planInputPartitions() {
     }
     return list;
   }
+
+  @Override
+  public boolean needsReconfiguration() {
+    return partitionCountReader.getPartitionCount() != topicPartitionCount;
+  }
 }

src/main/java/com/google/cloud/pubsublite/spark/PslDataSource.java

@@ -21,7 +21,6 @@
 import com.github.benmanes.caffeine.cache.Ticker;
 import com.google.auto.service.AutoService;
 import com.google.cloud.pubsublite.AdminClient;
-import com.google.cloud.pubsublite.PartitionLookupUtils;
 import com.google.cloud.pubsublite.SubscriptionPath;
 import com.google.cloud.pubsublite.TopicPath;
 import java.util.Objects;
@@ -55,17 +54,21 @@ public ContinuousReader createContinuousReader(
     PslDataSourceOptions pslDataSourceOptions =
         PslDataSourceOptions.fromSparkDataSourceOptions(options);
     SubscriptionPath subscriptionPath = pslDataSourceOptions.subscriptionPath();
-    long topicPartitionCount;
+    TopicPath topicPath;
     try (AdminClient adminClient = pslDataSourceOptions.newAdminClient()) {
-      topicPartitionCount = PartitionLookupUtils.numPartitions(subscriptionPath, adminClient);
+      topicPath = TopicPath.parse(adminClient.getSubscription(subscriptionPath).get().getTopic());
+    } catch (Throwable t) {
+      throw toCanonical(t).underlying;
     }
+    PartitionCountReader partitionCountReader =
+        new CachedPartitionCountReader(pslDataSourceOptions.newAdminClient(), topicPath);
     return new PslContinuousReader(
         pslDataSourceOptions.newCursorClient(),
-        pslDataSourceOptions.newMultiPartitionCommitter(topicPartitionCount),
+        pslDataSourceOptions.newMultiPartitionCommitter(partitionCountReader.getPartitionCount()),
         pslDataSourceOptions.getSubscriberFactory(),
         subscriptionPath,
         Objects.requireNonNull(pslDataSourceOptions.flowControlSettings()),
-        topicPartitionCount);
+        partitionCountReader);
   }
 
   @Override
@@ -80,25 +83,24 @@ public MicroBatchReader createMicroBatchReader(
         PslDataSourceOptions.fromSparkDataSourceOptions(options);
     SubscriptionPath subscriptionPath = pslDataSourceOptions.subscriptionPath();
     TopicPath topicPath;
-    long topicPartitionCount;
     try (AdminClient adminClient = pslDataSourceOptions.newAdminClient()) {
       topicPath = TopicPath.parse(adminClient.getSubscription(subscriptionPath).get().getTopic());
-      topicPartitionCount = PartitionLookupUtils.numPartitions(topicPath, adminClient);
     } catch (Throwable t) {
       throw toCanonical(t).underlying;
     }
+    PartitionCountReader partitionCountReader =
+        new CachedPartitionCountReader(pslDataSourceOptions.newAdminClient(), topicPath);
     return new PslMicroBatchReader(
         pslDataSourceOptions.newCursorClient(),
-        pslDataSourceOptions.newMultiPartitionCommitter(topicPartitionCount),
+        pslDataSourceOptions.newMultiPartitionCommitter(partitionCountReader.getPartitionCount()),
         pslDataSourceOptions.getSubscriberFactory(),
         new LimitingHeadOffsetReader(
             pslDataSourceOptions.newTopicStatsClient(),
             topicPath,
-            topicPartitionCount,
+            partitionCountReader,
             Ticker.systemTicker()),
         subscriptionPath,
         Objects.requireNonNull(pslDataSourceOptions.flowControlSettings()),
-        pslDataSourceOptions.maxMessagesPerBatch(),
-        topicPartitionCount);
+        pslDataSourceOptions.maxMessagesPerBatch());
   }
 }