feat: Implement internal CursorClient which will be used by kafka shi…

…m. (#252)

google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/internal/CursorClient.java

@@ -0,0 +1,61 @@
+/*
+ * 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.internal;
+
+import com.google.api.core.ApiFuture;
+import com.google.api.gax.core.BackgroundResource;
+import com.google.cloud.pubsublite.CloudRegion;
+import com.google.cloud.pubsublite.Offset;
+import com.google.cloud.pubsublite.Partition;
+import com.google.cloud.pubsublite.SubscriptionPath;
+import io.grpc.StatusException;
+import java.util.Map;
+
+public interface CursorClient extends BackgroundResource {
+
+  static CursorClient create(CursorClientSettings settings) throws StatusException {
+    return settings.instantiate();
+  }
+
+  /** The Google Cloud region this client operates on. */
+  CloudRegion region();
+
+  /**
+   * List the cursors for a given subscription.
+   *
+   * @param path The subscription to list cursors for.
+   * @return A future holding the map of Partition to Offset of the cursors.
+   */
+  ApiFuture<Map<Partition, Offset>> listPartitionCursors(SubscriptionPath path);
+
+  /**
+   * Commit a single cursor.
+   *
+   * @param path The subscription to commit a cursor for.
+   * @param partition The partition to commit a cursor for.
+   * @param offset The offset to commit.
+   * @return A future for the operation's completion.
+   */
+  ApiFuture<Void> commitCursor(SubscriptionPath path, Partition partition, Offset offset);
+
+  /**
+   * Tear down this admin client.
+   *
+   * @throws StatusException on a failure to properly terminate.
+   */
+  @Override
+  void close() throws StatusException;
+}

google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/internal/CursorClientImpl.java

@@ -0,0 +1,144 @@
+/*
+ * 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.internal;
+
+import com.google.api.core.ApiFuture;
+import com.google.api.gax.core.BackgroundResource;
+import com.google.api.gax.core.ExecutorAsBackgroundResource;
+import com.google.api.gax.retrying.RetrySettings;
+import com.google.api.gax.retrying.RetryingExecutor;
+import com.google.cloud.pubsublite.CloudRegion;
+import com.google.cloud.pubsublite.Offset;
+import com.google.cloud.pubsublite.Partition;
+import com.google.cloud.pubsublite.SubscriptionPath;
+import com.google.cloud.pubsublite.proto.CommitCursorRequest;
+import com.google.cloud.pubsublite.proto.CommitCursorResponse;
+import com.google.cloud.pubsublite.proto.Cursor;
+import com.google.cloud.pubsublite.proto.CursorServiceGrpc.CursorServiceBlockingStub;
+import com.google.cloud.pubsublite.proto.ListPartitionCursorsRequest;
+import com.google.cloud.pubsublite.proto.ListPartitionCursorsResponse;
+import com.google.cloud.pubsublite.proto.PartitionCursor;
+import com.google.common.collect.ImmutableMap;
+import io.grpc.StatusException;
+import java.util.Map;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+public class CursorClientImpl implements BackgroundResource, CursorClient {
+  private final ExecutorAsBackgroundResource executorResource;
+  private final CloudRegion region;
+  private final CursorServiceBlockingStub stub;
+  private final RetryingExecutor<Map<Partition, Offset>> listRetryingExecutor;
+  private final RetryingExecutor<Void> voidRetryingExecutor;
+
+  public CursorClientImpl(
+      CloudRegion region, CursorServiceBlockingStub stub, RetrySettings retrySettings) {
+    this(
+        region,
+        stub,
+        retrySettings,
+        // TODO: Consider allowing tuning in the future.
+        Executors.newScheduledThreadPool(6));
+  }
+
+  private CursorClientImpl(
+      CloudRegion region,
+      CursorServiceBlockingStub stub,
+      RetrySettings retrySettings,
+      ScheduledExecutorService executor) {
+    this.executorResource = new ExecutorAsBackgroundResource(executor);
+    this.region = region;
+    this.stub = stub;
+    this.listRetryingExecutor = RetryingExecutorUtil.retryingExecutor(retrySettings, executor);
+    this.voidRetryingExecutor = RetryingExecutorUtil.retryingExecutor(retrySettings, executor);
+  }
+
+  @Override
+  public CloudRegion region() {
+    return region;
+  }
+
+  // BackgroundResource implementation.
+  @Override
+  public void shutdown() {
+    executorResource.shutdown();
+  }
+
+  @Override
+  public boolean isShutdown() {
+    return executorResource.isShutdown();
+  }
+
+  @Override
+  public boolean isTerminated() {
+    return executorResource.isTerminated();
+  }
+
+  @Override
+  public void shutdownNow() {
+    executorResource.shutdownNow();
+  }
+
+  @Override
+  public boolean awaitTermination(long duration, TimeUnit unit) throws InterruptedException {
+    return executorResource.awaitTermination(duration, unit);
+  }
+
+  @Override
+  public void close() throws StatusException {
+    try {
+      executorResource.close();
+    } catch (Exception e) {
+      throw ExtractStatus.toCanonical(e);
+    }
+  }
+
+  // CursorClient Implementation
+  @Override
+  public ApiFuture<Map<Partition, Offset>> listPartitionCursors(SubscriptionPath path) {
+    return RetryingExecutorUtil.runWithRetries(
+        () -> {
+          ListPartitionCursorsResponse response =
+              stub.listPartitionCursors(
+                  ListPartitionCursorsRequest.newBuilder().setParent(path.toString()).build());
+          ImmutableMap.Builder<Partition, Offset> resultBuilder = ImmutableMap.builder();
+          for (PartitionCursor partitionCursor : response.getPartitionCursorsList()) {
+            resultBuilder.put(
+                Partition.of(partitionCursor.getPartition()),
+                Offset.of(partitionCursor.getCursor().getOffset()));
+          }
+          return resultBuilder.build();
+        },
+        listRetryingExecutor);
+  }
+
+  @Override
+  public ApiFuture<Void> commitCursor(SubscriptionPath path, Partition partition, Offset offset) {
+    return RetryingExecutorUtil.runWithRetries(
+        () -> {
+          CommitCursorResponse unusedResponse =
+              stub.commitCursor(
+                  CommitCursorRequest.newBuilder()
+                      .setSubscription(path.toString())
+                      .setPartition(partition.value())
+                      .setCursor(Cursor.newBuilder().setOffset(offset.value()))
+                      .build());
+          return null;
+        },
+        voidRetryingExecutor);
+  }
+}

google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/internal/CursorClientSettings.java

@@ -0,0 +1,67 @@
+/*
+ * 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.internal;
+
+import com.google.api.gax.retrying.RetrySettings;
+import com.google.auto.value.AutoValue;
+import com.google.cloud.pubsublite.CloudRegion;
+import com.google.cloud.pubsublite.Constants;
+import com.google.cloud.pubsublite.Stubs;
+import com.google.cloud.pubsublite.proto.CursorServiceGrpc;
+import com.google.cloud.pubsublite.proto.CursorServiceGrpc.CursorServiceBlockingStub;
+import io.grpc.StatusException;
+import java.util.Optional;
+
+@AutoValue
+public abstract class CursorClientSettings {
+
+  // Required parameters.
+  abstract CloudRegion region();
+
+  // Optional parameters.
+  abstract RetrySettings retrySettings();
+
+  abstract Optional<CursorServiceBlockingStub> stub();
+
+  public static Builder newBuilder() {
+    return new AutoValue_CursorClientSettings.Builder()
+        .setRetrySettings(Constants.DEFAULT_RETRY_SETTINGS);
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder {
+
+    // Required parameters.
+    public abstract Builder setRegion(CloudRegion region);
+
+    public abstract Builder setRetrySettings(RetrySettings retrySettings);
+
+    // Optional parameters.
+    public abstract Builder setStub(CursorServiceBlockingStub stub);
+
+    public abstract CursorClientSettings build();
+  }
+
+  CursorClient instantiate() throws StatusException {
+    CursorServiceBlockingStub stub;
+    if (stub().isPresent()) {
+      stub = stub().get();
+    } else {
+      stub = Stubs.defaultStub(region(), CursorServiceGrpc::newBlockingStub);
+    }
+    return new CursorClientImpl(region(), stub, retrySettings());
+  }
+}