Xeli commented on a change in pull request #6594: [FLINK-9311] [pubsub] Added PubSub source connector with support for checkpointing (ATLEAST_ONCE) URL: https://github.com/apache/flink/pull/6594#discussion_r257785238
########## File path: flink-connectors/flink-connector-pubsub/src/main/java/org/apache/flink/streaming/connectors/pubsub/PubSubSink.java ########## @@ -0,0 +1,239 @@ +/* + * 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.flink.streaming.connectors.pubsub; + +import org.apache.flink.api.common.serialization.SerializationSchema; +import org.apache.flink.configuration.Configuration; +import org.apache.flink.streaming.api.functions.sink.RichSinkFunction; +import org.apache.flink.streaming.api.functions.sink.SinkFunction; + +import com.google.api.gax.core.FixedCredentialsProvider; +import com.google.api.gax.grpc.GrpcTransportChannel; +import com.google.api.gax.rpc.FixedTransportChannelProvider; +import com.google.api.gax.rpc.TransportChannel; +import com.google.auth.Credentials; +import com.google.cloud.pubsub.v1.Publisher; +import com.google.protobuf.ByteString; +import com.google.pubsub.v1.ProjectTopicName; +import com.google.pubsub.v1.PubsubMessage; +import io.grpc.ManagedChannel; +import io.grpc.ManagedChannelBuilder; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.io.IOException; +import java.util.concurrent.TimeUnit; + +import static com.google.cloud.pubsub.v1.SubscriptionAdminSettings.defaultCredentialsProviderBuilder; + +/** + * A sink function that outputs to PubSub. + * + * @param <IN> type of PubSubSink messages to write + */ +public class PubSubSink<IN> extends RichSinkFunction<IN> { + private static final Logger LOG = LoggerFactory.getLogger(PubSubSink.class); + + private final Credentials credentials; + private final SerializationSchema<IN> serializationSchema; + private final String projectName; + private final String topicName; + private final String hostAndPort; + + private transient Publisher publisher; + + private PubSubSink( + Credentials credentials, + SerializationSchema<IN> serializationSchema, + String projectName, + String topicName, + String hostAndPort) { + this.credentials = credentials; + this.serializationSchema = serializationSchema; + this.projectName = projectName; + this.topicName = topicName; + this.hostAndPort = hostAndPort; + } + + private transient ManagedChannel managedChannel = null; + private transient TransportChannel channel = null; + + @Override + public void open(Configuration configuration) throws Exception { + Publisher.Builder builder = Publisher + .newBuilder(ProjectTopicName.of(projectName, topicName)) + .setCredentialsProvider(FixedCredentialsProvider.create(credentials)); + + if (hostAndPort != null) { + managedChannel = ManagedChannelBuilder + .forTarget(hostAndPort) + .usePlaintext(true) // This is 'Ok' because this is ONLY used for testing. + .build(); + channel = GrpcTransportChannel.newBuilder().setManagedChannel(managedChannel).build(); + builder.setChannelProvider(FixedTransportChannelProvider.create(channel)); + } + + publisher = builder.build(); + } + + @Override + public void close() throws Exception { + super.close(); + shutdownPublisher(); + shutdownTransportChannel(); + shutdownManagedChannel(); + } + + private void shutdownPublisher() { + try { + publisher.shutdown(); + } catch (Exception e) { + LOG.info("Shutting down Publisher failed: {}", e.getMessage()); + } + } + + private void shutdownTransportChannel() { + if (channel == null) { + return; + } + try { + channel.close(); + } catch (Exception e) { + LOG.info("Shutting down TransportChannel failed: {}", e.getMessage()); + } + } + + private void shutdownManagedChannel() { + if (managedChannel == null) { + return; + } + try { + managedChannel.shutdownNow(); + managedChannel.awaitTermination(1000L, TimeUnit.MILLISECONDS); + } catch (Exception e) { + LOG.info("Shutting down ManagedChannel failed: {}", e.getMessage()); + } + } + + @Override + public void invoke(IN message, SinkFunction.Context context) { + PubsubMessage pubsubMessage = PubsubMessage + .newBuilder() + .setData(ByteString.copyFrom(serializationSchema.serialize(message))) + .build(); + publisher.publish(pubsubMessage); + publisher.publishAllOutstanding(); Review comment: My rationale was that you do not want PubSub to batch / buffer messages. Because a checkpoint may be marked as successful but the PubSub messages have not been sent yet and on a failure you could have PubSub messages that won't ever be sent because from Flink's perspective they have already been send. I think an improvement of this sink could be to add a buffer in Flink state, so we would call the publishAllOutstanding() once every n messages. Do you have any ideas how to approach something like that? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
