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_r300075699
########## File path: flink-connectors/flink-connector-gcp-pubsub/src/main/java/org/apache/flink/streaming/connectors/gcp/pubsub/BlockingGrpcPubSubSubscriber.java ########## @@ -0,0 +1,133 @@ +/* + * 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.gcp.pubsub; + +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.streaming.connectors.gcp.pubsub.common.PubSubSubscriber; + +import com.google.pubsub.v1.AcknowledgeRequest; +import com.google.pubsub.v1.PullRequest; +import com.google.pubsub.v1.ReceivedMessage; +import com.google.pubsub.v1.SubscriberGrpc; +import io.grpc.ManagedChannel; +import io.grpc.StatusRuntimeException; + +import java.time.Duration; +import java.util.List; +import java.util.concurrent.TimeUnit; + +import static java.util.Collections.emptyList; +import static java.util.concurrent.TimeUnit.SECONDS; + +/** + * Implementation for {@link PubSubSubscriber}. + * This Grpc PubSubSubscriber allows for flexible timeouts and retries. + */ +public class BlockingGrpcPubSubSubscriber implements PubSubSubscriber { + private final String projectSubscriptionName; + private final ManagedChannel channel; + private final SubscriberGrpc.SubscriberBlockingStub stub; + private final int retries; + private final Duration timeout; + private final PullRequest pullRequest; + + public BlockingGrpcPubSubSubscriber(String projectSubscriptionName, ManagedChannel channel, SubscriberGrpc.SubscriberBlockingStub stub, PullRequest pullRequest, int retries, Duration timeout) { + this.projectSubscriptionName = projectSubscriptionName; + this.channel = channel; + this.stub = stub; + this.retries = retries; + this.timeout = timeout; + this.pullRequest = pullRequest; + } + + @Override + public List<ReceivedMessage> pull() { + return pull(retries); + } + + private List<ReceivedMessage> pull(int retriesRemaining) { + try { + return stub.withDeadlineAfter(timeout.toMillis(), TimeUnit.MILLISECONDS) + .pull(pullRequest) + .getReceivedMessagesList(); + } catch (StatusRuntimeException e) { + if (retriesRemaining > 0) { + return pull(retriesRemaining - 1); + } + + throw e; + } + } + + @Override + public void acknowledge(List<String> acknowledgementIds) { + if (acknowledgementIds.isEmpty()) { + return; + } + + //grpc servers won't accept acknowledge requests that are too large so we split the ackIds + Tuple2<List<String>, List<String>> splittedAckIds = splitAckIds(acknowledgementIds); + while (!splittedAckIds.f0.isEmpty()) { + AcknowledgeRequest acknowledgeRequest = + AcknowledgeRequest.newBuilder() + .setSubscription(projectSubscriptionName) + .addAllAckIds(splittedAckIds.f0) + .build(); + + stub.withDeadlineAfter(60, SECONDS).acknowledge(acknowledgeRequest); + + splittedAckIds = splitAckIds(splittedAckIds.f1); + } + } + + /* maxPayload is the maximum number of bytes to devote to actual ids in + * acknowledgement or modifyAckDeadline requests. A serialized + * AcknowledgeRequest grpc call has a small constant overhead, plus the size of the + * subscription name, plus 3 bytes per ID (a tag byte and two size bytes). A + * ModifyAckDeadlineRequest has an additional few bytes for the deadline. We + * don't know the subscription name here, so we just assume the size exclusive + * of ids is 100 bytes. + + * With gRPC there is no way for the client to know the server's max message size (it is + * configurable on the server). We know from experience that it is 512K. + * @return First list contains no more than 512k bytes, second list contains remaining ids + */ + private Tuple2<List<String>, List<String>> splitAckIds(List<String> ackIds) { + final int maxPayload = 500 * 1024; //little below 512k bytes to be on the safe side + final int fixedOverheadPerCall = 100; + final int overheadPerId = 3; + + int totalBytes = fixedOverheadPerCall; + + for (int i = 0; i < ackIds.size(); i++) { + totalBytes += ackIds.get(i).length() + overheadPerId; + if (totalBytes > maxPayload) { + return Tuple2.of(ackIds.subList(0, i), ackIds.subList(i, ackIds.size())); + } + } + + return Tuple2.of(ackIds, emptyList()); + } + + @Override + public void close() throws Exception { + channel.shutdownNow(); + channel.awaitTermination(20, SECONDS); Review comment: `timeout` relates to connection timeouts to `pubsub.googleapis.com`. I chose 20s because flink has a timeout of 30 seconds after it calls cancel() on the source function. I kinda fear if we set it to `timeout` it might be set too low. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
