cmccabe commented on a change in pull request #10366: URL: https://github.com/apache/kafka/pull/10366#discussion_r606374075
########## File path: metadata/src/main/java/org/apache/kafka/controller/SnapshotGenerator.java ########## @@ -0,0 +1,146 @@ +/* + * 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.kafka.controller; + +import java.util.Collections; +import java.util.Iterator; +import java.util.List; +import java.util.OptionalLong; + +import org.apache.kafka.common.utils.ExponentialBackoff; +import org.apache.kafka.common.utils.LogContext; +import org.apache.kafka.metadata.ApiMessageAndVersion; +import org.slf4j.Logger; + + +final class SnapshotGenerator { + static class Section { + private final String name; + private final Iterator<List<ApiMessageAndVersion>> iterator; + + Section(String name, Iterator<List<ApiMessageAndVersion>> iterator) { + this.name = name; + this.iterator = iterator; + } + + String name() { + return name; + } + + Iterator<List<ApiMessageAndVersion>> iterator() { + return iterator; + } + } + + private final Logger log; + private final SnapshotWriter writer; + private final int maxBatchesPerGenerateCall; + private final ExponentialBackoff exponentialBackoff; + private final List<Section> sections; + private final Iterator<Section> sectionIterator; + private Iterator<List<ApiMessageAndVersion>> batchIterator; + private List<ApiMessageAndVersion> batch; + private Section section; + private long numRecords; + private long numWriteTries; + + SnapshotGenerator(LogContext logContext, + SnapshotWriter writer, + int maxBatchesPerGenerateCall, + ExponentialBackoff exponentialBackoff, + List<Section> sections) { + this.log = logContext.logger(SnapshotGenerator.class); + this.writer = writer; + this.maxBatchesPerGenerateCall = maxBatchesPerGenerateCall; + this.exponentialBackoff = exponentialBackoff; + this.sections = sections; + this.sectionIterator = this.sections.iterator(); + this.batchIterator = Collections.emptyIterator(); + this.batch = null; + this.section = null; + this.numRecords = 0; + this.numWriteTries = 0; + } + + /** + * Returns the epoch of the snapshot that we are generating. + */ + long epoch() { + return writer.epoch(); + } + + SnapshotWriter writer() { + return writer; + } + + /** + * Generate the next batch of records. + * + * @return 0 if a batch was sent to the writer, + * -1 if there are no more batches to generate, + * or the number of times we tried to write and the writer + * was busy, otherwise. + */ + private long generateBatch() throws Exception { + if (batch == null) { + while (!batchIterator.hasNext()) { + if (section != null) { + log.info("Generated {} record(s) for the {} section of snapshot {}.", + numRecords, section.name(), writer.epoch()); + section = null; + numRecords = 0; + } + if (!sectionIterator.hasNext()) { + writer.completeSnapshot(); + return -1; + } + section = sectionIterator.next(); + log.info("Generating records for the {} section of snapshot {}.", + section.name(), writer.epoch()); + batchIterator = section.iterator(); + } + batch = batchIterator.next(); + } + if (writer.writeBatch(batch)) { + numRecords += batch.size(); + numWriteTries = 0; + batch = null; + return 0; + } else { + return ++numWriteTries; + } + } + + /** + * Generate the next few batches of records. + * + * @return The number of nanoseconds to delay before rescheduling the + * generateBatches event, or empty if the snapshot is done. + */ + OptionalLong generateBatches() throws Exception { + for (int numBatches = 0; numBatches < maxBatchesPerGenerateCall; numBatches++) { + long result = generateBatch(); + if (result < 0) { + return OptionalLong.empty(); + } else if (result > 0) { + return OptionalLong.of(exponentialBackoff.backoff(numWriteTries - 1)); Review comment: It's fine to use `result` here, I guess. -- 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: us...@infra.apache.org
