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Posted to jira@kafka.apache.org by GitBox <gi...@apache.org> on 2022/11/02 06:45:27 UTC
[GitHub] [kafka] cmccabe commented on a diff in pull request #12776: KAFKA-14327: Unify KRaft snapshot generation between broker and controller
cmccabe commented on code in PR #12776:
URL: https://github.com/apache/kafka/pull/12776#discussion_r1011251035
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metadata/src/main/java/org/apache/kafka/image/loader/MetadataLoader.java:
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@@ -0,0 +1,504 @@
+/*
+ * 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.image.loader;
+
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.image.MetadataDelta;
+import org.apache.kafka.image.MetadataImage;
+import org.apache.kafka.image.MetadataProvenance;
+import org.apache.kafka.image.MetadataVersionChange;
+import org.apache.kafka.image.MetadataVersionChangeException;
+import org.apache.kafka.image.publisher.MetadataPublisher;
+import org.apache.kafka.image.writer.ImageReWriter;
+import org.apache.kafka.image.writer.ImageWriterOptions;
+import org.apache.kafka.queue.KafkaEventQueue;
+import org.apache.kafka.raft.Batch;
+import org.apache.kafka.raft.BatchReader;
+import org.apache.kafka.raft.LeaderAndEpoch;
+import org.apache.kafka.raft.RaftClient;
+import org.apache.kafka.server.common.ApiMessageAndVersion;
+import org.apache.kafka.server.fault.FaultHandler;
+import org.apache.kafka.snapshot.SnapshotReader;
+import org.slf4j.Logger;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+
+
+/**
+ * The MetadataLoader follows changes provided by a RaftClient, and packages them into metadata
+ * deltas and images that can be consumed by publishers.
+ *
+ * The Loader maintains its own thread, which is used to make all callbacks into publishers. If a
+ * publisher A is installed before B, A will receive all callbacks before B. This is also true if
+ * A and B are installed as part of a list [A, B].
+ *
+ * Publishers should not modify any data structures passed to them.
+ *
+ * It is possible to change the list of publishers dynamically over time. Whenever a new publisher is
+ * added, it receives a catch-up delta which contains the full state. Any publisher installed when the
+ * loader is closed will itself be closed.
+ */
+public class MetadataLoader implements RaftClient.Listener<ApiMessageAndVersion>, AutoCloseable {
+ public static class Builder {
+ private int nodeId = -1;
+ private Time time = Time.SYSTEM;
+ private LogContext logContext = null;
+ private String threadNamePrefix = "";
+ private FaultHandler faultHandler = null;
+ private MetadataLoaderMetrics metrics = new MetadataLoaderMetrics() {
+ private volatile long lastAppliedOffset = -1L;
+
+ @Override
+ public void updateBatchProcessingTime(long elapsedNs) { }
+
+ @Override
+ public void updateBatchSize(int size) { }
+
+ @Override
+ public void updateLastAppliedImageProvenance(MetadataProvenance provenance) {
+ this.lastAppliedOffset = provenance.offset();
+ }
+
+ @Override
+ public long lastAppliedOffset() {
+ return lastAppliedOffset;
+ }
+
+ @Override
+ public void close() throws Exception { }
+ };
+
+ public Builder setNodeId(int nodeId) {
+ this.nodeId = nodeId;
+ return this;
+ }
+
+ public Builder setTime(Time time) {
+ this.time = time;
+ return this;
+ }
+
+ public Builder setThreadNamePrefix(String threadNamePrefix) {
+ this.threadNamePrefix = threadNamePrefix;
+ return this;
+ }
+
+ public Builder setFaultHandler(FaultHandler faultHandler) {
+ this.faultHandler = faultHandler;
+ return this;
+ }
+
+ public Builder setMetadataLoaderMetrics(MetadataLoaderMetrics metrics) {
+ this.metrics = metrics;
+ return this;
+ }
+
+ public MetadataLoader build() {
+ if (logContext == null) {
+ logContext = new LogContext("[MetadataLoader " + nodeId + "] ");
+ }
+ if (faultHandler == null) throw new RuntimeException("You must set a fault handler.");
+ return new MetadataLoader(
+ time,
+ logContext,
+ threadNamePrefix,
+ faultHandler,
+ metrics);
+ }
+ }
+
+ /**
+ * The log4j logger for this loader.
+ */
+ private final Logger log;
+
+ /**
+ * The clock used by this loader.
+ */
+ private final Time time;
+
+ /**
+ * The fault handler to use if metadata loading fails.
+ */
+ private final FaultHandler faultHandler;
+
+ /**
+ * Callbacks for updating metrics.
+ */
+ private final MetadataLoaderMetrics metrics;
+
+ /**
+ * The publishers which should receive cluster metadata updates.
+ */
+ private final List<MetadataPublisher> publishers;
+
+ /**
+ * The current leader and epoch.
+ */
+ private LeaderAndEpoch currentLeaderAndEpoch = LeaderAndEpoch.UNKNOWN;
+
+ /**
+ * The current metadata image. Accessed only from the event queue thread.
+ */
+ private MetadataImage image;
+
+ /**
+ * The event queue which runs this loader.
+ */
+ private final KafkaEventQueue eventQueue;
+
+ private MetadataLoader(
+ Time time,
+ LogContext logContext,
+ String threadNamePrefix,
+ FaultHandler faultHandler,
+ MetadataLoaderMetrics metrics
+ ) {
+ this.log = logContext.logger(MetadataLoader.class);
+ this.time = time;
+ this.faultHandler = faultHandler;
+ this.metrics = metrics;
+ this.publishers = new ArrayList<>();
+ this.image = MetadataImage.EMPTY;
+ this.eventQueue = new KafkaEventQueue(time, logContext, threadNamePrefix);
+ }
+
+ @Override
+ public void handleCommit(BatchReader<ApiMessageAndVersion> reader) {
+ eventQueue.append(() -> {
+ try {
+ MetadataDelta delta = new MetadataDelta.Builder().
+ setImage(image).
+ build();
+ LogDeltaManifest manifest = loadLogDelta(delta, reader);
+ try {
+ image = delta.apply(manifest.provenance());
+ } catch (Throwable e) {
+ faultHandler.handleFault("Error generating new metadata image from " +
+ "metadata delta between offset " + image.offset() +
+ " and " + manifest.provenance().offset(), e);
+ return;
+ }
+ for (MetadataPublisher publisher : publishers) {
+ try {
+ publisher.publishLogDelta(delta, image, manifest);
+ } catch (Throwable e) {
+ faultHandler.handleFault("Unhandled error publishing the new metadata " +
+ "image ending at " + manifest.provenance().offset() +
+ " with publisher " + publisher.name(), e);
+ }
+ }
+ metrics.updateLastAppliedImageProvenance(image.provenance());
+ } catch (Throwable e) {
+ // This is a general catch-all block where we don't expect to end up;
+ // failure-prone operations should have individual try/catch blocks around them.
+ faultHandler.handleFault("Unhandled fault in MetadataLoader#handleCommit. " +
+ "Last image offset was " + image.offset(), e);
+ } finally {
+ reader.close();
+ }
+ });
+ }
+
+ /**
+ * Load some batches of records from the log. We have to do some bookkeeping here to
+ * translate between batch offsets and record offsets, and track the number of bytes we
+ * have read. Additionally, there is the chance that one of the records is a metadata
+ * version change which needs to be handled differently.
+ *
+ * @param delta The metadata delta we are preparing.
+ * @param reader The reader which yields the batches.
+ * @return A manifest of what was loaded.
+ */
+ LogDeltaManifest loadLogDelta(
+ MetadataDelta delta,
+ BatchReader<ApiMessageAndVersion> reader
+ ) {
+ long startNs = time.nanoseconds();
+ int numBatches = 0;
+ long numBytes = 0L;
+ long lastOffset = image.provenance().offset();
+ int lastEpoch = image.provenance().epoch();
+ long lastContainedLogTimeMs = image.provenance().lastContainedLogTimeMs();
+
+ while (reader.hasNext()) {
+ Batch<ApiMessageAndVersion> batch = reader.next();
+ int indexWithinBatch = 0;
+ for (ApiMessageAndVersion record : batch.records()) {
+ try {
+ delta.replay(record.message());
+ } catch (MetadataVersionChangeException e) {
+ handleMetadataVersionChange(delta,
+ e.change(),
+ batch.baseOffset() + indexWithinBatch,
+ lastEpoch,
+ lastContainedLogTimeMs);
+ } catch (Throwable e) {
+ faultHandler.handleFault("Error loading metadata log record from offset " +
+ batch.baseOffset() + indexWithinBatch, e);
+ }
+ lastEpoch = batch.epoch();
+ lastContainedLogTimeMs = batch.appendTimestamp();
+ indexWithinBatch++;
+ }
+ metrics.updateBatchSize(batch.records().size());
+ lastOffset = batch.lastOffset();
+ numBytes += batch.sizeInBytes();
+ numBatches++;
+ }
+ MetadataProvenance provenance =
+ new MetadataProvenance(lastOffset, lastEpoch, lastContainedLogTimeMs);
+ long elapsedNs = time.nanoseconds() - startNs;
+ // TODO: this metric should be renamed something like "delta processing time"
Review Comment:
OK. I filed [KAFKA-14348](https://issues.apache.org/jira/browse/KAFKA-14348) for this.
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