AMashenkov commented on code in PR #3358: URL: https://github.com/apache/ignite-3/pull/3358#discussion_r1521470274
########## modules/table/src/main/java/org/apache/ignite/internal/table/distributed/LowWatermarkImpl.java: ########## @@ -0,0 +1,280 @@ +/* + * 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.ignite.internal.table.distributed; + +import static org.apache.ignite.internal.failure.FailureType.CRITICAL_ERROR; +import static org.apache.ignite.internal.util.CompletableFutures.nullCompletedFuture; +import static org.apache.ignite.internal.util.IgniteUtils.inBusyLock; + +import java.util.ArrayList; +import java.util.List; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.CopyOnWriteArrayList; +import java.util.concurrent.Executors; +import java.util.concurrent.ScheduledExecutorService; +import java.util.concurrent.ScheduledFuture; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.concurrent.atomic.AtomicReference; +import org.apache.ignite.internal.failure.FailureContext; +import org.apache.ignite.internal.failure.FailureProcessor; +import org.apache.ignite.internal.hlc.HybridClock; +import org.apache.ignite.internal.hlc.HybridTimestamp; +import org.apache.ignite.internal.lang.ByteArray; +import org.apache.ignite.internal.lang.NodeStoppingException; +import org.apache.ignite.internal.logger.IgniteLogger; +import org.apache.ignite.internal.logger.Loggers; +import org.apache.ignite.internal.manager.IgniteComponent; +import org.apache.ignite.internal.schema.configuration.LowWatermarkConfiguration; +import org.apache.ignite.internal.thread.NamedThreadFactory; +import org.apache.ignite.internal.tx.TxManager; +import org.apache.ignite.internal.util.ByteUtils; +import org.apache.ignite.internal.util.IgniteSpinBusyLock; +import org.apache.ignite.internal.util.IgniteUtils; +import org.apache.ignite.internal.vault.VaultEntry; +import org.apache.ignite.internal.vault.VaultManager; +import org.jetbrains.annotations.Nullable; + +/** + * Class to manage the low watermark. + * + * <p>Low watermark is the node's local time, which ensures that read-only transactions have completed by this time, and new read-only + * transactions will only be created after this time, and we can safely delete obsolete/garbage data such as: obsolete versions of table + * rows, remote indexes, remote tables, etc. + * + * @see <a href="https://cwiki.apache.org/confluence/display/IGNITE/IEP-91%3A+Transaction+protocol";>IEP-91</a> + */ +public class LowWatermarkImpl implements IgniteComponent, LowWatermark { + private static final IgniteLogger LOG = Loggers.forClass(LowWatermarkImpl.class); + + static final ByteArray LOW_WATERMARK_VAULT_KEY = new ByteArray("low-watermark"); + + private final LowWatermarkConfiguration lowWatermarkConfig; + + private final HybridClock clock; + + private final TxManager txManager; + + private final VaultManager vaultManager; + + private final List<LowWatermarkChangedListener> updateListeners = new CopyOnWriteArrayList<>(); + + private final ScheduledExecutorService scheduledThreadPool; + + private final IgniteSpinBusyLock busyLock = new IgniteSpinBusyLock(); + + private final AtomicBoolean closeGuard = new AtomicBoolean(); + + private volatile @Nullable HybridTimestamp lowWatermark; + + private final AtomicReference<ScheduledFuture<?>> lastScheduledTaskFuture = new AtomicReference<>(); + + private final FailureProcessor failureProcessor; + + /** + * Constructor. + * + * @param nodeName Node name. + * @param lowWatermarkConfig Low watermark configuration. + * @param clock A hybrid logical clock. + * @param txManager Transaction manager. + * @param vaultManager Vault manager. + * @param failureProcessor Failure processor tha is used to handle critical errors. + */ + public LowWatermarkImpl( + String nodeName, + LowWatermarkConfiguration lowWatermarkConfig, + HybridClock clock, + TxManager txManager, + VaultManager vaultManager, + FailureProcessor failureProcessor + ) { + this.lowWatermarkConfig = lowWatermarkConfig; + this.clock = clock; + this.txManager = txManager; + this.vaultManager = vaultManager; + this.failureProcessor = failureProcessor; + + scheduledThreadPool = Executors.newSingleThreadScheduledExecutor( + NamedThreadFactory.create(nodeName, "low-watermark-updater", LOG) + ); + } + + /** + * Starts the watermark manager. + */ + @Override + public CompletableFuture<Void> start() { + inBusyLock(busyLock, () -> { + lowWatermark = readLowWatermarkFromVault(); + }); + + return nullCompletedFuture(); + } + + /** + * Schedule watermark updates. + */ + public void scheduleUpdates() { + inBusyLock(busyLock, () -> { + HybridTimestamp lowWatermarkCandidate = lowWatermark; + + if (lowWatermarkCandidate == null) { + LOG.info("Previous value of the low watermark was not found, will schedule to update it"); + + scheduleUpdateLowWatermarkBusy(); + + return; + } + + LOG.info("Low watermark has been scheduled to be updated: {}", lowWatermarkCandidate); + + txManager.updateLowWatermark(lowWatermarkCandidate) + .thenComposeAsync(unused -> inBusyLock(busyLock, () -> notifyListeners(lowWatermarkCandidate)), scheduledThreadPool) + .whenComplete((unused, throwable) -> { + if (throwable == null) { + inBusyLock(busyLock, this::scheduleUpdateLowWatermarkBusy); + } else if (!(throwable instanceof NodeStoppingException)) { + LOG.error("Error during the Watermark manager start", throwable); + + failureProcessor.process(new FailureContext(CRITICAL_ERROR, throwable)); + + inBusyLock(busyLock, this::scheduleUpdateLowWatermarkBusy); + } + }); + }); + } + + private @Nullable HybridTimestamp readLowWatermarkFromVault() { + VaultEntry vaultEntry = vaultManager.get(LOW_WATERMARK_VAULT_KEY); + + return vaultEntry == null ? null : ByteUtils.fromBytes(vaultEntry.value()); + } + + @Override + public void stop() { + if (!closeGuard.compareAndSet(false, true)) { + return; + } + + busyLock.block(); + + ScheduledFuture<?> lastScheduledTaskFuture = this.lastScheduledTaskFuture.get(); + + if (lastScheduledTaskFuture != null) { + lastScheduledTaskFuture.cancel(true); + } + + IgniteUtils.shutdownAndAwaitTermination(scheduledThreadPool, 10, TimeUnit.SECONDS); + } + + @Override + public @Nullable HybridTimestamp getLowWatermark() { + return lowWatermark; + } + + void updateLowWatermark() { + inBusyLock(busyLock, () -> { + HybridTimestamp lowWatermarkCandidate = createNewLowWatermarkCandidate(); + + // Wait until all the read-only transactions are finished before the new candidate, since no new RO transactions could be + // created, then we can safely promote the candidate as a new low watermark, store it in vault, and we can safely start cleaning + // up the stale/junk data in the tables. + txManager.updateLowWatermark(lowWatermarkCandidate) + .thenComposeAsync(unused -> inBusyLock(busyLock, () -> { + vaultManager.put(LOW_WATERMARK_VAULT_KEY, ByteUtils.toBytes(lowWatermarkCandidate)); Review Comment: This code left "as is" after renaming the class. I disagree. If we save watermark after notifying listeners, then we may loose LWM update and notify some listeners. Thus we may read stale LWM on restart and some components may have destroyed data "in future" (above LWM). -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
