dcapwell commented on a change in pull request #1180: URL: https://github.com/apache/cassandra/pull/1180#discussion_r706404178
########## File path: src/java/org/apache/cassandra/service/reads/trackwarnings/TrackWarningsSnapshot.java ########## @@ -0,0 +1,136 @@ +/* + * 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.cassandra.service.reads.trackwarnings; + +import java.util.Set; +import java.util.concurrent.atomic.AtomicLong; + +import com.google.common.collect.ImmutableSet; + +import org.apache.cassandra.locator.InetAddressAndPort; + +public class TrackWarningsSnapshot +{ + private static final TrackWarningsSnapshot EMPTY = new TrackWarningsSnapshot(Warnings.EMPTY, Warnings.EMPTY, Warnings.EMPTY); + + public final Warnings tombstones, localReadSize, rowIndexTooLarge; + + private TrackWarningsSnapshot(Warnings tombstones, Warnings localReadSize, Warnings rowIndexTooLarge) + { + this.tombstones = tombstones; + this.localReadSize = localReadSize; + this.rowIndexTooLarge = rowIndexTooLarge; + } + + public static TrackWarningsSnapshot create(Warnings tombstones, Warnings localReadSize, Warnings rowIndexTooLarge) + { + if (tombstones == localReadSize && tombstones == rowIndexTooLarge && tombstones == Warnings.EMPTY) + return EMPTY; + return new TrackWarningsSnapshot(tombstones, localReadSize, rowIndexTooLarge); + } + + public static TrackWarningsSnapshot merge(TrackWarningsSnapshot... values) + { + if (values == null || values.length == 0) + return null; + + TrackWarningsSnapshot accum = EMPTY; + for (TrackWarningsSnapshot a : values) + accum = accum.merge(a); + return accum == EMPTY ? null : accum; + } + + public boolean isEmpty() + { + return this == EMPTY; + } + + private TrackWarningsSnapshot merge(TrackWarningsSnapshot other) + { + if (other == null || other == EMPTY) + return this; + return TrackWarningsSnapshot.create(tombstones.merge(other.tombstones), localReadSize.merge(other.localReadSize), rowIndexTooLarge.merge(other.rowIndexTooLarge)); + } + + public static final class Warnings + { + private static final Warnings EMPTY = new Warnings(Counter.EMPTY, Counter.EMPTY); + + public final Counter warnings; + public final Counter aborts; + + private Warnings(Counter warnings, Counter aborts) + { + this.warnings = warnings; + this.aborts = aborts; + } + + public static Warnings create(Counter warnings, Counter aborts) + { + if (warnings == Counter.EMPTY && aborts == Counter.EMPTY) + return EMPTY; + return new Warnings(warnings, aborts); + } + + public Warnings merge(Warnings other) + { + if (other == EMPTY) + return this; + return Warnings.create(warnings.merge(other.warnings), aborts.merge(other.aborts)); + } + } + + public static final class Counter + { + private static final Counter EMPTY = new Counter(ImmutableSet.of(), 0); + + public final ImmutableSet<InetAddressAndPort> instances; + public final long maxValue; + + private Counter(ImmutableSet<InetAddressAndPort> instances, long maxValue) + { + this.instances = instances; + this.maxValue = maxValue; + } + + public static Counter create(Set<InetAddressAndPort> instances, AtomicLong maxValue) Review comment: nope, race condition which I document =D ``` // if instances is empty ignore value // writes and reads are concurrent (write = networking callback, read = coordinator thread), so there is // an edge case where instances is empty and maxValue > 0; this is caused by the fact we update value first before count // we write: value then instance // we read: instance then value ``` if you make it `long` you need to eagerly get the value, which means we handle `instance` AFTER `maxValue`; which could again cause confusing metrics ``` T1 - call snapshot method, pulling maxValue=0 T2 - update maxValue=42 T2 - update instances (size=1) T1 - copy instances (size=1) T1 - return count(size=1, maxValue=0) ``` -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
