bdeggleston commented on code in PR #4708: URL: https://github.com/apache/cassandra/pull/4708#discussion_r3562106604
########## src/java/org/apache/cassandra/locator/WriteResponseTracker.java: ########## @@ -0,0 +1,237 @@ +/* + * 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.locator; + +import java.util.function.Predicate; + +import org.apache.cassandra.exceptions.RequestFailureReason; + +/** + * Response tracker for writes with pending replicas using the double count model. + * <p> + * Two requirements must be satisfied for success: + * <ol> + * <li>Committed replicas must satisfy base CL: {@code committedSuccesses >= baseBlockFor}</li> + * <li>Total replicas (committed + pending) must satisfy: {@code totalSuccesses >= totalBlockFor}</li> + * </ol> + * <p> + * This ensures both consistency (committed replicas have the data) and bootstrap safety + * (pending replicas also receive the write). + * <p> + * Implemented by composing two {@link SimpleResponseTracker}s: + * <ul> + * <li>committedTracker: tracks responses from committed replicas only</li> + * <li>totalTracker: tracks responses from all replicas (committed + pending)</li> + * </ul> + * <p> + * Thread-safe through delegation to thread-safe SimpleResponseTrackers. + */ +public class WriteResponseTracker implements ResponseTracker +{ + private final SimpleResponseTracker natural; + private final SimpleResponseTracker total; + + /** + * Create a write response tracker with the double count model. + * + * @param baseBlockFor number of committed replica responses required for CL + * @param totalBlockFor total responses required (baseBlockFor + pending count) + * @param committedReplicas number of committed replicas available + * @param pendingReplicas number of pending replicas available + * @param isPending predicate to determine if an endpoint is pending + */ + public WriteResponseTracker(int baseBlockFor, + int totalBlockFor, + int committedReplicas, + int pendingReplicas, + Predicate<InetAddressAndPort> isPending) + { + this(baseBlockFor, totalBlockFor, committedReplicas, pendingReplicas, isPending, null); + } + + /** + * Create a write response tracker with the double count model and a filter. + * + * @param naturalBlockFor number of committed replica responses required for CL + * @param totalBlockFor total responses required (naturalBlockFor + pending count) + * @param naturalReplicas number of committed replicas available + * @param pendingReplicas number of pending replicas available + * @param isPending predicate to determine if an endpoint is pending + * @param filter predicate to filter which responses count (e.g., InOurDc for LOCAL_QUORUM) + */ + public WriteResponseTracker(int naturalBlockFor, + int totalBlockFor, + int naturalReplicas, + int pendingReplicas, + Predicate<InetAddressAndPort> isPending, + Predicate<InetAddressAndPort> filter) + { + if (naturalBlockFor < 0) + throw new IllegalArgumentException("naturalBlockFor must be non-negative: " + naturalBlockFor); + if (totalBlockFor < naturalBlockFor) + throw new IllegalArgumentException("totalBlockFor (" + totalBlockFor + ") must be >= naturalBlockFor (" + naturalBlockFor + ")"); + if (naturalReplicas < 0) + throw new IllegalArgumentException("naturalReplicas must be non-negative: " + naturalReplicas); + if (pendingReplicas < 0) + throw new IllegalArgumentException("pendingReplicas must be non-negative: " + pendingReplicas); + if (naturalBlockFor > naturalReplicas) + throw new IllegalArgumentException("naturalBlockFor (" + naturalBlockFor + ") cannot exceed naturalReplicas (" + naturalReplicas + ")"); + if (totalBlockFor > naturalReplicas + pendingReplicas) + throw new IllegalArgumentException("totalBlockFor (" + totalBlockFor + ") cannot exceed total replicas (" + (naturalReplicas + pendingReplicas) + ")"); + if (isPending == null) + throw new IllegalArgumentException("isPending predicate cannot be null"); + + Predicate<InetAddressAndPort> naturalFilter = isPending.negate(); + if (filter != null) + naturalFilter = naturalFilter.and(filter); + + this.natural = new SimpleResponseTracker(naturalBlockFor, naturalReplicas, naturalFilter); + this.total = new SimpleResponseTracker(totalBlockFor, naturalReplicas + pendingReplicas, filter); + } + + private WriteResponseTracker(SimpleResponseTracker natural, SimpleResponseTracker total) + { + this.natural = natural; + this.total = total; + } + + @Override + public void onResponse(InetAddressAndPort from) + { + natural.onResponse(from); + total.onResponse(from); + } + + @Override + public void onFailure(InetAddressAndPort from, RequestFailureReason reason) + { + natural.onFailure(from, reason); + total.onFailure(from, reason); + } + + @Override + public boolean isComplete() + { + // Early failure if either tracker fails + if (natural.isComplete() && !natural.isSuccessful()) + return true; + if (total.isComplete() && !total.isSuccessful()) + return true; + + // Success requires both to succeed + return natural.isSuccessful() && total.isSuccessful(); + } + + @Override + public boolean isSuccessful() + { + return natural.isSuccessful() && total.isSuccessful(); + } + + @Override + public int required() + { + // Return total requirement for error messages + return total.required(); + } + + @Override + public int received() + { + // Return total successes for error messages + return total.received(); + } + + @Override + public int failures() + { + // Return total failures for error messages + return total.failures(); + } + + @Override + public boolean countsTowardQuorum(InetAddressAndPort from) + { + return total.countsTowardQuorum(from); + } + + public int committedReceived() + { + return natural.received(); + } + + public int pendingReceived() Review Comment: The ResponseTracker docs explains the thread safety concern, and how the class using them must handle concurrency -- This is an automated message from the Apache Git Service. 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