dcapwell commented on code in PR #4556: URL: https://github.com/apache/cassandra/pull/4556#discussion_r2729724663
########## src/java/org/apache/cassandra/service/thresholds/CoordinatorWarningsState.java: ########## @@ -0,0 +1,192 @@ +/* + * 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.thresholds; + +import java.util.function.BiConsumer; +import java.util.function.Consumer; +import java.util.function.Supplier; + +import javax.annotation.Nullable; + +import org.slf4j.Logger; + +import io.netty.util.concurrent.FastThreadLocal; + +/** + * Generic ThreadLocal state manager for coordinator warnings. + * Provides lifecycle management (init, update, done, reset) for accumulating + * warnings across a client request. + * + * @param <S> the type of state to manage (e.g., Map, custom holder class) + */ +public class CoordinatorWarningsState<S> +{ + private final FastThreadLocal<S> threadLocal; + private final S initSentinel; + private final S emptySentinel; + private final Supplier<S> stateFactory; + private final Logger logger; + private final String name; + private final boolean enableDefensiveChecks; + + /** + * Creates a new coordinator warnings state manager. + * + * @param name descriptive name for logging + * @param initSentinel sentinel value indicating initialized but empty state + * @param emptySentinel sentinel value indicating cleared state + * @param stateFactory factory to create new mutable state instances + * @param logger logger for diagnostic messages + * @param enableDefensiveChecks whether to enable defensive checks + */ + public CoordinatorWarningsState(String name, + S initSentinel, + @Nullable S emptySentinel, + Supplier<S> stateFactory, + Logger logger, + boolean enableDefensiveChecks) + { + this.name = name; + this.initSentinel = initSentinel; + this.emptySentinel = emptySentinel; + this.stateFactory = stateFactory; + this.logger = logger; + this.enableDefensiveChecks = enableDefensiveChecks; + this.threadLocal = new FastThreadLocal<>(); + } + + /** + * Initialize state for this thread. + * Must be called at the start of a client request. + */ + public void init() + { + if (logger.isTraceEnabled()) + logger.trace("{}.init()", name); + + S current = threadLocal.get(); + if (current != null && enableDefensiveChecks) + { + throw new AssertionError(name + ".init called while state is not null: " + current); + } + threadLocal.set(initSentinel); + } + + /** + * Reset/clear state for this thread. + */ + public void reset() + { + if (logger.isTraceEnabled()) + logger.trace("{}.reset()", name); + + if (emptySentinel != null) + threadLocal.set(emptySentinel); + else + threadLocal.remove(); + } + + /** + * Get current state, creating mutable state if needed. + * Transitions from initSentinel to mutable state on first access. + * + * @param fallbackSupplier supplies fallback state if not initialized + * @return current mutable state + */ + public S getMutableState(Supplier<S> fallbackSupplier) + { + S state = threadLocal.get(); + + if (state == null) + { + if (enableDefensiveChecks) + throw new AssertionError(name + " accessing state without calling .init() first"); + return fallbackSupplier.get(); + } + + if (state == initSentinel) + { + state = stateFactory.get(); + threadLocal.set(state); + } + + return state; + } + + /** + * Check if state is initialized and not empty. + */ + public boolean isActive() + { + S state = threadLocal.get(); + return state != null && state != initSentinel && state != emptySentinel; + } + + /** + * Process accumulated state and reset. + * Typical pattern for done() implementations. + * + * @param stateChecker checks if state should be processed (e.g., isEmpty()) + * @param processor processes the state + * @param errorHandler handles any errors during processing + */ + public void processAndReset(StateChecker<S> stateChecker, + Consumer<S> processor, + BiConsumer<S, Exception> errorHandler) + { + try + { + S state = threadLocal.get(); + + if (state == null || state == initSentinel) + { + return; + } + + boolean shouldProcess = stateChecker.shouldProcess(state); + + if (!shouldProcess) + { + return; + } + + processor.accept(state); + } + catch (Exception e) + { + S state = threadLocal.get(); + if (errorHandler != null) + errorHandler.accept(state, e); + else + logger.error("Error processing " + name, e); + } + finally + { + reset(); + } + } + + /** + * Functional interface for checking if state should be processed. + */ + @FunctionalInterface + public interface StateChecker<S> Review Comment: isn't this just a `Predicate`? -- This is an automated message from the Apache Git Service. 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