belliottsmith commented on code in PR #1845: URL: https://github.com/apache/cassandra/pull/1845#discussion_r979003381
########## src/java/org/apache/cassandra/service/accord/async/AsyncLoader.java: ########## @@ -0,0 +1,232 @@ +/* + * 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.accord.async; + +import java.util.ArrayList; +import java.util.List; +import java.util.Map; +import java.util.function.BiConsumer; +import java.util.function.Function; + +import com.google.common.annotations.VisibleForTesting; +import com.google.common.base.Preconditions; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import accord.primitives.TxnId; +import org.apache.cassandra.concurrent.Stage; +import org.apache.cassandra.service.accord.AccordCommand; +import org.apache.cassandra.service.accord.AccordCommandStore; +import org.apache.cassandra.service.accord.AccordCommandsForKey; +import org.apache.cassandra.service.accord.AccordKeyspace; +import org.apache.cassandra.service.accord.AccordStateCache; +import org.apache.cassandra.service.accord.AccordState; +import org.apache.cassandra.service.accord.api.AccordKey.PartitionKey; +import org.apache.cassandra.utils.concurrent.Future; +import org.apache.cassandra.utils.concurrent.FutureCombiner; + + +public class AsyncLoader +{ + private static final Logger logger = LoggerFactory.getLogger(AsyncLoader.class); + enum State + { + INITIALIZED, + SETUP, + LOADING, + FINISHED + } + + private State state = State.INITIALIZED; + private final AccordCommandStore commandStore; + + private final Iterable<TxnId> txnIds; + private final Iterable<PartitionKey> keys; + + protected Future<?> readFuture; + + public AsyncLoader(AccordCommandStore commandStore, Iterable<TxnId> txnIds, Iterable<PartitionKey> keys) + { + this.commandStore = commandStore; + this.txnIds = txnIds; + this.keys = keys; + } + + private <K, V extends AccordState<K>> Future<?> referenceAndDispatch(K key, + AccordStateCache.Instance<K, V> cache, + Map<K, V> context, + Function<V, Future<?>> readFunction, + Object callback) + { + V item; + Future<?> future = cache.getLoadFuture(key); + if (future != null) + { + // if a load future exists for this, it must be present in the cache + item = cache.getOrNull(key); + Preconditions.checkState(item != null); + context.put(key, item); + if (logger.isTraceEnabled()) + logger.trace("Existing load future found for {} while loading for {}. ({})", item.key(), callback, item); + return future; + } + + item = cache.getOrCreate(key); + context.put(key, item); + if (item.isLoaded()) + { + if (logger.isTraceEnabled()) + logger.trace("Cached item found for {} while loading for {}. ({})", item.key(), callback, item); + return null; + } + + future = readFunction.apply(item); + cache.setLoadFuture(item.key(), future); + if (logger.isTraceEnabled()) + logger.trace("Loading new item for {} while loading for {}. ({})", item.key(), callback, item); + return future; + } + + + private <K, V extends AccordState<K>> List<Future<?>> referenceAndDispatchReads(Iterable<K> keys, + AccordStateCache.Instance<K, V> cache, + Map<K, V> context, + Function<V, Future<?>> readFunction, + List<Future<?>> futures, + Object callback) + { + for (K key : keys) + { + Future<?> future = referenceAndDispatch(key, cache, context, readFunction, callback); + if (future == null) + continue; + + if (futures == null) + futures = new ArrayList<>(); + + futures.add(future); + } + + return futures; + } + + @VisibleForTesting + Function<AccordCommand, Future<?>> loadCommandFunction(Object callback) + { + return command -> Stage.READ.submit(() -> { + try + { + logger.trace("Starting load of {} for {}", command.txnId(), callback); + AccordKeyspace.loadCommand(command); + logger.trace("Completed load of {} for {}", command.txnId(), callback); + } + catch (Throwable t) + { + logger.error(String.format("Exception loading %s for %s", command.txnId(), callback), t); + throw t; + } + }); + } + + @VisibleForTesting + Function<AccordCommandsForKey, Future<?>> loadCommandsPerKeyFunction(Object callback) + { + return cfk -> Stage.READ.submit(() -> { + try + { + logger.trace("Starting load of {} for {}", cfk.key(), callback); + AccordKeyspace.loadCommandsForKey(cfk); + logger.trace("Completed load of {} for {}", cfk.key(), callback); + } + catch (Throwable t) + { + logger.error(String.format("Exception loading %s for %s", cfk.key(), callback), t); + throw t; + } + }); + } + + private Future<?> referenceAndDispatchReads(AsyncContext context, Object callback) + { + List<Future<?>> futures = null; + + futures = referenceAndDispatchReads(txnIds, + commandStore.commandCache(), + context.commands.items, + loadCommandFunction(callback), + futures, + callback); + + futures = referenceAndDispatchReads(keys, + commandStore.commandsForKeyCache(), + context.commandsForKey.items, + loadCommandsPerKeyFunction(callback), + futures, + callback); + + return futures != null ? FutureCombiner.allOf(futures) : null; + } + + public boolean load(AsyncContext context, BiConsumer<Object, Throwable> callback) + { + logger.trace("Running load for {} with state {}: {} {}", callback, state, txnIds, keys); + commandStore.checkInStoreThread(); + switch (state) + { + case INITIALIZED: + state = State.SETUP; + case SETUP: + // notify any pending write only groups we're loading a full instance so the pending changes aren't removed + txnIds.forEach(commandStore.commandCache()::lockWriteOnlyGroupIfExists); + keys.forEach(commandStore.commandsForKeyCache()::lockWriteOnlyGroupIfExists); Review Comment: oops, I am mid rebase (and it isn't a fun one). oh well, too late. -- 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. 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