maedhroz commented on code in PR #1723: URL: https://github.com/apache/cassandra/pull/1723#discussion_r983715632
########## src/java/org/apache/cassandra/db/tries/MemtableTrie.java: ########## @@ -0,0 +1,1039 @@ +/* + * 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.db.tries; + +import java.nio.ByteBuffer; +import java.util.Arrays; +import java.util.Iterator; +import java.util.NoSuchElementException; +import java.util.concurrent.atomic.AtomicReferenceArray; + +import com.google.common.annotations.VisibleForTesting; + +import org.agrona.concurrent.UnsafeBuffer; +import org.apache.cassandra.io.compress.BufferType; +import org.apache.cassandra.io.util.FileUtils; +import org.apache.cassandra.utils.bytecomparable.ByteSource; +import org.apache.cassandra.utils.bytecomparable.ByteComparable; +import org.apache.cassandra.utils.ObjectSizes; +import org.github.jamm.MemoryLayoutSpecification; + +/** + * Memtable trie, i.e. an in-memory trie built for fast modification and reads executing concurrently with writes from + * a single mutator thread. + * + * Writes to this should be atomic (i.e. reads should see either the content before the write, or the content after the + * write; if any read sees the write, then any subsequent (i.e. started after it completed) read should also see it). + * This implementation does not currently guarantee this, but we still get the desired result as `apply` is only used + * with singleton tries. + */ +public class MemtableTrie<T> extends MemtableReadTrie<T> +{ + // See the trie format description in MemtableReadTrie. + + /** + * Trie size limit. This is not enforced, but users must check from time to time that it is not exceeded (using + * reachedAllocatedSizeThreshold()) and start switching to a new trie if it is. + * This must be done to avoid tries growing beyond their hard 2GB size limit (due to the 32-bit pointers). + */ + private static final int ALLOCATED_SIZE_THRESHOLD; + static + { + String propertyName = "dse.trie_size_limit_mb"; + // Default threshold + 10% == 1 GB. Adjusted slightly up to avoid a tiny final allocation for the 2G max. + int limitInMB = Integer.parseInt(System.getProperty(propertyName, + Integer.toString(1024 * 10 / 11 + 1))); + if (limitInMB < 1 || limitInMB > 2047) + throw new AssertionError(propertyName + " must be within 1 and 2047"); Review Comment: nit: Untested codepath. In this case, perhaps a little static method that provides the value for `ALLOCATED_SIZE_THRESHOLD` would make testing easier. -- 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]
