magibney commented on code in PR #13555: URL: https://github.com/apache/lucene/pull/13555#discussion_r1674096237
########## lucene/core/src/java21/org/apache/lucene/store/GroupedArena.java: ########## @@ -0,0 +1,212 @@ +/* + * 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.lucene.store; + +import java.lang.foreign.AddressLayout; +import java.lang.foreign.Arena; +import java.lang.foreign.MemoryLayout; +import java.lang.foreign.MemorySegment; +import java.lang.foreign.ValueLayout; +import java.nio.file.Path; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.atomic.AtomicInteger; +import org.apache.lucene.index.IndexFileNames; + +@SuppressWarnings("preview") +final class GroupedArena implements Arena { + + private final String scopeId; + + private final ConcurrentHashMap<String, GroupedArena> arenas; + + private final Arena backing; + + private final AtomicInteger refCt; + + static Arena get(Path p, ConcurrentHashMap<String, GroupedArena> arenas) { + String filename = p.getFileName().toString(); + String segmentName = IndexFileNames.parseSegmentName(filename); + if (filename.length() == segmentName.length()) { + // no segment found; return a 1-off Arena + return Arena.ofShared(); + } + String scopeId = p.getParent().resolve(segmentName).toString(); + Arena ret; + do { + boolean[] computed = new boolean[1]; + final GroupedArena template = + arenas.computeIfAbsent( + scopeId, + (s) -> { + computed[0] = true; + return new GroupedArena(s, arenas); + }); + if (computed[0]) { + return template; + } + ret = template.cloneIfActive(); + } while (ret == null); // TODO: will this ever actually loop? + return ret; + } + + GroupedArena(String scopeId, ConcurrentHashMap<String, GroupedArena> arenas) { + this.scopeId = scopeId; + this.arenas = arenas; + this.backing = Arena.ofShared(); + this.refCt = new AtomicInteger(1); + } + + private GroupedArena(GroupedArena template) { + this.scopeId = template.scopeId; + this.arenas = template.arenas; + this.backing = template.backing; + this.refCt = template.refCt; + } + + private GroupedArena cloneIfActive() { + if (refCt.getAndIncrement() > 0) { + // the usual (always?) case + return new GroupedArena(this); + } else { + // TODO: this should never happen? + return null; + } + } + + @Override + public void close() { + int ct = refCt.decrementAndGet(); + if (ct == 0) { + arenas.remove(scopeId); + if (refCt.get() == 0) { + // TODO: this should always be the case? But if it's not, it should be a benign + // race condition. Whatever caller incremented `refCt` will close it, and if + // anyone tries to open a new arena with the same `scopeId` that we removed + // above, they'll simply create a new Arena, and we're no worse off than we + // would have been if every Arena was created as a one-off. + backing.close(); + } + } else { + assert ct > 0 : "refCt should never be negative; found " + ct; + } + } + + @Override Review Comment: Ah right; I hadn't bothered looking at how Arena is actually used. Should we not throw UOE for _all_ of them? All of these have default implementations, so we end up only having to override `scope()` and `close()`, which are the only required to implement (and also the only ones we actually call). -- 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: issues-unsubscr...@lucene.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For additional commands, e-mail: issues-h...@lucene.apache.org
