omkreddy commented on code in PR #16263: URL: https://github.com/apache/kafka/pull/16263#discussion_r1636245524
########## server/src/main/java/org/apache/kafka/server/share/ShareSessionCache.java: ########## @@ -0,0 +1,174 @@ +/* + * 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.kafka.server.share; + +import java.util.HashMap; +import java.util.Map; +import java.util.TreeMap; +import org.apache.kafka.common.Uuid; +import org.apache.kafka.common.requests.ShareFetchMetadata; +import org.apache.kafka.common.utils.ImplicitLinkedHashCollection; + +/** + * Caches share sessions. + * <p> + * See tryEvict for an explanation of the cache eviction strategy. + * <p> + * The ShareSessionCache is thread-safe because all of its methods are synchronized. + * Note that individual share sessions have their own locks which are separate from the + * ShareSessionCache lock. In order to avoid deadlock, the ShareSessionCache lock + * must never be acquired while an individual ShareSession lock is already held. + */ +public class ShareSessionCache { + private final int maxEntries; + private final long evictionMs; + private long numPartitions = 0; + + // A map of session key to ShareSession. + private Map<ShareSessionKey, ShareSession> sessions = new HashMap<>(); + + // Maps last used times to sessions. + + private TreeMap<LastUsedKey, ShareSession> lastUsed = new TreeMap<>(); + + // Visible for testing + public TreeMap<LastUsedKey, ShareSession> lastUsed() { + return lastUsed; + } + + public ShareSessionCache(int maxEntries, long evictionMs) { + this.maxEntries = maxEntries; + this.evictionMs = evictionMs; + } + + /** + * Get a session by session key. + * + * @param key The share session key. + * @return The session, or None if no such session was found. + */ + public ShareSession get(ShareSessionKey key) { + synchronized (this) { + return sessions.getOrDefault(key, null); + } + } + + /** + * Get the number of entries currently in the share session cache. + */ + public int size() { + synchronized (this) { + return sessions.size(); + } + } + + public long totalPartitions() { + synchronized (this) { + return numPartitions; + } + } + + public ShareSession remove(ShareSessionKey key) { + synchronized (this) { + ShareSession session = get(key); + if (session != null) + return remove(session); + return null; + } + } + + /** + * Remove an entry from the session cache. + * + * @param session The session. + * @return The removed session, or None if there was no such session. + */ + public ShareSession remove(ShareSession session) { + synchronized (this) { + synchronized (session) { + lastUsed.remove(session.lastUsedKey()); + } + ShareSession removeResult = sessions.remove(session.key()); + if (removeResult != null) { + numPartitions = numPartitions - session.cachedSize(); + } + return removeResult; + } + } + + /** + * Update a session's position in the lastUsed tree. + * + * @param session The session. + * @param now The current time in milliseconds. + */ + public void touch(ShareSession session, long now) { + synchronized (this) { + synchronized (session) { + // Update the lastUsed map. + lastUsed.remove(session.lastUsedKey()); Review Comment: Do we need to remove here? it will replaced at line no:126 -- 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: jira-unsubscr...@kafka.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
