Github user denalex commented on a diff in the pull request: https://github.com/apache/incubator-hawq/pull/1379#discussion_r202129998 --- Diff: pxf/pxf-service/src/main/java/org/apache/hawq/pxf/service/UGICache.java --- @@ -0,0 +1,318 @@ +package org.apache.hawq.pxf.service; + +/* + * 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. + */ + +import java.io.IOException; +import java.util.HashMap; +import java.util.Map; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.DelayQueue; +import java.util.concurrent.Delayed; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; + +import com.google.common.base.Ticker; +import org.apache.commons.logging.Log; +import org.apache.commons.logging.LogFactory; +import org.apache.hadoop.security.UserGroupInformation; + +/** + * Stores UserGroupInformation instances for each active session. The UGIs are cleaned up if they + * have not been accessed for 15 minutes. + * <p> + * The motivation for caching is that destroying UGIs is slow. The alternative, creating and + * destroying a UGI per-request, is wasteful. + */ +public class UGICache { + + private static final Log LOG = LogFactory.getLog(UGICache.class); + private Map<SessionId, Entry> cache = new ConcurrentHashMap<>(); + @SuppressWarnings("unchecked") + // There is a separate DelayQueue for each segment (also being used for locking) + private final Map<Integer, DelayQueue<Entry>> queueMap = new HashMap<>(); + private final UGIProvider ugiProvider; + private Ticker ticker; + private final static long UGI_CACHE_EXPIRY = 15 * 60 * 1000L; // 15 Minutes + + /** + * Create a UGICache with the given {@link UGIProvider}. Intended for use by tests which need + * to substitute a mock UGIProvider. + */ + UGICache(UGIProvider provider, Ticker ticker) { + this.ticker = ticker; + this.ugiProvider = provider; + } + + /** + * Create a UGICache. Automatically creates a {@link UGIProvider} that this cache will use to + * create and destroy UserGroupInformation instances. + */ + public UGICache() { + this(new UGIProvider(), Ticker.systemTicker()); + } + + /** + * Create new proxy UGI if not found in cache and increment reference count + */ + public UserGroupInformation getUserGroupInformation(SessionId session) throws IOException { + Integer segmentId = session.getSegmentId(); + String user = session.getUser(); + DelayQueue<Entry> delayQueue = getExpirationQueue(segmentId); + synchronized (delayQueue) { + // Use the opportunity to cleanup any expired entries + cleanup(session); + Entry entry = cache.get(session); + if (entry == null) { + LOG.info(session.toString() + " Creating proxy user = " + user); + entry = new Entry(ticker, ugiProvider.createProxyUGI(user)); + delayQueue.offer(entry); + cache.put(session, entry); + } + entry.acquireReference(); + return entry.getUGI(); + } + } + + /** + * Decrement reference count for the given session's UGI. Resets the time at which the UGI will + * expire to 15 minutes in the future. + * + * @param session the session for which we want to release the UGI. + * @param cleanImmediatelyIfNoRefs if true, destroys the UGI for the given session (only if it is + * now unreferenced). + */ + public void release(SessionId session, boolean cleanImmediatelyIfNoRefs) { + + Entry timedProxyUGI = cache.get(session); --- End diff -- rename variable to cacheEntry ?
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