Github user denalex commented on a diff in the pull request:
https://github.com/apache/incubator-hawq/pull/1379#discussion_r202131246
--- 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);
+
+ if (timedProxyUGI == null) return;
+
+ timedProxyUGI.resetTime();
+ timedProxyUGI.releaseReference();
+ if (cleanImmediatelyIfNoRefs) {
+ synchronized (getExpirationQueue(session.getSegmentId())) {
+ timedProxyUGI.setExpired();
+ closeUGI(session, timedProxyUGI);
+ }
+ }
+ }
+
+ /**
+ * Get the queue of cache entries associated with a segment, creating
it if it doesn't
+ * yet exist. This lets us lazily populate the queueMap.
+ *
+ * @param segmentId
+ * @return the {@link DelayQueue} associated to the segment.
+ */
+ private DelayQueue<Entry> getExpirationQueue(Integer segmentId) {
+ DelayQueue<Entry> queue = queueMap.get(segmentId);
+ if (queue == null) {
+ synchronized (queueMap) {
+ queue = queueMap.get(segmentId);
+ if (queue == null) {
+ queue = new DelayQueue<>();
+ queueMap.put(segmentId, queue);
+ }
+ }
+ }
+ return queue;
+ }
+
+ /**
+ * Iterate through all the entries in the queue for the given
session's segment
+ * and close expired {@link UserGroupInformation}, otherwise it resets
+ * the timer for every non-expired entry.
+ *
+ * @param session
+ */
+ private void cleanup(SessionId session) {
+
+ Entry ugi;
+ DelayQueue<Entry> delayQueue =
getExpirationQueue(session.getSegmentId());
+ while ((ugi = delayQueue.poll()) != null) {
+ // Place it back in the queue if still in use and was not
closed
+ if (!closeUGI(session, ugi)) {
+ ugi.resetTime();
+ delayQueue.offer(ugi);
+ }
+ LOG.debug("Delay Queue Size for segment " +
+ session.getSegmentId() + " = " + delayQueue.size());
+ }
+ }
+
+ /**
+ * This method must be called from a synchronized block for the
delayQueue for the given
+ * session.getSegmentId(). When the reference count is 0, the Entry is
removed from the
+ * cache where it will then be processed to be destroyed by the
UGIProvider.
+ *
+ * @param session
+ * @param toDelete
+ * @return true if the UGI entry was cleaned, false when the UGI entry
was still in use
+ * and cleaning up was skipped
+ */
+ private boolean closeUGI(SessionId session, Entry toDelete) {
+ // There is no need to synchronize this method because it should
be called
+ // from within a synchronized block
+ String fsMsg = "FileSystem for proxy user = " +
toDelete.getUGI().getUserName();
+ try {
+ // The UGI object is still being used by another thread
+ if (toDelete.isInUse()) {
--- End diff --
name "toDelete" does not carry enough context to read the code easily -- we
don't know what kind of object this is
---
