nfsv4: caching implementation of NfsIdMapping

A decorator to cache reuslts from an other NfsIdMapping
implemetation.
Acked-by: Karsten Schwank <karsten.schwank@desy.de>

pom.xml

@@ -250,7 +250,7 @@
         <dependency>
             <groupId>com.google.guava</groupId>
             <artifactId>guava</artifactId>
-            <version>r07</version>
+            <version>r09</version>
         </dependency>
         <dependency>
             <groupId>org.liquibase</groupId>

src/org/dcache/chimera/nfs/v4/CachingIdmap.java

+/*
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this program (see the file COPYING.LIB for more
+ * details); if not, write to the Free Software Foundation, Inc.,
+ * 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+package org.dcache.chimera.nfs.v4;
+
+import com.google.common.base.Function;
+import com.google.common.collect.MapMaker;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * {@link NfsIdMapping} implementation which caches results from defined source.
+ *
+ * @since 0.0.4
+ */
+public class CachingIdmap implements NfsIdMapping {
+
+    /**
+     * Inner {@link NfsIdMapping} used as source by this CachingIdmap.
+     */
+    private final NfsIdMapping _inner;
+
+    /*
+     * forward mapping cache
+     */
+    private final ConcurrentMap<String, Integer> _uidByNameCache;
+    private final ConcurrentMap<String, Integer> _gidByNameCache;
+    /*
+     * reverse mapping cache
+     */
+    private final ConcurrentMap<Integer, String> _userNameByIdCache;
+    private final ConcurrentMap<Integer, String> _groupNameByIdCache;
+
+    /**
+     * Construct caching {@link NfsIdMapping}.
+     *
+     * @param idmapd used as source.
+     * @param size maximal number to cache.
+     * @param timeout in seconds to cache successful results.
+     */
+    public CachingIdmap(NfsIdMapping idmapd, int size, long timeout) {
+        _inner = idmapd;
+
+        _uidByNameCache = new MapMaker().
+                expireAfterWrite(timeout, TimeUnit.SECONDS).
+                softKeys().
+                softValues().
+                maximumSize(size).
+                makeComputingMap( new ForwardUidMapping());
+
+        _gidByNameCache  = new MapMaker().
+                expireAfterWrite(timeout, TimeUnit.SECONDS).
+                softKeys().
+                softValues().
+                maximumSize(size).
+                makeComputingMap( new ForwardGidMapping());
+
+         _userNameByIdCache = new MapMaker().
+                expireAfterWrite(timeout, TimeUnit.SECONDS).
+                softKeys().
+                softValues().
+                maximumSize(size).
+                makeComputingMap(new ReverseUidMapping());
+
+        _groupNameByIdCache = new MapMaker().
+                expireAfterWrite(timeout, TimeUnit.SECONDS).
+                softKeys().
+                softValues().
+                maximumSize(size).
+                makeComputingMap(new ReverseGidMapping());
+    }
+
+    @Override
+    public String uidToPrincipal(int id) {
+        return _userNameByIdCache.get(id);
+    }
+
+    @Override
+    public String gidToPrincipal(int id) {
+        return _groupNameByIdCache.get(id);
+    }
+
+    @Override
+    public int principalToUid(String principal) {
+        return _uidByNameCache.get(principal);
+    }
+
+    @Override
+    public int principalToGid(String principal) {
+        return _gidByNameCache.get(principal);
+    }
+
+    /*
+     * Forward mapping functions which delegate to inner NfsIdMapping
+     */
+    private class ForwardGidMapping implements Function<String, Integer> {
+
+        @Override
+        public Integer apply(String s) {
+            return _inner.principalToGid(s);
+        }
+    }
+
+    private class ForwardUidMapping implements Function<String, Integer> {
+
+        @Override
+        public Integer apply(String s) {
+            return _inner.principalToUid(s);
+        }
+    }
+
+    /*
+     * Reverse mapping functions which delegate to inner NfsIdMapping
+     */
+    private class ReverseUidMapping implements Function<Integer, String> {
+
+        @Override
+        public String apply(Integer id) {
+            return _inner.uidToPrincipal(id);
+        }
+    }
+
+    private class ReverseGidMapping implements Function<Integer, String> {
+
+        @Override
+        public String apply(Integer id) {
+            return _inner.gidToPrincipal(id);
+        }
+    }
+}