While investigating problems, add much paranoid profiling. Also let's do an explicit keyset copy during enumeration rather than the fancy concurrent hashmaps and iterable mappings. Finally, let's fully synchronize the other maps we're using.

src/java/com/samskivert/depot/EHCacheAdapter.java

@@ -25,9 +25,6 @@ import java.util.Collections;
 import java.util.Map;
 import java.util.Set;
 
-import com.google.common.base.Function;
-import com.google.common.base.Predicates;
-import com.google.common.collect.Iterables;
 import com.google.common.collect.Maps;
 import com.google.common.collect.Sets;
 import com.samskivert.util.Tuple;
@@ -44,7 +41,7 @@ import static com.samskivert.depot.Log.log;
  * in one {@link Ehcache}. All (cacheId, key) combinations within one category is stuffed into the
  * same {@link Ehcache}, and all elements are cached under {@link EHCacheKey}, which basically
  * wraps just such a tuple.
- * 
+ *
  * Thus there are currently only three Ehcaches in play, called 'depotRecord', 'depotKeyset', and
  * 'depotResult'. These must be defined in your ehcache.xml configuration. If you use distributed
  * replication/invalidation, you should replicate updates and removes but not puts nor
@@ -72,17 +69,25 @@ public class EHCacheAdapter
     // from CacheAdapter
     public <T> CachedValue<T> lookup (String cacheId, Serializable key)
     {
+        long now = System.currentTimeMillis();
         @SuppressWarnings("unchecked")
         EHCacheBin<T> bin = (EHCacheBin<T>) _bins.get(cacheId);
         if (bin == null) {
             return null;
         }
-        return lookup(bin.getCache(), cacheId, key);
+        CachedValue<T> result = lookup(bin.getCache(), cacheId, key);
+        long dT = System.currentTimeMillis() - now;
+        if (dT > 50) {
+            log.warning("Aii! A simple ehcache lookup took over 50 ms!", "cacheId", cacheId,
+                "key", key, "dT", dT);
+        }
+        return result;
     }
 
     // from CacheAdapter
     public <T> void store (CacheCategory category, String cacheId, Serializable key, T value)
     {
+        long now = System.currentTimeMillis();
         Ehcache cache = _categories.get(category);
         if (cache == null) {
             throw new IllegalArgumentException("Unknown category: " + category);
@@ -94,35 +99,57 @@ public class EHCacheAdapter
             _bins.put(cacheId, bin);
         }
         bin.getCache().put(new Element(new EHCacheKey(cacheId, key), value != null ? value : NULL));
+        long dT = System.currentTimeMillis() - now;
+        if (dT > 50) {
+            log.warning("Aii! A simple ehcache store took over 50 ms!", "cacheId", cacheId,
+                "key", key, "dT", dT);
+        }
     }
 
     // from CacheAdapter
     public void remove (String cacheId, Serializable key)
     {
+        long now = System.currentTimeMillis();
         EHCacheBin<?> bin = _bins.get(cacheId);
         if (bin != null) {
             bin.getCache().remove(new EHCacheKey(cacheId, key));
         }
+        long dT = System.currentTimeMillis() - now;
+        if (dT > 50) {
+            log.warning("Aii! A simple ehcache remove took over 50 ms!", "cacheId", cacheId,
+                "key", key, "dT", dT);
+        }
     }
 
     // from CacheAdapter
     public <T> Iterable<Tuple<Serializable, CachedValue<T>>> enumerate (final String cacheId)
     {
+        if (_slowEnumerations > 5) {
+            return Collections.emptySet();
+        }
+        long now = System.currentTimeMillis();
+
         EHCacheBin<?> bin = _bins.get(cacheId);
         if (bin == null) {
             return Collections.emptySet();
         }
 
-        final Ehcache cache = bin.getCache();
-        Iterable<Tuple<Serializable, CachedValue<T>>> tuples = Iterables.transform(
-            bin.getKeys(), new Function<Serializable, Tuple<Serializable, CachedValue<T>>> () {
-                public Tuple<Serializable, CachedValue<T>> apply (Serializable key) {
-                    CachedValue<T> value = lookup(cache, cacheId, key);
-                    return (value != null) ? Tuple.newTuple(key, value) : null;
-                }
-            });
-        
-        return Iterables.filter(tuples, Predicates.notNull());
+        Set<Tuple<Serializable, CachedValue<T>>> result = Sets.newHashSet();
+        Ehcache cache = bin.getCache();
+
+        for (Serializable key : bin.getKeys()) {
+            CachedValue<T> value = lookup(cache, cacheId, key);
+            if (value != null) {
+                result.add(Tuple.newTuple(key, value));
+            }
+        }
+        long dT = System.currentTimeMillis() - now;
+        if (dT > 50) {
+            _slowEnumerations ++;
+            log.warning("Aii! Enumerating cache took a long time!", "cacheId", cacheId, "dT", dT,
+                "cacheSize", result.size(), "disabled", _slowEnumerations > 5);
+        }
+        return result;
     }
 
     // from CacheAdapter
@@ -163,8 +190,13 @@ public class EHCacheAdapter
         return cache;
     }
 
-    protected Map<CacheCategory, Ehcache> _categories = Maps.newConcurrentHashMap();
-    protected Map<String, EHCacheBin<?>> _bins = Maps.newConcurrentHashMap();
+    // TODO: To be removed when we're done investigating potential sluggishness
+    protected int _slowEnumerations = 0;
+
+    protected Map<CacheCategory, Ehcache> _categories =
+        Collections.synchronizedMap(Maps.<CacheCategory, Ehcache>newHashMap());
+    protected Map<String, EHCacheBin<?>> _bins =
+        Collections.synchronizedMap(Maps.<String, EHCacheBin<?>> newHashMap());
 
     protected CacheEventListener _cacheEventListener = new CacheEventListener() {
         public Object clone () throws CloneNotSupportedException {
@@ -214,7 +246,7 @@ public class EHCacheAdapter
             bin.addKey(key.getCacheKey());
         }
     };
-    
+
     protected static class EHCacheBin<T>
     {
         public EHCacheBin (Ehcache cache, String id)
@@ -242,7 +274,7 @@ public class EHCacheAdapter
         {
             return _cache;
         }
-        
+
         protected Ehcache _cache;
         protected String _id;
 
@@ -268,18 +300,18 @@ public class EHCacheAdapter
         public String getCacheId () {
             return _id;
         }
-        
+
         public Serializable getCacheKey ()
         {
             return _key;
         }
-        
+
         @Override
         public String toString ()
         {
             return "[" + _id + ", " + _key + "]";
         }
-        
+
         @Override
         public int hashCode ()
         {