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From kkhatua <...@git.apache.org>
Subject [GitHub] drill pull request #827: DRILL-5481: Persist profiles in-memory only with a ...
Date Tue, 09 May 2017 17:13:17 GMT
Github user kkhatua commented on a diff in the pull request:

    https://github.com/apache/drill/pull/827#discussion_r115546712
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/sys/store/EphemeralPersistentStore.java
---
    @@ -15,28 +15,42 @@
      * See the License for the specific language governing permissions and
      * limitations under the License.
      */
    -package org.apache.drill.exec.testing.store;
    +package org.apache.drill.exec.store.sys.store;
     
     import java.util.Iterator;
     import java.util.Map;
     import java.util.concurrent.ConcurrentMap;
    +import java.util.concurrent.ConcurrentSkipListMap;
    +import java.util.concurrent.atomic.AtomicInteger;
     import java.util.concurrent.locks.ReadWriteLock;
     import java.util.concurrent.locks.ReentrantReadWriteLock;
     
    -import com.google.common.collect.Iterables;
    -import com.google.common.collect.Maps;
     import org.apache.drill.common.concurrent.AutoCloseableLock;
    +import org.apache.drill.exec.exception.StoreException;
     import org.apache.drill.exec.exception.VersionMismatchException;
     import org.apache.drill.exec.store.sys.BasePersistentStore;
    +import org.apache.drill.exec.store.sys.PersistentStoreConfig;
     import org.apache.drill.exec.store.sys.PersistentStoreMode;
    -import org.apache.drill.exec.store.sys.store.DataChangeVersion;
     
    -public class NoWriteLocalStore<V> extends BasePersistentStore<V> {
    +import com.google.common.collect.Iterables;
    +
    +public class EphemeralPersistentStore<V> extends BasePersistentStore<V> {
    +  private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(EphemeralPersistentStore.class);
    +
       private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
       private final AutoCloseableLock readLock = new AutoCloseableLock(readWriteLock.readLock());
       private final AutoCloseableLock writeLock = new AutoCloseableLock(readWriteLock.writeLock());
    -  private final ConcurrentMap<String, V> store = Maps.newConcurrentMap();
    +  private ConcurrentMap<String, V> store;
       private int version = -1;
    +  private int maxCapacity;
    +  private AtomicInteger currentSize = new AtomicInteger();
    --- End diff --
    
    There is already a writelock. However, with a SkipList, the call of using size() is expensive.
To minimize this computation, we have an atomic counter.  With the writeLock, if I hit the
max "virtual" capacity, I am simply inserting the latest entry and popping out the last (oldest
entry). Unlike Concurrent Queues, ConcurrentSkipListMap allows natural ordering of the keys
(which is required for serving via the WebUI).  


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