HBASE-674 Memcache size unreliable

git-svn-id: https://svn.apache.org/repos/asf/hadoop/hbase/trunk@674108 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -167,6 +167,7 @@ Trunk (unreleased changes)
    HBASE-719   Find out why users have network problems in HBase and not in Hadoop
                and HConnectionManager (Jean-Daniel Cryans via Stack)
    HBASE-703   Invalid regions listed by regionserver.jsp (Izaak Rubin via Stack)
+   HBASE-674   Memcache size unreliable
    
   IMPROVEMENTS
    HBASE-559   MR example job to count table rows

src/java/org/apache/hadoop/hbase/regionserver/HRegion.java

@@ -1002,6 +1002,9 @@ public class HRegion implements HConstants {
     // to do this for a moment.  Its quick.  The subsequent sequence id that
     // goes into the HLog after we've flushed all these snapshots also goes
     // into the info file that sits beside the flushed files.
+    // We also set the memcache size to zero here before we allow updates
+    // again so its value will represent the size of the updates received
+    // during the flush
     long sequenceId = -1L;
     this.updatesLock.writeLock().lock();
     try {
@@ -1009,6 +1012,7 @@ public class HRegion implements HConstants {
         s.snapshot();
       }
       sequenceId = log.startCacheFlush();
+      this.memcacheSize.set(0);
     } finally {
       this.updatesLock.writeLock().unlock();
     }
@@ -1017,20 +1021,13 @@ public class HRegion implements HConstants {
     // restart so hlog content can be replayed and put back into the memcache.
     // Otherwise, the snapshot content while backed up in the hlog, it will not
     // be part of the current running servers state.
+    long flushed = 0;
     try {
       // A.  Flush memcache to all the HStores.
       // Keep running vector of all store files that includes both old and the
       // just-made new flush store file.
       for (HStore hstore: stores.values()) {
-        long flushed = hstore.flushCache(sequenceId);
-        // Subtract amount flushed.
-        long size = this.memcacheSize.addAndGet(-flushed);
-        if (size < 0) {
-           if (LOG.isDebugEnabled()) {
-             LOG.warn("Memcache size went negative " + size + "; resetting");
-           }
-           this.memcacheSize.set(0);
-        }
+        flushed += hstore.flushCache(sequenceId);
       }
     } catch (Throwable t) {
       // An exception here means that the snapshot was not persisted.
@@ -1068,7 +1065,7 @@ public class HRegion implements HConstants {
         " in " +
           (System.currentTimeMillis() - startTime) + "ms, sequence id=" +
           sequenceId + ", " +
-          StringUtils.humanReadableInt(this.memcacheSize.get()));
+          StringUtils.humanReadableInt(flushed));
       if (!regionInfo.isMetaRegion()) {
         this.historian.addRegionFlush(regionInfo, timeTaken);
       }
@@ -1538,9 +1535,8 @@ public class HRegion implements HConstants {
       long size = 0;
       for (Map.Entry<HStoreKey, byte[]> e: updatesByColumn.entrySet()) {
         HStoreKey key = e.getKey();
-        byte[] val = e.getValue();
-        size = this.memcacheSize.addAndGet(getEntrySize(key, val));
-        getStore(key.getColumn()).add(key, val);
+        size = this.memcacheSize.addAndGet(
+            getStore(key.getColumn()).add(key, e.getValue()));
       }
       flush = this.flushListener != null && !this.flushRequested &&
         size > this.memcacheFlushSize;
@@ -1578,19 +1574,6 @@ public class HRegion implements HConstants {
     return this.stores.get(HStoreKey.getFamilyMapKey(column)); 
   }
   
-  /*
-   * Calculate size of passed key/value pair.
-   * Used here when we update region to figure what to add to this.memcacheSize
-   * Also used in Store when flushing calculating size of flush.  Both need to
-   * use same method making size calculation.
-   * @param key
-   * @param value
-   * @return Size of the passed key + value
-   */
-  static long getEntrySize(final HStoreKey key, byte [] value) {
-    return key.getSize() + (value == null ? 0 : value.length);
-  }
-
   //////////////////////////////////////////////////////////////////////////////
   // Support code
   //////////////////////////////////////////////////////////////////////////////

src/java/org/apache/hadoop/hbase/regionserver/HStore.java

@@ -620,11 +620,12 @@ public class HStore implements HConstants {
    * 
    * @param key
    * @param value
+   * @return memcache size delta
    */
-  protected void add(HStoreKey key, byte[] value) {
+  protected long add(HStoreKey key, byte[] value) {
     lock.readLock().lock();
     try {
-      this.memcache.add(key, value);
+      return this.memcache.add(key, value);
     } finally {
       lock.readLock().unlock();
     }
@@ -726,7 +727,7 @@ public class HStore implements HConstants {
                   now < curkey.getTimestamp() + ttl) {
               entries++;
               out.append(curkey, new ImmutableBytesWritable(bytes));
-              flushed += HRegion.getEntrySize(curkey, bytes);
+              flushed += curkey.getSize() + (bytes == null ? 0 : bytes.length);
             } else {
               if (LOG.isDebugEnabled()) {
                 LOG.debug("internalFlushCache: " + curkey +

src/java/org/apache/hadoop/hbase/regionserver/Memcache.java

@@ -158,11 +158,15 @@ class Memcache {
    * Write an update
    * @param key
    * @param value
+   * @return memcache size delta
    */
-  void add(final HStoreKey key, final byte[] value) {
+  long add(final HStoreKey key, final byte[] value) {
     this.lock.readLock().lock();
     try {
+      byte[] oldValue = this.memcache.remove(key);
       this.memcache.put(key, value);
+      return key.getSize() + (value == null ? 0 : value.length) -
+          (oldValue == null ? 0 : oldValue.length);
     } finally {
       this.lock.readLock().unlock();
     }