HBASE-17057 Minor compactions should also drop page cache (Ashu Pachauri)

Signed-off-by: Gary Helmling <garyh@apache.org>

hbase-common/src/main/resources/hbase-default.xml

@@ -802,6 +802,24 @@ possible configurations would overwhelm and obscure the important.
       The value field assumes that the value of hbase.hregion.memstore.flush.size is unchanged from
       the default.</description>
   </property>
+  <property>
+    <name>hbase.regionserver.majorcompaction.pagecache.drop</name>
+    <value>true</value>
+    <description>Specifies whether to drop pages read/written into the system page cache by
+      major compactions. Setting it to true helps prevent major compactions from
+      polluting the page cache, which is almost always required, especially for clusters
+      with low/moderate memory to storage ratio.</description>
+  </property>
+  <property>
+    <name>hbase.regionserver.minorcompaction.pagecache.drop</name>
+    <value>true</value>
+    <description>Specifies whether to drop pages read/written into the system page cache by
+      minor compactions. Setting it to true helps prevent minor compactions from
+      polluting the page cache, which is most beneficial on clusters with low
+      memory to storage ratio or very write heavy clusters. You may want to set it to
+      false under moderate to low write workload when bulk of the reads are
+      on the most recently written data.</description>
+  </property>
   <property>
     <name>hbase.hstore.compaction.kv.max</name>
     <value>10</value>

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/compactions/Compactor.java

@@ -79,6 +79,15 @@ public abstract class Compactor<T extends CellSink> {
   /** specify how many days to keep MVCC values during major compaction **/ 
   protected int keepSeqIdPeriod;
 
+  // Configs that drive whether we drop page cache behind compactions
+  protected static final String  MAJOR_COMPACTION_DROP_CACHE =
+      "hbase.regionserver.majorcompaction.pagecache.drop";
+  protected static final String MINOR_COMPACTION_DROP_CACHE =
+      "hbase.regionserver.minorcompaction.pagecache.drop";
+
+  private boolean dropCacheMajor;
+  private boolean dropCacheMinor;
+
   //TODO: depending on Store is not good but, realistically, all compactors currently do.
   Compactor(final Configuration conf, final Store store) {
     this.conf = conf;
@@ -89,8 +98,12 @@ public abstract class Compactor<T extends CellSink> {
         Compression.Algorithm.NONE : this.store.getFamily().getCompactionCompressionType();
     this.keepSeqIdPeriod = Math.max(this.conf.getInt(HConstants.KEEP_SEQID_PERIOD, 
       HConstants.MIN_KEEP_SEQID_PERIOD), HConstants.MIN_KEEP_SEQID_PERIOD);
+    this.dropCacheMajor = conf.getBoolean(MAJOR_COMPACTION_DROP_CACHE, true);
+    this.dropCacheMinor = conf.getBoolean(MINOR_COMPACTION_DROP_CACHE, true);
   }
 
+
+
   protected interface CellSinkFactory<S> {
     S createWriter(InternalScanner scanner, FileDetails fd, boolean shouldDropBehind)
         throws IOException;
@@ -271,6 +284,13 @@ public abstract class Compactor<T extends CellSink> {
     List<StoreFileScanner> scanners;
     Collection<StoreFile> readersToClose;
     T writer = null;
+    boolean dropCache;
+    if (request.isMajor() || request.isAllFiles()) {
+      dropCache = this.dropCacheMajor;
+    } else {
+      dropCache = this.dropCacheMinor;
+    }
+
     if (this.conf.getBoolean("hbase.regionserver.compaction.private.readers", true)) {
       // clone all StoreFiles, so we'll do the compaction on a independent copy of StoreFiles,
       // HFiles, and their readers
@@ -282,12 +302,10 @@ public abstract class Compactor<T extends CellSink> {
         clonedStoreFile.createReader();
         readersToClose.add(clonedStoreFile);
       }
-      scanners = createFileScanners(readersToClose, smallestReadPoint,
+      scanners = createFileScanners(readersToClose, smallestReadPoint, dropCache);
-        store.throttleCompaction(request.getSize()));
     } else {
       readersToClose = Collections.emptyList();
-      scanners = createFileScanners(request.getFiles(), smallestReadPoint,
+      scanners = createFileScanners(request.getFiles(), smallestReadPoint, dropCache);
-        store.throttleCompaction(request.getSize()));
     }
     InternalScanner scanner = null;
     boolean finished = false;
@@ -309,7 +327,7 @@ public abstract class Compactor<T extends CellSink> {
         smallestReadPoint = Math.min(fd.minSeqIdToKeep, smallestReadPoint);
         cleanSeqId = true;
       }
-      writer = sinkFactory.createWriter(scanner, fd, store.throttleCompaction(request.getSize()));
+      writer = sinkFactory.createWriter(scanner, fd, dropCache);
       finished = performCompaction(fd, scanner, writer, smallestReadPoint, cleanSeqId,
         throughputController, request.isAllFiles(), request.getFiles().size());
       if (!finished) {