Update javadoc and code for evictor

Alluxio · Jun 27, 2015 · b542a18 · b542a18
1 parent ad792e5
commit b542a18
Show file tree

Hide file tree

Showing 2 changed files with 22 additions and 14 deletions.
diff --git a/servers/src/main/java/tachyon/worker/block/evictor/Evictor.java b/servers/src/main/java/tachyon/worker/block/evictor/Evictor.java
@@ -24,13 +24,15 @@
  */
 public interface Evictor {
   /**
-   * Frees space in the given block store location. The location can be a specific location, or
-   * {@link BlockStoreLocation#anyTier()} or {@link BlockStoreLocation#anyDirInTier(int)}. Return
-   * absent if Evictor can not propose such a feasible plan to meet the requirement.
+   * Frees space in the given block store location to ensure a specific amount of free space
+   * available. The location can be a specific location, or {@link BlockStoreLocation#anyTier()} or
+   * {@link BlockStoreLocation#anyDirInTier(int)}. This operation returns absent if Evictor fails to
+   * propose a feasible plan to meet its requirement, or an eviction plan (possibly an empty one) to
+   * ensure the free space.
    *
-   * @param bytes the size in bytes
+   * @param availableBytes the size in bytes
    * @param location the location in block store
-   * @return an eviction plan to achieve the freed space, or absent if no feasible plan
+   * @return an eviction plan (possibly empty) to get the free space, or absent if no feasible plan
    */
-  Optional<EvictionPlan> freeSpace(long bytes, BlockStoreLocation location);
+  Optional<EvictionPlan> freeSpace(long availableBytes, BlockStoreLocation location);
 }
diff --git a/servers/src/main/java/tachyon/worker/block/evictor/NaiveEvictor.java b/servers/src/main/java/tachyon/worker/block/evictor/NaiveEvictor.java
@@ -40,18 +40,24 @@ public NaiveEvictor(BlockMetadataManager metadata) {
   }
 
   @Override
-  public Optional<EvictionPlan> freeSpace(long bytes, BlockStoreLocation location) {
+  public Optional<EvictionPlan> freeSpace(long availableBytes, BlockStoreLocation location) {
     List<Pair<Long, BlockStoreLocation>> toMove = new ArrayList<Pair<Long, BlockStoreLocation>>();
     List<Long> toEvict = new ArrayList<Long>();
 
-    long spaceFreed = 0;
+    long freed = 0;
+    long available = mMetaManager.getAvailableBytes(location);
+    if (available >= availableBytes) {
+      // The current space is sufficient, no need for eviction
+      return Optional.of(new EvictionPlan(toMove, toEvict));
+    }
+
     if (location.equals(BlockStoreLocation.anyTier())) {
       for (StorageTier tier : mMetaManager.getTiers()) {
         for (StorageDir dir : tier.getStorageDirs()) {
           for (BlockMeta block : dir.getBlocks()) {
             toEvict.add(block.getBlockId());
-            spaceFreed += block.getBlockSize();
-            if (spaceFreed >= bytes) {
+            freed += block.getBlockSize();
+            if (available + freed >= availableBytes) {
               return Optional.of(new EvictionPlan(toMove, toEvict));
             }
           }
@@ -67,8 +73,8 @@ public Optional<EvictionPlan> freeSpace(long bytes, BlockStoreLocation location)
       for (StorageDir dir : tier.getStorageDirs()) {
         for (BlockMeta block : dir.getBlocks()) {
           toEvict.add(block.getBlockId());
-          spaceFreed += block.getBlockSize();
-          if (spaceFreed >= bytes) {
+          freed += block.getBlockSize();
+          if (available + freed >= availableBytes) {
             return Optional.of(new EvictionPlan(toMove, toEvict));
           }
         }
@@ -80,8 +86,8 @@ public Optional<EvictionPlan> freeSpace(long bytes, BlockStoreLocation location)
     StorageDir dir = tier.getDir(dirIndex);
     for (BlockMeta block : dir.getBlocks()) {
       toEvict.add(block.getBlockId());
-      spaceFreed += block.getBlockSize();
-      if (spaceFreed >= bytes) {
+      freed += block.getBlockSize();
+      if (available + freed >= availableBytes) {
         return Optional.of(new EvictionPlan(toMove, toEvict));
       }
     }