Added system properties to control performance characteristics of MergeSortBuffer.

1 files changed, 61 insertions, 4 deletions

diff --git a/src/main/java/com/amazon/carbonado/cursor/MergeSortBuffer.java b/src/main/java/com/amazon/carbonado/cursor/MergeSortBuffer.java
index 807a0b6..3f645fb 100644
--- a/src/main/java/com/amazon/carbonado/cursor/MergeSortBuffer.java
+++ b/src/main/java/com/amazon/carbonado/cursor/MergeSortBuffer.java
@@ -20,6 +20,7 @@ package com.amazon.carbonado.cursor;
 

 import java.io.BufferedInputStream;

 import java.io.BufferedOutputStream;

+import java.io.File;

 import java.io.InputStream;

 import java.io.OutputStream;

 import java.io.EOFException;

@@ -51,6 +52,28 @@ import com.amazon.carbonado.spi.StorableSerializer;
  * storables to fit in the reserved memory buffer, they are sorted and

  * serialized to temporary files.

  *

+ * <p>The following system properties can be set to change the default

+ * performance characteristics of the merge sort. Each property name must be

+ * prefixed with "com.amazon.carbonado.MergeSortBuffer."

+ *

+ * <pre>

+ * Property            Default    Notes

+ * ------------------- ---------- ----------------------------------------------

+ * maxArrayCapacity    8192       Larger value greatly improves performance, but

+ *                                more memory is used for each running sort.

+ *

+ * maxOpenFileCount    100        Larger value may reduce the amount of file

+ *                                merges, but there is an increased risk of

+ *                                running out of file descriptors.

+ *

+ * outputBufferSize    10000      Larger value may improve performance of file

+ *                                writing, but not by much.

+ *

+ * tmpdir                         Merge sort files by default are placed in the

+ *                                Java temp directory. Override to place them

+ *                                somewhere else.

+ * </pre>

+ *

  * @author Brian S O'Neill

  * @see SortedCursor

  */

@@ -60,13 +83,43 @@ public class MergeSortBuffer<S extends Storable> extends AbstractCollection<S>
     private static final int MIN_ARRAY_CAPACITY = 64;

 

     // Bigger means better performance, but more memory is used.

-    private static final int MAX_ARRAY_CAPACITY = 8192;

+    private static final int MAX_ARRAY_CAPACITY;

+    private static final int DEFAULT_MAX_ARRAY_CAPACITY = 8192;

 

     // Bigger means better performance, but more file handles may be used.

-    private static final int MAX_FILE_COUNT = 100;

+    private static final int MAX_OPEN_FILE_COUNT;

+    private static final int DEFAULT_MAX_OPEN_FILE_COUNT = 100;

 

     // Bigger may improve write performance, but not by much.

-    private static final int OUTPUT_BUFFER_SIZE = 10000;

+    private static final int OUTPUT_BUFFER_SIZE;

+    private static final int DEFAULT_OUTPUT_BUFFER_SIZE = 10000;

+

+    private static final String TEMP_DIR;

+

+    static {

+        String prefix = MergeSortBuffer.class.getName() + '.';

+

+        MAX_ARRAY_CAPACITY = Integer.getInteger(prefix + "maxArrayCapacity",

+                                                DEFAULT_MAX_ARRAY_CAPACITY);

+

+        MAX_OPEN_FILE_COUNT = Integer.getInteger(prefix + "maxOpenFileCount",

+                                                 DEFAULT_MAX_OPEN_FILE_COUNT);

+

+        OUTPUT_BUFFER_SIZE = Integer.getInteger(prefix + "outputBufferSize",

+                                                DEFAULT_OUTPUT_BUFFER_SIZE);

+

+        // Null means use system temp dir.

+        String tempDir = System.getProperty(prefix + "tmpdir", null);

+

+        if (tempDir != null) {

+            File f = new File(tempDir);

+            if (!f.exists() || !f.isDirectory() || !f.canRead() || !f.canWrite()) {

+                tempDir = null;

+            }

+        }

+

+        TEMP_DIR = tempDir;

+    }

 

     private final Storage<S> mStorage;

     private final String mTempDir;

@@ -104,9 +157,13 @@ public class MergeSortBuffer<S extends Storable> extends AbstractCollection<S>
      * @param tempDir directory to store temp files for merging, or null for default

      * @param maxArrayCapacity maximum amount of storables to keep in an array

      * before serializing to a file

+     * @throws IllegalArgumentException if storage is null

      */

     @SuppressWarnings("unchecked")

     public MergeSortBuffer(Storage<S> storage, String tempDir, int maxArrayCapacity) {

+        if (storage == null) {

+            throw new IllegalArgumentException();

+        }

         mStorage = storage;

         mTempDir = tempDir;

         mMaxArrayCapacity = maxArrayCapacity;

@@ -164,7 +221,7 @@ public class MergeSortBuffer<S extends Storable> extends AbstractCollection<S>
 

                 StorableSerializer<S> serializer = mSerializer;

 

-                if (mFilesInUse.size() < (MAX_FILE_COUNT - 1)) {

+                if (mFilesInUse.size() < (MAX_OPEN_FILE_COUNT - 1)) {

                     mFilesInUse.add(raf);

                     int count = 0;

                     for (S element : mElements) {