Move JournalSegmentWriter switchover logic

[controller.git] / atomix-storage / src / main / java / io / atomix / storage / journal / MappedJournalSegmentWriter.java

diff --git a/atomix-storage/src/main/java/io/atomix/storage/journal/MappedJournalSegmentWriter.java b/atomix-storage/src/main/java/io/atomix/storage/journal/MappedJournalSegmentWriter.java
index d461b81aec7001e900c77b61836209b809745667..f5d4ed9d04a9554de4ec935c6b54b85720158973 100644 (file)
--- a/atomix-storage/src/main/java/io/atomix/storage/journal/MappedJournalSegmentWriter.java
+++ b/atomix-storage/src/main/java/io/atomix/storage/journal/MappedJournalSegmentWriter.java
@@ -23,7 +23,9 @@ import java.nio.BufferOverflowException;
 import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
 import java.util.zip.CRC32;
+import org.eclipse.jdt.annotation.NonNull;
 
 /**
  * Segment writer.
@@ -40,41 +42,44 @@ import java.util.zip.CRC32;
  *
  * @author <a href="http://github.com/kuujo">Jordan Halterman</a>
  */
-class MappedJournalSegmentWriter<E> implements JournalWriter<E> {
-  private final MappedByteBuffer mappedBuffer;
+final class MappedJournalSegmentWriter<E> extends JournalSegmentWriter<E> {
+  private final @NonNull MappedByteBuffer mappedBuffer;
   private final ByteBuffer buffer;
-  private final JournalSegment<E> segment;
-  private final int maxEntrySize;
-  private final JournalIndex index;
-  private final JournalSerdes namespace;
-  private final long firstIndex;
+
   private Indexed<E> lastEntry;
 
   MappedJournalSegmentWriter(
-      MappedByteBuffer buffer,
+      FileChannel channel,
       JournalSegment<E> segment,
       int maxEntrySize,
       JournalIndex index,
       JournalSerdes namespace) {
-    this.mappedBuffer = buffer;
-    this.buffer = buffer.slice();
-    this.segment = segment;
-    this.maxEntrySize = maxEntrySize;
-    this.index = index;
-    this.namespace = namespace;
-    this.firstIndex = segment.index();
+    super(channel, segment, maxEntrySize, index, namespace);
+    try {
+      mappedBuffer = channel.map(FileChannel.MapMode.READ_WRITE, 0, segment.descriptor().maxSegmentSize());
+    } catch (IOException e) {
+      throw new StorageException(e);
+    }
+    this.buffer = mappedBuffer.slice();
     reset(0);
   }
 
-  /**
-   * Returns the mapped buffer underlying the segment writer.
-   *
-   * @return the mapped buffer underlying the segment writer
-   */
-  MappedByteBuffer buffer() {
+  @Override
+  @NonNull MappedByteBuffer buffer() {
     return mappedBuffer;
   }
 
+  @Override
+  MappedJournalSegmentWriter<E> toMapped() {
+    return this;
+  }
+
+  @Override
+  FileChannelJournalSegmentWriter<E> toFileChannel() {
+    close();
+    return new FileChannelJournalSegmentWriter<>(channel, segment, maxEntrySize, index, namespace);
+  }
+
   @Override
   public void reset(long index) {
     long nextIndex = firstIndex;
@@ -97,23 +102,25 @@ class MappedJournalSegmentWriter<E> implements JournalWriter<E> {
         // Read the checksum of the entry.
         final long checksum = buffer.getInt() & 0xFFFFFFFFL;
 
+        // Slice off the entry's bytes
+        final ByteBuffer entryBytes = buffer.slice();
+        entryBytes.limit(length);
+
         // Compute the checksum for the entry bytes.
         final CRC32 crc32 = new CRC32();
-        ByteBuffer slice = buffer.slice();
-        slice.limit(length);
-        crc32.update(slice);
-
-        // If the stored checksum equals the computed checksum, return the entry.
-        if (checksum == crc32.getValue()) {
-          slice.rewind();
-          final E entry = namespace.deserialize(slice);
-          lastEntry = new Indexed<>(nextIndex, entry, length);
-          this.index.index(nextIndex, position);
-          nextIndex++;
-        } else {
+        crc32.update(entryBytes);
+
+        // If the stored checksum does not equal the computed checksum, do not proceed further
+        if (checksum != crc32.getValue()) {
           break;
         }
 
+        entryBytes.rewind();
+        final E entry = namespace.deserialize(entryBytes);
+        lastEntry = new Indexed<>(nextIndex, entry, length);
+        this.index.index(nextIndex, position);
+        nextIndex++;
+
         // Update the current position for indexing.
         position = buffer.position() + length;
         buffer.position(position);
@@ -148,24 +155,6 @@ class MappedJournalSegmentWriter<E> implements JournalWriter<E> {
     }
   }
 
-  /**
-   * Returns the size of the underlying buffer.
-   *
-   * @return The size of the underlying buffer.
-   */
-  public long size() {
-    return buffer.position() + JournalSegmentDescriptor.BYTES;
-  }
-
-  /**
-   * Returns a boolean indicating whether the segment is empty.
-   *
-   * @return Indicates whether the segment is empty.
-   */
-  public boolean isEmpty() {
-    return lastEntry == null;
-  }
-
   @Override
   public void append(Indexed<E> entry) {
     final long nextIndex = getNextIndex();
@@ -232,10 +221,6 @@ class MappedJournalSegmentWriter<E> implements JournalWriter<E> {
     return (Indexed<T>) indexedEntry;
   }
 
-  @Override
-  public void commit(long index) {
-
-  }
 
   @Override
   public void truncate(long index) {
@@ -251,20 +236,18 @@ class MappedJournalSegmentWriter<E> implements JournalWriter<E> {
     this.index.truncate(index);
 
     if (index < segment.index()) {
-      buffer.position(JournalSegmentDescriptor.BYTES);
-      buffer.putInt(0);
-      buffer.putInt(0);
+      // Reset the writer to the first entry.
       buffer.position(JournalSegmentDescriptor.BYTES);
     } else {
       // Reset the writer to the given index.
       reset(index);
-
-      // Zero entries after the given index.
-      int position = buffer.position();
-      buffer.putInt(0);
-      buffer.putInt(0);
-      buffer.position(position);
     }
+
+    // Zero the entry header at current buffer position.
+    int position = buffer.position();
+    // Note: we issue a single putLong() instead of two putInt()s.
+    buffer.putLong(0);
+    buffer.position(position);
   }
 
   @Override