Read reverse

managed-ledger/src/main/java/org/apache/bookkeeper/mledger/ManagedCursor.java

@@ -839,4 +839,10 @@ Set<? extends Position> asyncReplayEntries(
      * @return whether this cursor is closed.
      */
     boolean isClosed();
+
+    /**
+     * Checks if the cursor is read reverse mode.
+     * @return: whether this cursor is reading in a reverse way
+     */
+    boolean isReadReverse();
 }

managed-ledger/src/main/java/org/apache/bookkeeper/mledger/ManagedLedger.java

@@ -225,8 +225,8 @@ void asyncAddEntry(byte[] data, int numberOfMessages, int offset, int length, Ad
      * @return the ManagedCursor
      * @throws ManagedLedgerException
      */
-    ManagedCursor openCursor(String name, InitialPosition initialPosition) throws InterruptedException,
-            ManagedLedgerException;
+    ManagedCursor openCursor(String name, InitialPosition initialPosition, boolean readReverse)
+            throws InterruptedException, ManagedLedgerException;
 
     /**
      * Open a ManagedCursor in this ManagedLedger.
@@ -245,8 +245,8 @@ ManagedCursor openCursor(String name, InitialPosition initialPosition) throws In
      * @return the ManagedCursor
      * @throws ManagedLedgerException
      */
-    ManagedCursor openCursor(String name, InitialPosition initialPosition, Map<String, Long> properties,
-                             Map<String, String> cursorProperties)
+    ManagedCursor openCursor(String name, InitialPosition initialPosition, boolean readReverse,
+                             Map<String, Long> properties, Map<String, String> cursorProperties)
             throws InterruptedException, ManagedLedgerException;
 
     /**
@@ -267,7 +267,7 @@ ManagedCursor openCursor(String name, InitialPosition initialPosition, Map<Strin
     ManagedCursor newNonDurableCursor(Position startCursorPosition) throws ManagedLedgerException;
     ManagedCursor newNonDurableCursor(Position startPosition, String subscriptionName) throws ManagedLedgerException;
     ManagedCursor newNonDurableCursor(Position startPosition, String subscriptionName, InitialPosition initialPosition,
-                                      boolean isReadCompacted) throws ManagedLedgerException;
+                                      boolean isReadReverse, boolean isReadCompacted) throws ManagedLedgerException;
 
     /**
      * Delete a ManagedCursor asynchronously.
@@ -330,6 +330,24 @@ ManagedCursor newNonDurableCursor(Position startPosition, String subscriptionNam
      */
     void asyncOpenCursor(String name, InitialPosition initialPosition, OpenCursorCallback callback, Object ctx);
 
+    /**
+     * Open a ManagedCursor asynchronously.
+     *
+     * @see #openCursor(String)
+     * @param name
+     *            the name associated with the ManagedCursor
+     * @param initialPosition
+     *            if null, the cursor will be set at latest position when first created
+     * @param readReverse
+     *            if true, the cursor will read ledger from current to previous messages
+     * @param callback
+     *            callback object
+     * @param ctx
+     *            opaque context
+     */
+    void asyncOpenCursor(String name, InitialPosition initialPosition, boolean readReverse,
+                         OpenCursorCallback callback, Object ctx);
+
     /**
      * Open a ManagedCursor asynchronously.
      *
@@ -348,6 +366,27 @@ ManagedCursor newNonDurableCursor(Position startPosition, String subscriptionNam
     void asyncOpenCursor(String name, InitialPosition initialPosition, Map<String, Long> properties,
                          Map<String, String> cursorProperties, OpenCursorCallback callback, Object ctx);
 
+    /**
+     * Open a ManagedCursor asynchronously.
+     *
+     * @see #openCursor(String)
+     * @param name
+     *            the name associated with the ManagedCursor
+     * @param initialPosition
+     *            if null, the cursor will be set at latest position when first created
+     * @param readReverse
+     *            if true, the cursor will read ledger from current to previous messages
+     * @param cursorProperties
+     *            the properties for the Cursor
+     * @param callback
+     *            callback object
+     * @param ctx
+     *            opaque context
+     */
+    void asyncOpenCursor(String name, InitialPosition initialPosition, boolean readReverse,
+                         Map<String, Long> properties, Map<String, String> cursorProperties,
+                         OpenCursorCallback callback, Object ctx);
+
     /**
      * Get a list of all the cursors reading from this ManagedLedger.
      *

managed-ledger/src/main/java/org/apache/bookkeeper/mledger/Position.java

@@ -35,6 +35,13 @@ public interface Position {
      */
     Position getNext();
 
+    /**
+     * Get the position of the entry previous to this one. The returned position might point to a non-existing entry
+     *
+     * @return the position of the previous logical entry
+     */
+    Position getPrevious();
+
     long getLedgerId();
 
     long getEntryId();