Method openReverseScanner

src/HBaseClient.java:1524–1548

Called instead of openScanner() in order to do an additional META lookup to find next region we will be scanning. @param scanner The scanner to open. @return A deferred scanner ID (long) if HBase 0.94 and before, or a deferred Scanner.Response if HBase 0.95 and up.

(final Scanner scanner)

   * deferred {@link Scanner.Response} if HBase 0.95 and up.
   */
  Deferred<Object> openReverseScanner(final Scanner scanner){
    return locateRegionClosestBeforeKey(
            scanner.getOpenRequest(), scanner.table(), scanner.startKey())
            .addCallbacks(
                    new Callback<Object, Object>() {
                      public Object call(final Object arg) {
                        return openScanner(scanner,
                                scanner.getOpenRequestForReverseScan(
                                        ((RegionLocation) arg).startKey()));
                      }
                    },
                    new Callback<Object, Object>() {
                      public Object call(final Object error) {
                        LOG.info("Lookup to construct reverse scanner failed on table " +
                                Bytes.pretty(scanner.table()) + " and start key " +
                                Bytes.pretty(scanner.startKey()));
                        return error;
                      }

                      public String toString() {
                        return "openReverseScanner errback";
                      }
              }
            );
  }

  /** Singleton callback to handle responses of "openScanner" RPCs.  */
  private static final Callback<Object, Object> scanner_opened =