Method nextRowErrback

src/Scanner.java:844–883

Creates a new errback to handle errors while trying to get more rows.

()

   * Creates a new errback to handle errors while trying to get more rows.
   */
  final Callback<Object, Object> nextRowErrback() {
    return new Callback<Object, Object>() {
      public Object call(final Object error) {
        final RegionInfo old_region = region;  // Save before invalidate().
        invalidate();  // If there was an error, don't assume we're still OK.
        if (error instanceof NotServingRegionException) {
          // We'll resume scanning on another region, and we want to pick up
          // right after the last key we successfully returned.  Padding the
          // last key with an extra 0 gives us the next possible key.
          // TODO(tsuna): If we get 2 NSRE in a row, well pad the key twice!
          start_key = Arrays.copyOf(start_key, start_key.length + 1);
          return nextRows();  // XXX dangerous endless retry
        } else if (error instanceof UnknownScannerException) {
          // This can happen when our scanner lease expires.  Unfortunately
          // there's no way for us to distinguish between an expired lease
          // and a real problem, for 2 reasons: the server doesn't keep track
          // of recently expired scanners and the lease time is only known by
          // the server and never communicated to the client.  The normal
          // HBase client assumes that the client will share the same
          // hbase-site.xml configuration so that both the client and the
          // server will know the same lease time, but this assumption is bad
          // as nothing guarantees that the client's configuration will be in
          // sync with the server's.  This unnecessarily increases deployment
          // complexity and it's brittle.
          final Scanner scnr = Scanner.this;
          LOG.warn(old_region + " pretends to not know " + scnr + ".  I will"
            + " retry to open a scanner but this is typically because you've"
            + " been holding the scanner open and idle for too long (possibly"
            + " due to a long GC pause on your side or in the RegionServer)",
            error);
          // Let's re-open ourselves and keep scanning.
          return nextRows();  // XXX dangerous endless retry
        }
        return error;  // Let the error propagate.
      }
      public String toString() {
        return "NextRow errback";
      }
    };
  }

  /**
   * Closes this scanner (don't forget to call this when you're done with it!).