@Override
    protected void endSendAttempt(ConnectionStats stats, long start) {
      stats.endRollbackSend(start, hasFailed());
    }
Does a rollback on the server for given transaction

@param pool the pool to use to communicate with the server.
@param txId the id of the transaction to rollback
geode-core/src/main/java/org/apache/geode/cache/client/internal/RollbackOp.java