book_policy.py 文件源码

def _policy_RequestIG(self, books_needed):
        '''Select books from IGs specified in interleave_request attribute.
           If interleave_request_pos is present use it as the starting point.'''
        db = self.LCEobj.db
        ig_req = db.get_xattr(self.shelf, self.XATTR_IG_REQ)
        self.LCEobj.errno = errno.ERANGE
        assert ig_req is not None, \
            'RequestIG policy requires prior %s' % self.XATTR_IG_REQ
        assert len(ig_req), \
            'RequestIG policy requires prior %s' % self.XATTR_IG_REQ

        # Get a starting position for the interleave_request list
        self.LCEobj.errno = errno.ENOSPC
        pos = db.get_xattr(self.shelf, self.XATTR_IG_REQ_POS)
        try:
            ig_pos = int(pos)
            if ig_pos < 0 or ig_pos > (len(ig_req) - 1):
                ig_pos = 0
        except TypeError as err:    # TSNH, see create_shelf.  Legacy paranoia.
            ig_pos = 0
            resp = db.create_xattr(self.shelf, self.XATTR_IG_REQ_POS, ig_pos)
        except ValueError as err:
            ig_pos = 0

        reqIGs = [ord(ig_req[i:i+1]) for i in range(0, len(ig_req), 1)]

        # Determine number of books needed from each IG
        igCnt = defaultdict(int)
        cur = ig_pos
        for cnt in range(0, books_needed):
            ig = reqIGs[cur % len(reqIGs)]
            igCnt[ig] += 1
            cur += 1

        # Allocate specified number of books from each selected IG
        booksIG = {}
        for ig in igCnt.keys():
            booksIG[ig] = db.get_books_by_intlv_group(
                igCnt[ig], (ig, ), exclude=False)

        # Build list of books using request_interleave pattern
        self.LCEobj.errno = errno.ENOSPC
        bookList = []
        cur = ig_pos
        for cnt in range(0, books_needed):
            ig = reqIGs[cur % len(reqIGs)]
            assert len(booksIG[ig]) != 0, 'Not enough books remaining in IG'
            bookList.append(booksIG[ig].pop(0))
            cur += 1

        # Save current position in interleave_request list
        db.modify_xattr(self.shelf, self.XATTR_IG_REQ_POS, cur % len(reqIGs))

        return bookList