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1 zone tree refactor
Libor Peltan edited this page 2019-01-25 09:51:12 +00:00
Table of Contents

Reason

Zone updates (including incomming IXFR, ...) are slow. Tiny updates to gigantic zones are hell slow. The reason that Copy-On-Write trie doesn't fix it is that there are pointers between nodes in tree (pointer to previous node, pointer to additionals, pointer to nsec3 node and wildcard-proving nsec3 ....), which need to be refreshed when a node is replaced (thus need to replace further nodes...).

New structure for zone node

zone_binode_t will consist of two node_t instances, as one allocated piece in memory. The flag of which one of them shall be used for responding DNS queries will be in zone_contents_t. Any pointer to zone_binode_t will be used like a pointer to zone_node_t using the central flag. Consequence: by atomically exchanging zone_contents_t, all pointers will immediately point to updated nodes.

Another consequence: from the view of COW, there will only be nodes added or removed during txn, no just modified ones.

New requirements for Trie

  • Node lookup will return not only found node and its predeccesor, but also its successor and its parent.
  • The same will return when inserting new node.
  • Ability to iterate through sub-tree.

TODO continue...