CZ-NIC / knot-resolver / 926

96%

master: 68%

Build Type

push

travis-ci

Committed by Marek Vavrusa

Commit Message

lib/cache: reuse read-only transactions

usual pattern is that several read transactions
are spawned for each query, which has a modest
cost for some backends such as LMDB. in order to
amortize this cost, a read-only transaction is
reused as long as:
* there is no write transaction
* cache is not cleared/closed

this has potential drawbacks and risks:
* stale read transaction will prevent freeing
  pages if running in multi-process mode, but
  in practice this shouldn't happen, only if one
  process was doing nothing and the other busy
* some other backends use the concept of transaction
  to cache content from remote servers (Redis),
  in this case we shouldn't reuse it indefinitely

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