tarantool / go-tarantool / 34917214265

77%

master: 76%

Pull #605

github

future: make Release() of an unfinished future a no-op

Release() zeroed the object and returned it to futurePool without
checking that the request had completed. The documented lifecycle is
Do -> Get -> Release, but the natural fire-and-forget reading
`fut := conn.Do(req); fut.Release()` recycled a node that was still
linked into the connection's list of pending requests. Request ids are
never 0, so the zeroed node truncated the list for findFuture() and
clear(): the response was never matched back, markDone() never ran for
it, requestCnt never dropped (so CloseGraceful() hung) and with
Opts.Timeout == 0 the owners of the futures behind it blocked forever.
The recycled node could also be linked into a second list through the
pool.

Return early when the future is not finished, leaving the object to the
garbage collector, and document the precondition on Future.Release(), on
the implementation and in the migration guide. NewFutureWithErr() and
NewFutureWithResponse() return already finished futures, so they are
unaffected.

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