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v2.0.5

v2.0.5: Merge #27868 #28225
tagged this 06 Aug 19:28 
27868: backport-2.0: storage: prevent unbounded raft log growth without quorum r=nvanbenschoten a=nvanbenschoten

Backport 2/2 commits from #27774.

/cc @cockroachdb/release

---

Fixes #27772.

This change adds safeguards to prevent cases where a raft log
would grow without bound during loss of quorum scenarios. It
also adds a new test that demonstrates that the raft log does
not grow without bound in these cases.

There are two cases that need to be handled to prevent the
unbounded raft log growth observed in #27772.
1. When the leader proposes a command and cannot establish a
   quorum. In this case, we know the leader has the entry in
   its log, so there's no need to refresh it with `reasonTicks`.
   To avoid this, we no longer use `refreshTicks` as a leader.
2. When a follower proposes a command that is forwarded to the
   leader who cannot establish a quorum. In this case, the
   follower can't be sure (currently) that the leader got the
   proposal, so it needs to refresh using `reasonTicks`. However,
   the leader now detects duplicate forwarded proposals and
   avoids appending redundant entries to its log. It does so
   by maintaining a set of in-flight forwarded proposals that
   it has received during its term as leader. This set is reset
   after every leadership change.

Both of these cases are tested against in the new
TestLogGrowthWhenRefreshingPendingCommands. Without both of
the safeguards introduced in this commit, the test fails.

Release note (bug fix): Prevent loss of quorum situations from
allowing unbounded growth of a Range's Raft log.


28225: release-2.0: importccl: Preserve '\r\n' during CSV import r=dt a=dt

Backport 1/1 commits from #28181.

/cc @cockroachdb/release

---

See #25344.


Co-authored-by: Nathan VanBenschoten <nvanbenschoten@gmail.com>
Co-authored-by: neeral <neeral@users.noreply.github.com>
Co-authored-by: David Taylor <tinystatemachine@gmail.com>
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