[backport] [v25.3.x] raft: fix offset translator inconsistencies arising from incorrect truncation #29849#29872
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bharathv merged 2 commits intoredpanda-data:v25.3.xfrom Mar 20, 2026
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When append_entries triggers a truncation and has leftover batches, the recursive do_append_entries call reuses the original (stale) prev_log_index. With large ghost batches from compaction, this causes the matching loop to place the incoming batches at incorrect offsets since they matched relative to prev_log_index. Instead of recursing, return success after truncation and let the leader's recovery loop send remaining batches with correct metadata from its own log. We return success instead of recursing with a mutated append_entries request because we do not want to risk corrupting the request with an incorrect prev_log_delta based on the local log. We rather want to populate it from the leader log, which is the source of truth and easier to reason about. This may can an additional round trip but that is ok since this is very very rare and also on a follower, so not in a typical read/write path. (cherry picked from commit 889bde3)
scenario and bug described in https://docs.google.com/document/d/16GOxClpx_BHPh6Eg7WsLoOwStJhkS0o2jkIRb8hKvs0/edit?tab=t.0#heading=h.6bs87ao57qdi (cherry picked from commit e32d384)
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mmaslankaprv
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Mar 19, 2026
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Backport of #29849
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