Todd Lipcon has submitted this change and it was merged. ( http://gerrit.cloudera.org:8080/8964 )
Change subject: [mvcc] Fix watermark advancement in the absence of committed transactions ...................................................................... [mvcc] Fix watermark advancement in the absence of committed transactions MvccSnapshot's 'none_committed_at_or_after_' (ncaoa) watermark indicates the point after which no transactions are committed. This is used to cull redo deltas that cannot contain any committed transactions under a snapshot, thus reducing work when applying deltas. By definition, this watermark is never supposed to be lower than the 'all_committed_before_' watermark. If this invariant is broken delta selection might be wrong by skipping whole delta files. Normally the ncaoa watermark is advanced when transactions are marked as committed, in which case this is done correctly. However there is problem when the 'all_committed_before_' watermark is advanced and there are no committed or in flight transactions. In this case the ncaoa watermark might be left behind, manifesting as incorrect delta application/skipping or even crashes. This patch includes a fix and a very directed test that makes sure it is correct. A follow up patch includes a new test in fuzz-itest that would trigger a crash without the fix. Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db Reviewed-on: http://gerrit.cloudera.org:8080/8964 Tested-by: David Ribeiro Alves <davidral...@gmail.com> Reviewed-by: Todd Lipcon <t...@apache.org> --- M src/kudu/tablet/mvcc-test.cc M src/kudu/tablet/mvcc.cc M src/kudu/tablet/mvcc.h 3 files changed, 50 insertions(+), 1 deletion(-) Approvals: David Ribeiro Alves: Verified Todd Lipcon: Looks good to me, approved -- To view, visit http://gerrit.cloudera.org:8080/8964 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: kudu Gerrit-Branch: master Gerrit-MessageType: merged Gerrit-Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db Gerrit-Change-Number: 8964 Gerrit-PatchSet: 3 Gerrit-Owner: David Ribeiro Alves <davidral...@gmail.com> Gerrit-Reviewer: David Ribeiro Alves <davidral...@gmail.com> Gerrit-Reviewer: Kudu Jenkins Gerrit-Reviewer: Todd Lipcon <t...@apache.org>
