tree e562964a3fbda75e4ed9b3e90c6bdebc3a00b8aa
parent b3bb51ec89c7f1856aa25c1fb015ce305b28aba3
author Andrew Wong <awong@cloudera.com> 1536047758 -0700
committer Attila Bukor <abukor@apache.org> 1539679222 +0000

KUDU-2463 pt 3: don't scan if MVCC hasn't moved

In cases when a tablet bootstrap yields an MvccManager whose safe time
has not been advanced (e.g. if there are no write ops in the WAL), and
the tablet has otherwise not bumped its MVCC timestamps (e.g. if it has
not yet elected a leader), a scan (whose correctness depends on the
MvccManager to determine what transactions have been applied) will
return incorrect results.

In the same way that we prevent compactions from occuring if MVCC's
timestamps have not been moved, this patch prevents incorrect results
from being returend from a scan by returning an error that can be
retried elsewhere.

New tests are added to attempt to scan in this state, verifying that we
get an error. A couple of tests that use the mock clock are also updated
so the initial timestamp assigned to a no-op is a more organic, non-zero
timestamp.

Change-Id: Idc0f77673e1f04a34ab1f5c1930bbaa2498b39bf
Reviewed-on: http://gerrit.cloudera.org:8080/11428
Reviewed-by: Mike Percy <mpercy@apache.org>
Tested-by: Kudu Jenkins
Reviewed-on: http://gerrit.cloudera.org:8080/11690
Reviewed-by: Grant Henke <granthenke@apache.org>