This patch introduces a queue to store ids of transactions that failed
to send a rollback fragment in streaming_rollback(). This is to avoid
potentially missed rollback fragments when a cluster splits and then
later reforms. Rollback fragments would be missing if a node rolled
back a transaction locally (either BFed or voluntary rollback) while
non-primary, and the attempt to send rollback fragment failed in
transaction::streaming_rollback().
Transaction that fail to send rollback fragment can proceed to
rollback locally. However we must ensure that rollback fragments for
those transactions are eventually delivered by the cluster. This must
be done before a potentially conflicting writeset causes BF-BF
conflicts in the rest of the cluster.
Fixes a bug where the fact that an SR master leaves the primary view
gets missed. When two consecutive primary views have the same
membership we now assume that every SR needs to be rolled back, as the
system may have been through a state of only non-primary components.
Use iterators for scanning members vector in order to avoid
issues with integer signedness and range checks. The vector is
usually rather small and not in hot codepath, so performance
is here not an issue.
Added unit test for member_index() method.
