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raft: (testing) test non-voter can vote

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When a non-voter is requested a vote, it must vote
to preserve liveness. In Raft, servers respond
to messages without consulting with their current configuration,
and the non-voter may not have the latest configuration
when it is requested to vote.
This commit is contained in:
Konstantin Osipov
2021-04-17 22:36:01 +03:00
parent eaf32f2c3c
commit 2be8a73c34
1 changed files with 36 additions and 0 deletions
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36
test/raft/fsm_test.cc
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@@ -1782,3 +1782,39 @@ BOOST_AUTO_TEST_CASE(test_non_voter_confchange_in_snapshot) {
communicate(C, B);
BOOST_CHECK(C.is_leader());
}
BOOST_AUTO_TEST_CASE(test_non_voter_can_vote) {
// Test non-voter can vote when it is requested to - it may
// not be aware of the configuration in which it is a voter
discrete_failure_detector fd;
server_id A_id = id(), B_id = id(), C_id = id();
raft::configuration cfg(raft::server_address_set{
raft::server_address{A_id},
raft::server_address{B_id},
raft::server_address{C_id, false}});
raft::log log(raft::snapshot{.idx = index_t{0}, .config = cfg});
auto A = create_follower(A_id, log, fd);
auto B = create_follower(B_id, log, fd);
auto C = create_follower(C_id, log, fd);
election_timeout(A);
communicate(A, B, C);
BOOST_CHECK(A.is_leader());
raft::configuration cfg_all_voters({A_id, B_id, C_id});
A.add_entry(cfg_all_voters);
// Majority commits the configuration change
communicate(A, B);
BOOST_CHECK_EQUAL(A.get_configuration().is_joint(), false);
BOOST_CHECK_EQUAL(A.get_configuration().current.find(raft::server_address{C_id})->can_vote, true);
BOOST_CHECK_EQUAL(A.log_last_idx(), B.log_last_idx());
fd.mark_dead(A_id);
election_timeout(B);
election_threshold(C);
// B and C are enough to elect B in the new configuration.
communicate(B, C);
BOOST_CHECK(B.is_leader());
BOOST_CHECK_EQUAL(B.get_current_term(), C.get_current_term());
BOOST_CHECK_EQUAL(B.log_last_idx(), C.log_last_idx());
}