We want to prevent older version of scylla which has fewer features to
join a cluster with newer version of scylla which has more features,
because when scylla sees a feature is enabled on all other nodes, it
will start to use the feature and assume existing nodes and future nodes
will always have this feature.
In order to support downgrade during rolling upgrade, we need to support
mixed old and new nodes case.
1) All old nodes
O O O O O <- N OK
O O O O O <- O OK
2) All new nodes
N N N N N <- N OK
N N N N N <- O FAIL
3) Mixed old and new nodes
O N O N O <- N OK
O N O N O <- O OK
(O == old node, N == new node, <- == joining the cluster)
With this patch, I tested:
1.1) Add new node to new node cluster
gossip - Feature check passed. Local node 127.0.0.4 features =
{RANGE_TOMBSTONES}, Remote common_features = {RANGE_TOMBSTONES}
1.2) Add old node to old node cluster
gossip - Feature check passed. Local node 127.0.0.4 features = {},
Remote common_features = {}
2.1) Add new node to new node cluster
gossip - Feature check passed. Local node 127.0.0.4 features =
{RANGE_TOMBSTONES}, Remote common_features = {RANGE_TOMBSTONES}
2.2) Add old node to new node cluster
seastar - Exiting on unhandled exception: std::runtime_error (Feature
check failed. This node can not join the cluster because it does not
understand the feature. Local node 127.0.0.4 features = {}, Remote
common_features = {RANGE_TOMBSTONES})
3.1) Add new node to mixed cluster
gossip - Feature check passed. Local node 127.0.0.4 features =
{RANGE_TOMBSTONES}, Remote common_features = {}
3.2) Add old node to mixed cluster
gossip - Feature check passed. Local node 127.0.0.4 features = {},
Remote common_features = {}
Fixes#1253
4f3ce42163