Struct openraft::MembershipState

pub struct MembershipState<NID, N>
where
    NID: NodeId,
    N: Node,
{ /* private fields */ }

The state of membership configs a raft node needs to know.

A raft node needs to store at most 2 membership config log:

• The first(committed) one must have been committed, because (1): raft allows to propose new membership only when the previous one is committed.
• The second(effective) may be committed or not.

From (1) we have: (2) there is at most one outstanding, uncommitted membership log. On either leader or follower, the second last one must have been committed. A committed log must be consistent with the leader.

(3) By raft design, the last membership takes effect.

When handling append-entries RPC: (4) a raft follower will delete logs that are inconsistent with the leader.

From (3) and (4), a follower needs to revert the effective membership to the previous one.

From (2), a follower only need to revert at most one membership log.

Thus a raft node will only need to store at most two recent membership logs.

Implementations

impl<NID, N> MembershipState<NID, N>

where NID: NodeId, N: Node,

pub fn committed(&self) -> &Arc<EffectiveMembership<NID, N>>

Returns a reference to the last committed membership config.

A committed membership config may or may not be the same as the effective one.

pub fn effective(&self) -> &Arc<EffectiveMembership<NID, N>>

Returns a reference to the presently effective membership config.

In openraft the last seen membership config, whether committed or not, is the effective one.

A committed membership config may or may not be the same as the effective one.

Trait Implementations

impl<NID, N> Clone for MembershipState<NID, N>

where NID: NodeId + Clone, N: Node + Clone,

fn clone(&self) -> MembershipState<NID, N>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<NID, N> Debug for MembershipState<NID, N>

where NID: NodeId + Debug, N: Node + Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<NID, N> Default for MembershipState<NID, N>

where NID: NodeId + Default, N: Node + Default,

fn default() -> MembershipState<NID, N>

Returns the “default value” for a type.

impl<NID, N> MessageSummary<MembershipState<NID, N>> for MembershipState<NID, N>

where NID: NodeId, N: Node,

fn summary(&self) -> String

Return a string of a big message

impl<NID, N> PartialEq for MembershipState<NID, N>

where NID: NodeId + PartialEq, N: Node + PartialEq,

fn eq(&self, other: &MembershipState<NID, N>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<NID, N> Eq for MembershipState<NID, N>

where NID: NodeId + Eq, N: Node + Eq,

impl<NID, N> StructuralPartialEq for MembershipState<NID, N>

where NID: NodeId, N: Node,