Struct raftstore::store::util::Lease

pub struct Lease {
    bound: Option<Either<Timespec, Timespec>>,
    max_lease: Duration,
    max_drift: Duration,
    last_update: Timespec,
    remote: Option<RemoteLease>,
}

Lease records an expired time, for examining the current moment is in lease or not. It’s dedicated to the Raft leader lease mechanism, contains either state of

1. Suspect Timestamp A suspicious leader lease timestamp, which marks the leader may still hold or lose its lease until the clock time goes over this timestamp.
2. Valid Timestamp A valid leader lease timestamp, which marks the leader holds the lease for now. The lease is valid until the clock time goes over this timestamp.

Time
|---------------------------------->
        ^               ^
       Now           Suspect TS
State:  |    Suspect    |   Suspect

|---------------------------------->
        ^               ^
       Now           Valid TS
State:  |     Valid     |   Expired

Note:

• Valid timestamp would increase when raft log entries are applied in current term.
• Suspect timestamp would be set after the message MsgTimeoutNow is sent by current peer. The message MsgTimeoutNow starts a leader transfer procedure. During this procedure, current peer as an old leader may still hold its lease or lose it. It’s possible there is a new leader elected and current peer as an old leader doesn’t step down due to network partition from the new leader. In that case, current peer lose its leader lease. Within this suspect leader lease expire time, read requests could not be performed locally.
• The valid leader lease should be lease = max_lease - (commit_ts - send_ts) And the expired timestamp for that leader lease is commit_ts + lease, which is send_ts + max_lease in short.

Fields

bound: Option<Either<Timespec, Timespec>>

max_lease: Duration

max_drift: Duration

last_update: Timespec

remote: Option<RemoteLease>

Implementations

impl Lease

pub fn new(max_lease: Duration) -> Lease

fn next_expired_time(&self, send_ts: Timespec) -> Timespec

The valid leader lease should be lease = max_lease - (commit_ts - send_ts) And the expired timestamp for that leader lease is commit_ts + lease, which is send_ts + max_lease in short.

pub fn renew(&mut self, send_ts: Timespec)

Renew the lease to the bound.

pub fn suspect(&mut self, send_ts: Timespec)

Suspect the lease to the bound.

pub fn inspect(&self, ts: Option<Timespec>) -> LeaseState

Inspect the lease state for the ts or now.

pub fn expire(&mut self)

pub fn expire_remote_lease(&mut self)

pub fn maybe_new_remote_lease(&mut self, term: u64) -> Option<RemoteLease>

Return a new RemoteLease if there is none.

Trait Implementations

impl Debug for Lease

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

Formats the value using the given formatter.