election

type Config struct {
	// ID is id of the current member.
	// It is used to distinguish different members.
	// It must be unique among all members.
	ID string
	// Name is the human-readable name of the current member.
	// It is used for logging and diagnostics.
	Name string
	// Address is the address of the current member.
	Address string
	// Storage is the storage to store the election record.
	Storage Storage
	// LeaderCallback is the callback function when the current member becomes leader.
	// If current member loses the leadership, the ctx will be canceled. Callback should
	// return as soon as possible when the ctx is canceled.
	LeaderCallback func(ctx context.Context) error
	// LeaseDuration is the duration that a client will wait before
	// it can remove this member when the client hasn't observed any
	// renewals from the member.
	//
	// A client will wait a full LeaseDuration without observing any
	// renewals from the member before it can remove the member.
	// When all clients are shutdown and a new set of clients are started
	// with different id against the same storage, they must wait a full
	// LeaseDuration before they can acquire a leadership. So the LeaseDuration
	// should be set as short as possible to avoid the long waits in this case.
	//
	// It defaults to 10 seconds if not set.
	LeaseDuration time.Duration
	// RenewInterval is the interval that the current member tries to
	// refresh the election record and renew the lease.
	//
	// It defaults to 2 seconds if not set.
	RenewInterval time.Duration
	// RenewDeadline is the duration that the current member waits before
	// it gives up on the leadership when it can't renew the lease. To avoid
	// two members from both acting as leader at the same time, RenewDeadline
	// should be set shorter than LeaseDuration - RenewInterval.
	//
	// It defaults to 8 seconds if not set.
	RenewDeadline time.Duration
	// ExitOnRenewFail indicates whether the current member should exit when
	// failing to renew the lease.
	ExitOnRenewFail bool
}

type DO struct {
	ID       uint32  `gorm:"column:id;type:int(10) unsigned;primaryKey" json:"id"`
	LeaderID string  `gorm:"column:leader_id;type:text;not null" json:"leader_id"`
	Record   *Record `gorm:"column:record;type:text" json:"record"`
	Version  uint64  `gorm:"column:version;type:bigint(20) unsigned;not null" json:"version"`
}

type Elector interface {
	// RunElection runs the elector to continuously campaign for leadership
	// until the context is canceled.
	RunElection(ctx context.Context) error
	// IsLeader returns true if the current member is the leader
	// and its lease is still valid.
	IsLeader() bool
	// GetLeader returns the last observed leader whose lease is still valid.
	GetLeader() (*Member, bool)
	// GetMembers returns all members.
	GetMembers() []*Member
	// ResignLeader resigns the leadership and let the elector
	// not to try to campaign for leadership during the duration.
	ResignLeader(ctx context.Context, duration time.Duration) error
}

type Member struct {
	// ID is the ID of the member.
	ID string `json:"id"`
	// Name is the human-readable name of the member.
	// It is used for logging and diagnostics.
	Name string `json:"name"`
	// Address is the address of the member.
	Address string `json:"address"`
	// LeaseDuration is the duration that a client will wait before
	// it can remove this member when the client hasn't observed
	// any renewals from the member.
	LeaseDuration time.Duration `json:"lease_duration"`
	// RenewTime is the last time when the member renewed its lease.
	RenewTime time.Time `json:"renew_time"`
}

type ORMStorage struct {
	// contains filtered or unexported fields
}

type Record struct {
	// LeaderID is the ID of the leader. If it is empty, it means
	// there is no leader and all members may try to become leader.
	LeaderID string `json:"leader_id"`
	// Members is the members that are eligible to become leader,
	// which includes the leader itself.
	Members []*Member `json:"members"`
	// Version is the internal version of the record. It can be used by
	// specific storage implementation to determine whether the record has
	// been changed by another writer. The caller of the storage interface
	// should treat this value as opaque.
	//
	// Skip serializing this field, because it is not part of the record content.
	Version int64 `json:"-"`
}

type SQLStorage struct {
	// contains filtered or unexported fields
}

type Storage interface {
	// Get gets the current record from the storage. It returns the current record stored
	// in the storage and any error encountered. Note that if the record has not created yet,
	// it should return an empty record and a nil error.
	Get(ctx context.Context) (*Record, error)
	// Update updates the record in the storage if the stored record version matches the given
	// record version. It returns ErrRecordConflict if the stored record version does not match
	// or any other error encountered.
	Update(ctx context.Context, record *Record, isLeaderChanged bool) error
}