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Constants ¶
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Variables ¶
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var TableNameElection = "election"
TableNameElection is the table name of election.
Functions ¶
This section is empty.
Types ¶
type Config ¶
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
}
Config is the configuration for the leader election.
func (*Config) AdjustAndValidate ¶
AdjustAndValidate adjusts the config and validates it.
type DO ¶
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"`
}
DO mapped from table <election>
type Elector ¶
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
}
Elector is a leader election client.
type Member ¶
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"`
}
Member is a member in a leader election.
type ORMStorage ¶
type ORMStorage struct {
// contains filtered or unexported fields
}
ORMStorage is a storage implementation based on SQL database.
func NewORMStorage ¶
func NewORMStorage(db *gorm.DB, tableName string) (*ORMStorage, error)
NewORMStorage creates a new ORMStorage.
func NewORMStorageFromSQLDB ¶
func NewORMStorageFromSQLDB(backendDB *sql.DB, tableName string) (*ORMStorage, error)
NewORMStorageFromSQLDB creates a new ORMStorage from sql.DB.
func (*ORMStorage) Get ¶
func (s *ORMStorage) Get(ctx context.Context) (*Record, error)
Get implements Storage.Get.
func (*ORMStorage) TxnWithLeaderLock ¶
func (s *ORMStorage) TxnWithLeaderLock(ctx context.Context, leaderID string, fc func(tx *gorm.DB) error) error
TxnWithLeaderLock execute a transaction with leader row locked.
type Record ¶
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:"-"`
}
Record holds the information of a leader election.
func (*Record) FindMember ¶
FindMember finds the member with the given ID in the record.
type SQLStorage ¶
type SQLStorage struct {
// contains filtered or unexported fields
}
SQLStorage is a storage implementation based on SQL database.
func NewInMemorySQLStorage ¶
func NewInMemorySQLStorage(dbName string, tableName string) (*SQLStorage, error)
NewInMemorySQLStorage creates a new SQLStorage in memory based on SQLite.
func NewSQLStorage ¶
func NewSQLStorage(db *sql.DB, tableName string) (*SQLStorage, error)
NewSQLStorage creates a new SQLStorage.
type Storage ¶
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
}
Storage describes the requirements of a storage that can be used for leader election.
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