Documentation
¶
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ( // ErrNotLeader is the error returned whn an operation that is // only permitted on the leader is attempted on a follower node. ErrNotLeader error = fmt.Errorf("operation not permitted on followers") )
Functions ¶
This section is empty.
Types ¶
type Command ¶
type Command struct {
Type CommandType `json:"type"`
Key string `json:"key"`
Value string `json:"value,omitempty"`
}
Command is the Finite State Machine command.
type CommandType ¶
type CommandType int8
CommandType represents the type of command.
const ( // Get is the "Get" command type. Get CommandType = iota // Set is the "Set" command type. Set // Delete is the "Delete" command type. Delete )
type KVStore ¶
type KVStore interface {
// Get retrieves a value from the store, given its key.
Get(key string) (string, error)
// Set sets a value into the store, creating it if non existing.
Set(key string, value string) error
// Delete removes a key/value pair from the store.
Delete(key string) error
}
KVStore is the common interface to all key/value stores.
type LocalStore ¶
LocalStore is the non-replicated, local-only SQLite-based implementation of the KVStore interface.
func NewLocalStore ¶
func NewLocalStore(options ...sqlite.Option) (*LocalStore, error)
NewLocalStore creates a new SQLite-based, non-replicated implementation of the KVSTore interface.
func (*LocalStore) Delete ¶
func (s *LocalStore) Delete(key string) error
Delete removes the key/value pair from the store.
type ReplicatedStore ¶
type ReplicatedStore struct {
// contains filtered or unexported fields
}
ReplicatedStore is the replicated, Raft-based implementation of the KVStore interface; it achieves this by coordinating the Raft cluster and the local database.
func NewReplicatedStore ¶
func NewReplicatedStore(allowGetOnFollower bool, store *LocalStore, cluster *cluster.Cluster) *ReplicatedStore
NewReplicatedStore allocates a new ReplicatedStore which will funnel the commands through the Raft log, leaving it to the cluster to apply the log entries to the underlying, local version of the KVStore (localStore). If allowGetOnFollower is true, the ReplicatedStore will
func (*ReplicatedStore) Delete ¶
func (s *ReplicatedStore) Delete(key string) error
Delete deletes the given key.
func (*ReplicatedStore) Get ¶
func (s *ReplicatedStore) Get(key string) (string, error)
Get retrieves the value corresponding to the given key; since the Get command is non-mutating, it needs not go through the Apply() rigmarole; it can be served directly from the LocalStore; if the cluster allows it, the values can be served by the followers, which can speed things up but there is a non-null probability that the follower will serve stale data, when the log has not been acknowledged yet, ot it has been acknowledged but not applied yet to the local store.
func (*ReplicatedStore) Set ¶
func (s *ReplicatedStore) Set(key, value string) error
Set sets the value for the given key.
type ReplicatedStoreFSM ¶
type ReplicatedStoreFSM struct {
// contains filtered or unexported fields
}
ReplicatedStoreFSM is an SQLite-base Raft Finite State Machine.
func NewReplicatedStoreFSM ¶
func NewReplicatedStoreFSM(store *LocalStore) *ReplicatedStoreFSM
func (*ReplicatedStoreFSM) Apply ¶
func (s *ReplicatedStoreFSM) Apply(l *raft.Log) interface{}
Apply log is invoked once a log entry is committed. It returns a value which will be made available in the ApplyFuture returned by Raft.Apply method if that method was called on the same Raft node as the FSM.
func (*ReplicatedStoreFSM) Restore ¶
func (s *ReplicatedStoreFSM) Restore(data io.ReadCloser) error
Restore restores the FSM to a previous state from a snapshot.
func (*ReplicatedStoreFSM) Snapshot ¶
func (s *ReplicatedStoreFSM) Snapshot() (raft.FSMSnapshot, error)
Snapshot returns a snapshot of the key-value store, to support log compaction; the returned ReplicatedStoreFSM...
type SQLiteFSMSnapshot ¶
type SQLiteFSMSnapshot struct {
// contains filtered or unexported fields
}
SQLiteFSMSnapshot is a transient object, capable of generating a snaphot of the SQLite DB contents at the moment it was created.
func (*SQLiteFSMSnapshot) Persist ¶
func (s *SQLiteFSMSnapshot) Persist(sink raft.SnapshotSink) error
Persist writes the SQLiteFSMSnapshot contents to the Raft-provided sink.
func (*SQLiteFSMSnapshot) Release ¶
func (s *SQLiteFSMSnapshot) Release()
Release is called when a snapshot can be dismissed, so any resources and locks can be removed.
Source Files