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// Package store provides a distributed SQLite instance.
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//
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// Distributed consensus is provided via the Raft algorithm.
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package store
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import (
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"bytes"
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"encoding/binary"
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"io/ioutil"
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"log"
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"net"
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"os"
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"path/filepath"
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"sync"
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"time"
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"github.com/hashicorp/raft"
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"github.com/hashicorp/raft-boltdb"
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sql "github.com/otoolep/rqlite/db"
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mux "github.com/otoolep/rqlite/tcp"
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)
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var (
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// ErrFieldsRequired is returned when a node attempts to execute a leader-only
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// operation.
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ErrNotLeader = errors.New("not leader")
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)
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const (
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retainSnapshotCount = 2
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raftTimeout = 10 * time.Second
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sqliteFile = "db.sqlite"
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leaderWaitDelay = 100 * time.Millisecond
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appliedWaitDelay = 100 * time.Millisecond
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)
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const (
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muxRaftHeader = 1 // Raft consensus communications
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muxClusterHeader = 2 // Cluster communications
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)
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// commandType are commands that affect the state of the cluster, and must go through Raft.
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type commandType int
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const (
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execute commandType = iota // Commands which modify the database.
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query // Commands which query the database.
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peer // Commands that modify peers map.
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)
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type command struct {
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Typ commandType `json:"typ,omitempty"`
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Sub json.RawMessage `json:"sub,omitempty"`
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}
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func newCommand(t commandType, d interface{}) (*command, error) {
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b, err := json.Marshal(d)
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if err != nil {
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return nil, err
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}
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return &command{
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Typ: t,
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Sub: b,
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}, nil
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}
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// databaseSub is a command sub which involves interaction with the database.
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type databaseSub struct {
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Tx bool `json:"tx,omitempty"`
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Queries []string `json:"queries,omitempty"`
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Timings bool `json:"timings,omitempty"`
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}
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// peersSub is a command which sets the API address for a Raft address.
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type peersSub map[string]string
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// ConsistencyLevel represents the available read consistency levels.
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type ConsistencyLevel int
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const (
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None ConsistencyLevel = iota
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Weak
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Strong
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)
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// clusterMeta represents cluster meta which must be kept in consensus.
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type clusterMeta struct {
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APIPeers map[string]string // Map from Raft address to API address
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}
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func newClusterMeta() *clusterMeta {
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return &clusterMeta{
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APIPeers: make(map[string]string),
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}
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}
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// DBConfig represents the configuration of the underlying SQLite database.
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type DBConfig struct {
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DSN string // Any custom DSN
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Memory bool // Whether the database is in-memory only.
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}
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// NewDBConfig returns a new DB config instance.
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func NewDBConfig(dsn string, memory bool) *DBConfig {
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return &DBConfig{DSN: dsn, Memory: memory}
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}
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// Store is a SQLite database, where all changes are made via Raft consensus.
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type Store struct {
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raftDir string
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raftBind string
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mux *mux.Mux
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mu sync.RWMutex // Sync access between queries and snapshots.
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ln *networkLayer // Raft network between nodes.
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raft *raft.Raft // The consensus mechanism.
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dbConf *DBConfig // SQLite database config.
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dbPath string // Path to underlying SQLite file, if not in-memory.
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db *sql.DB // The underlying SQLite store.
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metaMu sync.RWMutex
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meta *clusterMeta
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logger *log.Logger
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}
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// New returns a new Store.
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func New(dbConf *DBConfig, dir, bind string) *Store {
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return &Store{
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raftDir: dir,
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raftBind: bind,
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mux: mux.NewMux(),
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dbConf: dbConf,
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dbPath: filepath.Join(dir, sqliteFile),
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meta: newClusterMeta(),
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logger: log.New(os.Stderr, "[store] ", log.LstdFlags),
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}
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}
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// Open opens the store. If enableSingle is set, and there are no existing peers,
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// then this node becomes the first node, and therefore leader, of the cluster.
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func (s *Store) Open(enableSingle bool) error {
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if err := os.MkdirAll(s.raftDir, 0755); err != nil {
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return err
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}
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// Create the database. Unless it's a memory-based database, it must be deleted
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var db *sql.DB
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var err error
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if !s.dbConf.Memory {
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// as it will be rebuilt from (possibly) a snapshot and committed log entries.
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if err := os.Remove(s.dbPath); err != nil && !os.IsNotExist(err) {
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return err
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}
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db, err = sql.OpenWithDSN(s.dbPath, s.dbConf.DSN)
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if err != nil {
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return err
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}
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s.logger.Println("SQLite database opened at", s.dbPath)
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} else {
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db, err = sql.OpenInMemoryWithDSN(s.dbConf.DSN)
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if err != nil {
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return err
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}
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s.logger.Println("SQLite in-memory database opened")
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}
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s.db = db
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// Setup Raft configuration.
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config := raft.DefaultConfig()
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// Check for any existing peers.
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peers, err := readPeersJSON(filepath.Join(s.raftDir, "peers.json"))
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if err != nil {
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return err
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}
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// Allow the node to entry single-mode, potentially electing itself, if
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// explicitly enabled and there is only 1 node in the cluster already.
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if enableSingle && len(peers) <= 1 {
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s.logger.Println("enabling single-node mode")
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config.EnableSingleNode = true
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config.DisableBootstrapAfterElect = false
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}
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// Set up TCP communication between nodes.
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ln, err := net.Listen("tcp", s.raftBind)
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if err != nil {
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return err
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}
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go s.mux.Serve(ln)
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// Setup Raft communication.
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s.ln = newNetworkLayer(s.mux.Listen(muxRaftHeader), ln.Addr())
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transport := raft.NewNetworkTransport(s.ln, 3, 10*time.Second, os.Stderr)
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// Create peer storage.
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peerStore := raft.NewJSONPeers(s.raftDir, transport)
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// Create the snapshot store. This allows Raft to truncate the log.
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snapshots, err := raft.NewFileSnapshotStore(s.raftDir, retainSnapshotCount, os.Stderr)
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if err != nil {
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return fmt.Errorf("file snapshot store: %s", err)
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}
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// Create the log store and stable store.
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logStore, err := raftboltdb.NewBoltStore(filepath.Join(s.raftDir, "raft.db"))
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if err != nil {
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return fmt.Errorf("new bolt store: %s", err)
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}
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// Instantiate the Raft system.
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ra, err := raft.NewRaft(config, s, logStore, logStore, snapshots, peerStore, transport)
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if err != nil {
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return fmt.Errorf("new raft: %s", err)
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}
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s.raft = ra
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return nil
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}
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// Close closes the store. If wait is true, waits for a graceful shutdown.
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func (s *Store) Close(wait bool) error {
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if err := s.db.Close(); err != nil {
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return err
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}
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f := s.raft.Shutdown()
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if wait {
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if e := f.(raft.Future); e.Error() != nil {
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return e.Error()
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}
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}
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return nil
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}
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// Path returns the path to the store's storage directory.
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func (s *Store) Path() string {
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return s.raftDir
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}
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func (s *Store) Addr() net.Addr {
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return s.ln.Addr()
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}
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// Leader returns the current leader. Returns a blank string if there is
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// no leader.
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func (s *Store) Leader() string {
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return s.raft.Leader()
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}
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// WaitForLeader blocks until a leader is detected, or the timeout expires.
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func (s *Store) WaitForLeader(timeout time.Duration) (string, error) {
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tck := time.NewTicker(leaderWaitDelay)
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defer tck.Stop()
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tmr := time.NewTimer(timeout)
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defer tmr.Stop()
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for {
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select {
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case <-tck.C:
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l := s.Leader()
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if l != "" {
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return l, nil
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}
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case <-tmr.C:
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return "", fmt.Errorf("timeout expired")
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}
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}
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}
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// WaitForAppliedIndex blocks until a given log index has been applied,
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// or the timeout expires.
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func (s *Store) WaitForAppliedIndex(idx uint64, timeout time.Duration) error {
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tck := time.NewTicker(appliedWaitDelay)
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defer tck.Stop()
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tmr := time.NewTimer(timeout)
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defer tmr.Stop()
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for {
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select {
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case <-tck.C:
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if s.raft.AppliedIndex() >= idx {
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return nil
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}
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case <-tmr.C:
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return fmt.Errorf("timeout expired")
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}
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}
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}
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// Stats returns stats for the store.
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func (s *Store) Stats() (map[string]interface{}, error) {
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dbStatus := map[string]interface{}{
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"dns": s.dbConf.DSN,
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"version": sql.DBVersion,
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}
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if !s.dbConf.Memory {
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dbStatus["path"] = s.dbPath
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stat, err := os.Stat(s.dbPath)
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if err != nil {
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return nil, err
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}
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dbStatus["size"] = stat.Size()
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} else {
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dbStatus["path"] = ":memory:"
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}
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status := map[string]interface{}{
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"raft": s.raft.Stats(),
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"addr": s.Addr().String(),
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"leader": s.Leader(),
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"sqlite3": dbStatus,
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}
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return status, nil
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}
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// Execute executes queries that return no rows, but do modify the database.
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func (s *Store) Execute(queries []string, timings, tx bool) ([]*sql.Result, error) {
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if s.raft.State() != raft.Leader {
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return nil, ErrNotLeader
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}
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d := &databaseSub{
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Tx: tx,
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Queries: queries,
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Timings: timings,
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}
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c, err := newCommand(execute, d)
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if err != nil {
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return nil, err
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}
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b, err := json.Marshal(c)
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if err != nil {
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return nil, err
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}
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f := s.raft.Apply(b, raftTimeout)
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if e := f.(raft.Future); e.Error() != nil {
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return nil, e.Error()
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}
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r := f.Response().(*fsmExecuteResponse)
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return r.results, r.error
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}
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// Backup return a consistent snapshot of the underlying database.
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func (s *Store) Backup(leader bool) ([]byte, error) {
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if leader && s.raft.State() != raft.Leader {
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return nil, fmt.Errorf("not leader")
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}
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f, err := ioutil.TempFile("", "rqlilte-bak-")
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if err != nil {
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return nil, err
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}
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f.Close()
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defer os.Remove(f.Name())
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if err := s.db.Backup(f.Name()); err != nil {
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return nil, err
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}
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b, err := ioutil.ReadFile(f.Name())
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if err != nil {
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return nil, err
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}
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return b, nil
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}
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// Query executes queries that return rows, and do not modify the database.
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func (s *Store) Query(queries []string, timings, tx bool, lvl ConsistencyLevel) ([]*sql.Rows, error) {
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// Allow concurrent queries.
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s.mu.RLock()
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defer s.mu.RUnlock()
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if lvl == Strong {
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d := &databaseSub{
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Tx: tx,
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Queries: queries,
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Timings: timings,
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}
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c, err := newCommand(query, d)
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if err != nil {
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return nil, err
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}
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b, err := json.Marshal(c)
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if err != nil {
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return nil, err
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}
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f := s.raft.Apply(b, raftTimeout)
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if e := f.(raft.Future); e.Error() != nil {
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return nil, e.Error()
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}
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r := f.Response().(*fsmQueryResponse)
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|
return r.rows, r.error
|
|
|
|
}
|
|
|
|
|
|
|
|
if lvl == Weak && s.raft.State() != raft.Leader {
|
|
|
|
return nil, ErrNotLeader
|
|
|
|
}
|
|
|
|
|
|
|
|
r, err := s.db.Query(queries, tx, timings)
|
|
|
|
return r, err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Join joins a node, located at addr, to this store. The node must be ready to
|
|
|
|
// respond to Raft communications at that address.
|
|
|
|
func (s *Store) Join(addr string) error {
|
|
|
|
s.logger.Printf("received request to join node at %s", addr)
|
|
|
|
|
|
|
|
f := s.raft.AddPeer(addr)
|
|
|
|
if f.Error() != nil {
|
|
|
|
return f.Error()
|
|
|
|
}
|
|
|
|
s.logger.Printf("node at %s joined successfully", addr)
|
|
|
|
return nil
|
|
|
|
}
|
|
|
|
|
|
|
|
type fsmExecuteResponse struct {
|
|
|
|
results []*sql.Result
|
|
|
|
error error
|
|
|
|
}
|
|
|
|
|
|
|
|
type fsmQueryResponse struct {
|
|
|
|
rows []*sql.Rows
|
|
|
|
error error
|
|
|
|
}
|
|
|
|
|
|
|
|
type fsmGenericResponse struct {
|
|
|
|
error error
|
|
|
|
}
|
|
|
|
|
|
|
|
// Apply applies a Raft log entry to the database.
|
|
|
|
func (s *Store) Apply(l *raft.Log) interface{} {
|
|
|
|
var c command
|
|
|
|
if err := json.Unmarshal(l.Data, &c); err != nil {
|
|
|
|
panic(fmt.Sprintf("failed to unmarshal cluster command: %s", err.Error()))
|
|
|
|
}
|
|
|
|
|
|
|
|
switch c.Typ {
|
|
|
|
case execute, query:
|
|
|
|
var d databaseSub
|
|
|
|
if err := json.Unmarshal(c.Sub, &d); err != nil {
|
|
|
|
return &fsmGenericResponse{error: err}
|
|
|
|
}
|
|
|
|
if c.Typ == execute {
|
|
|
|
r, err := s.db.Execute(d.Queries, d.Tx, d.Timings)
|
|
|
|
return &fsmExecuteResponse{results: r, error: err}
|
|
|
|
}
|
|
|
|
r, err := s.db.Query(d.Queries, d.Tx, d.Timings)
|
|
|
|
return &fsmQueryResponse{rows: r, error: err}
|
|
|
|
case peer:
|
|
|
|
var d peersSub
|
|
|
|
if err := json.Unmarshal(c.Sub, &d); err != nil {
|
|
|
|
return &fsmGenericResponse{error: err}
|
|
|
|
}
|
|
|
|
func() {
|
|
|
|
s.metaMu.Lock()
|
|
|
|
defer s.metaMu.Unlock()
|
|
|
|
for k, v := range d {
|
|
|
|
s.meta.APIPeers[k] = v
|
|
|
|
}
|
|
|
|
}()
|
|
|
|
return &fsmGenericResponse{}
|
|
|
|
default:
|
|
|
|
return &fsmGenericResponse{error: fmt.Errorf("unknown command: %v", c.Typ)}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
// Snapshot returns a snapshot of the database. The caller must ensure that
|
|
|
|
// no transaction is taking place during this call. Hashsicorp Raft guarantees
|
|
|
|
// that this function will not be called concurrently with Apply.
|
|
|
|
//
|
|
|
|
// http://sqlite.org/howtocorrupt.html states it is safe to do this
|
|
|
|
// as long as no transaction is in progress.
|
|
|
|
func (s *Store) Snapshot() (raft.FSMSnapshot, error) {
|
|
|
|
// Ensure only one snapshot can take place at once, and block all queries.
|
|
|
|
s.mu.Lock()
|
|
|
|
defer s.mu.Unlock()
|
|
|
|
|
|
|
|
f, err := ioutil.TempFile("", "rqlilte-snap-")
|
|
|
|
if err != nil {
|
|
|
|
return nil, err
|
|
|
|
}
|
|
|
|
f.Close()
|
|
|
|
defer os.Remove(f.Name())
|
|
|
|
|
|
|
|
if err := s.db.Backup(f.Name()); err != nil {
|
|
|
|
return nil, err
|
|
|
|
}
|
|
|
|
|
|
|
|
fsm := &fsmSnapshot{}
|
|
|
|
fsm.database, err = ioutil.ReadFile(f.Name())
|
|
|
|
if err != nil {
|
|
|
|
log.Printf("Failed to read database for snapshot: %s", err.Error())
|
|
|
|
return nil, err
|
|
|
|
}
|
|
|
|
|
|
|
|
fsm.meta, err = json.Marshal(s.meta)
|
|
|
|
if err != nil {
|
|
|
|
log.Printf("Failed to encode meta for snapshot: %s", err.Error())
|
|
|
|
return nil, err
|
|
|
|
}
|
|
|
|
|
|
|
|
return fsm, nil
|
|
|
|
}
|
|
|
|
|
|
|
|
// Restore restores the node to a previous state.
|
|
|
|
func (s *Store) Restore(rc io.ReadCloser) error {
|
|
|
|
if err := s.db.Close(); err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Get size of database.
|
|
|
|
var sz uint64
|
|
|
|
if err := binary.Read(rc, binary.LittleEndian, &sz); err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Now read in the database file data and restore.
|
|
|
|
database := make([]byte, sz)
|
|
|
|
if _, err := io.ReadFull(rc, database); err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
var db *sql.DB
|
|
|
|
var err error
|
|
|
|
if !s.dbConf.Memory {
|
|
|
|
// Write snapshot over any existing database file.
|
|
|
|
if err := ioutil.WriteFile(s.dbPath, database, 0660); err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Re-open it.
|
|
|
|
db, err = sql.OpenWithDSN(s.dbPath, s.dbConf.DSN)
|
|
|
|
if err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
} else {
|
|
|
|
// In memory. Copy to temporary file, and then load memory from file.
|
|
|
|
f, err := ioutil.TempFile("", "rqlilte-snap-")
|
|
|
|
if err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
f.Close()
|
|
|
|
defer os.Remove(f.Name())
|
|
|
|
|
|
|
|
if err := ioutil.WriteFile(f.Name(), database, 0660); err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Load an in-memory database from the snapshot now on disk.
|
|
|
|
db, err = sql.LoadInMemoryWithDSN(f.Name(), s.dbConf.DSN)
|
|
|
|
if err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
}
|
|
|
|
s.db = db
|
|
|
|
|
|
|
|
// Read remaining bytes, and set to cluster meta.
|
|
|
|
b, err := ioutil.ReadAll(rc)
|
|
|
|
if err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
return func() error {
|
|
|
|
s.metaMu.Lock()
|
|
|
|
defer s.metaMu.Unlock()
|
|
|
|
return json.Unmarshal(b, &s.meta)
|
|
|
|
}()
|
|
|
|
}
|
|
|
|
|
|
|
|
type fsmSnapshot struct {
|
|
|
|
database []byte
|
|
|
|
meta []byte
|
|
|
|
}
|
|
|
|
|
|
|
|
// Persist writes the snapshot to the given sink.
|
|
|
|
func (f *fsmSnapshot) Persist(sink raft.SnapshotSink) error {
|
|
|
|
err := func() error {
|
|
|
|
// Start by writing size of database.
|
|
|
|
b := new(bytes.Buffer)
|
|
|
|
sz := uint64(len(f.database))
|
|
|
|
err := binary.Write(b, binary.LittleEndian, sz)
|
|
|
|
if err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
if _, err := sink.Write(b.Bytes()); err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Next write database to sink.
|
|
|
|
if _, err := sink.Write(f.database); err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Finally write the meta.
|
|
|
|
if _, err := sink.Write(f.meta); err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Close the sink.
|
|
|
|
if err := sink.Close(); err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
return nil
|
|
|
|
}()
|
|
|
|
|
|
|
|
if err != nil {
|
|
|
|
sink.Cancel()
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
return nil
|
|
|
|
}
|
|
|
|
|
|
|
|
// Release is a no-op.
|
|
|
|
func (f *fsmSnapshot) Release() {}
|
|
|
|
|
|
|
|
// readPeersJSON reads the peers from the path.
|
|
|
|
func readPeersJSON(path string) ([]string, error) {
|
|
|
|
b, err := ioutil.ReadFile(path)
|
|
|
|
if err != nil && !os.IsNotExist(err) {
|
|
|
|
return nil, err
|
|
|
|
}
|
|
|
|
|
|
|
|
if len(b) == 0 {
|
|
|
|
return nil, nil
|
|
|
|
}
|
|
|
|
|
|
|
|
var peers []string
|
|
|
|
dec := json.NewDecoder(bytes.NewReader(b))
|
|
|
|
if err := dec.Decode(&peers); err != nil {
|
|
|
|
return nil, err
|
|
|
|
}
|
|
|
|
|
|
|
|
return peers, nil
|
|
|
|
}
|