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sqlite3_store.go
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sqlite3_store.go
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package raftsqlite3
import (
"errors"
"database/sql"
"fmt"
"log"
"math"
"os"
"strings"
"time"
"github.com/mattn/go-sqlite3"
"github.com/hashicorp/raft"
)
const (
tag = "raftsqlite3"
// Table names we perform transactions in
dbLogs = "logs"
dbConf = "conf"
)
var (
// An error indicating a given key does not exist
ErrKeyNotFound = errors.New("not found")
)
// Sqlite3Store provides access to sqlite3 for Raft to store and retrieve
// log entries. It also provides key/value storage, and can be used as
// a LogStore and StableStore.
type Sqlite3Store struct {
// db is the underlying handle to the db.
db *sql.DB
logger *log.Logger
}
func NewSqlite3Store(dataSourceName string) (*Sqlite3Store, error) {
return New(dataSourceName)
}
// New uses the supplied dataSourceName to open the sqlite3 and prepare it for use as a raft backend.
func New(dataSourceName string) (*Sqlite3Store, error) {
logger := log.New(os.Stderr, "", log.LstdFlags)
if strings.Index(dataSourceName, "?") == -1 {
const extra = "_busy_timeout=30000&_journal_mode=WAL"//"&_synchronous=NORMAL"
dataSourceName = fmt.Sprintf("%s?%s", dataSourceName, extra)
}
// Try to open and connect
logger.Printf("[INFO ] %s: Open %s", tag, dataSourceName)
db, err := sql.Open("sqlite3", dataSourceName)
if err != nil {
return nil, err
}
// Create the new store
store := &Sqlite3Store{
db: db,
logger: logger,
}
// If the store was opened read-only, don't try and create tables
readOnly, err := store.readOnly()
if err != nil {
store.Close()
return nil, err
}
if !readOnly {
// Set up our buckets
if err := store.initialize(); err != nil {
store.Close()
return nil, err
}
}
return store, nil
}
// readOnly returns true if the open store is in query_only mode [this can be
// useful to tools that want to examine the log]
func (s *Sqlite3Store) readOnly() (bool, error) {
readOnly := true
row := s.db.QueryRow("pragma query_only")
err := row.Scan(&readOnly)
return readOnly, err
}
// initialize is used to set up all of the tables.
func (s *Sqlite3Store) initialize() error {
tx, err := s.db.Begin()
if err != nil {
return err
}
defer func(){
if err != nil {
tx.Rollback()
return
}
if m := recover(); m != nil{
tx.Rollback()
err = fmt.Errorf("%s", m)
}
}()
// Create all the tables
query := fmt.Sprintf("create table if not exists %s(id integer not null primary key, value blob)", dbLogs)
if _, err := tx.Exec(query); err != nil {
return err
}
query = fmt.Sprintf("create table if not exists %s(id blob not null primary key, value blob)", dbConf)
if _, err := tx.Exec(query); err != nil {
return err
}
return tx.Commit()
}
// Close is used to gracefully close the DB connection.
func (s *Sqlite3Store) Close() error {
if s.db == nil {
return nil
}
return s.db.Close()
}
// FirstIndex returns the first known index from the Raft log.
func (s *Sqlite3Store) FirstIndex() (uint64, error) {
query := fmt.Sprintf("select id from %s order by id asc limit 1", dbLogs)
stmt, err := s.db.Prepare(query)
if err != nil {
return 0, err
}
defer stmt.Close()
var first uint64
row := stmt.QueryRow()
err = row.Scan(&first)
if err == sql.ErrNoRows {
return 0, nil
}
return first, err
}
// LastIndex returns the last known index from the Raft log.
func (s *Sqlite3Store) LastIndex() (uint64, error) {
query := fmt.Sprintf("select id from %s order by id desc limit 1", dbLogs)
stmt, err := s.db.Prepare(query)
if err != nil {
return 0, err
}
defer stmt.Close()
var last uint64
row := stmt.QueryRow()
err = row.Scan(&last)
if err == sql.ErrNoRows {
return 0, nil
}
return last, err
}
// GetLog is used to retrieve a log from sqlite3 at a given index.
func (s *Sqlite3Store) GetLog(idx uint64, log *raft.Log) error {
query := fmt.Sprintf("select value from %s where id = ?", dbLogs)
stmt, err := s.db.Prepare(query)
if err != nil {
return err
}
defer stmt.Close()
var val []byte
row := stmt.QueryRow(idx)
err = row.Scan(&val)
if err == sql.ErrNoRows {
return raft.ErrLogNotFound
}
return decodeMsgPack(val, log)
}
// StoreLog is used to store a single raft log
func (s *Sqlite3Store) StoreLog(log *raft.Log) error {
return s.StoreLogs([]*raft.Log{log})
}
// StoreLogs is used to store a set of raft logs
func (s *Sqlite3Store) StoreLogs(logs []*raft.Log) (err error) {
// Try to do when busy
// @since 2019-06-11 little-pan
for {
if err = s.doStoreLogs(logs); err != nil {
if s.waitIfBusy("StoreLogs()", err, 100 * time.Millisecond) {
continue
}
return err
}
return nil
}
}
func (s *Sqlite3Store) doStoreLogs(logs []*raft.Log) (err error) {
tx, err := s.db.Begin()
if err != nil {
return
}
defer func(){
if err != nil {
tx.Rollback()
return
}
if m := recover(); m != nil{
tx.Rollback()
err = fmt.Errorf("%s", m)
}
}()
query := fmt.Sprintf("insert into %s(id, value)values(?, ?)", dbLogs)
stmt, err := tx.Prepare(query)
if err != nil {
return err
}
defer stmt.Close()
for _, log := range logs {
key := log.Index
val, err := encodeMsgPack(log)
if err != nil {
return err
}
if _, err = stmt.Exec(key, val.Bytes()) ; err != nil {
return err
}
}
return tx.Commit()
}
// DeleteRange is used to delete logs within a given range inclusively.
func (s *Sqlite3Store) DeleteRange(min, max uint64) error {
// Delete range by batch for database locked issue
// @since 2019-06-11 little-pan
a, batch := min, uint64(999)
b := uint64(math.Min(float64(a + batch), float64(max - a + uint64(1))))
for {
if err := s.doDeleteRange(a, b); err != nil {
if s.waitIfBusy("DeleteRange()", err, 250 * time.Millisecond) {
continue
}
return err
}
a = b + uint64(1)
if a > max {
return nil
}
b += uint64(math.Min(float64(a + batch), float64(max - a + uint64(1))))
}
}
func (s *Sqlite3Store) waitIfBusy(method string, err error, sleep time.Duration) bool {
e := err.(sqlite3.Error)
if e.Code == sqlite3.ErrLocked || e.Code == sqlite3.ErrBusy {
// Try to do again when busy
log.Printf("[WARN ] %s: %s %s, sleep %s then retry", tag, method, err, sleep)
time.Sleep(sleep)
return true
}
return false
}
func (s *Sqlite3Store) doDeleteRange(min, max uint64) error {
query := fmt.Sprintf("delete from %s where id >= ? and id <= ?", dbLogs)
stmt, err := s.db.Prepare(query)
if err != nil {
return err
}
defer stmt.Close()
_, err = stmt.Exec(min, max)
return err
}
// Set is used to set a key/value set outside of the raft log
func (s *Sqlite3Store) Set(k, v []byte) error {
query := fmt.Sprintf("replace into %s(id, value)values(?, ?)", dbConf)
stmt, err := s.db.Prepare(query)
if err != nil {
return err
}
defer stmt.Close()
if _, err := stmt.Exec(k, v); err != nil {
return err
}
return nil
}
// Get is used to retrieve a value from the k/v store by key
func (s *Sqlite3Store) Get(k []byte) ([]byte, error) {
query := fmt.Sprintf("select value from %s where id = ?", dbConf)
stmt, err := s.db.Prepare(query)
if err != nil {
return nil, err
}
defer stmt.Close()
var val []byte
row := stmt.QueryRow(k)
err = row.Scan(&val)
if err == sql.ErrNoRows {
return nil, ErrKeyNotFound
}
if err != nil {
return nil, err
}
return append([]byte(nil), val...), nil
}
// SetUint64 is like Set, but handles uint64 values
func (s *Sqlite3Store) SetUint64(key []byte, val uint64) error {
return s.Set(key, uint64ToBytes(val))
}
// GetUint64 is like Get, but handles uint64 values
func (s *Sqlite3Store) GetUint64(key []byte) (uint64, error) {
val, err := s.Get(key)
if err != nil {
return 0, err
}
return bytesToUint64(val), nil
}