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|
package tntengine
import (
"context"
"errors"
"sync"
"time"
"github.com/FZambia/tarantool"
)
type ConnectionMode int
const (
ConnectionModeSingleInstance ConnectionMode = 0
ConnectionModeLeaderFollower ConnectionMode = 1
ConnectionModeLeaderFollowerRaft ConnectionMode = 2
)
type MultiConnection struct {
opts MultiOpts
leaderMu sync.RWMutex
leaderAddr string
conns map[string]*tarantool.Connection
closeCh chan struct{}
closeOnce sync.Once
}
type MultiOpts struct {
ConnectionMode ConnectionMode
LeaderCheckInterval time.Duration
}
func Connect(addrs []string, opts tarantool.Opts, multiOpts MultiOpts) (*MultiConnection, error) {
conns, err := getConns(addrs, opts)
if err != nil {
return nil, err
}
mc := &MultiConnection{
opts: multiOpts,
conns: conns,
closeCh: make(chan struct{}),
}
leaderFound := mc.checkLeaderOnce()
if !leaderFound {
return nil, ErrNoLeader
}
go mc.checkLeader()
return mc, nil
}
var ErrNoLeader = errors.New("no leader")
func (c *MultiConnection) NewLeaderConn(opts tarantool.Opts) (*tarantool.Connection, error) {
c.leaderMu.RLock()
if c.leaderAddr == "" {
c.leaderMu.RUnlock()
return nil, ErrNoLeader
}
c.leaderMu.RUnlock()
return tarantool.Connect(c.leaderAddr, opts)
}
func (c *MultiConnection) LeaderChanged() {
if c.opts.ConnectionMode == ConnectionModeSingleInstance {
return
}
c.leaderMu.Lock()
defer c.leaderMu.Unlock()
c.leaderAddr = ""
}
func (c *MultiConnection) LeaderConn() (*tarantool.Connection, error) {
c.leaderMu.RLock()
defer c.leaderMu.RUnlock()
if c.leaderAddr != "" {
return c.conns[c.leaderAddr], nil
}
return nil, ErrNoLeader
}
func getConns(addrs []string, opts tarantool.Opts) (map[string]*tarantool.Connection, error) {
conns := map[string]*tarantool.Connection{}
var wg sync.WaitGroup
var connsMu sync.Mutex
var firstErr error
var numErrors int
wg.Add(len(addrs))
for _, addr := range addrs {
go func(addr string) {
defer wg.Done()
conn, err := tarantool.Connect(addr, opts)
if err != nil {
connsMu.Lock()
if firstErr == nil {
firstErr = err
}
numErrors++
connsMu.Unlock()
return
}
connsMu.Lock()
conns[addr] = conn
connsMu.Unlock()
}(addr)
}
wg.Wait()
if numErrors == len(addrs) {
return nil, firstErr
}
return conns, nil
}
func (c *MultiConnection) checkLeader() {
if c.opts.ConnectionMode == ConnectionModeSingleInstance {
return
}
checkInterval := c.opts.LeaderCheckInterval
if checkInterval == 0 {
checkInterval = time.Second
}
for {
select {
case <-c.closeCh:
return
case <-time.After(checkInterval):
c.checkLeaderOnce()
}
}
}
func (c *MultiConnection) IsLeader(conn *tarantool.Connection) (bool, error) {
if c.opts.ConnectionMode == ConnectionModeSingleInstance {
return true, nil
}
ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
defer cancel()
leaderCheck := "return box.info.ro == false"
if c.opts.ConnectionMode == ConnectionModeLeaderFollowerRaft {
leaderCheck = "return box.info.election.state == 'leader'"
}
resp, err := conn.ExecContext(ctx, tarantool.Eval(leaderCheck, []interface{}{}))
if err != nil {
return false, err
}
if len(resp.Data) < 1 {
return false, errors.New("unexpected leader check result")
}
isLeader, ok := resp.Data[0].(bool)
if !ok {
return false, errors.New("malformed leader check result")
}
return isLeader, nil
}
func (c *MultiConnection) checkLeaderOnce() bool {
for addr, conn := range c.conns {
if len(c.conns) == 1 {
c.leaderAddr = addr
return true
}
isLeader, err := c.IsLeader(conn)
if err != nil {
continue
}
if isLeader {
c.leaderMu.Lock()
c.leaderAddr = addr
c.leaderMu.Unlock()
return true
}
}
return false
}
func (c *MultiConnection) Close() error {
c.closeOnce.Do(func() {
close(c.closeCh)
for _, conn := range c.conns {
_ = conn.Close()
}
})
return nil
}
|
