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lock.go
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lock.go
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package db
import (
"fmt"
"hash/crc32"
"strconv"
"strings"
"sync"
"code.cloudfoundry.org/lager"
)
const (
LockTypeResourceChecking = iota
LockTypeResourceTypeChecking
LockTypeBuildTracking
LockTypePipelineScheduling
LockTypeResourceCheckingForJob
LockTypeBatch
)
func buildTrackingLockID(buildID int) LockID {
return LockID{LockTypeBuildTracking, buildID}
}
func resourceCheckingLockID(resourceID int) LockID {
return LockID{LockTypeResourceChecking, resourceID}
}
func resourceTypeCheckingLockID(resourceTypeID int) LockID {
return LockID{LockTypeResourceTypeChecking, resourceTypeID}
}
func pipelineSchedulingLockLockID(pipelineID int) LockID {
return LockID{LockTypePipelineScheduling, pipelineID}
}
func resourceCheckingForJobLockID(jobID int) LockID {
return LockID{LockTypeResourceCheckingForJob, jobID}
}
func taskLockID(taskName string) LockID {
return LockID{LockTypeBatch, lockIDFromString(taskName)}
}
//go:generate counterfeiter . LockFactory
type LockFactory interface {
NewLock(logger lager.Logger, ids LockID) Lock
}
type lockFactory struct {
db LockDB
locks lockRepo
acquireMutex *sync.Mutex
}
func NewLockFactory(conn *RetryableConn) LockFactory {
return &lockFactory{
db: &lockDB{
conn: conn,
mutex: &sync.Mutex{},
},
locks: lockRepo{
locks: map[string]bool{},
mutex: &sync.Mutex{},
},
acquireMutex: &sync.Mutex{},
}
}
func NewTestLockFactory(db LockDB) LockFactory {
return &lockFactory{
db: db,
locks: lockRepo{
locks: map[string]bool{},
mutex: &sync.Mutex{},
},
acquireMutex: &sync.Mutex{},
}
}
func (f *lockFactory) NewLock(logger lager.Logger, id LockID) Lock {
return &lock{
logger: logger,
db: f.db,
id: id,
locks: f.locks,
acquireMutex: f.acquireMutex,
}
}
//go:generate counterfeiter . Lock
type Lock interface {
Acquire() (bool, error)
Release() error
AfterRelease(func() error)
}
//go:generate counterfeiter . LockDB
type LockDB interface {
Acquire(id LockID) (bool, error)
Release(id LockID) error
}
type lock struct {
id LockID
logger lager.Logger
db LockDB
locks lockRepo
acquireMutex *sync.Mutex
afterRelease func() error
}
func (l *lock) Acquire() (bool, error) {
l.acquireMutex.Lock()
defer l.acquireMutex.Unlock()
logger := l.logger.Session("acquire", lager.Data{"id": l.id})
if l.locks.IsRegistered(l.id) {
logger.Debug("already-registered")
return false, nil
}
acquired, err := l.db.Acquire(l.id)
if err != nil {
logger.Debug("failed-to-register-in-db")
return false, err
}
if !acquired {
return false, err
}
logger.Debug("registering-in-repo")
l.locks.Register(l.id)
return true, nil
}
func (l *lock) Release() error {
logger := l.logger.Session("release", lager.Data{"id": l.id})
logger.Debug("releasing-in-db")
l.db.Release(l.id)
logger.Debug("unregistering-from-repo")
l.locks.Unregister(l.id)
if l.afterRelease != nil {
logger.Debug("running-after-release")
return l.afterRelease()
}
return nil
}
func (l *lock) AfterRelease(afterReleaseFunc func() error) {
l.afterRelease = afterReleaseFunc
}
type lockDB struct {
conn *RetryableConn
mutex *sync.Mutex
}
func (db *lockDB) Acquire(id LockID) (bool, error) {
db.mutex.Lock()
defer db.mutex.Unlock()
var acquired bool
err := db.conn.QueryRow(`SELECT pg_try_advisory_lock(`+id.toDBParams()+`)`, id.toDBArgs()...).Scan(&acquired)
if err != nil {
return false, err
}
return acquired, nil
}
func (db *lockDB) Release(id LockID) error {
db.mutex.Lock()
defer db.mutex.Unlock()
_, err := db.conn.Exec(`SELECT pg_advisory_unlock(`+id.toDBParams()+`)`, id.toDBArgs()...)
return err
}
type lockRepo struct {
locks map[string]bool
mutex *sync.Mutex
}
func (lr lockRepo) IsRegistered(id LockID) bool {
lr.mutex.Lock()
defer lr.mutex.Unlock()
if _, ok := lr.locks[id.toKey()]; ok {
return true
}
return false
}
func (lr lockRepo) Register(id LockID) {
lr.mutex.Lock()
defer lr.mutex.Unlock()
lr.locks[id.toKey()] = true
}
func (lr lockRepo) Unregister(id LockID) {
lr.mutex.Lock()
defer lr.mutex.Unlock()
delete(lr.locks, id.toKey())
}
type LockID []int
func (l LockID) toKey() string {
s := []string{}
for i := range l {
s = append(s, strconv.Itoa(l[i]))
}
return strings.Join(s, "+")
}
func (l LockID) toDBParams() string {
s := []string{}
for i := range l {
s = append(s, fmt.Sprintf("$%d", i+1))
}
return strings.Join(s, ",")
}
func (l LockID) toDBArgs() []interface{} {
result := []interface{}{}
for i := range l {
result = append(result, l[i])
}
return result
}
func lockIDFromString(taskName string) int {
return int(int32(crc32.ChecksumIEEE([]byte(taskName))))
}