minio/cmd/namespace-lock.go
2019-11-19 17:42:27 -08:00

288 lines
7.7 KiB
Go

/*
* MinIO Cloud Storage, (C) 2016, 2017, 2018, 2019 MinIO, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cmd
import (
"context"
"errors"
pathutil "path"
"runtime"
"strings"
"sync"
"fmt"
"time"
"github.com/minio/lsync"
"github.com/minio/minio/cmd/logger"
"github.com/minio/minio/pkg/dsync"
)
// local lock servers
var globalLockServers = make(map[Endpoint]*localLocker)
// RWLocker - locker interface to introduce GetRLock, RUnlock.
type RWLocker interface {
GetLock(timeout *dynamicTimeout) (timedOutErr error)
Unlock()
GetRLock(timeout *dynamicTimeout) (timedOutErr error)
RUnlock()
}
// newNSLock - return a new name space lock map.
func newNSLock(isDistXL bool) *nsLockMap {
nsMutex := nsLockMap{
isDistXL: isDistXL,
}
if isDistXL {
return &nsMutex
}
nsMutex.lockMap = make(map[nsParam]*nsLock)
return &nsMutex
}
// nsParam - carries name space resource.
type nsParam struct {
volume string
path string
}
// nsLock - provides primitives for locking critical namespace regions.
type nsLock struct {
*lsync.LRWMutex
ref uint
}
// nsLockMap - namespace lock map, provides primitives to Lock,
// Unlock, RLock and RUnlock.
type nsLockMap struct {
// Indicates if namespace is part of a distributed setup.
isDistXL bool
lockMap map[nsParam]*nsLock
lockMapMutex sync.RWMutex
}
// Lock the namespace resource.
func (n *nsLockMap) lock(ctx context.Context, volume, path string, lockSource, opsID string, readLock bool, timeout time.Duration) (locked bool) {
var nsLk *nsLock
n.lockMapMutex.Lock()
param := nsParam{volume, path}
nsLk, found := n.lockMap[param]
if !found {
n.lockMap[param] = &nsLock{
LRWMutex: lsync.NewLRWMutex(ctx),
ref: 1,
}
nsLk = n.lockMap[param]
} else {
// Update ref count here to avoid multiple races.
nsLk.ref++
}
n.lockMapMutex.Unlock()
// Locking here will block (until timeout).
if readLock {
locked = nsLk.GetRLock(opsID, lockSource, timeout)
} else {
locked = nsLk.GetLock(opsID, lockSource, timeout)
}
if !locked { // We failed to get the lock
// Decrement ref count since we failed to get the lock
n.lockMapMutex.Lock()
nsLk.ref--
if nsLk.ref == 0 {
// Remove from the map if there are no more references.
delete(n.lockMap, param)
}
n.lockMapMutex.Unlock()
}
return
}
// Unlock the namespace resource.
func (n *nsLockMap) unlock(volume, path string, readLock bool) {
param := nsParam{volume, path}
n.lockMapMutex.RLock()
nsLk, found := n.lockMap[param]
n.lockMapMutex.RUnlock()
if !found {
return
}
if readLock {
nsLk.RUnlock()
} else {
nsLk.Unlock()
}
n.lockMapMutex.Lock()
if nsLk.ref == 0 {
logger.LogIf(context.Background(), errors.New("Namespace reference count cannot be 0"))
} else {
nsLk.ref--
if nsLk.ref == 0 {
// Remove from the map if there are no more references.
delete(n.lockMap, param)
}
}
n.lockMapMutex.Unlock()
}
// Lock - locks the given resource for writes, using a previously
// allocated name space lock or initializing a new one.
func (n *nsLockMap) Lock(volume, path, opsID string, timeout time.Duration) (locked bool) {
readLock := false // This is a write lock.
lockSource := getSource() // Useful for debugging
return n.lock(context.Background(), volume, path, lockSource, opsID, readLock, timeout)
}
// Unlock - unlocks any previously acquired write locks.
func (n *nsLockMap) Unlock(volume, path, opsID string) {
readLock := false
n.unlock(volume, path, readLock)
}
// RLock - locks any previously acquired read locks.
func (n *nsLockMap) RLock(volume, path, opsID string, timeout time.Duration) (locked bool) {
readLock := true
lockSource := getSource() // Useful for debugging
return n.lock(context.Background(), volume, path, lockSource, opsID, readLock, timeout)
}
// RUnlock - unlocks any previously acquired read locks.
func (n *nsLockMap) RUnlock(volume, path, opsID string) {
readLock := true
n.unlock(volume, path, readLock)
}
// dsync's distributed lock instance.
type distLockInstance struct {
rwMutex *dsync.DRWMutex
volume, path, opsID string
}
// Lock - block until write lock is taken or timeout has occurred.
func (di *distLockInstance) GetLock(timeout *dynamicTimeout) (timedOutErr error) {
lockSource := getSource()
start := UTCNow()
if !di.rwMutex.GetLock(di.opsID, lockSource, timeout.Timeout()) {
timeout.LogFailure()
return OperationTimedOut{Path: di.path}
}
timeout.LogSuccess(UTCNow().Sub(start))
return nil
}
// Unlock - block until write lock is released.
func (di *distLockInstance) Unlock() {
di.rwMutex.Unlock()
}
// RLock - block until read lock is taken or timeout has occurred.
func (di *distLockInstance) GetRLock(timeout *dynamicTimeout) (timedOutErr error) {
lockSource := getSource()
start := UTCNow()
if !di.rwMutex.GetRLock(di.opsID, lockSource, timeout.Timeout()) {
timeout.LogFailure()
return OperationTimedOut{Path: di.path}
}
timeout.LogSuccess(UTCNow().Sub(start))
return nil
}
// RUnlock - block until read lock is released.
func (di *distLockInstance) RUnlock() {
di.rwMutex.RUnlock()
}
// localLockInstance - frontend/top-level interface for namespace locks.
type localLockInstance struct {
ctx context.Context
ns *nsLockMap
volume, path, opsID string
}
// NewNSLock - returns a lock instance for a given volume and
// path. The returned lockInstance object encapsulates the nsLockMap,
// volume, path and operation ID.
func (n *nsLockMap) NewNSLock(ctx context.Context, lockersFn func() []dsync.NetLocker, volume, path string) RWLocker {
opsID := mustGetUUID()
if n.isDistXL {
return &distLockInstance{dsync.NewDRWMutex(ctx, pathJoin(volume, path), &dsync.Dsync{
GetLockersFn: lockersFn,
}), volume, path, opsID}
}
return &localLockInstance{ctx, n, volume, path, opsID}
}
// Lock - block until write lock is taken or timeout has occurred.
func (li *localLockInstance) GetLock(timeout *dynamicTimeout) (timedOutErr error) {
lockSource := getSource()
start := UTCNow()
readLock := false
if !li.ns.lock(li.ctx, li.volume, li.path, lockSource, li.opsID, readLock, timeout.Timeout()) {
timeout.LogFailure()
return OperationTimedOut{Path: li.path}
}
timeout.LogSuccess(UTCNow().Sub(start))
return
}
// Unlock - block until write lock is released.
func (li *localLockInstance) Unlock() {
readLock := false
li.ns.unlock(li.volume, li.path, readLock)
}
// RLock - block until read lock is taken or timeout has occurred.
func (li *localLockInstance) GetRLock(timeout *dynamicTimeout) (timedOutErr error) {
lockSource := getSource()
start := UTCNow()
readLock := true
if !li.ns.lock(li.ctx, li.volume, li.path, lockSource, li.opsID, readLock, timeout.Timeout()) {
timeout.LogFailure()
return OperationTimedOut{Path: li.path}
}
timeout.LogSuccess(UTCNow().Sub(start))
return
}
// RUnlock - block until read lock is released.
func (li *localLockInstance) RUnlock() {
readLock := true
li.ns.unlock(li.volume, li.path, readLock)
}
func getSource() string {
var funcName string
pc, filename, lineNum, ok := runtime.Caller(2)
if ok {
filename = pathutil.Base(filename)
funcName = strings.TrimPrefix(runtime.FuncForPC(pc).Name(),
"github.com/minio/minio/cmd.")
} else {
filename = "<unknown>"
lineNum = 0
}
return fmt.Sprintf("[%s:%d:%s()]", filename, lineNum, funcName)
}