mirror of
https://github.com/seaweedfs/seaweedfs.git
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139 lines
3.3 KiB
Go
139 lines
3.3 KiB
Go
package weed_server
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import (
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"context"
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"fmt"
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"math/rand"
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"sync"
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"time"
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"github.com/chrislusf/seaweedfs/weed/pb/master_pb"
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)
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/*
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How exclusive lock works?
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-----------
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Shell
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------
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When shell lock,
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* lease an admin token (lockTime, token)
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* start a goroutine to renew the admin token periodically
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When shell unlock
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* stop the renewal goroutine
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* sends a release lock request
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Master
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------
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Master maintains:
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* randomNumber
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* lastLockTime
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When master receives the lease/renew request from shell
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If lastLockTime still fresh {
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if is a renew and token is valid {
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// for renew
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generate the randomNumber => token
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return
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}
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refuse
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return
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} else {
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// for fresh lease request
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generate the randomNumber => token
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return
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}
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When master receives the release lock request from shell
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set the lastLockTime to zero
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The volume server does not need to verify.
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This makes the lock/unlock optional, similar to what golang code usually does.
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*/
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const (
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LockDuration = 10 * time.Second
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)
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type AdminLock struct {
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accessSecret int64
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accessLockTime time.Time
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}
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type AdminLocks struct {
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locks map[string]*AdminLock
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sync.RWMutex
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}
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func NewAdminLocks() *AdminLocks {
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return &AdminLocks{
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locks: make(map[string]*AdminLock),
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}
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}
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func (locks *AdminLocks) isLocked(lockName string) bool {
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locks.RLock()
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defer locks.RUnlock()
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adminLock, found := locks.locks[lockName]
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if !found {
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return false
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}
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return adminLock.accessLockTime.Add(LockDuration).After(time.Now())
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}
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func (locks *AdminLocks) isValidToken(lockName string, ts time.Time, token int64) bool {
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locks.RLock()
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defer locks.RUnlock()
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adminLock, found := locks.locks[lockName]
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if !found {
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return false
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}
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return adminLock.accessLockTime.Equal(ts) && adminLock.accessSecret == token
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}
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func (locks *AdminLocks) generateToken(lockName string) (ts time.Time, token int64) {
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locks.Lock()
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defer locks.Unlock()
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lock := &AdminLock{
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accessSecret: rand.Int63(),
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accessLockTime: time.Now(),
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}
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locks.locks[lockName] = lock
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return lock.accessLockTime, lock.accessSecret
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}
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func (locks *AdminLocks) deleteLock(lockName string) {
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locks.Lock()
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defer locks.Unlock()
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delete(locks.locks, lockName)
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}
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func (ms *MasterServer) LeaseAdminToken(ctx context.Context, req *master_pb.LeaseAdminTokenRequest) (*master_pb.LeaseAdminTokenResponse, error) {
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resp := &master_pb.LeaseAdminTokenResponse{}
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if ms.adminLocks.isLocked(req.LockName) {
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if req.PreviousToken != 0 && ms.adminLocks.isValidToken(req.LockName, time.Unix(0, req.PreviousLockTime), req.PreviousToken) {
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// for renew
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ts, token := ms.adminLocks.generateToken(req.LockName)
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resp.Token, resp.LockTsNs = token, ts.UnixNano()
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return resp, nil
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}
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// refuse since still locked
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return resp, fmt.Errorf("already locked")
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}
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// for fresh lease request
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ts, token := ms.adminLocks.generateToken(req.LockName)
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resp.Token, resp.LockTsNs = token, ts.UnixNano()
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return resp, nil
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}
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func (ms *MasterServer) ReleaseAdminToken(ctx context.Context, req *master_pb.ReleaseAdminTokenRequest) (*master_pb.ReleaseAdminTokenResponse, error) {
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resp := &master_pb.ReleaseAdminTokenResponse{}
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if ms.adminLocks.isValidToken(req.LockName, time.Unix(0, req.PreviousLockTime), req.PreviousToken) {
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ms.adminLocks.deleteLock(req.LockName)
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}
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return resp, nil
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}
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