minio/cmd/shared-lock.go
2022-12-05 11:18:50 -08:00

86 lines
2.2 KiB
Go

// Copyright (c) 2015-2022 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package cmd
import (
"context"
"time"
)
var sharedLockTimeout = newDynamicTimeoutWithOpts(dynamicTimeoutOpts{
timeout: 30 * time.Second,
minimum: 10 * time.Second,
retryInterval: time.Minute,
})
type sharedLock struct {
lockContext chan LockContext
}
func (ld sharedLock) backgroundRoutine(ctx context.Context, objAPI ObjectLayer, lockName string) {
for {
locker := objAPI.NewNSLock(minioMetaBucket, lockName)
lkctx, err := locker.GetLock(ctx, sharedLockTimeout)
if err != nil {
continue
}
keepLock:
for {
select {
case <-ctx.Done():
return
case <-lkctx.Context().Done():
// The context of the lock is canceled, this can happen
// if one lock lost quorum due to cluster instability
// in that case, try to lock again.
break keepLock
case ld.lockContext <- lkctx:
// Send the lock context to anyone asking for it
}
}
}
}
func mergeContext(ctx1, ctx2 context.Context) (context.Context, context.CancelFunc) {
ctx, cancel := context.WithCancel(context.Background())
go func() {
select {
case <-ctx1.Done():
case <-ctx2.Done():
}
cancel()
}()
return ctx, cancel
}
func (ld sharedLock) GetLock(ctx context.Context) (context.Context, context.CancelFunc) {
l := <-ld.lockContext
return mergeContext(l.Context(), ctx)
}
func newSharedLock(ctx context.Context, objAPI ObjectLayer, lockName string) *sharedLock {
l := &sharedLock{
lockContext: make(chan LockContext),
}
go l.backgroundRoutine(ctx, objAPI, lockName)
return l
}