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minio/cmd/lock-rpc-server.go

193 lines
5.9 KiB

/*
* Minio Cloud Storage, (C) 2016, 2017 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"
"math/rand"
"path"
"time"
"github.com/gorilla/mux"
"github.com/minio/dsync"
"github.com/minio/minio/cmd/logger"
xrpc "github.com/minio/minio/cmd/rpc"
xnet "github.com/minio/minio/pkg/net"
)
const (
// Lock rpc server endpoint.
lockServiceSubPath = "/lock"
// Lock rpc service name.
lockServiceName = "Dsync"
// Lock maintenance interval.
lockMaintenanceInterval = 1 * time.Minute
// Lock validity check interval.
lockValidityCheckInterval = 2 * time.Minute
)
var lockServicePath = path.Join(minioReservedBucketPath, lockServiceSubPath)
// LockArgs represents arguments for any authenticated lock RPC call.
type LockArgs struct {
AuthArgs
LockArgs dsync.LockArgs
}
// lockRPCReceiver is type for RPC handlers
type lockRPCReceiver struct {
ll localLocker
}
// Lock - rpc handler for (single) write lock operation.
func (l *lockRPCReceiver) Lock(args *LockArgs, reply *bool) (err error) {
*reply, err = l.ll.Lock(args.LockArgs)
return err
}
// Unlock - rpc handler for (single) write unlock operation.
func (l *lockRPCReceiver) Unlock(args *LockArgs, reply *bool) (err error) {
*reply, err = l.ll.Unlock(args.LockArgs)
return err
}
// RLock - rpc handler for read lock operation.
func (l *lockRPCReceiver) RLock(args *LockArgs, reply *bool) (err error) {
*reply, err = l.ll.RLock(args.LockArgs)
return err
}
// RUnlock - rpc handler for read unlock operation.
func (l *lockRPCReceiver) RUnlock(args *LockArgs, reply *bool) (err error) {
*reply, err = l.ll.RUnlock(args.LockArgs)
return err
}
// ForceUnlock - rpc handler for force unlock operation.
func (l *lockRPCReceiver) ForceUnlock(args *LockArgs, reply *bool) (err error) {
*reply, err = l.ll.ForceUnlock(args.LockArgs)
return err
}
// Expired - rpc handler for expired lock status.
func (l *lockRPCReceiver) Expired(args *LockArgs, reply *bool) error {
l.ll.mutex.Lock()
defer l.ll.mutex.Unlock()
// Lock found, proceed to verify if belongs to given uid.
if lri, ok := l.ll.lockMap[args.LockArgs.Resource]; ok {
// Check whether uid is still active
for _, entry := range lri {
if entry.uid == args.LockArgs.UID {
*reply = false // When uid found, lock is still active so return not expired.
return nil // When uid found *reply is set to true.
}
}
}
// When we get here lock is no longer active due to either args.LockArgs.Resource
// being absent from map or uid not found for given args.LockArgs.Resource
*reply = true
return nil
}
// lockMaintenance loops over locks that have been active for some time and checks back
// with the original server whether it is still alive or not
//
// Following logic inside ignores the errors generated for Dsync.Active operation.
// - server at client down
// - some network error (and server is up normally)
//
// We will ignore the error, and we will retry later to get a resolve on this lock
func (l *lockRPCReceiver) lockMaintenance(interval time.Duration) {
l.ll.mutex.Lock()
// Get list of long lived locks to check for staleness.
nlripLongLived := getLongLivedLocks(l.ll.lockMap, interval)
l.ll.mutex.Unlock()
// Validate if long lived locks are indeed clean.
for _, nlrip := range nlripLongLived {
// Initialize client based on the long live locks.
host, err := xnet.ParseHost(nlrip.lri.node)
logger.CriticalIf(context.Background(), err)
c, err := NewLockRPCClient(host)
if err != nil {
logger.LogIf(context.Background(), err)
continue
}
// Call back to original server verify whether the lock is still active (based on name & uid)
expired, _ := c.Expired(dsync.LockArgs{
UID: nlrip.lri.uid,
Resource: nlrip.name,
})
// Close the connection regardless of the call response.
c.Close()
// For successful response, verify if lock is indeed active or stale.
if expired {
// The lock is no longer active at server that originated the lock
// So remove the lock from the map.
l.ll.mutex.Lock()
l.ll.removeEntryIfExists(nlrip) // Purge the stale entry if it exists.
l.ll.mutex.Unlock()
}
}
}
// Start lock maintenance from all lock servers.
func startLockMaintenance(lkSrv *lockRPCReceiver) {
// Initialize a new ticker with a minute between each ticks.
ticker := time.NewTicker(lockMaintenanceInterval)
// Stop the timer upon service closure and cleanup the go-routine.
defer ticker.Stop()
// Start with random sleep time, so as to avoid "synchronous checks" between servers
time.Sleep(time.Duration(rand.Float64() * float64(lockMaintenanceInterval)))
for {
// Verifies every minute for locks held more than 2minutes.
select {
case <-globalServiceDoneCh:
return
case <-ticker.C:
lkSrv.lockMaintenance(lockValidityCheckInterval)
}
}
}
// NewLockRPCServer - returns new lock RPC server.
func NewLockRPCServer() (*xrpc.Server, error) {
rpcServer := xrpc.NewServer()
if err := rpcServer.RegisterName(lockServiceName, globalLockServer); err != nil {
return nil, err
}
return rpcServer, nil
}
// Register distributed NS lock handlers.
func registerDistNSLockRouter(router *mux.Router) {
rpcServer, err := NewLockRPCServer()
logger.CriticalIf(context.Background(), err)
// Start lock maintenance from all lock servers.
go startLockMaintenance(globalLockServer)
subrouter := router.PathPrefix(minioReservedBucketPath).Subrouter()
subrouter.Path(lockServiceSubPath).Handler(rpcServer)
}