mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2025-10-31 08:12:26 -05:00
121 lines
3.2 KiB
Go
121 lines
3.2 KiB
Go
/*
|
|
GoToSocial
|
|
Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
|
|
|
|
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 federatingdb
|
|
|
|
import (
|
|
"context"
|
|
"errors"
|
|
"net/url"
|
|
"sync"
|
|
"sync/atomic"
|
|
|
|
"github.com/sirupsen/logrus"
|
|
)
|
|
|
|
// Lock takes a lock for the object at the specified id. If an error
|
|
// is returned, the lock must not have been taken.
|
|
//
|
|
// The lock must be able to succeed for an id that does not exist in
|
|
// the database. This means acquiring the lock does not guarantee the
|
|
// entry exists in the database.
|
|
//
|
|
// Locks are encouraged to be lightweight and in the Go layer, as some
|
|
// processes require tight loops acquiring and releasing locks.
|
|
//
|
|
// Used to ensure race conditions in multiple requests do not occur.
|
|
func (f *federatingDB) Lock(c context.Context, id *url.URL) error {
|
|
// Before any other Database methods are called, the relevant `id`
|
|
// entries are locked to allow for fine-grained concurrency.
|
|
|
|
// Strategy: create a new lock, if stored, continue. Otherwise, lock the
|
|
// existing mutex.
|
|
if id == nil {
|
|
return errors.New("Lock: id was nil")
|
|
}
|
|
idStr := id.String()
|
|
|
|
// Acquire map lock
|
|
f.mutex.Lock()
|
|
|
|
// Get mutex, or create new
|
|
mu, ok := f.locks[idStr]
|
|
if !ok {
|
|
mu, ok = f.pool.Get().(*mutex)
|
|
if !ok {
|
|
logrus.Panic("Lock: pool entry was not a *mutex")
|
|
}
|
|
f.locks[idStr] = mu
|
|
}
|
|
|
|
// Unlock map, acquire mutex lock
|
|
f.mutex.Unlock()
|
|
mu.Lock()
|
|
return nil
|
|
}
|
|
|
|
// Unlock makes the lock for the object at the specified id available.
|
|
// If an error is returned, the lock must have still been freed.
|
|
//
|
|
// Used to ensure race conditions in multiple requests do not occur.
|
|
func (f *federatingDB) Unlock(c context.Context, id *url.URL) error {
|
|
// Once Go-Fed is done calling Database methods, the relevant `id`
|
|
// entries are unlocked.
|
|
if id == nil {
|
|
return errors.New("Unlock: id was nil")
|
|
}
|
|
idStr := id.String()
|
|
|
|
// Check map for mutex
|
|
f.mutex.Lock()
|
|
mu, ok := f.locks[idStr]
|
|
f.mutex.Unlock()
|
|
|
|
if !ok {
|
|
return errors.New("missing an id in unlock")
|
|
}
|
|
|
|
// Unlock the mutex
|
|
mu.Unlock()
|
|
return nil
|
|
}
|
|
|
|
// mutex defines a mutex we can check the lock status of.
|
|
// this is not perfect, but it's good enough for a semi
|
|
// regular mutex cleanup routine
|
|
type mutex struct {
|
|
mu sync.Mutex
|
|
st uint32
|
|
}
|
|
|
|
// inUse returns if the mutex is in use
|
|
func (mu *mutex) inUse() bool {
|
|
return atomic.LoadUint32(&mu.st) == 1
|
|
}
|
|
|
|
// Lock acquire mutex lock
|
|
func (mu *mutex) Lock() {
|
|
mu.mu.Lock()
|
|
atomic.StoreUint32(&mu.st, 1)
|
|
}
|
|
|
|
// Unlock releases mutex lock
|
|
func (mu *mutex) Unlock() {
|
|
mu.mu.Unlock()
|
|
atomic.StoreUint32(&mu.st, 0)
|
|
}
|