/
etcdwatcher.go
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/
etcdwatcher.go
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/*
* Copyright (C) 2018 Red Hat, 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 ofthe 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 specificlanguage governing permissions and
* limitations under the License.
*
*/
package rbac
import (
"context"
"runtime"
"github.com/casbin/casbin/persist"
etcd "go.etcd.io/etcd/client/v2"
)
// EtcdWatcher listens for etcd events
type EtcdWatcher struct {
kapi etcd.KeysAPI
running bool
callback func(string)
cancel context.CancelFunc
}
// finalizer is the destructor for EtcdWatcher.
func finalizer(w *EtcdWatcher) {
w.running = false
w.cancel()
}
// NewEtcdWatcher returns new etcd change watcher
func NewEtcdWatcher(kapi etcd.KeysAPI, parent context.Context) persist.Watcher {
ctx, cancel := context.WithCancel(parent)
w := &EtcdWatcher{
kapi: kapi,
running: true,
cancel: cancel,
}
// Call the destructor when the object is released.
runtime.SetFinalizer(w, finalizer)
go w.startWatch(ctx)
return w
}
// SetUpdateCallback sets the callback function that the watcher will call
// when the policy in DB has been changed by other instances.
// A classic callback is Enforcer.LoadPolicy().
func (w *EtcdWatcher) SetUpdateCallback(callback func(string)) error {
w.callback = callback
return nil
}
// Update calls the update callback of other instances to synchronize their policy.
// It is usually called after changing the policy in DB, like Enforcer.SavePolicy(),
// Enforcer.AddPolicy(), Enforcer.RemovePolicy(), etc.
func (w *EtcdWatcher) Update() error {
return nil
}
func (w *EtcdWatcher) Close() {
w.cancel()
}
// startWatch is a goroutine that watches the policy change.
func (w *EtcdWatcher) startWatch(ctx context.Context) error {
watcher := w.kapi.Watcher(etcdPolicyKey, &etcd.WatcherOptions{Recursive: false})
for {
if !w.running {
return nil
}
res, err := watcher.Next(ctx)
if err != nil {
return err
}
if res.Action == "set" || res.Action == "update" {
if w.callback != nil {
w.callback(res.Node.Value)
}
}
}
}