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factory.go
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factory.go
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// Copyright 2014 Google Inc. All Rights Reserved.
//
// 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 container
import (
"fmt"
"sync"
"github.com/golang/glog"
)
type ContainerHandlerFactory interface {
// Create a new ContainerHandler using this factory. CanHandle() must have returned true.
NewContainerHandler(name string) (ContainerHandler, error)
// Returns whether this factory can handle the specified container.
CanHandle(name string) (bool, error)
// Name of the factory.
String() string
}
// TODO(vmarmol): Consider not making this global.
// Global list of factories.
var (
factories []ContainerHandlerFactory
factoriesLock sync.RWMutex
)
// Register a ContainerHandlerFactory. These should be registered from least general to most general
// as they will be asked in order whether they can handle a particular container.
func RegisterContainerHandlerFactory(factory ContainerHandlerFactory) {
factoriesLock.Lock()
defer factoriesLock.Unlock()
factories = append(factories, factory)
}
// Returns whether there are any container handler factories registered.
func HasFactories() bool {
factoriesLock.Lock()
defer factoriesLock.Unlock()
return len(factories) != 0
}
// Create a new ContainerHandler for the specified container.
func NewContainerHandler(name string) (ContainerHandler, error) {
factoriesLock.RLock()
defer factoriesLock.RUnlock()
// Create the ContainerHandler with the first factory that supports it.
for _, factory := range factories {
canHandle, err := factory.CanHandle(name)
if err != nil {
glog.V(4).Infof("Error trying to work out if we can hande %s: %v", name, err)
}
if canHandle {
glog.V(3).Infof("Using factory %q for container %q", factory, name)
return factory.NewContainerHandler(name)
} else {
glog.V(4).Infof("Factory %q was unable to handle container %q", factory, name)
}
}
return nil, fmt.Errorf("no known factory can handle creation of container")
}
// Clear the known factories.
func ClearContainerHandlerFactories() {
factoriesLock.Lock()
defer factoriesLock.Unlock()
factories = make([]ContainerHandlerFactory, 0, 4)
}