/
resourcemanager.go
68 lines (56 loc) · 1.44 KB
/
resourcemanager.go
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package query
import (
"io"
"sync"
)
// ResourceManager A ResourceManager is a manager that used to manage resources.
type ResourceManager struct {
resources map[string]io.Closer
singleFlight SingleFlight
lock sync.RWMutex
}
// NewResourceManager returns a ResourceManager.
func NewResourceManager() *ResourceManager {
return &ResourceManager{
resources: make(map[string]io.Closer),
singleFlight: NewSingleFlight(),
}
}
// Close closes the manager.
// Don't use the ResourceManager after Close() called.
func (manager *ResourceManager) Close() error {
manager.lock.Lock()
defer manager.lock.Unlock()
var be BatchError
for _, resource := range manager.resources {
if err := resource.Close(); err != nil {
be.Add(err)
}
}
// release resources to avoid using it later
manager.resources = nil
return be.Err()
}
// GetResource returns the resource associated with given key.
func (manager *ResourceManager) GetResource(key string, create func() (io.Closer, error)) (io.Closer, error) {
val, err := manager.singleFlight.Do(key, func() (interface{}, error) {
manager.lock.RLock()
resource, ok := manager.resources[key]
manager.lock.RUnlock()
if ok {
return resource, nil
}
resource, err := create()
if err != nil {
return nil, err
}
manager.lock.Lock()
manager.resources[key] = resource
manager.lock.Unlock()
return resource, nil
})
if err != nil {
return nil, err
}
return val.(io.Closer), nil
}