package syncx import ( "sync" "time" "git.i2edu.net/i2/go-zero/core/timex" ) const defaultRefreshInterval = time.Second type ( // ImmutableResourceOption defines the method to customize an ImmutableResource. ImmutableResourceOption func(resource *ImmutableResource) // An ImmutableResource is used to manage an immutable resource. ImmutableResource struct { fetch func() (interface{}, error) resource interface{} err error lock sync.RWMutex refreshInterval time.Duration lastTime *AtomicDuration } ) // NewImmutableResource returns an ImmutableResource. func NewImmutableResource(fn func() (interface{}, error), opts ...ImmutableResourceOption) *ImmutableResource { // cannot use executors.LessExecutor because of cycle imports ir := ImmutableResource{ fetch: fn, refreshInterval: defaultRefreshInterval, lastTime: NewAtomicDuration(), } for _, opt := range opts { opt(&ir) } return &ir } // Get gets the immutable resource, fetches automatically if not loaded. func (ir *ImmutableResource) Get() (interface{}, error) { ir.lock.RLock() resource := ir.resource ir.lock.RUnlock() if resource != nil { return resource, nil } ir.maybeRefresh(func() { res, err := ir.fetch() ir.lock.Lock() if err != nil { ir.err = err } else { ir.resource, ir.err = res, nil } ir.lock.Unlock() }) ir.lock.RLock() resource, err := ir.resource, ir.err ir.lock.RUnlock() return resource, err } func (ir *ImmutableResource) maybeRefresh(execute func()) { now := timex.Now() lastTime := ir.lastTime.Load() if lastTime == 0 || lastTime+ir.refreshInterval < now { ir.lastTime.Set(now) execute() } } // WithRefreshIntervalOnFailure sets refresh interval on failure. // Set interval to 0 to enforce refresh every time if not succeeded, default is time.Second. func WithRefreshIntervalOnFailure(interval time.Duration) ImmutableResourceOption { return func(resource *ImmutableResource) { resource.refreshInterval = interval } }