| /* |
| * Copyright 2018-present Open Networking Foundation |
| * 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 meter |
| |
| import ( |
| "context" |
| "fmt" |
| "sync" |
| |
| "github.com/opencord/voltha-go/db/model" |
| "github.com/opencord/voltha-lib-go/v7/pkg/log" |
| ofp "github.com/opencord/voltha-protos/v5/go/openflow_13" |
| "google.golang.org/grpc/codes" |
| "google.golang.org/grpc/status" |
| ) |
| |
| // Loader hides all low-level locking & synchronization related to meter state updates |
| type Loader struct { |
| dbProxy *model.Proxy |
| // this lock protects the meters map, it does not protect individual meters |
| lock sync.RWMutex |
| meters map[uint32]*chunk |
| } |
| |
| // chunk keeps a meter and the lock for this meter |
| type chunk struct { |
| // this lock is used to synchronize all access to the meter, and also to the "deleted" variable |
| lock sync.Mutex |
| deleted bool |
| meter *ofp.OfpMeterEntry |
| } |
| |
| func NewLoader(dbProxy *model.Proxy) *Loader { |
| return &Loader{ |
| dbProxy: dbProxy, |
| meters: make(map[uint32]*chunk), |
| } |
| } |
| |
| // Load queries existing meters from the kv, |
| // and should only be called once when first created. |
| func (loader *Loader) Load(ctx context.Context) { |
| loader.lock.Lock() |
| defer loader.lock.Unlock() |
| var meters []*ofp.OfpMeterEntry |
| if err := loader.dbProxy.List(ctx, &meters); err != nil { |
| logger.Errorw(ctx, "failed-to-list-meters-from-cluster-data-proxy", log.Fields{"error": err}) |
| return |
| } |
| for _, meter := range meters { |
| loader.meters[meter.Config.MeterId] = &chunk{meter: meter} |
| } |
| } |
| |
| // LockOrCreate locks this meter if it exists, or creates a new meter if it does not. |
| // In the case of meter creation, the provided "meter" must not be modified afterwards. |
| func (loader *Loader) LockOrCreate(ctx context.Context, meter *ofp.OfpMeterEntry) (*Handle, bool, error) { |
| // try to use read lock instead of full lock if possible |
| if handle, have := loader.Lock(meter.Config.MeterId); have { |
| return handle, false, nil |
| } |
| loader.lock.Lock() |
| entry, have := loader.meters[meter.Config.MeterId] |
| if !have { |
| entry := &chunk{meter: meter} |
| loader.meters[meter.Config.MeterId] = entry |
| entry.lock.Lock() |
| loader.lock.Unlock() |
| if err := loader.dbProxy.Set(ctx, fmt.Sprint(meter.Config.MeterId), meter); err != nil { |
| // revert the map |
| loader.lock.Lock() |
| delete(loader.meters, meter.Config.MeterId) |
| loader.lock.Unlock() |
| entry.deleted = true |
| entry.lock.Unlock() |
| return nil, false, err |
| } |
| return &Handle{loader: loader, chunk: entry}, true, nil |
| } |
| loader.lock.Unlock() |
| entry.lock.Lock() |
| if entry.deleted { |
| entry.lock.Unlock() |
| return loader.LockOrCreate(ctx, meter) |
| } |
| return &Handle{loader: loader, chunk: entry}, false, nil |
| } |
| |
| // Lock acquires the lock for this meter, and returns a handle which can be used to access the meter until it's unlocked. |
| // This handle ensures that the meter cannot be accessed if the lock is not held. |
| // Returns false if the meter is not present. |
| // TODO: consider accepting a ctx and aborting the lock attempt on cancellation |
| func (loader *Loader) Lock(id uint32) (*Handle, bool) { |
| loader.lock.RLock() |
| entry, have := loader.meters[id] |
| loader.lock.RUnlock() |
| if !have { |
| return nil, false |
| } |
| entry.lock.Lock() |
| if entry.deleted { |
| entry.lock.Unlock() |
| return loader.Lock(id) |
| } |
| return &Handle{loader: loader, chunk: entry}, true |
| } |
| |
| // Handle is allocated for each Lock() call, all modifications are made using it, and it is invalidated by Unlock() |
| // This enforces correct Lock()-Usage()-Unlock() ordering. |
| type Handle struct { |
| loader *Loader |
| chunk *chunk |
| } |
| |
| // GetReadOnly returns an *ofp.OfpMeterEntry which MUST NOT be modified externally, but which is safe to keep indefinitely |
| func (h *Handle) GetReadOnly() *ofp.OfpMeterEntry { |
| return h.chunk.meter |
| } |
| |
| // Update updates an existing meter in the kv. |
| // The provided "meter" must not be modified afterwards. |
| func (h *Handle) Update(ctx context.Context, meter *ofp.OfpMeterEntry) error { |
| if err := h.loader.dbProxy.Set(ctx, fmt.Sprint(meter.Config.MeterId), meter); err != nil { |
| return status.Errorf(codes.Internal, "failed-update-meter-%v: %s", meter.Config.MeterId, err) |
| } |
| h.chunk.meter = meter |
| return nil |
| } |
| |
| // Delete removes the device from the kv |
| func (h *Handle) Delete(ctx context.Context) error { |
| if err := h.loader.dbProxy.Remove(ctx, fmt.Sprint(h.chunk.meter.Config.MeterId)); err != nil { |
| return fmt.Errorf("couldnt-delete-meter-from-store-%v", h.chunk.meter.Config.MeterId) |
| } |
| h.chunk.deleted = true |
| h.loader.lock.Lock() |
| delete(h.loader.meters, h.chunk.meter.Config.MeterId) |
| h.loader.lock.Unlock() |
| h.Unlock() |
| return nil |
| } |
| |
| // Unlock releases the lock on the meter |
| func (h *Handle) Unlock() { |
| if h.chunk != nil { |
| h.chunk.lock.Unlock() |
| h.chunk = nil // attempting to access the meter through this handle in future will panic |
| } |
| } |
| |
| // ListIDs returns a snapshot of all the managed meter IDs |
| // TODO: iterating through meters safely is expensive now, since all meters are stored & locked separately |
| // should avoid this where possible |
| func (loader *Loader) ListIDs() map[uint32]struct{} { |
| loader.lock.RLock() |
| defer loader.lock.RUnlock() |
| // copy the IDs so caller can safely iterate |
| ret := make(map[uint32]struct{}, len(loader.meters)) |
| for id := range loader.meters { |
| ret[id] = struct{}{} |
| } |
| return ret |
| } |