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/*
* 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
}