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placement_mgr.go
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placement_mgr.go
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// Copyright (c) 2017 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package aggregator
import (
"errors"
"sync"
"github.com/m3db/m3/src/cluster/placement"
"github.com/m3db/m3/src/cluster/shard"
"github.com/m3db/m3/src/x/clock"
"github.com/uber-go/tally"
)
var (
// ErrInstanceNotFoundInPlacement is returned when instance is not found in placement.
ErrInstanceNotFoundInPlacement = errors.New("instance not found in placement")
errPlacementManagerNotOpenOrClosed = errors.New("placement manager not open or closed")
errPlacementManagerOpenOrClosed = errors.New("placement manager already open or closed")
)
// PlacementManager manages agg tier placements.
type PlacementManager interface {
// Open opens the placement manager.
Open() error
// Placement returns the active staged placement and the active placement.
Placement() (placement.ActiveStagedPlacement, placement.Placement, error)
// Instance returns the current instance in the current placement.
Instance() (placement.Instance, error)
// InstanceFrom returns the current instance from the given placement.
InstanceFrom(placement placement.Placement) (placement.Instance, error)
// HasReplacementInstance returns true if there is an instance in the same group replacing
// the current instance, and false otherwise.
HasReplacementInstance() (bool, error)
// Shards returns the current shards owned by the instance.
Shards() (shard.Shards, error)
// Close closes the placement manager.
Close() error
}
type placementManagerMetrics struct {
activeStagedPlacementErrors tally.Counter
activePlacementErrors tally.Counter
instanceNotFound tally.Counter
}
func newPlacementManagerMetrics(scope tally.Scope) placementManagerMetrics {
return placementManagerMetrics{
activeStagedPlacementErrors: scope.Counter("active-staged-placement-errors"),
activePlacementErrors: scope.Counter("active-placement-errors"),
instanceNotFound: scope.Counter("instance-not-found"),
}
}
type placementManagerState int
const (
placementManagerNotOpen placementManagerState = iota
placementManagerOpen
placementManagerClosed
)
type placementManager struct {
sync.RWMutex
nowFn clock.NowFn
instanceID string
placementWatcher placement.StagedPlacementWatcher
state placementManagerState
metrics placementManagerMetrics
}
// NewPlacementManager creates a new placement manager.
func NewPlacementManager(opts PlacementManagerOptions) PlacementManager {
instrumentOpts := opts.InstrumentOptions()
return &placementManager{
nowFn: opts.ClockOptions().NowFn(),
instanceID: opts.InstanceID(),
placementWatcher: opts.StagedPlacementWatcher(),
metrics: newPlacementManagerMetrics(instrumentOpts.MetricsScope()),
}
}
func (mgr *placementManager) Open() error {
mgr.Lock()
defer mgr.Unlock()
if mgr.state != placementManagerNotOpen {
return errPlacementManagerOpenOrClosed
}
if err := mgr.placementWatcher.Watch(); err != nil {
return err
}
mgr.state = placementManagerOpen
return nil
}
func (mgr *placementManager) Placement() (placement.ActiveStagedPlacement, placement.Placement, error) {
mgr.RLock()
stagedPlacement, placement, err := mgr.placementWithLock()
mgr.RUnlock()
return stagedPlacement, placement, err
}
func (mgr *placementManager) Instance() (placement.Instance, error) {
mgr.RLock()
instance, err := mgr.instanceWithLock()
mgr.RUnlock()
return instance, err
}
func (mgr *placementManager) InstanceFrom(placement placement.Placement) (placement.Instance, error) {
return mgr.instanceFrom(placement)
}
// TODO(xichen): move the method to placement interface.
func (mgr *placementManager) HasReplacementInstance() (bool, error) {
_, placement, err := mgr.Placement()
if err != nil {
return false, err
}
currInstance, err := mgr.instanceFrom(placement)
if err != nil {
return false, err
}
currShardSetID := currInstance.ShardSetID()
currShards := currInstance.Shards().All()
for _, currShard := range currShards {
if currShard.State() != shard.Leaving {
return false, nil
}
}
allInstances := placement.Instances()
for _, instance := range allInstances {
if instance.ShardSetID() != currShardSetID || instance.ID() == mgr.instanceID {
continue
}
otherShards := instance.Shards().All()
if len(otherShards) != len(currShards) {
continue
}
match := true
for i := 0; i < len(otherShards); i++ {
if otherShards[i].State() != shard.Initializing ||
otherShards[i].ID() != currShards[i].ID() ||
otherShards[i].CutoverNanos() != currShards[i].CutoffNanos() {
match = false
break
}
}
if match {
return true, nil
}
}
return false, nil
}
func (mgr *placementManager) Shards() (shard.Shards, error) {
mgr.RLock()
instance, err := mgr.instanceWithLock()
mgr.RUnlock()
if err != nil {
return nil, err
}
return instance.Shards(), nil
}
func (mgr *placementManager) Close() error {
mgr.Lock()
defer mgr.Unlock()
if mgr.state != placementManagerOpen {
return errPlacementManagerNotOpenOrClosed
}
if err := mgr.placementWatcher.Unwatch(); err != nil {
return err
}
mgr.state = placementManagerClosed
return nil
}
func (mgr *placementManager) placementWithLock() (placement.ActiveStagedPlacement, placement.Placement, error) {
if mgr.state != placementManagerOpen {
return nil, nil, errPlacementManagerNotOpenOrClosed
}
// NB(xichen): avoid using defer here because this is called on the write path
// for every incoming metric and defered return and func execution is expensive.
stagedPlacement, onStagedPlacementDoneFn, err := mgr.placementWatcher.ActiveStagedPlacement()
if err != nil {
mgr.metrics.activeStagedPlacementErrors.Inc(1)
return nil, nil, err
}
placement, onPlacementDoneFn, err := stagedPlacement.ActivePlacement()
if err != nil {
onStagedPlacementDoneFn()
mgr.metrics.activePlacementErrors.Inc(1)
return nil, nil, err
}
onPlacementDoneFn()
onStagedPlacementDoneFn()
return stagedPlacement, placement, nil
}
func (mgr *placementManager) instanceWithLock() (placement.Instance, error) {
_, placement, err := mgr.placementWithLock()
if err != nil {
return nil, err
}
return mgr.instanceFrom(placement)
}
func (mgr *placementManager) instanceFrom(placement placement.Placement) (placement.Instance, error) {
instance, found := placement.Instance(mgr.instanceID)
if !found {
mgr.metrics.instanceNotFound.Inc(1)
return nil, ErrInstanceNotFoundInPlacement
}
return instance, nil
}