writer.go

// Copyright (c) 2018 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 writer

import (
	"errors"
	"fmt"
	"sync"

	"github.com/m3db/m3/src/cluster/services"
	"github.com/m3db/m3/src/msg/producer"
	"github.com/m3db/m3/src/msg/topic"
	xerrors "github.com/m3db/m3/src/x/errors"
	"github.com/m3db/m3/src/x/watch"

	"github.com/uber-go/tally"
	"go.uber.org/zap"
)

var (
	errWriterClosed = errors.New("writer is closed")
)

type writerMetrics struct {
	topicUpdateSuccess  tally.Counter
	topicUpdateError    tally.Counter
	invalidTopicUpdate  tally.Counter
	invalidShard        tally.Counter
	numConsumerServices tally.Gauge
}

func newWriterMetrics(scope tally.Scope) writerMetrics {
	return writerMetrics{
		topicUpdateSuccess: scope.Counter("topic-update-success"),
		topicUpdateError:   scope.Counter("topic-update-error"),
		invalidTopicUpdate: scope.Counter("invalid-topic"),
		invalidShard: scope.Tagged(map[string]string{"reason": "invalid-shard"}).
			Counter("invalid-shard-write"),
		numConsumerServices: scope.Gauge("num-consumer-services"),
	}
}

// nolint: maligned
type writer struct {
	sync.RWMutex

	topic  string
	ts     topic.Service
	opts   Options
	logger *zap.Logger

	value                  watch.Value
	initType               initType
	numShards              uint32
	consumerServiceWriters map[string]consumerServiceWriter
	filterRegistry         map[string]producer.FilterFunc
	isClosed               bool
	m                      writerMetrics

	processFn watch.ProcessFn
}

// NewWriter creates a new writer.
func NewWriter(opts Options) producer.Writer {
	w := &writer{
		topic:                  opts.TopicName(),
		ts:                     opts.TopicService(),
		opts:                   opts,
		logger:                 opts.InstrumentOptions().Logger(),
		initType:               failOnError,
		consumerServiceWriters: make(map[string]consumerServiceWriter),
		filterRegistry:         make(map[string]producer.FilterFunc),
		isClosed:               false,
		m:                      newWriterMetrics(opts.InstrumentOptions().MetricsScope()),
	}
	w.processFn = w.process
	return w
}

func (w *writer) Write(rm *producer.RefCountedMessage) error {
	w.RLock()
	if w.isClosed {
		rm.Drop()
		w.RUnlock()
		return errWriterClosed
	}
	shard := rm.Shard()
	if shard >= w.numShards {
		w.m.invalidShard.Inc(1)
		rm.Drop()
		w.RUnlock()
		return fmt.Errorf("could not write message for shard %d which is larger than max shard id %d", shard, w.numShards-1)
	}
	// NB(cw): Need to inc ref here in case a consumer service
	// writes the message too fast and close the message.
	rm.IncRef()
	for _, csw := range w.consumerServiceWriters {
		csw.Write(rm)
	}
	rm.DecRef()
	w.RUnlock()
	return nil
}

func (w *writer) Init() error {
	newUpdatableFn := func() (watch.Updatable, error) {
		return w.ts.Watch(w.topic)
	}
	getUpdateFn := func(value watch.Updatable) (interface{}, error) {
		t, err := value.(topic.Watch).Get()
		if err != nil {
			w.m.invalidTopicUpdate.Inc(1)
			return nil, err
		}
		return t, nil
	}
	vOptions := watch.NewOptions().
		SetInitWatchTimeout(w.opts.TopicWatchInitTimeout()).
		SetInstrumentOptions(w.opts.InstrumentOptions()).
		SetNewUpdatableFn(newUpdatableFn).
		SetGetUpdateFn(getUpdateFn).
		SetProcessFn(w.processFn).
		SetKey(w.opts.TopicName())
	w.value = watch.NewValue(vOptions)
	if err := w.value.Watch(); err != nil {
		return fmt.Errorf("writer init error: %v", err)
	}
	return nil
}

func (w *writer) NumShards() uint32 {
	w.RLock()
	n := w.numShards
	w.RUnlock()
	return n
}

func (w *writer) process(update interface{}) error {
	t := update.(topic.Topic)
	if err := t.Validate(); err != nil {
		return err
	}
	// We don't allow changing number of shards for topics, it will be
	// prevented on topic service side, but also being defensive here as well.
	numShards := w.NumShards()
	if numShards != 0 && numShards != t.NumberOfShards() {
		w.m.topicUpdateError.Inc(1)
		return fmt.Errorf("invalid topic update with %d shards, expecting %d", t.NumberOfShards(), numShards)
	}
	var (
		iOpts                     = w.opts.InstrumentOptions()
		newConsumerServiceWriters = make(map[string]consumerServiceWriter, len(t.ConsumerServices()))
		toBeClosed                []consumerServiceWriter
		multiErr                  xerrors.MultiError
	)
	for _, cs := range t.ConsumerServices() {
		key := cs.ServiceID().String()
		csw, ok := w.consumerServiceWriters[key]
		if ok {
			csw.SetMessageTTLNanos(cs.MessageTTLNanos())
			newConsumerServiceWriters[key] = csw
			continue
		}
		scope := iOpts.MetricsScope().Tagged(map[string]string{
			"consumer-service-name": cs.ServiceID().Name(),
			"consumer-service-zone": cs.ServiceID().Zone(),
			"consumer-service-env":  cs.ServiceID().Environment(),
			"consumption-type":      cs.ConsumptionType().String(),
		})
		csw, err := newConsumerServiceWriter(cs, t.NumberOfShards(), w.opts.SetInstrumentOptions(iOpts.SetMetricsScope(scope)))
		if err != nil {
			w.logger.Error("could not create consumer service writer",
				zap.String("writer", cs.String()), zap.Error(err))
			multiErr = multiErr.Add(err)
			continue
		}
		if err = csw.Init(w.initType); err != nil {
			w.logger.Error("could not init consumer service writer",
				zap.String("writer", cs.String()), zap.Error(err))
			multiErr = multiErr.Add(err)
			// Could not initialize the consumer service, simply close it.
			csw.Close()
			continue
		}
		csw.SetMessageTTLNanos(cs.MessageTTLNanos())
		newConsumerServiceWriters[key] = csw
		w.logger.Info("initialized consumer service writer", zap.String("writer", cs.String()))
	}
	for key, csw := range w.consumerServiceWriters {
		if _, ok := newConsumerServiceWriters[key]; !ok {
			toBeClosed = append(toBeClosed, csw)
		}
	}
	// Allow InitValueError for any future topic updates after starting up.
	// This is to handle the case when a new consumer service got added to
	// the topic, but the producer could not get initial value for its
	// placement. We will continue to watch for placement updates for the new
	// consumer service in the background, so the producer can write to it once
	// the placement came in.
	w.initType = allowInitValueError
	w.m.numConsumerServices.Update(float64(len(newConsumerServiceWriters)))

	// Apply the new consumer service writers.
	w.Lock()
	for key, csw := range newConsumerServiceWriters {
		if filter, ok := w.filterRegistry[key]; ok {
			csw.RegisterFilter(filter)
		}
	}
	w.consumerServiceWriters = newConsumerServiceWriters
	w.numShards = t.NumberOfShards()
	w.Unlock()

	// Close removed consumer service.
	go func() {
		for _, csw := range toBeClosed {
			csw.Close()
		}
	}()

	if err := multiErr.FinalError(); err != nil {
		w.m.topicUpdateError.Inc(1)
		return err
	}
	w.m.topicUpdateSuccess.Inc(1)
	return nil
}

func (w *writer) Close() {
	w.Lock()
	if w.isClosed {
		w.Unlock()
		return
	}
	w.isClosed = true
	w.Unlock()

	w.value.Unwatch()
	for _, csw := range w.consumerServiceWriters {
		csw.Close()
	}
}

func (w *writer) RegisterFilter(sid services.ServiceID, filter producer.FilterFunc) {
	w.Lock()
	defer w.Unlock()

	key := sid.String()
	w.filterRegistry[key] = filter
	csw, ok := w.consumerServiceWriters[key]
	if ok {
		csw.RegisterFilter(filter)
	}
}

func (w *writer) UnregisterFilter(sid services.ServiceID) {
	w.Lock()
	defer w.Unlock()

	key := sid.String()
	delete(w.filterRegistry, key)
	csw, ok := w.consumerServiceWriters[key]
	if ok {
		csw.UnregisterFilter()
	}
}