logmower-shipper/cmd/sender.go

package logmower

import (
	"context"
	"time"

	"github.com/jtagcat/util"
	prom "github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
	"go.mongodb.org/mongo-driver/bson"
	"go.uber.org/zap"
)

var (
	promShipperMongoSent = promauto.NewCounterVec(prom.CounterOpts{
		Subsystem: "shipper",
		Name:      "sent_count",
		Help:      "Items successfully committed to mongo",
	}, []string{"filename"})
	promShipperMongoSentError = promauto.NewCounterVec(prom.CounterOpts{
		Subsystem: "shipper",
		Name:      "mongo_errors_count",
		Help:      "Errors while submitting to mongo", // TODO:
	}, []string{"filename"})
	promShipperDropped = promauto.NewCounterVec(prom.CounterOpts{
		Subsystem: "shipper",
		Name:      "queue_dropped_count",
		Help:      "Items ready to be batched and sent to mongo, but dropped due to full queue",
	}, []string{"filename"})
	promShipperQueueItems = promauto.NewHistogramVec(prom.HistogramOpts{
		Subsystem: "shipper",
		Name:      "queue_items",
		Help:      "Items in queue to be batched and sent to mongo",
	}, []string{"filename"})
	promShipperSynced = promauto.NewGaugeVec(prom.GaugeOpts{
		Subsystem: "shipper",
		Name:      "batches_synced",
		Help:      "All batches available have been sent to mongo",
	}, []string{"filename"})
)

const (
	SendQueueLimit = 1024
	MaxBatchItems  = 100
	MaxBatchTime   = time.Second
)

func init() {
	promauto.NewGaugeFunc(prom.GaugeOpts{
		Subsystem: "shipper",
		Name:      "queue_size",
		Help:      "Submit queue size cap",
	}, func() float64 {
		return float64(SendQueueLimit)
	})
	promauto.NewGaugeFunc(prom.GaugeOpts{
		Subsystem: "shipper",
		Name:      "batch_size",
		Help:      "batching size cap",
	}, func() float64 {
		return float64(MaxBatchItems)
	})
	promauto.NewGaugeFunc(prom.GaugeOpts{
		Subsystem: "shipper",
		Name:      "batch_time",
		Help:      "batching delay cap",
	}, func() float64 {
		return float64(MaxBatchTime)
	})
}

func (s *submitter) sender(name string, sendQueue <-chan mLog) (synced func() bool) {
	batched := make(chan []mLog)

	go func() {
		ctx, cancel := context.WithCancel(context.Background())
		defer cancel()

		go func() {
			for {
				promShipperQueueItems.WithLabelValues(name).Observe(float64(
					len(sendQueue)))

				timer := time.NewTimer(time.Second)
				select {
				case <-ctx.Done():
					return
				case <-timer.C:
				}
			}
		}()

		util.Batch(MaxBatchItems, MaxBatchTime, sendQueue, batched)
	}()

	var batchSynced bool
	s.Add(1)
	go s.senderRoutine(name, batched, &batchSynced)

	return func() bool {
		return batchSynced && len(sendQueue) == 0
	}
}

func (s *submitter) senderRoutine(name string, batched <-chan []mLog, synced *bool) {
	defer s.Done()

	for {
		*synced = true
		promShipperSynced.WithLabelValues(name).Set(1)

		batch, ok := <-batched
		if !ok {
			return
		}

		*synced = false
		promShipperSynced.WithLabelValues(name).Set(0)

		var batchBson []interface{} // mongo does not like typing
		for _, b := range batch {
			batchBson = append(batchBson, b.toBson())
		}

		result, err := s.db.InsertMany(mongoTimeoutCtx(context.Background()), batchBson, nil)
		promShipperMongoSent.WithLabelValues(name).Add(float64(
			len(result.InsertedIDs)))

		if err != nil {
			s.l.Error("mongo send returned error; TODO: add some selective retry here or something", zap.Error(err)) // TODO:
		}
	}
}

// when editing, also edit toBson(); all bson.D (and bson.M) uses
type mLog struct {
	HostInfo HostInfo
	Filename string
	Offset   int64  // byte offset where log entry ends at
	Content  string // TODO:
	Time     time.Time
}

// not using marshal, since it is <0.1x performance
func (l *mLog) toBson() bson.M {
	return bson.M{
		"host_info": l.HostInfo,
		"filename":  l.Filename,
		"offset":    l.Offset,
		"content":   l.Content,
		"time":      l.Time,
	}
}