swarm: LocalStore metrics

* swarm/shed: remove metrics fields from DB struct

* swarm/schunk: add String methods to modes

* swarm/storage/localstore: add metrics and traces

* swarm/chunk: unknown modes without spaces in String methods

* swarm/storage/localstore: remove bin number from pull subscription metrics

* swarm/storage/localstore: add resetting time metrics and code improvements

swarm/storage/localstore/subscription_pull.go

@@ -20,10 +20,15 @@ import (
 	"context"
 	"errors"
 	"sync"
+	"time"
 
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/swarm/chunk"
 	"github.com/ethereum/go-ethereum/swarm/shed"
+	"github.com/ethereum/go-ethereum/swarm/spancontext"
+	"github.com/opentracing/opentracing-go"
+	olog "github.com/opentracing/opentracing-go/log"
 	"github.com/syndtr/goleveldb/leveldb"
 )
 
@@ -36,6 +41,9 @@ import (
 // Make sure that you check the second returned parameter from the channel to stop iteration when its value
 // is false.
 func (db *DB) SubscribePull(ctx context.Context, bin uint8, since, until uint64) (c <-chan chunk.Descriptor, stop func()) {
+	metricName := "localstore.SubscribePull"
+	metrics.GetOrRegisterCounter(metricName, nil).Inc(1)
+
 	chunkDescriptors := make(chan chunk.Descriptor)
 	trigger := make(chan struct{}, 1)
 
@@ -57,6 +65,7 @@ func (db *DB) SubscribePull(ctx context.Context, bin uint8, since, until uint64)
 	var errStopSubscription = errors.New("stop subscription")
 
 	go func() {
+		defer metrics.GetOrRegisterCounter(metricName+".stop", nil).Inc(1)
 		// close the returned chunk.Descriptor channel at the end to
 		// signal that the subscription is done
 		defer close(chunkDescriptors)
@@ -77,12 +86,20 @@ func (db *DB) SubscribePull(ctx context.Context, bin uint8, since, until uint64)
 				// - last index Item is reached
 				// - subscription stop is called
 				// - context is done
+				metrics.GetOrRegisterCounter(metricName+".iter", nil).Inc(1)
+
+				ctx, sp := spancontext.StartSpan(ctx, metricName+".iter")
+				sp.LogFields(olog.Int("bin", int(bin)), olog.Uint64("since", since), olog.Uint64("until", until))
+
+				iterStart := time.Now()
+				var count int
 				err := db.pullIndex.Iterate(func(item shed.Item) (stop bool, err error) {
 					select {
 					case chunkDescriptors <- chunk.Descriptor{
 						Address: item.Address,
 						BinID:   item.BinID,
 					}:
+						count++
 						// until chunk descriptor is sent
 						// break the iteration
 						if until > 0 && item.BinID >= until {
@@ -111,12 +128,25 @@ func (db *DB) SubscribePull(ctx context.Context, bin uint8, since, until uint64)
 					SkipStartFromItem: !first,
 					Prefix:            []byte{bin},
 				})
+
+				totalTimeMetric(metricName+".iter", iterStart)
+
+				sp.FinishWithOptions(opentracing.FinishOptions{
+					LogRecords: []opentracing.LogRecord{
+						{
+							Timestamp: time.Now(),
+							Fields:    []olog.Field{olog.Int("count", count)},
+						},
+					},
+				})
+
 				if err != nil {
 					if err == errStopSubscription {
 						// stop subscription without any errors
 						// if until is reached
 						return
 					}
+					metrics.GetOrRegisterCounter(metricName+".iter.error", nil).Inc(1)
 					log.Error("localstore pull subscription iteration", "bin", bin, "since", since, "until", until, "err", err)
 					return
 				}
@@ -162,6 +192,8 @@ func (db *DB) SubscribePull(ctx context.Context, bin uint8, since, until uint64)
 // in pull syncing index for a provided bin. If there are no chunks in
 // that bin, 0 value is returned.
 func (db *DB) LastPullSubscriptionBinID(bin uint8) (id uint64, err error) {
+	metrics.GetOrRegisterCounter("localstore.LastPullSubscriptionBinID", nil).Inc(1)
+
 	item, err := db.pullIndex.Last([]byte{bin})
 	if err != nil {
 		if err == leveldb.ErrNotFound {