Track disk vs meta write durations

carstore/bs.go

···
 		offset += nw
 	}
 
+	start := time.Now()
 	path, err := cs.writeNewShardFile(ctx, user, seq, buf.Bytes())
 	if err != nil {
 		return nil, fmt.Errorf("failed to write shard file: %w", err)
 	}
+	writeShardFileDuration.Observe(time.Since(start).Seconds())
 
 	shard := CarShard{
 		Root:      models.DbCID{CID: root},
···
 		Rev:       rev,
 	}
 
+	start = time.Now()
 	if err := cs.putShard(ctx, &shard, brefs, rmcids, false); err != nil {
 		return nil, err
 	}
+	writeShardMetadataDuration.Observe(time.Since(start).Seconds())
 
 	return buf.Bytes(), nil
 }

carstore/metrics.go

···
+package carstore
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var writeShardFileDuration = promauto.NewHistogram(prometheus.HistogramOpts{
+	Name:    "carstore_write_shard_file_duration",
+	Help:    "Duration of writing shard file to disk",
+	Buckets: prometheus.ExponentialBuckets(0.001, 2, 15),
+})
+
+var writeShardMetadataDuration = promauto.NewHistogram(prometheus.HistogramOpts{
+	Name:    "carstore_write_shard_metadata_duration",
+	Help:    "Duration of writing shard metadata to DB",
+	Buckets: prometheus.ExponentialBuckets(0.001, 2, 15),
+})