Emit histogram for blob size (#9233)

* Emit gauge for blob size

* use histogram instead of gauge

* add buckets

op-batcher/batcher/driver.go

@@ -372,6 +372,7 @@ func (l *BatchSubmitter) sendTransaction(txdata txData, queue *txmgr.Queue[txDat
 			// or configuration issue.
 			return fmt.Errorf("could not create blob tx candidate: %w", err)
 		}
+		l.Metr.RecordBlobUsedBytes(len(data))
 	} else {
 		candidate = l.calldataTxCandidate(data)
 	}

op-batcher/metrics/metrics.go

@@ -46,6 +46,8 @@ type Metricer interface {
 	RecordBatchTxSuccess()
 	RecordBatchTxFailed()
 
+	RecordBlobUsedBytes(num int)
+
 	Document() []opmetrics.DocumentedMetric
 }
 
@@ -79,6 +81,8 @@ type Metrics struct {
 	channelOutputBytesTotal prometheus.Counter
 
 	batcherTxEvs opmetrics.EventVec
+
+	blobUsedBytes prometheus.Histogram
 }
 
 var _ Metricer = (*Metrics)(nil)
@@ -181,6 +185,12 @@ func NewMetrics(procName string) *Metrics {
 			Name:      "output_bytes_total",
 			Help:      "Total number of compressed output bytes from a channel.",
 		}),
+		blobUsedBytes: factory.NewHistogram(prometheus.HistogramOpts{
+			Namespace: ns,
+			Name:      "blob_used_bytes",
+			Help:      "Blob size in bytes being submitted.",
+			Buckets:   prometheus.LinearBuckets(0.0, eth.MaxBlobDataSize/13, 13),
+		}),
 
 		batcherTxEvs: opmetrics.NewEventVec(factory, ns, "", "batcher_tx", "BatcherTx", []string{"stage"}),
 	}
@@ -304,6 +314,10 @@ func (m *Metrics) RecordBatchTxFailed() {
 	m.batcherTxEvs.Record(TxStageFailed)
 }
 
+func (m *Metrics) RecordBlobUsedBytes(num int) {
+	m.blobUsedBytes.Observe(float64(num))
+}
+
 // estimateBatchSize estimates the size of the batch
 func estimateBatchSize(block *types.Block) uint64 {
 	size := uint64(70) // estimated overhead of batch metadata

op-batcher/metrics/noop.go

@@ -42,6 +42,7 @@ func (*noopMetrics) RecordChannelTimedOut(derive.ChannelID)       {}
 func (*noopMetrics) RecordBatchTxSubmitted() {}
 func (*noopMetrics) RecordBatchTxSuccess()   {}
 func (*noopMetrics) RecordBatchTxFailed()    {}
+func (*noopMetrics) RecordBlobUsedBytes(int) {}
 func (*noopMetrics) StartBalanceMetrics(log.Logger, *ethclient.Client, common.Address) io.Closer {
 	return nil
 }