add double signed blocks metric (#1180)

* add ds metric

* add 1 instead of 2

Author: YeahNotSewerSide

cmd/thor/node/metrics.go

@@ -15,4 +15,5 @@ var (
 	metricBlockProcessedGas      = metrics.LazyLoadGaugeVec("block_processed_gas_gauge", []string{"type"})
 	metricBlockProcessedDuration = metrics.LazyLoadHistogram("block_processed_duration_ms", metrics.Bucket10s)
 	metricChainForkCount         = metrics.LazyLoadCounter("chain_fork_count")
+	metricDoubleSignedBlocks     = metrics.LazyLoadCounterVec("double_signed_blocks_counter", []string{"signer"})
 )

cmd/thor/node/node.go

@@ -338,6 +338,7 @@ func (n *Node) processBlock(newBlock *block.Block, stats *blockStats) (bool, err
 					conflictBlock.Header().ID() != newBlock.Header().ID() &&
 					conflictBlock.Header().StateRoot() != newBlock.Header().StateRoot() {
 					log.Warn("Double signing", "block", shortID(newBlock.Header().ID()), "previous", shortID(thor.BytesToBytes32(conflict)))
+					metricDoubleSignedBlocks().AddWithLabel(1, map[string]string{"signer": signer.String()})
 				}
 			}