Add tablet-tags/--init_tags stats

Signed-off-by: Tim Vaillancourt <[email protected]>

go/vt/vttablet/tabletmanager/tm_init.go

@@ -117,6 +117,9 @@ var (
 	// statsIsInSrvKeyspace is set to 1 (true), 0 (false) whether the tablet is in the serving keyspace
 	statsIsInSrvKeyspace *stats.Gauge
 
+	// statsTabletTags is set to 1 (true) if a tablet tag exists.
+	statsTabletTags *stats.GaugesWithMultiLabels
+
 	statsKeyspace      = stats.NewString("TabletKeyspace")
 	statsShard         = stats.NewString("TabletShard")
 	statsKeyRangeStart = stats.NewString("TabletKeyRangeStart")
@@ -136,6 +139,7 @@ func init() {
 	statsTabletTypeCount = stats.NewCountersWithSingleLabel("TabletTypeCount", "Number of times the tablet changed to the labeled type", "type")
 	statsBackupIsRunning = stats.NewGaugesWithMultiLabels("BackupIsRunning", "Whether a backup is running", []string{"mode"})
 	statsIsInSrvKeyspace = stats.NewGauge("IsInSrvKeyspace", "Whether the vttablet is in the serving keyspace (1 = true / 0 = false)")
+	statsTabletTags = stats.NewGaugesWithMultiLabels("TabletTags", "Tablet tags key/values", []string{"key", "value"})
 }
 
 // TabletManager is the main class for the tablet manager.
@@ -264,6 +268,11 @@ func BuildTabletFromInput(alias *topodatapb.TabletAlias, port, grpcPort int32, d
 		charset = collations.Local().DefaultConnectionCharset()
 	}
 
+	tags := mergeTags(buildTags, initTags)
+	for k, v := range tags {
+		statsTabletTags.Set([]string{k, v}, 1)
+	}
+
 	return &topodatapb.Tablet{
 		Alias:    alias,
 		Hostname: hostname,
@@ -276,7 +285,7 @@ func BuildTabletFromInput(alias *topodatapb.TabletAlias, port, grpcPort int32, d
 		KeyRange:             keyRange,
 		Type:                 tabletType,
 		DbNameOverride:       initDbNameOverride,
-		Tags:                 mergeTags(buildTags, initTags),
+		Tags:                 tags,
 		DbServerVersion:      dbServerVersion,
 		DefaultConnCollation: uint32(charset),
 	}, nil