app/vmagent: add -influxDBLabel in the same way as for app/vminsert

This is a follow-up for 3d19fa6932

README.md

@@ -1713,6 +1713,8 @@ Pass `-help` to VictoriaMetrics in order to see the list of supported command-li
   -influx.maxLineSize size
     	The maximum size in bytes for a single InfluxDB line during parsing
     	Supports the following optional suffixes for size values: KB, MB, GB, KiB, MiB, GiB (default 262144)
+  -influxDBLabel string
+    	Default label for the DB name sent over '?db={db_name}' query parameter (default "db")
   -influxListenAddr string
     	TCP and UDP address to listen for InfluxDB line protocol data. Usually :8189 must be set. Doesn't work if empty. This flag isn't needed when ingesting data over HTTP - just send it to http://<victoriametrics>:8428/write
   -influxMeasurementFieldSeparator string

app/vmagent/README.md

@@ -771,6 +771,8 @@ See the docs at https://docs.victoriametrics.com/vmagent.html .
   -influx.maxLineSize size
     	The maximum size in bytes for a single InfluxDB line during parsing
     	Supports the following optional suffixes for size values: KB, MB, GB, KiB, MiB, GiB (default 262144)
+  -influxDBLabel string
+    	Default label for the DB name sent over '?db={db_name}' query parameter (default "db")
   -influxListenAddr string
     	TCP and UDP address to listen for InfluxDB line protocol data. Usually :8189 must be set. Doesn't work if empty. This flag isn't needed when ingesting data over HTTP - just send it to http://<vmagent>:8429/write
   -influxMeasurementFieldSeparator string

app/vmagent/influx/request_handler.go

@@ -24,6 +24,7 @@ var (
 	measurementFieldSeparator = flag.String("influxMeasurementFieldSeparator", "_", "Separator for '{measurement}{separator}{field_name}' metric name when inserted via InfluxDB line protocol")
 	skipSingleField           = flag.Bool("influxSkipSingleField", false, "Uses '{measurement}' instead of '{measurement}{separator}{field_name}' for metic name if InfluxDB line contains only a single field")
 	skipMeasurement           = flag.Bool("influxSkipMeasurement", false, "Uses '{field_name}' as a metric name while ignoring '{measurement}' and '-influxMeasurementFieldSeparator'")
+	dbLabel                   = flag.String("influxDBLabel", "db", "Default label for the DB name sent over '?db={db_name}' query parameter")
 )
 
 var (
@@ -80,7 +81,7 @@ func insertRows(at *auth.Token, db string, rows []parser.Row, extraLabels []prom
 		hasDBKey := false
 		for j := range r.Tags {
 			tag := &r.Tags[j]
-			if tag.Key == "db" {
+			if tag.Key == *dbLabel {
 				hasDBKey = true
 			}
 			commonLabels = append(commonLabels, prompbmarshal.Label{
@@ -90,7 +91,7 @@ func insertRows(at *auth.Token, db string, rows []parser.Row, extraLabels []prom
 		}
 		if len(db) > 0 && !hasDBKey {
 			commonLabels = append(commonLabels, prompbmarshal.Label{
-				Name:  "db",
+				Name:  *dbLabel,
 				Value: db,
 			})
 		}

docs/README.md

@@ -1713,6 +1713,8 @@ Pass `-help` to VictoriaMetrics in order to see the list of supported command-li
   -influx.maxLineSize size
     	The maximum size in bytes for a single InfluxDB line during parsing
     	Supports the following optional suffixes for size values: KB, MB, GB, KiB, MiB, GiB (default 262144)
+  -influxDBLabel string
+    	Default label for the DB name sent over '?db={db_name}' query parameter (default "db")
   -influxListenAddr string
     	TCP and UDP address to listen for InfluxDB line protocol data. Usually :8189 must be set. Doesn't work if empty. This flag isn't needed when ingesting data over HTTP - just send it to http://<victoriametrics>:8428/write
   -influxMeasurementFieldSeparator string

docs/Single-server-VictoriaMetrics.md

@@ -1717,6 +1717,8 @@ Pass `-help` to VictoriaMetrics in order to see the list of supported command-li
   -influx.maxLineSize size
     	The maximum size in bytes for a single InfluxDB line during parsing
     	Supports the following optional suffixes for size values: KB, MB, GB, KiB, MiB, GiB (default 262144)
+  -influxDBLabel string
+    	Default label for the DB name sent over '?db={db_name}' query parameter (default "db")
   -influxListenAddr string
     	TCP and UDP address to listen for InfluxDB line protocol data. Usually :8189 must be set. Doesn't work if empty. This flag isn't needed when ingesting data over HTTP - just send it to http://<victoriametrics>:8428/write
   -influxMeasurementFieldSeparator string

docs/vmagent.md

@@ -775,6 +775,8 @@ See the docs at https://docs.victoriametrics.com/vmagent.html .
   -influx.maxLineSize size
     	The maximum size in bytes for a single InfluxDB line during parsing
     	Supports the following optional suffixes for size values: KB, MB, GB, KiB, MiB, GiB (default 262144)
+  -influxDBLabel string
+    	Default label for the DB name sent over '?db={db_name}' query parameter (default "db")
   -influxListenAddr string
     	TCP and UDP address to listen for InfluxDB line protocol data. Usually :8189 must be set. Doesn't work if empty. This flag isn't needed when ingesting data over HTTP - just send it to http://<vmagent>:8429/write
   -influxMeasurementFieldSeparator string