Add possibility to specify measurement per register (#7231)

plugins/inputs/modbus/README.md

@@ -52,6 +52,7 @@ The Modbus plugin collects Discrete Inputs, Coils, Input Registers and Holding R
  ]
 
  ## Analog Variables, Input Registers and Holding Registers
+ ## measurement - the (optional) measurement name, defaults to "modbus"
  ## name       - the variable name 
  ## byte_order - the ordering of bytes
  ##  |---AB, ABCD   - Big Endian

plugins/inputs/modbus/modbus.go

@@ -7,10 +7,12 @@ import (
 	"net"
 	"net/url"
 	"sort"
+	"time"
 
 	mb "github.com/goburrow/modbus"
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/metric"
 	"github.com/influxdata/telegraf/plugins/inputs"
 )
 
@@ -44,6 +46,7 @@ type register struct {
 }
 
 type fieldContainer struct {
+	Measurement string   `toml:"measurement"`
 	Name        string   `toml:"name"`
 	ByteOrder   string   `toml:"byte_order"`
 	DataType    string   `toml:"data_type"`
@@ -97,6 +100,7 @@ const sampleConfig = `
  ##
 
  ## Digital Variables, Discrete Inputs and Coils
+ ## measurement - the (optional) measurement name, defaults to "modbus"
  ## name        - the variable name
  ## address     - variable address
 
@@ -113,6 +117,7 @@ const sampleConfig = `
  ]
 
  ## Analog Variables, Input Registers and Holding Registers
+ ## measurement - the (optional) measurement name, defaults to "modbus"
  ## name        - the variable name
  ## byte_order  - the ordering of bytes
  ##  |---AB, ABCD   - Big Endian
@@ -319,10 +324,11 @@ func validateFieldContainers(t []fieldContainer, n string) error {
 		}
 
 		//search name duplicate
-		if nameEncountered[item.Name] {
-			return fmt.Errorf("name '%s' is duplicated in '%s' - '%s'", item.Name, n, item.Name)
+		canonical_name := item.Measurement + "." + item.Name
+		if nameEncountered[canonical_name] {
+			return fmt.Errorf("name '%s' is duplicated in measurement '%s' '%s' - '%s'", item.Name, item.Measurement, n, item.Name)
 		} else {
-			nameEncountered[item.Name] = true
+			nameEncountered[canonical_name] = true
 		}
 
 		if n == cInputRegisters || n == cHoldingRegisters {
@@ -635,6 +641,7 @@ func (m *Modbus) Gather(acc telegraf.Accumulator) error {
 		}
 	}
 
+	timestamp := time.Now()
 	err := m.getFields()
 	if err != nil {
 		disconnect(m)
@@ -642,18 +649,28 @@ func (m *Modbus) Gather(acc telegraf.Accumulator) error {
 		return err
 	}
 
+	grouper := metric.NewSeriesGrouper()
 	for _, reg := range m.registers {
-		fields := make(map[string]interface{})
 		tags := map[string]string{
 			"name": m.Name,
 			"type": reg.Type,
 		}
 
 		for _, field := range reg.Fields {
-			fields[field.Name] = field.value
+			// In case no measurement was specified we use "modbus" as default
+			measurement := "modbus"
+			if field.Measurement != "" {
+				measurement = field.Measurement
 			}
 
-		acc.AddFields("modbus", fields, tags)
+			// Group the data by series
+			grouper.Add(measurement, tags, timestamp, field.Name, field.value)
+		}
+
+		// Add the metrics grouped by series to the accumulator
+		for _, metric := range grouper.Metrics() {
+			acc.AddMetric(metric)
+		}
 	}
 
 	return nil