Add processor to look up service name by port

Makefile

@@ -72,6 +72,7 @@ test-windows:
 	go test -short ./plugins/inputs/win_services/...
 	go test -short ./plugins/inputs/procstat/...
 	go test -short ./plugins/inputs/ntpq/...
+	go test -short ./plugins/processors/port_name/...
 
 .PHONY: vet
 vet:

plugins/processors/all/all.go

@@ -10,6 +10,7 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/processors/override"
 	_ "github.com/influxdata/telegraf/plugins/processors/parser"
 	_ "github.com/influxdata/telegraf/plugins/processors/pivot"
+	_ "github.com/influxdata/telegraf/plugins/processors/port_name"
 	_ "github.com/influxdata/telegraf/plugins/processors/printer"
 	_ "github.com/influxdata/telegraf/plugins/processors/regex"
 	_ "github.com/influxdata/telegraf/plugins/processors/rename"

plugins/processors/port_name/README.md

@@ -0,0 +1,26 @@
+# Port Name Lookup Processor Plugin
+
+Use the `port_name` processor to convert a tag containing a well-known port number to the registered service name.
+
+Tag can contain a number ("80") or number and protocol separated by slash ("443/tcp"). If protocol is not provided it defaults to tcp but can be changed with the default_protocol setting.
+
+### Configuration
+
+```toml
+[[processors.port_name]]
+  ## Name of tag holding the port number
+  # tag = "port"
+
+  ## Name of output tag where service name will be added
+  # dest = "service"
+
+  ## Default tcp or udp
+  # default_protocol = "tcp"
+```
+
+### Example
+
+```diff
+- measurement,port=80 field=123 1560540094000000000
++ measurement,port=80,service=http field=123 1560540094000000000
+```

plugins/processors/port_name/port_name.go

@@ -0,0 +1,174 @@
+package portname
+
+import (
+	"bufio"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/processors"
+)
+
+var sampleConfig = `
+[[processors.port_name]]
+  ## Name of tag holding the port number
+  # tag = "port"
+
+  ## Name of output tag where service name will be added
+  # dest = "service"
+
+  ## Default tcp or udp
+  # default_protocol = "tcp"
+`
+
+type sMap map[string]map[int]string // "https" == services["tcp"][443]
+
+var services sMap
+
+type PortName struct {
+	SourceTag       string `toml:"tag"`
+	DestTag         string `toml:"dest"`
+	DefaultProtocol string `toml:"default_protocol"`
+
+	Log telegraf.Logger `toml:"-"`
+}
+
+func (d *PortName) SampleConfig() string {
+	return sampleConfig
+}
+
+func (d *PortName) Description() string {
+	return "Given a tag of a TCP or UDP port number, add a tag of the service name looked up in the system services file"
+}
+
+func readServicesFile() {
+	file, err := os.Open(servicesPath())
+	if err != nil {
+		return
+	}
+	defer file.Close()
+
+	services = readServices(file)
+}
+
+// Read the services file into a map.
+//
+// This function takes a similar approach to parsing as the go
+// standard library (see src/net/port_unix.go in golang source) but
+// maps protocol and port number to service name, not protocol and
+// service to port number.
+func readServices(r io.Reader) sMap {
+	services = make(sMap)
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := scanner.Text()
+		// "http 80/tcp www www-http # World Wide Web HTTP"
+		if i := strings.Index(line, "#"); i >= 0 {
+			line = line[:i]
+		}
+		f := strings.Fields(line)
+		if len(f) < 2 {
+			continue
+		}
+		service := f[0]   // "http"
+		portProto := f[1] // "80/tcp"
+		portProtoSlice := strings.SplitN(portProto, "/", 2)
+		if len(portProtoSlice) < 2 {
+			continue
+		}
+		port, err := strconv.Atoi(portProtoSlice[0]) // "80"
+		if err != nil || port <= 0 {
+			continue
+		}
+		proto := portProtoSlice[1] // "tcp"
+		proto = strings.ToLower(proto)
+
+		protoMap, ok := services[proto]
+		if !ok {
+			protoMap = make(map[int]string)
+			services[proto] = protoMap
+		}
+		protoMap[port] = service
+	}
+	return services
+}
+
+func (d *PortName) Apply(metrics ...telegraf.Metric) []telegraf.Metric {
+	for _, m := range metrics {
+		portProto, ok := m.GetTag(d.SourceTag)
+		if !ok {
+			// Nonexistent tag
+			continue
+		}
+		portProtoSlice := strings.SplitN(portProto, "/", 2)
+		l := len(portProtoSlice)
+
+		if l == 0 {
+			// Empty tag
+			d.Log.Errorf("empty port tag: %v", d.SourceTag)
+			continue
+		}
+
+		var port int
+		if l > 0 {
+			var err error
+			val := portProtoSlice[0]
+			port, err = strconv.Atoi(val)
+			if err != nil {
+				// Can't convert port to string
+				d.Log.Errorf("error converting port to integer: %v", val)
+				continue
+			}
+		}
+
+		proto := d.DefaultProtocol
+		if l > 1 && len(portProtoSlice[1]) > 0 {
+			proto = portProtoSlice[1]
+		}
+		proto = strings.ToLower(proto)
+
+		protoMap, ok := services[proto]
+		if !ok {
+			// Unknown protocol
+			//
+			// Protocol is normally tcp or udp.  The services file
+			// normally has entries for both, so our map does too.  If
+			// not, it's very likely the source tag or the services
+			// file doesn't make sense.
+			d.Log.Errorf("protocol not found in services map: %v", proto)
+			continue
+		}
+
+		service, ok := protoMap[port]
+		if !ok {
+			// Unknown port
+			//
+			// Not all ports are named so this isn't an error, but
+			// it's helpful to know when debugging.
+			d.Log.Debugf("port not found in services map: %v", port)
+			continue
+		}
+
+		m.AddTag(d.DestTag, service)
+	}
+
+	return metrics
+}
+
+func (h *PortName) Init() error {
+	services = make(sMap)
+	readServicesFile()
+	return nil
+}
+
+func init() {
+	processors.Add("port_name", func() telegraf.Processor {
+		return &PortName{
+			SourceTag:       "port",
+			DestTag:         "service",
+			DefaultProtocol: "tcp",
+		}
+	})
+}