Rewriting Riemann output plugin (#1900)

* rename to riemann_legacy

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* initial draft for Riemann output plugin rewrite

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add unit tests

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add option to send string metrics as states

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add integration tests

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add plugin README.md

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* bump riemann library

* clarify settings description

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* update Readme.md with updated description

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add Riemann event examples

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* use full URL for Riemann server address

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

closes #1878

plugins/outputs/riemann_legacy/riemann.go

@@ -0,0 +1,156 @@
+package riemann_legacy
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"sort"
+	"strings"
+
+	"github.com/amir/raidman"
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/outputs"
+)
+
+const deprecationMsg = "E! Error: this Riemann output plugin will be deprecated in a future release, see https://github.com/influxdata/telegraf/issues/1878 for more details & discussion."
+
+type Riemann struct {
+	URL       string
+	Transport string
+	Separator string
+
+	client *raidman.Client
+}
+
+var sampleConfig = `
+  ## URL of server
+  url = "localhost:5555"
+  ## transport protocol to use either tcp or udp
+  transport = "tcp"
+  ## separator to use between input name and field name in Riemann service name
+  separator = " "
+`
+
+func (r *Riemann) Connect() error {
+	log.Printf(deprecationMsg)
+	c, err := raidman.Dial(r.Transport, r.URL)
+
+	if err != nil {
+		r.client = nil
+		return err
+	}
+
+	r.client = c
+	return nil
+}
+
+func (r *Riemann) Close() error {
+	if r.client == nil {
+		return nil
+	}
+	r.client.Close()
+	r.client = nil
+	return nil
+}
+
+func (r *Riemann) SampleConfig() string {
+	return sampleConfig
+}
+
+func (r *Riemann) Description() string {
+	return "Configuration for the Riemann server to send metrics to"
+}
+
+func (r *Riemann) Write(metrics []telegraf.Metric) error {
+	log.Printf(deprecationMsg)
+	if len(metrics) == 0 {
+		return nil
+	}
+
+	if r.client == nil {
+		err := r.Connect()
+		if err != nil {
+			return fmt.Errorf("FAILED to (re)connect to Riemann. Error: %s\n", err)
+		}
+	}
+
+	var events []*raidman.Event
+	for _, p := range metrics {
+		evs := buildEvents(p, r.Separator)
+		for _, ev := range evs {
+			events = append(events, ev)
+		}
+	}
+
+	var senderr = r.client.SendMulti(events)
+	if senderr != nil {
+		r.Close() // always retuns nil
+		return fmt.Errorf("FAILED to send riemann message (will try to reconnect). Error: %s\n",
+			senderr)
+	}
+
+	return nil
+}
+
+func buildEvents(p telegraf.Metric, s string) []*raidman.Event {
+	events := []*raidman.Event{}
+	for fieldName, value := range p.Fields() {
+		host, ok := p.Tags()["host"]
+		if !ok {
+			hostname, err := os.Hostname()
+			if err != nil {
+				host = "unknown"
+			} else {
+				host = hostname
+			}
+		}
+
+		event := &raidman.Event{
+			Host:    host,
+			Service: serviceName(s, p.Name(), p.Tags(), fieldName),
+		}
+
+		switch value.(type) {
+		case string:
+			event.State = value.(string)
+		default:
+			event.Metric = value
+		}
+
+		events = append(events, event)
+	}
+
+	return events
+}
+
+func serviceName(s string, n string, t map[string]string, f string) string {
+	serviceStrings := []string{}
+	serviceStrings = append(serviceStrings, n)
+
+	// we'll skip the 'host' tag
+	tagStrings := []string{}
+	tagNames := []string{}
+
+	for tagName := range t {
+		tagNames = append(tagNames, tagName)
+	}
+	sort.Strings(tagNames)
+
+	for _, tagName := range tagNames {
+		if tagName != "host" {
+			tagStrings = append(tagStrings, t[tagName])
+		}
+	}
+	var tagString string = strings.Join(tagStrings, s)
+	if tagString != "" {
+		serviceStrings = append(serviceStrings, tagString)
+	}
+	serviceStrings = append(serviceStrings, f)
+	return strings.Join(serviceStrings, s)
+}
+
+func init() {
+	outputs.Add("riemann_legacy", func() telegraf.Output {
+		return &Riemann{}
+	})
+}