feat: add nomad input plugin

plugins/inputs/all/all.go

@@ -127,6 +127,7 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/inputs/nginx_sts"
 	_ "github.com/influxdata/telegraf/plugins/inputs/nginx_upstream_check"
 	_ "github.com/influxdata/telegraf/plugins/inputs/nginx_vts"
+	_ "github.com/influxdata/telegraf/plugins/inputs/nomad"
 	_ "github.com/influxdata/telegraf/plugins/inputs/nsd"
 	_ "github.com/influxdata/telegraf/plugins/inputs/nsq"
 	_ "github.com/influxdata/telegraf/plugins/inputs/nsq_consumer"

plugins/inputs/nomad/README.md

@@ -0,0 +1,35 @@
+# Hashicorp Nomad Input Plugin
+
+The Nomad plugin must grab metrics from every Nomad agent of the cluster. Telegraf may be present in every node and connect to the agent locally. In this case should be something like `http://127.0.0.1:4646`.
+
+> Tested on Nomad 1.1.6
+
+## Configuration
+
+```toml
+[[inputs.nomad]]
+  ## URL for the Nomad agent
+  # url = "http://127.0.0.1:4646"
+
+  ## Use auth token for authorization. 
+  ## If both are set, an error is thrown.
+  ## If both are empty, no token will be used.
+  # nomad_token = "/path/to/auth/token"
+  ## OR
+  # nomad_token_string = "a1234567-40c7-9048-7bae-378687048181"
+
+  ## Set response_timeout (default 5 seconds)
+  # response_timeout = "5s"
+
+  ## Optional TLS Config
+  # tls_ca = /path/to/cafile
+  # tls_cert = /path/to/certfile
+  # tls_key = /path/to/keyfile
+```
+
+## Metrics
+
+Both Nomad servers and agents collect various metrics. For every details, please have a look at Nomad following documentation:
+
+- [https://www.nomadproject.io/docs/operations/metrics](https://www.nomadproject.io/docs/operations/metrics)
+- [https://www.nomadproject.io/docs/operations/telemetry](https://www.nomadproject.io/docs/operations/telemetry)

plugins/inputs/nomad/nomad.go

@@ -0,0 +1,203 @@
+package nomad
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/config"
+	"github.com/influxdata/telegraf/plugins/common/tls"
+	"github.com/influxdata/telegraf/plugins/inputs"
+)
+
+// Nomad configuration object
+type Nomad struct {
+	URL string `toml:"url"`
+
+	NomadToken       string `toml:"nomad_token"`
+	NomadTokenString string `toml:"nomad_token_string"`
+
+	ResponseTimeout config.Duration `toml:"response_timeout"`
+
+	tls.ClientConfig
+
+	roundTripper http.RoundTripper
+}
+
+const timeLayout = "2006-01-02 15:04:05 -0700 MST"
+
+var sampleConfig = `
+  ## URL for the Nomad agent
+  # url = "http://127.0.0.1:4646"
+
+  ## Use auth token for authorization. 
+  ## Only one of the options can be set. Leave empty to not use any token.
+  # nomad_token = "/path/to/auth/token"
+  ## OR
+  # nomad_token_string = "a1234567-40c7-9048-7bae-378687048181"
+
+  ## Set response_timeout (default 5 seconds)
+  # response_timeout = "5s"
+
+  ## Optional TLS Config
+  # tls_ca = /path/to/cafile
+  # tls_cert = /path/to/certfile
+  # tls_key = /path/to/keyfile
+`
+
+func init() {
+	inputs.Add("nomad", func() telegraf.Input {
+		return &Nomad{
+			ResponseTimeout: config.Duration(5 * time.Second),
+		}
+	})
+}
+
+// SampleConfig returns a sample config
+func (n *Nomad) SampleConfig() string {
+	return sampleConfig
+}
+
+// Description returns a description of the plugin
+func (n *Nomad) Description() string {
+	return "Read metrics from the Nomad API"
+}
+
+func (n *Nomad) Init() error {
+	if n.URL == "" {
+		n.URL = "http://127.0.0.1:4646"
+	}
+
+	if n.NomadToken != "" && n.NomadTokenString != "" {
+		return fmt.Errorf("config error: both nomad_token and nomad_token_string are set")
+	}
+
+	if n.NomadToken != "" {
+		token, err := os.ReadFile(n.NomadToken)
+		if err != nil {
+			return fmt.Errorf("reading file failed: %v", err)
+		}
+		n.NomadTokenString = strings.TrimSpace(string(token))
+	}
+
+	tlsCfg, err := n.ClientConfig.TLSConfig()
+	if err != nil {
+		return fmt.Errorf("setting up TLS configuration failed: %v", err)
+	}
+
+	n.roundTripper = &http.Transport{
+		TLSHandshakeTimeout:   5 * time.Second,
+		TLSClientConfig:       tlsCfg,
+		ResponseHeaderTimeout: time.Duration(n.ResponseTimeout),
+	}
+
+	return nil
+}
+
+// Gather, collects metrics from Nomad endpoint
+func (n *Nomad) Gather(acc telegraf.Accumulator) error {
+	summaryMetrics := &MetricsSummary{}
+	err := n.loadJSON(n.URL+"/v1/metrics", summaryMetrics)
+	if err != nil {
+		return err
+	}
+
+	err = buildNomadMetrics(acc, summaryMetrics)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (n *Nomad) loadJSON(url string, v interface{}) error {
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return err
+	}
+
+	req.Header.Set("Authorization", "X-Nomad-Token "+n.NomadTokenString)
+	req.Header.Add("Accept", "application/json")
+
+	resp, err := n.roundTripper.RoundTrip(req)
+	if err != nil {
+		return fmt.Errorf("error making HTTP request to %s: %s", url, err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("%s returned HTTP status %s", url, resp.Status)
+	}
+
+	err = json.NewDecoder(resp.Body).Decode(v)
+	if err != nil {
+		return fmt.Errorf("error parsing json response: %s", err)
+	}
+
+	return nil
+}
+
+// buildNomadMetrics, it builds all the metrics and adds them to the accumulator)
+func buildNomadMetrics(acc telegraf.Accumulator, summaryMetrics *MetricsSummary) error {
+	t, err := time.Parse(timeLayout, summaryMetrics.Timestamp)
+	if err != nil {
+		return fmt.Errorf("error parsing time: %s", err)
+	}
+
+	for _, counters := range summaryMetrics.Counters {
+		tags := counters.DisplayLabels
+
+		fields := map[string]interface{}{
+			"count": counters.Count,
+			"rate":  counters.Rate,
+			"sum":   counters.Sum,
+			"sumsq": counters.SumSq,
+			"min":   counters.Min,
+			"max":   counters.Max,
+			"mean":  counters.Mean,
+		}
+		acc.AddCounter(counters.Name, fields, tags, t)
+	}
+
+	for _, gauges := range summaryMetrics.Gauges {
+		tags := gauges.DisplayLabels
+
+		fields := map[string]interface{}{
+			"value": gauges.Value,
+		}
+
+		acc.AddGauge(gauges.Name, fields, tags, t)
+	}
+
+	for _, points := range summaryMetrics.Points {
+		tags := make(map[string]string)
+
+		fields := map[string]interface{}{
+			"value": points.Points,
+		}
+
+		acc.AddFields(points.Name, fields, tags, t)
+	}
+
+	for _, samples := range summaryMetrics.Samples {
+		tags := samples.DisplayLabels
+
+		fields := map[string]interface{}{
+			"count":  samples.Count,
+			"rate":   samples.Rate,
+			"sum":    samples.Sum,
+			"stddev": samples.Stddev,
+			"sumsq":  samples.SumSq,
+			"min":    samples.Min,
+			"max":    samples.Max,
+			"mean":   samples.Mean,
+		}
+		acc.AddCounter(samples.Name, fields, tags, t)
+	}
+
+	return nil
+}

plugins/inputs/nomad/nomad_metrics.go

@@ -0,0 +1,53 @@
+package nomad
+
+import (
+	"time"
+)
+
+type MetricsSummary struct {
+	Timestamp string         `json:"timestamp"`
+	Gauges    []GaugeValue   `json:"gauges"`
+	Points    []PointValue   `json:"points"`
+	Counters  []SampledValue `json:"counters"`
+	Samples   []SampledValue `json:"samples"`
+}
+
+type GaugeValue struct {
+	Name  string  `json:"name"`
+	Hash  string  `json:"-"`
+	Value float32 `json:"value"`
+
+	Labels        []Label           `json:"-"`
+	DisplayLabels map[string]string `json:"Labels"`
+}
+
+type PointValue struct {
+	Name   string    `json:"name"`
+	Points []float32 `json:"points"`
+}
+
+type SampledValue struct {
+	Name string `json:"name"`
+	Hash string `json:"-"`
+	*AggregateSample
+	Mean   float64 `json:"mean"`
+	Stddev float64 `json:"stddev"`
+
+	Labels        []Label           `json:"-"`
+	DisplayLabels map[string]string `json:"Labels"`
+}
+
+type AggregateSample struct {
+	Count       int       `json:"count"`
+	Rate        float64   `json:"rate"`
+	Sum         float64   `json:"sum"`
+	SumSq       float64   `json:"-"`
+	Min         float64   `json:"min"`
+	Max         float64   `json:"max"`
+	LastUpdated time.Time `json:"-"`
+}
+
+type Label struct {
+	Name  string `json:"name"`
+	Value string `json:"value"`
+}