feat(parsers.openmetrics): Add parser for OpenMetrics format

docs/DATA_FORMATS_INPUT.md

@@ -18,6 +18,7 @@ Protocol, JSON format, or Apache Avro format.
 - [JSON v2](/plugins/parsers/json_v2)
 - [Logfmt](/plugins/parsers/logfmt)
 - [Nagios](/plugins/parsers/nagios)
+- [OpenMetrics](/plugins/parsers/openmetrics)
 - [OpenTSDB](/plugins/parsers/opentsdb)
 - [Parquet](/plugins/parsers/parquet)
 - [Prometheus](/plugins/parsers/prometheus)

plugins/inputs/prometheus/README.md

@@ -32,6 +32,14 @@ See the [CONFIGURATION.md][CONFIGURATION.md] for more details.
   ## If set to true, the gather time will be used.
   # ignore_timestamp = false
 
+  ## Override content-type of the returned message
+  ## Available options are for prometheus:
+  ##   text, protobuf-delimiter, protobuf-compact, protobuf-text,
+  ## and for openmetrics:
+  ##   openmetrics-text, openmetrics-protobuf
+  ## By default the content-type of the response is used.
+  # content_type_override = ""
+
   ## An array of Kubernetes services to scrape metrics from.
   # kubernetes_services = ["http://my-service-dns.my-namespace:9100/metrics"]
 

plugins/inputs/prometheus/prometheus.go

@@ -15,6 +15,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/prometheus/common/expfmt"
 	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/client-go/tools/cache"
@@ -26,6 +27,7 @@ import (
 	"github.com/influxdata/telegraf/models"
 	httpconfig "github.com/influxdata/telegraf/plugins/common/http"
 	"github.com/influxdata/telegraf/plugins/inputs"
+	"github.com/influxdata/telegraf/plugins/parsers/openmetrics"
 	parser "github.com/influxdata/telegraf/plugins/parsers/prometheus"
 )
 
@@ -46,94 +48,71 @@ const (
 type PodID string
 
 type Prometheus struct {
-	// An array of urls to scrape metrics from.
-	URLs []string `toml:"urls"`
-
-	// An array of Kubernetes services to scrape metrics from.
-	KubernetesServices []string
-
-	// Location of kubernetes config file
-	KubeConfig string
-
-	// Label Selector/s for Kubernetes
-	KubernetesLabelSelector string `toml:"kubernetes_label_selector"`
-
-	// Field Selector/s for Kubernetes
-	KubernetesFieldSelector string `toml:"kubernetes_field_selector"`
-
-	// Consul SD configuration
+	URLs                 []string          `toml:"urls"`
+	BearerToken          string            `toml:"bearer_token"`
+	BearerTokenString    string            `toml:"bearer_token_string"`
+	Username             string            `toml:"username"`
+	Password             string            `toml:"password"`
+	HTTPHeaders          map[string]string `toml:"http_headers"`
+	ContentLengthLimit   config.Size       `toml:"content_length_limit"`
+	ContentTypeOverride  string            `toml:"content_type_override"`
+	EnableRequestMetrics bool              `toml:"enable_request_metrics"`
+	MetricVersion        int               `toml:"metric_version"`
+	URLTag               string            `toml:"url_tag"`
+	IgnoreTimestamp      bool              `toml:"ignore_timestamp"`
+
+	// Kubernetes service discovery
+	MonitorPods                 bool                `toml:"monitor_kubernetes_pods"`
+	PodScrapeScope              string              `toml:"pod_scrape_scope"`
+	NodeIP                      string              `toml:"node_ip"`
+	PodScrapeInterval           int                 `toml:"pod_scrape_interval"`
+	PodNamespace                string              `toml:"monitor_kubernetes_pods_namespace"`
+	PodNamespaceLabelName       string              `toml:"pod_namespace_label_name"`
+	KubernetesServices          []string            `toml:"kubernetes_services"`
+	KubeConfig                  string              `toml:"kube_config"`
+	KubernetesLabelSelector     string              `toml:"kubernetes_label_selector"`
+	KubernetesFieldSelector     string              `toml:"kubernetes_field_selector"`
+	MonitorKubernetesPodsMethod MonitorMethod       `toml:"monitor_kubernetes_pods_method"`
+	MonitorKubernetesPodsScheme string              `toml:"monitor_kubernetes_pods_scheme"`
+	MonitorKubernetesPodsPath   string              `toml:"monitor_kubernetes_pods_path"`
+	MonitorKubernetesPodsPort   int                 `toml:"monitor_kubernetes_pods_port"`
+	NamespaceAnnotationPass     map[string][]string `toml:"namespace_annotation_pass"`
+	NamespaceAnnotationDrop     map[string][]string `toml:"namespace_annotation_drop"`
+	PodAnnotationInclude        []string            `toml:"pod_annotation_include"`
+	PodAnnotationExclude        []string            `toml:"pod_annotation_exclude"`
+	PodLabelInclude             []string            `toml:"pod_label_include"`
+	PodLabelExclude             []string            `toml:"pod_label_exclude"`
+	CacheRefreshInterval        int                 `toml:"cache_refresh_interval"`
+
+	// Consul discovery
 	ConsulConfig ConsulConfig `toml:"consul"`
 
-	// Bearer Token authorization file path
-	BearerToken       string `toml:"bearer_token"`
-	BearerTokenString string `toml:"bearer_token_string"`
-
-	// Basic authentication credentials
-	Username string `toml:"username"`
-	Password string `toml:"password"`
-
-	HTTPHeaders map[string]string `toml:"http_headers"`
-
-	ContentLengthLimit   config.Size `toml:"content_length_limit"`
-	EnableRequestMetrics bool        `toml:"enable_request_metrics"`
-
-	MetricVersion int `toml:"metric_version"`
-
-	URLTag string `toml:"url_tag"`
-
-	IgnoreTimestamp bool `toml:"ignore_timestamp"`
-
-	Log telegraf.Logger
-
+	Log telegraf.Logger `toml:"-"`
 	httpconfig.HTTPClientConfig
 
-	client  *http.Client
-	headers map[string]string
-
-	nsStore cache.Store
+	client      *http.Client
+	headers     map[string]string
+	contentType string
 
+	nsStore          cache.Store
 	nsAnnotationPass []models.TagFilter
 	nsAnnotationDrop []models.TagFilter
 
 	// Should we scrape Kubernetes services for prometheus annotations
-	MonitorPods           bool   `toml:"monitor_kubernetes_pods"`
-	PodScrapeScope        string `toml:"pod_scrape_scope"`
-	NodeIP                string `toml:"node_ip"`
-	PodScrapeInterval     int    `toml:"pod_scrape_interval"`
-	PodNamespace          string `toml:"monitor_kubernetes_pods_namespace"`
-	PodNamespaceLabelName string `toml:"pod_namespace_label_name"`
-	lock                  sync.Mutex
-	kubernetesPods        map[PodID]URLAndAddress
-	cancel                context.CancelFunc
-	wg                    sync.WaitGroup
+	lock           sync.Mutex
+	kubernetesPods map[PodID]URLAndAddress
+	cancel         context.CancelFunc
+	wg             sync.WaitGroup
 
 	// Only for monitor_kubernetes_pods=true and pod_scrape_scope="node"
-	podLabelSelector  labels.Selector
-	podFieldSelector  fields.Selector
-	isNodeScrapeScope bool
-
-	MonitorKubernetesPodsMethod MonitorMethod `toml:"monitor_kubernetes_pods_method"`
-	MonitorKubernetesPodsScheme string        `toml:"monitor_kubernetes_pods_scheme"`
-	MonitorKubernetesPodsPath   string        `toml:"monitor_kubernetes_pods_path"`
-	MonitorKubernetesPodsPort   int           `toml:"monitor_kubernetes_pods_port"`
-
-	NamespaceAnnotationPass map[string][]string `toml:"namespace_annotation_pass"`
-	NamespaceAnnotationDrop map[string][]string `toml:"namespace_annotation_drop"`
-
-	PodAnnotationInclude []string `toml:"pod_annotation_include"`
-	PodAnnotationExclude []string `toml:"pod_annotation_exclude"`
-
-	PodLabelInclude []string `toml:"pod_label_include"`
-	PodLabelExclude []string `toml:"pod_label_exclude"`
-
+	podLabelSelector           labels.Selector
+	podFieldSelector           fields.Selector
+	isNodeScrapeScope          bool
 	podAnnotationIncludeFilter filter.Filter
 	podAnnotationExcludeFilter filter.Filter
 	podLabelIncludeFilter      filter.Filter
 	podLabelExcludeFilter      filter.Filter
 
-	// Only for monitor_kubernetes_pods=true
-	CacheRefreshInterval int `toml:"cache_refresh_interval"`
-
 	// List of consul services to scrape
 	consulServices map[string]URLAndAddress
 }
@@ -143,6 +122,29 @@ func (*Prometheus) SampleConfig() string {
 }
 
 func (p *Prometheus) Init() error {
+	// Setup content-type override if requested
+	switch p.ContentTypeOverride {
+	case "": // No override
+	case "text":
+		p.contentType = string(expfmt.NewFormat(expfmt.TypeTextPlain))
+	case "protobuf-delimiter":
+		p.contentType = string(expfmt.NewFormat(expfmt.TypeProtoDelim))
+	case "protobuf-compact":
+		p.contentType = string(expfmt.NewFormat(expfmt.TypeProtoCompact))
+	case "protobuf-text":
+		p.contentType = string(expfmt.NewFormat(expfmt.TypeProtoText))
+	case "openmetrics-text":
+		f, err := expfmt.NewOpenMetricsFormat(expfmt.OpenMetricsVersion_1_0_0)
+		if err != nil {
+			return err
+		}
+		p.contentType = string(f)
+	case "openmetrics-protobuf":
+		p.contentType = "application/openmetrics-protobuf;version=1.0.0"
+	default:
+		return fmt.Errorf("invalid 'content_type_override' setting %q", p.ContentTypeOverride)
+	}
+
 	// Config processing for node scrape scope for monitor_kubernetes_pods
 	p.isNodeScrapeScope = strings.EqualFold(p.PodScrapeScope, "node")
 	if p.isNodeScrapeScope {
@@ -491,14 +493,29 @@ func (p *Prometheus) gatherURL(u URLAndAddress, acc telegraf.Accumulator) (map[s
 			return requestFields, tags, fmt.Errorf("error reading body: %w", err)
 		}
 	}
-
 	requestFields["content_length"] = len(body)
+
+	// Override the response format if the user requested it
+	if p.contentType != "" {
+		resp.Header.Set("Content-Type", p.contentType)
+	}
+
 	// Parse the metrics
-	metricParser := parser.Parser{
-		Header:          resp.Header,
-		MetricVersion:   p.MetricVersion,
-		IgnoreTimestamp: p.IgnoreTimestamp,
-		Log:             p.Log,
+	var metricParser telegraf.Parser
+	if openmetrics.AcceptsContent(resp.Header) {
+		metricParser = &openmetrics.Parser{
+			Header:          resp.Header,
+			MetricVersion:   p.MetricVersion,
+			IgnoreTimestamp: p.IgnoreTimestamp,
+			Log:             p.Log,
+		}
+	} else {
+		metricParser = &parser.Parser{
+			Header:          resp.Header,
+			MetricVersion:   p.MetricVersion,
+			IgnoreTimestamp: p.IgnoreTimestamp,
+			Log:             p.Log,
+		}
 	}
 	metrics, err := metricParser.Parse(body)
 	if err != nil {