Backend plugins: Exclude plugin metrics in Grafana's metrics endpoint (#22857)

Excludes backend plugin metrics in Grafana's metrics endpoint
Adds /api/:pluginId/metrics endpoint for retrieving metrics
from backend plugin as Prometheus text-based exposition format.

Fixes #22814

pkg/api/api.go

@@ -258,6 +258,7 @@ func (hs *HTTPServer) registerRoutes() {
 		apiRoute.Group("/plugins", func(pluginRoute routing.RouteRegister) {
 			pluginRoute.Get("/:pluginId/dashboards/", Wrap(GetPluginDashboards))
 			pluginRoute.Post("/:pluginId/settings", bind(models.UpdatePluginSettingCmd{}), Wrap(UpdatePluginSetting))
+			pluginRoute.Get("/:pluginId/metrics", Wrap(hs.CollectPluginMetrics))
 		}, reqOrgAdmin)
 
 		apiRoute.Get("/frontend/settings/", hs.GetFrontendSettings)

pkg/api/plugins.go

@@ -2,6 +2,7 @@ package api
 
 import (
 	"errors"
+	"net/http"
 	"sort"
 	"time"
 
@@ -247,6 +248,39 @@ func ImportDashboard(c *models.ReqContext, apiCmd dtos.ImportDashboardCommand) R
 	return JSON(200, cmd.Result)
 }
 
+// CollectPluginMetrics collect metrics from a plugin.
+//
+// /api/plugins/:pluginId/metrics
+func (hs *HTTPServer) CollectPluginMetrics(c *models.ReqContext) Response {
+	pluginID := c.Params("pluginId")
+	plugin, exists := plugins.Plugins[pluginID]
+	if !exists {
+		return Error(404, "Plugin not found, no installed plugin with that id", nil)
+	}
+
+	resp, err := hs.BackendPluginManager.CollectMetrics(c.Req.Context(), plugin.Id)
+	if err != nil {
+		if err == backendplugin.ErrPluginNotRegistered {
+			return Error(404, "Plugin not found", err)
+		}
+
+		if err == backendplugin.ErrDiagnosticsNotSupported {
+			return Error(404, "Health check not implemented", err)
+		}
+
+		return Error(500, "Collect plugin metrics failed", err)
+	}
+
+	headers := make(http.Header)
+	headers.Set("Content-Type", "text/plain")
+
+	return &NormalResponse{
+		header: headers,
+		body:   resp.PrometheusMetrics,
+		status: http.StatusOK,
+	}
+}
+
 // CheckHealth returns the health of a plugin.
 // /api/plugins/:pluginId/health
 func (hs *HTTPServer) CheckHealth(c *models.ReqContext) Response {

pkg/plugins/backendplugin/backend_plugin.go

@@ -1,26 +1,20 @@
 package backendplugin
 
 import (
-	"bytes"
 	"context"
 	"errors"
-	"fmt"
 	"net/http"
 	"time"
 
 	"github.com/grafana/grafana-plugin-sdk-go/genproto/pluginv2"
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/common/expfmt"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 
 	datasourceV1 "github.com/grafana/grafana-plugin-model/go/datasource"
 	rendererV1 "github.com/grafana/grafana-plugin-model/go/renderer"
 	"github.com/grafana/grafana/pkg/infra/log"
-	"github.com/grafana/grafana/pkg/plugins/backendplugin/collector"
 	"github.com/grafana/grafana/pkg/util/errutil"
 	plugin "github.com/hashicorp/go-plugin"
-	dto "github.com/prometheus/client_model/go"
 )
 
 // BackendPlugin a registered backend plugin.
@@ -140,49 +134,27 @@ func (p *BackendPlugin) supportsDiagnostics() bool {
 }
 
 // CollectMetrics implements the collector.Collector interface.
-func (p *BackendPlugin) CollectMetrics(ctx context.Context, ch chan<- prometheus.Metric) error {
-	if p.diagnostics == nil {
-		return nil
-	}
-
-	if p.client == nil || p.client.Exited() {
-		return nil
+func (p *BackendPlugin) CollectMetrics(ctx context.Context) (*pluginv2.CollectMetricsResponse, error) {
+	if p.diagnostics == nil || p.client == nil || p.client.Exited() {
+		return &pluginv2.CollectMetricsResponse{
+			Metrics: &pluginv2.CollectMetricsResponse_Payload{},
+		}, nil
 	}
 
 	res, err := p.diagnostics.CollectMetrics(ctx, &pluginv2.CollectMetricsRequest{})
 	if err != nil {
 		if st, ok := status.FromError(err); ok {
 			if st.Code() == codes.Unimplemented {
-				return nil
+				return &pluginv2.CollectMetricsResponse{
+					Metrics: &pluginv2.CollectMetricsResponse_Payload{},
+				}, nil
 			}
 		}
 
-		return err
+		return nil, err
 	}
 
-	if res == nil || res.Metrics == nil || res.Metrics.Prometheus == nil {
-		return nil
-	}
-
-	reader := bytes.NewReader(res.Metrics.Prometheus)
-	var parser expfmt.TextParser
-	families, err := parser.TextToMetricFamilies(reader)
-	if err != nil {
-		return errutil.Wrap("failed to parse collected metrics", err)
-	}
-
-	for _, mf := range families {
-		if mf.Help == nil {
-			help := fmt.Sprintf("Metric read from %s plugin", p.id)
-			mf.Help = &help
-		}
-	}
-
-	for _, mf := range families {
-		convertMetricFamily(p.id, mf, ch, p.logger)
-	}
-
-	return nil
+	return res, nil
 }
 
 func (p *BackendPlugin) checkHealth(ctx context.Context, config *PluginConfig) (*pluginv2.CheckHealthResponse, error) {
@@ -321,112 +293,3 @@ func (p *BackendPlugin) callResource(ctx context.Context, req CallResourceReques
 		stream: protoStream,
 	}, nil
 }
-
-// convertMetricFamily converts metric family to prometheus.Metric.
-// Copied from https://github.com/prometheus/node_exporter/blob/3ddc82c2d8d11eec53ed5faa8db969a1bb81f8bb/collector/textfile.go#L66-L165
-func convertMetricFamily(pluginID string, metricFamily *dto.MetricFamily, ch chan<- prometheus.Metric, logger log.Logger) {
-	var valType prometheus.ValueType
-	var val float64
-
-	allLabelNames := map[string]struct{}{}
-	for _, metric := range metricFamily.Metric {
-		labels := metric.GetLabel()
-		for _, label := range labels {
-			if _, ok := allLabelNames[label.GetName()]; !ok {
-				allLabelNames[label.GetName()] = struct{}{}
-			}
-		}
-	}
-
-	for _, metric := range metricFamily.Metric {
-		if metric.TimestampMs != nil {
-			logger.Warn("Ignoring unsupported custom timestamp on metric", "metric", metric)
-		}
-
-		labels := metric.GetLabel()
-		var names []string
-		var values []string
-		for _, label := range labels {
-			names = append(names, label.GetName())
-			values = append(values, label.GetValue())
-		}
-		names = append(names, "plugin_id")
-		values = append(values, pluginID)
-
-		for k := range allLabelNames {
-			present := false
-			for _, name := range names {
-				if k == name {
-					present = true
-					break
-				}
-			}
-			if !present {
-				names = append(names, k)
-				values = append(values, "")
-			}
-		}
-
-		metricName := prometheus.BuildFQName(collector.Namespace, "", *metricFamily.Name)
-
-		metricType := metricFamily.GetType()
-		switch metricType {
-		case dto.MetricType_COUNTER:
-			valType = prometheus.CounterValue
-			val = metric.Counter.GetValue()
-
-		case dto.MetricType_GAUGE:
-			valType = prometheus.GaugeValue
-			val = metric.Gauge.GetValue()
-
-		case dto.MetricType_UNTYPED:
-			valType = prometheus.UntypedValue
-			val = metric.Untyped.GetValue()
-
-		case dto.MetricType_SUMMARY:
-			quantiles := map[float64]float64{}
-			for _, q := range metric.Summary.Quantile {
-				quantiles[q.GetQuantile()] = q.GetValue()
-			}
-			ch <- prometheus.MustNewConstSummary(
-				prometheus.NewDesc(
-					metricName,
-					metricFamily.GetHelp(),
-					names, nil,
-				),
-				metric.Summary.GetSampleCount(),
-				metric.Summary.GetSampleSum(),
-				quantiles, values...,
-			)
-		case dto.MetricType_HISTOGRAM:
-			buckets := map[float64]uint64{}
-			for _, b := range metric.Histogram.Bucket {
-				buckets[b.GetUpperBound()] = b.GetCumulativeCount()
-			}
-			ch <- prometheus.MustNewConstHistogram(
-				prometheus.NewDesc(
-					metricName,
-					metricFamily.GetHelp(),
-					names, nil,
-				),
-				metric.Histogram.GetSampleCount(),
-				metric.Histogram.GetSampleSum(),
-				buckets, values...,
-			)
-		default:
-			logger.Error("unknown metric type", "type", metricType)
-			continue
-		}
-
-		if metricType == dto.MetricType_GAUGE || metricType == dto.MetricType_COUNTER || metricType == dto.MetricType_UNTYPED {
-			ch <- prometheus.MustNewConstMetric(
-				prometheus.NewDesc(
-					metricName,
-					metricFamily.GetHelp(),
-					names, nil,
-				),
-				valType, val, values...,
-			)
-		}
-	}
-}

pkg/plugins/backendplugin/collector/collector.go

@@ -1,89 +0,0 @@
-package collector
-
-import (
-	"context"
-	"sync"
-	"time"
-
-	"github.com/grafana/grafana/pkg/infra/log"
-	"github.com/prometheus/client_golang/prometheus"
-)
-
-// Namespace collector metric namespace
-const Namespace = "grafana_plugin"
-
-var (
-	scrapeDurationDesc = prometheus.NewDesc(
-		prometheus.BuildFQName(Namespace, "scrape", "duration_seconds"),
-		"grafana_plugin: Duration of a plugin collector scrape.",
-		[]string{"plugin_id"},
-		nil,
-	)
-	scrapeSuccessDesc = prometheus.NewDesc(
-		prometheus.BuildFQName(Namespace, "scrape", "success"),
-		"grafana_plugin: Whether a plugin collector succeeded.",
-		[]string{"plugin_id"},
-		nil,
-	)
-)
-
-// Collector is the interface a plugin collector has to implement.
-type Collector interface {
-	// Get new metrics and expose them via prometheus registry.
-	CollectMetrics(ctx context.Context, ch chan<- prometheus.Metric) error
-}
-
-// PluginCollector implements the prometheus.Collector interface.
-type PluginCollector struct {
-	collectors map[string]Collector
-	logger     log.Logger
-}
-
-// NewPluginCollector creates a new PluginCollector..
-func NewPluginCollector() PluginCollector {
-	return PluginCollector{
-		collectors: make(map[string]Collector),
-		logger:     log.New("plugins.backend.collector"),
-	}
-}
-
-func (pc PluginCollector) Register(pluginID string, c Collector) {
-	pc.collectors[pluginID] = c
-}
-
-// Describe implements the prometheus.Collector interface.
-func (pc PluginCollector) Describe(ch chan<- *prometheus.Desc) {
-	ch <- scrapeDurationDesc
-	ch <- scrapeSuccessDesc
-}
-
-// Collect implements the prometheus.Collector interface.
-func (pc PluginCollector) Collect(ch chan<- prometheus.Metric) {
-	ctx := context.Background()
-	wg := sync.WaitGroup{}
-	wg.Add(len(pc.collectors))
-	for name, c := range pc.collectors {
-		go func(name string, c Collector) {
-			execute(ctx, name, c, ch, pc.logger)
-			wg.Done()
-		}(name, c)
-	}
-	wg.Wait()
-}
-
-func execute(ctx context.Context, pluginID string, c Collector, ch chan<- prometheus.Metric, logger log.Logger) {
-	begin := time.Now()
-	err := c.CollectMetrics(ctx, ch)
-	duration := time.Since(begin)
-	var success float64
-
-	if err != nil {
-		logger.Error("collector failed", "pluginId", pluginID, "took", duration, "error", err)
-		success = 0
-	} else {
-		logger.Debug("collector succeeded", "pluginId", pluginID, "took", duration)
-		success = 1
-	}
-	ch <- prometheus.MustNewConstMetric(scrapeDurationDesc, prometheus.GaugeValue, duration.Seconds(), pluginID)
-	ch <- prometheus.MustNewConstMetric(scrapeSuccessDesc, prometheus.GaugeValue, success, pluginID)
-}

pkg/plugins/backendplugin/contracts.go

@@ -59,6 +59,23 @@ func checkHealthResultFromProto(protoResp *pluginv2.CheckHealthResponse) *CheckH
 	}
 }
 
+func collectMetricsResultFromProto(protoResp *pluginv2.CollectMetricsResponse) *CollectMetricsResult {
+	var prometheusMetrics []byte
+
+	if protoResp.Metrics != nil {
+		prometheusMetrics = protoResp.Metrics.Prometheus
+	}
+
+	return &CollectMetricsResult{
+		PrometheusMetrics: prometheusMetrics,
+	}
+}
+
+// CollectMetricsResult collect metrics result.
+type CollectMetricsResult struct {
+	PrometheusMetrics []byte
+}
+
 type DataSourceConfig struct {
 	ID                      int64
 	Name                    string

pkg/plugins/backendplugin/manager.go

@@ -10,10 +10,7 @@ import (
 	"github.com/grafana/grafana/pkg/models"
 	"github.com/grafana/grafana/pkg/util/proxyutil"
 
-	"github.com/prometheus/client_golang/prometheus"
-
 	"github.com/grafana/grafana/pkg/infra/log"
-	"github.com/grafana/grafana/pkg/plugins/backendplugin/collector"
 	"github.com/grafana/grafana/pkg/registry"
 	plugin "github.com/hashicorp/go-plugin"
 	"golang.org/x/xerrors"
@@ -42,6 +39,8 @@ type Manager interface {
 	Register(descriptor PluginDescriptor) error
 	// StartPlugin starts a non-managed backend plugin
 	StartPlugin(ctx context.Context, pluginID string) error
+	// CollectMetrics collects metrics from a registered backend plugin.
+	CollectMetrics(ctx context.Context, pluginID string) (*CollectMetricsResult, error)
 	// CheckHealth checks the health of a registered backend plugin.
 	CheckHealth(ctx context.Context, pluginConfig *PluginConfig) (*CheckHealthResult, error)
 	// CallResource calls a plugin resource.
@@ -49,17 +48,14 @@ type Manager interface {
 }
 
 type manager struct {
-	pluginsMu       sync.RWMutex
-	plugins         map[string]*BackendPlugin
-	pluginCollector collector.PluginCollector
-	logger          log.Logger
+	pluginsMu sync.RWMutex
+	plugins   map[string]*BackendPlugin
+	logger    log.Logger
 }
 
 func (m *manager) Init() error {
 	m.plugins = make(map[string]*BackendPlugin)
 	m.logger = log.New("plugins.backend")
-	m.pluginCollector = collector.NewPluginCollector()
-	prometheus.MustRegister(m.pluginCollector)
 
 	return nil
 }
@@ -111,11 +107,6 @@ func (m *manager) start(ctx context.Context) {
 			p.logger.Error("Failed to start plugin", "error", err)
 			continue
 		}
-
-		if p.supportsDiagnostics() {
-			p.logger.Debug("Registering metrics collector")
-			m.pluginCollector.Register(p.id, p)
-		}
 	}
 }
 
@@ -150,6 +141,28 @@ func (m *manager) stop() {
 	}
 }
 
+// CollectMetrics collects metrics from a registered backend plugin.
+func (m *manager) CollectMetrics(ctx context.Context, pluginID string) (*CollectMetricsResult, error) {
+	m.pluginsMu.RLock()
+	p, registered := m.plugins[pluginID]
+	m.pluginsMu.RUnlock()
+
+	if !registered {
+		return nil, ErrPluginNotRegistered
+	}
+
+	if !p.supportsDiagnostics() {
+		return nil, ErrDiagnosticsNotSupported
+	}
+
+	res, err := p.CollectMetrics(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	return collectMetricsResultFromProto(res), nil
+}
+
 // CheckHealth checks the health of a registered backend plugin.
 func (m *manager) CheckHealth(ctx context.Context, pluginConfig *PluginConfig) (*CheckHealthResult, error) {
 	m.pluginsMu.RLock()