convert plugin config to scraper config

server/configuration.go

@@ -34,6 +34,10 @@ type configuration struct {
 	HonorTimestamps *bool
 	// Option to enable the experimental in-memory metadata storage and append metadata to the WAL.
 	EnableMetadataStorage *bool
+	// Scrape interval is the time between polling the /metrics endpoint
+	ScrapeIntervalSeconds *int
+	// Screap timeout tells scraper to give up on the poll for a single scrape attempt
+	ScrapeTimeoutSeconds *int
 }
 
 func (c *configuration) SetDefaults() {
@@ -61,9 +65,24 @@ func (c *configuration) SetDefaults() {
 	if c.EnableMetadataStorage == nil {
 		c.EnableMetadataStorage = model.NewBool(true)
 	}
+	if c.ScrapeIntervalSeconds == nil {
+		c.ScrapeIntervalSeconds = model.NewInt(60)
+	}
+	if c.ScrapeTimeoutSeconds == nil {
+		c.ScrapeTimeoutSeconds = model.NewInt(10)
+	}
 }
 
 func (c *configuration) IsValid() error {
+	if *c.ScrapeIntervalSeconds < 1 {
+		return errors.New("scrape interval should be greater than zero")
+	}
+	if *c.ScrapeTimeoutSeconds < 1 {
+		return errors.New("scrape timeout should be greater than zero")
+	}
+	if *c.BodySizeLimitBytes < 100 {
+		return errors.New("openmetrics body size is not realistic, should be greater than 100 bytes")
+	}
 	return nil
 }
 

server/const.go

@@ -0,0 +1,9 @@
+package main
+
+import (
+	"github.com/prometheus/prometheus/model/labels"
+)
+
+var (
+	sampleMutator func(labels.Labels) labels.Labels //nolint:unused
+)

server/plugin.go

@@ -3,11 +3,17 @@ package main
 import (
 	"fmt"
 	"net/http"
+	"net/url"
 	"sync"
 	"time"
 
 	"github.com/mattermost/mattermost/server/public/plugin"
 	"github.com/mattermost/mattermost/server/v8/platform/shared/filestore"
+	"github.com/prometheus/common/model"
+	"github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/model/relabel"
+	"github.com/prometheus/prometheus/scrape"
 	"github.com/prometheus/prometheus/tsdb"
 )
 
@@ -54,6 +60,10 @@ func (p *Plugin) OnActivate() error {
 		p.configuration.SetDefaults()
 	}
 
+	if err = p.configuration.IsValid(); err != nil {
+		return fmt.Errorf("could not validate config: %w", err)
+	}
+
 	// check if cluster is enabled
 	if p.isHA() {
 		// TODO(isacikgoz): get cluster info
@@ -72,6 +82,30 @@ func (p *Plugin) OnActivate() error {
 		return fmt.Errorf("could not open target tsdb: %w", err)
 	}
 
+	scrapeInterval := *p.configuration.ScrapeIntervalSeconds
+
+	// TODO(isacikgoz): Use multiple targets for HA env
+	ls := labels.FromMap(map[string]string{
+		model.AddressLabel:        "localhost:8067",
+		model.ScrapeIntervalLabel: fmt.Sprintf("%ds", scrapeInterval),
+		model.ScrapeTimeoutLabel:  fmt.Sprintf("%ds", *p.configuration.ScrapeTimeoutSeconds),
+	})
+	lb := labels.NewBuilder(ls)
+
+	lset, origLabels, err := scrape.PopulateLabels(lb, &config.ScrapeConfig{
+		JobName: "prometheus",
+	}, true)
+	if err != nil {
+		return err
+	}
+
+	target := scrape.NewTarget(lset, origLabels, url.Values{})
+
+	// Mutator is being used to apply labels to the metric samples
+	sampleMutator = func(l labels.Labels) labels.Labels {
+		return mutateSampleLabels(l, target, *p.configuration.HonorTimestamps, []*relabel.Config{})
+	}
+
 	return nil
 }
 

server/sample.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"github.com/prometheus/common/model"
+	"github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/model/relabel"
+	"github.com/prometheus/prometheus/scrape"
+	"golang.org/x/exp/slices"
+)
+
+func mutateSampleLabels(lset labels.Labels, target *scrape.Target, honor bool, rc []*relabel.Config) labels.Labels {
+	lb := labels.NewBuilder(lset)
+
+	if honor {
+		target.LabelsRange(func(l labels.Label) {
+			if !lset.Has(l.Name) {
+				lb.Set(l.Name, l.Value)
+			}
+		})
+	} else {
+		var conflictingExposedLabels []labels.Label
+		target.LabelsRange(func(l labels.Label) {
+			existingValue := lset.Get(l.Name)
+			if existingValue != "" {
+				conflictingExposedLabels = append(conflictingExposedLabels, labels.Label{Name: l.Name, Value: existingValue})
+			}
+			// It is now safe to set the target label.
+			lb.Set(l.Name, l.Value)
+		})
+
+		if len(conflictingExposedLabels) > 0 {
+			resolveConflictingExposedLabels(lb, conflictingExposedLabels)
+		}
+	}
+
+	res := lb.Labels()
+
+	if len(rc) > 0 {
+		res, _ = relabel.Process(res, rc...)
+	}
+
+	return res
+}
+
+func resolveConflictingExposedLabels(lb *labels.Builder, conflictingExposedLabels []labels.Label) {
+	slices.SortStableFunc(conflictingExposedLabels, func(a, b labels.Label) bool {
+		return len(a.Name) < len(b.Name)
+	})
+
+	for _, l := range conflictingExposedLabels {
+		newName := l.Name
+		for {
+			newName = model.ExportedLabelPrefix + newName
+			if lb.Get(newName) == "" {
+				lb.Set(newName, l.Value)
+				break
+			}
+		}
+	}
+}