[v10.0.x] Alerting: Add heuristics back to datasource healthchecks (#69541)

This commit adds heuristics back to datasource healthchecks as
it was removed in #66198. The healthcheck for Prometheus datasources
also returns the kind (Prometheus or Mimir) and a boolean if the
ruler is enabled or disabled.

pkg/tsdb/prometheus/heuristics.go

@@ -0,0 +1,112 @@
+package prometheus
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+)
+
+const (
+	KindPrometheus = "Prometheus"
+	KindMimir      = "Mimir"
+)
+
+var (
+	ErrNoBuildInfo = errors.New("no build info")
+)
+
+type BuildInfoRequest struct {
+	PluginContext backend.PluginContext
+}
+
+type BuildInfoResponse struct {
+	Status string                `json:"status"`
+	Data   BuildInfoResponseData `json:"data"`
+}
+
+type BuildInfoResponseData struct {
+	Version   string            `json:"version"`
+	Revision  string            `json:"revision"`
+	Branch    string            `json:"branch"`
+	Features  map[string]string `json:"features"`
+	BuildUser string            `json:"buildUser"`
+	BuildDate string            `json:"buildDate"`
+	GoVersion string            `json:"goVersion"`
+}
+
+func (s *Service) GetBuildInfo(ctx context.Context, req BuildInfoRequest) (*BuildInfoResponse, error) {
+	ds, err := s.getInstance(req.PluginContext)
+	if err != nil {
+		return nil, err
+	}
+	return getBuildInfo(ctx, ds)
+}
+
+// getBuildInfo queries /api/v1/status/buildinfo
+func getBuildInfo(ctx context.Context, i *instance) (*BuildInfoResponse, error) {
+	resp, err := i.resource.Execute(ctx, &backend.CallResourceRequest{
+		Path: "api/v1/status/buildinfo",
+	})
+	if err != nil {
+		return nil, err
+	}
+	if resp.Status == http.StatusNotFound {
+		return nil, ErrNoBuildInfo
+	}
+	if resp.Status != http.StatusOK {
+		return nil, fmt.Errorf("unexpected response %d", resp.Status)
+	}
+	res := BuildInfoResponse{}
+	if err := json.Unmarshal(resp.Body, &res); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal JSON: %w", err)
+	}
+	return &res, nil
+}
+
+type HeuristicsRequest struct {
+	PluginContext backend.PluginContext
+}
+
+type Heuristics struct {
+	Application string   `json:"application"`
+	Features    Features `json:"features"`
+}
+
+type Features struct {
+	RulerApiEnabled bool `json:"rulerApiEnabled"`
+}
+
+func (s *Service) GetHeuristics(ctx context.Context, req HeuristicsRequest) (*Heuristics, error) {
+	ds, err := s.getInstance(req.PluginContext)
+	if err != nil {
+		return nil, err
+	}
+	return getHeuristics(ctx, ds)
+}
+
+func getHeuristics(ctx context.Context, i *instance) (*Heuristics, error) {
+	heuristics := Heuristics{
+		Application: "unknown",
+		Features: Features{
+			RulerApiEnabled: false,
+		},
+	}
+	buildInfo, err := getBuildInfo(ctx, i)
+	if err != nil {
+		logger.Warn("failed to get prometheus buildinfo", "err", err.Error())
+		return nil, fmt.Errorf("failed to get buildinfo: %w", err)
+	}
+	if len(buildInfo.Data.Features) == 0 {
+		// If there are no features then this is a Prometheus datasource
+		heuristics.Application = KindPrometheus
+		heuristics.Features.RulerApiEnabled = false
+	} else {
+		heuristics.Application = KindMimir
+		heuristics.Features.RulerApiEnabled = true
+	}
+	return &heuristics, nil
+}