Change GeneratorURL to use configurable Grafana explore URL (#8500)

**What this PR does / why we need it**:
This PR changes the `GeneratorURL` associated with alerts generated by
Loki. The new `GeneratorURL` uses a Grafana URL path.

docs/sources/configuration/_index.md

@@ -763,10 +763,14 @@ results_cache:
 The `ruler` block configures the Loki ruler.
 
 ```yaml
-# URL of alerts return path.
+# Base URL of the Grafana instance.
 # CLI flag: -ruler.external.url
 [external_url: <url>]
 
+# Datasource UID for the dashboard.
+# CLI flag: -ruler.datasource-uid
+[datasource_uid: <string> | default = ""]
+
 # Labels to add to all alerts.
 [external_labels: <list of Labels>]
 

pkg/ruler/base/compat.go

@@ -277,7 +277,7 @@ func DefaultTenantManagerFactory(cfg Config, p Pusher, q storage.Queryable, engi
 			QueryFunc:       RecordAndReportRuleQueryMetrics(MetricsQueryFunc(EngineQueryFunc(engine, q, overrides, userID), totalQueries, failedQueries), queryTime, logger),
 			Context:         user.InjectOrgID(ctx, userID),
 			ExternalURL:     cfg.ExternalURL.URL,
-			NotifyFunc:      SendAlerts(notifier, cfg.ExternalURL.URL.String()),
+			NotifyFunc:      SendAlerts(notifier, cfg.ExternalURL.URL.String(), cfg.DatasourceUID),
 			Logger:          log.With(logger, "user", userID),
 			Registerer:      reg,
 			OutageTolerance: cfg.OutageTolerance,

pkg/ruler/base/ruler.go

@@ -2,6 +2,7 @@ package base
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"hash/fnv"
@@ -28,7 +29,6 @@ import (
 	"github.com/prometheus/prometheus/model/rulefmt"
 	"github.com/prometheus/prometheus/notifier"
 	promRules "github.com/prometheus/prometheus/rules"
-	"github.com/prometheus/prometheus/util/strutil"
 	"github.com/weaveworks/common/user"
 	"golang.org/x/sync/errgroup"
 
@@ -76,6 +76,8 @@ const (
 type Config struct {
 	// This is used for template expansion in alerts; must be a valid URL.
 	ExternalURL flagext.URLValue `yaml:"external_url"`
+	// This is used for template expansion in alerts, and represents the corresponding Grafana datasource UID.
+	DatasourceUID string `yaml:"datasource_uid"`
 	// Labels to add to all alerts
 	ExternalLabels labels.Labels `yaml:"external_labels,omitempty" doc:"description=Labels to add to all alerts."`
 	// GRPC Client configuration.
@@ -158,7 +160,8 @@ func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
 	flagext.DeprecatedFlag(f, "ruler.num-workers", "This flag is no longer functional. For increased concurrency horizontal sharding is recommended", util_log.Logger)
 
 	cfg.ExternalURL.URL, _ = url.Parse("") // Must be non-nil
-	f.Var(&cfg.ExternalURL, "ruler.external.url", "URL of alerts return path.")
+	f.Var(&cfg.ExternalURL, "ruler.external.url", "Base URL of the Grafana instance.")
+	f.StringVar(&cfg.DatasourceUID, "ruler.datasource-uid", "", "Datasource UID for the dashboard.")
 	f.DurationVar(&cfg.EvaluationInterval, "ruler.evaluation-interval", 1*time.Minute, "How frequently to evaluate rules.")
 	f.DurationVar(&cfg.PollInterval, "ruler.poll-interval", 1*time.Minute, "How frequently to poll for rule changes.")
 
@@ -374,11 +377,41 @@ type sender interface {
 	Send(alerts ...*notifier.Alert)
 }
 
+type query struct {
+	Expr       string      `json:"expr"`
+	QueryType  string      `json:"queryType"`
+	Datasource *datasource `json:"datasource,omitempty"`
+}
+
+type datasource struct {
+	Type string `json:"type"`
+	UID  string `json:"uid"`
+}
+
+func grafanaLinkForExpression(expr, datasourceUID string) string {
+	exprStruct := query{
+		Expr:      expr,
+		QueryType: "range",
+	}
+
+	if datasourceUID != "" {
+		exprStruct.Datasource = &datasource{
+			Type: "loki",
+			UID:  datasourceUID,
+		}
+	}
+
+	marshaledExpression, _ := json.Marshal(exprStruct)
+	escapedExpression := url.QueryEscape(string(marshaledExpression))
+	str := `/explore?left={"queries":[%s]}`
+	return fmt.Sprintf(str, escapedExpression)
+}
+
 // SendAlerts implements a rules.NotifyFunc for a Notifier.
 // It filters any non-firing alerts from the input.
 //
 // Copied from Prometheus's main.go.
-func SendAlerts(n sender, externalURL string) promRules.NotifyFunc {
+func SendAlerts(n sender, externalURL, datasourceUID string) promRules.NotifyFunc {
 	return func(ctx context.Context, expr string, alerts ...*promRules.Alert) {
 		var res []*notifier.Alert
 
@@ -387,7 +420,7 @@ func SendAlerts(n sender, externalURL string) promRules.NotifyFunc {
 				StartsAt:     alert.FiredAt,
 				Labels:       alert.Labels,
 				Annotations:  alert.Annotations,
-				GeneratorURL: externalURL + strutil.TableLinkForExpression(expr),
+				GeneratorURL: externalURL + grafanaLinkForExpression(expr, datasourceUID),
 			}
 			if !alert.ResolvedAt.IsZero() {
 				a.EndsAt = alert.ResolvedAt

pkg/ruler/base/ruler_test.go

@@ -7,6 +7,7 @@ import (
 	"math/rand"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"os"
 	"reflect"
 	"sort"
@@ -1645,6 +1646,7 @@ func (s senderFunc) Send(alerts ...*notifier.Alert) {
 }
 
 func TestSendAlerts(t *testing.T) {
+	escapedExpression := url.QueryEscape("{\"expr\":\"up\",\"queryType\":\"range\",\"datasource\":{\"type\":\"loki\",\"uid\":\"uid\"}}")
 	testCases := []struct {
 		in  []*promRules.Alert
 		exp []*notifier.Alert
@@ -1665,7 +1667,7 @@ func TestSendAlerts(t *testing.T) {
 					Annotations:  []labels.Label{{Name: "a2", Value: "v2"}},
 					StartsAt:     time.Unix(2, 0),
 					EndsAt:       time.Unix(3, 0),
-					GeneratorURL: "http://localhost:9090/graph?g0.expr=up&g0.tab=1",
+					GeneratorURL: fmt.Sprintf("http://localhost:8080/explore?left={\"queries\":[%s]}", escapedExpression),
 				},
 			},
 		},
@@ -1685,7 +1687,7 @@ func TestSendAlerts(t *testing.T) {
 					Annotations:  []labels.Label{{Name: "a2", Value: "v2"}},
 					StartsAt:     time.Unix(2, 0),
 					EndsAt:       time.Unix(4, 0),
-					GeneratorURL: "http://localhost:9090/graph?g0.expr=up&g0.tab=1",
+					GeneratorURL: fmt.Sprintf("http://localhost:8080/explore?left={\"queries\":[%s]}", escapedExpression),
 				},
 			},
 		},
@@ -1703,7 +1705,7 @@ func TestSendAlerts(t *testing.T) {
 				}
 				require.Equal(t, tc.exp, alerts)
 			})
-			SendAlerts(senderFunc, "http://localhost:9090")(context.TODO(), "up", tc.in...)
+			SendAlerts(senderFunc, "http://localhost:8080", "uid")(context.TODO(), "up", tc.in...)
 		})
 	}
 }

pkg/ruler/compat.go

@@ -157,7 +157,7 @@ func MultiTenantRuleManager(cfg Config, evaluator Evaluator, overrides RulesLimi
 			QueryFunc:       queryFn,
 			Context:         user.InjectOrgID(ctx, userID),
 			ExternalURL:     cfg.ExternalURL.URL,
-			NotifyFunc:      ruler.SendAlerts(notifier, cfg.ExternalURL.URL.String()),
+			NotifyFunc:      ruler.SendAlerts(notifier, cfg.ExternalURL.URL.String(), cfg.DatasourceUID),
 			Logger:          logger,
 			Registerer:      reg,
 			OutageTolerance: cfg.OutageTolerance,