QueryCaching: Use CachingServiceClient for query caching (#112128)

* Integrate mt querier with query caching

* typo

* let the caller set cache status response header

* fix TestQueryAPI

* make gen-go

* handle CachingServiceClient being nil and make gen-go

* include namespace in cache key

* set signed in user namespace in query_test.go

* fix test

* remove commented out code

* undo services/query/query.go changes

* make gen-go

* remove namespace requirement

* fix tests

* fix test

* remove namespace from SignedInUser in tests

* make gen-go

pkg/services/caching/metrics.go

@@ -0,0 +1,43 @@
+package caching
+
+import (
+	"github.com/grafana/grafana/pkg/infra/metrics"
+	contextmodel "github.com/grafana/grafana/pkg/services/contexthandler/model"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const (
+	QueryPubdash   = "pubdash"
+	QueryDashboard = "dashboard"
+)
+
+var QueryCachingRequestHistogram = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+	Namespace: metrics.ExporterName,
+	Subsystem: "caching",
+	Name:      "query_caching_request_duration_seconds",
+	Help:      "histogram of grafana query endpoint requests in seconds",
+	Buckets:   []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10, 25, 50, 100},
+}, []string{"datasource_type", "cache", "query_type"})
+
+var ShouldCacheQueryHistogram = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+	Namespace: metrics.ExporterName,
+	Subsystem: "caching",
+	Name:      "should_cache_query_request_duration_seconds",
+	Help:      "histogram of grafana query endpoint requests in seconds",
+	Buckets:   []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10, 25, 50, 100},
+}, []string{"datasource_type", "cache", "shouldCache", "query_type"})
+
+var ResourceCachingRequestHistogram = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+	Namespace: metrics.ExporterName,
+	Subsystem: "caching",
+	Name:      "resource_caching_request_duration_seconds",
+	Help:      "histogram of grafana resource endpoint requests in seconds",
+	Buckets:   []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10, 25, 50, 100},
+}, []string{"plugin_id", "cache"})
+
+func getQueryType(req *contextmodel.ReqContext) string {
+	if req.IsPublicDashboardView() {
+		return QueryPubdash
+	}
+	return QueryDashboard
+}