Chore: Refactor Prometheus HTTP client middleware (grafana#34473)

Following grafana#33439 this refactors the Prometheus HTTP transport 
which is replaced by HTTP client middleware.

pkg/models/datasource_cache.go

@@ -50,15 +50,18 @@ func (ds *DataSource) GetHTTPClient(provider httpclient.Provider) (*http.Client,
 	}, nil
 }
 
-func (ds *DataSource) GetHTTPTransport(provider httpclient.Provider) (http.RoundTripper, error) {
+func (ds *DataSource) GetHTTPTransport(provider httpclient.Provider, customMiddlewares ...sdkhttpclient.Middleware) (http.RoundTripper, error) {
 	ptc.Lock()
 	defer ptc.Unlock()
 
 	if t, present := ptc.cache[ds.Id]; present && ds.Updated.Equal(t.updated) {
 		return t.roundTripper, nil
 	}
 
-	rt, err := provider.GetTransport(ds.HTTPClientOptions())
+	opts := ds.HTTPClientOptions()
+	opts.Middlewares = customMiddlewares
+
+	rt, err := provider.GetTransport(opts)
 	if err != nil {
 		return nil, err
 	}

pkg/tsdb/prometheus/custom_query_params_middleware.go

@@ -0,0 +1,48 @@
+package prometheus
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+
+	sdkhttpclient "github.com/grafana/grafana-plugin-sdk-go/backend/httpclient"
+)
+
+const (
+	customQueryParametersMiddlewareName = "prom-custom-query-parameters"
+	customQueryParametersKey            = "customQueryParameters"
+)
+
+func customQueryParametersMiddleware() sdkhttpclient.Middleware {
+	return sdkhttpclient.NamedMiddlewareFunc(customQueryParametersMiddlewareName, func(opts sdkhttpclient.Options, next http.RoundTripper) http.RoundTripper {
+		customQueryParamsVal, exists := opts.CustomOptions[customQueryParametersKey]
+		if !exists {
+			return next
+		}
+		customQueryParams, ok := customQueryParamsVal.(string)
+		if !ok || customQueryParams == "" {
+			return next
+		}
+
+		return sdkhttpclient.RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
+			params := url.Values{}
+			for _, param := range strings.Split(customQueryParams, "&") {
+				parts := strings.Split(param, "=")
+				if len(parts) == 1 {
+					// This is probably a mistake on the users part in defining the params but we don't want to crash.
+					params.Add(parts[0], "")
+				} else {
+					params.Add(parts[0], parts[1])
+				}
+			}
+			if req.URL.RawQuery != "" {
+				req.URL.RawQuery = fmt.Sprintf("%s&%s", req.URL.RawQuery, params.Encode())
+			} else {
+				req.URL.RawQuery = params.Encode()
+			}
+
+			return next.RoundTrip(req)
+		})
+	})
+}

pkg/tsdb/prometheus/custom_query_params_middleware_test.go

@@ -0,0 +1,109 @@
+package prometheus
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend/httpclient"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCustomQueryParametersMiddleware(t *testing.T) {
+	require.Equal(t, "customQueryParameters", customQueryParametersKey)
+
+	finalRoundTripper := httpclient.RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
+		return &http.Response{StatusCode: http.StatusOK}, nil
+	})
+
+	t.Run("Without custom query parameters set should not apply middleware", func(t *testing.T) {
+		mw := customQueryParametersMiddleware()
+		rt := mw.CreateMiddleware(httpclient.Options{}, finalRoundTripper)
+		require.NotNil(t, rt)
+		middlewareName, ok := mw.(httpclient.MiddlewareName)
+		require.True(t, ok)
+		require.Equal(t, customQueryParametersMiddlewareName, middlewareName.MiddlewareName())
+
+		req, err := http.NewRequest(http.MethodGet, "http://test.com/query?hello=name", nil)
+		require.NoError(t, err)
+		res, err := rt.RoundTrip(req)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+		if res.Body != nil {
+			require.NoError(t, res.Body.Close())
+		}
+
+		require.Equal(t, "http://test.com/query?hello=name", req.URL.String())
+	})
+
+	t.Run("Without custom query parameters set as string should not apply middleware", func(t *testing.T) {
+		mw := customQueryParametersMiddleware()
+		rt := mw.CreateMiddleware(httpclient.Options{
+			CustomOptions: map[string]interface{}{
+				customQueryParametersKey: 64,
+			},
+		}, finalRoundTripper)
+		require.NotNil(t, rt)
+		middlewareName, ok := mw.(httpclient.MiddlewareName)
+		require.True(t, ok)
+		require.Equal(t, customQueryParametersMiddlewareName, middlewareName.MiddlewareName())
+
+		req, err := http.NewRequest(http.MethodGet, "http://test.com/query?hello=name", nil)
+		require.NoError(t, err)
+		res, err := rt.RoundTrip(req)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+		if res.Body != nil {
+			require.NoError(t, res.Body.Close())
+		}
+
+		require.Equal(t, "http://test.com/query?hello=name", req.URL.String())
+	})
+
+	t.Run("With custom query parameters set as empty string should not apply middleware", func(t *testing.T) {
+		mw := customQueryParametersMiddleware()
+		rt := mw.CreateMiddleware(httpclient.Options{
+			CustomOptions: map[string]interface{}{
+				customQueryParametersKey: "",
+			},
+		}, finalRoundTripper)
+		require.NotNil(t, rt)
+		middlewareName, ok := mw.(httpclient.MiddlewareName)
+		require.True(t, ok)
+		require.Equal(t, customQueryParametersMiddlewareName, middlewareName.MiddlewareName())
+
+		req, err := http.NewRequest(http.MethodGet, "http://test.com/query?hello=name", nil)
+		require.NoError(t, err)
+		res, err := rt.RoundTrip(req)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+		if res.Body != nil {
+			require.NoError(t, res.Body.Close())
+		}
+
+		require.Equal(t, "http://test.com/query?hello=name", req.URL.String())
+	})
+
+	t.Run("With custom query parameters set as string should apply middleware", func(t *testing.T) {
+		mw := customQueryParametersMiddleware()
+		rt := mw.CreateMiddleware(httpclient.Options{
+			CustomOptions: map[string]interface{}{
+				customQueryParametersKey: "custom=par/am&second=f oo",
+			},
+		}, finalRoundTripper)
+		require.NotNil(t, rt)
+		middlewareName, ok := mw.(httpclient.MiddlewareName)
+		require.True(t, ok)
+		require.Equal(t, customQueryParametersMiddlewareName, middlewareName.MiddlewareName())
+
+		req, err := http.NewRequest(http.MethodGet, "http://test.com/query?hello=name", nil)
+		require.NoError(t, err)
+		res, err := rt.RoundTrip(req)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+		if res.Body != nil {
+			require.NoError(t, res.Body.Close())
+		}
+
+		require.Equal(t, "http://test.com/query?hello=name&custom=par%2Fam&second=f+oo", req.URL.String())
+	})
+}

pkg/tsdb/prometheus/prometheus.go

@@ -4,133 +4,68 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"net/url"
 	"regexp"
 	"strings"
 	"time"
 
-	"github.com/opentracing/opentracing-go"
-
-	"net/http"
-
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 	"github.com/grafana/grafana/pkg/infra/httpclient"
 	"github.com/grafana/grafana/pkg/infra/log"
 	"github.com/grafana/grafana/pkg/models"
 	"github.com/grafana/grafana/pkg/plugins"
 	"github.com/grafana/grafana/pkg/tsdb/interval"
+	"github.com/opentracing/opentracing-go"
 	"github.com/prometheus/client_golang/api"
 	apiv1 "github.com/prometheus/client_golang/api/prometheus/v1"
 	"github.com/prometheus/common/model"
 )
 
-type PrometheusExecutor struct {
-	baseRoundTripperFactory func(dsInfo *models.DataSource) (http.RoundTripper, error)
-	intervalCalculator      interval.Calculator
-}
-
-type prometheusTransport struct {
-	Transport http.RoundTripper
-
-	hasBasicAuth bool
-	username     string
-	password     string
+var (
+	plog         log.Logger
+	legendFormat *regexp.Regexp = regexp.MustCompile(`\{\{\s*(.+?)\s*\}\}`)
+)
 
-	customQueryParameters string
+func init() {
+	plog = log.New("tsdb.prometheus")
 }
 
-func (transport *prometheusTransport) RoundTrip(req *http.Request) (*http.Response, error) {
-	if transport.hasBasicAuth {
-		req.SetBasicAuth(transport.username, transport.password)
-	}
-
-	if transport.customQueryParameters != "" {
-		params := url.Values{}
-		for _, param := range strings.Split(transport.customQueryParameters, "&") {
-			parts := strings.Split(param, "=")
-			if len(parts) == 1 {
-				// This is probably a mistake on the users part in defining the params but we don't want to crash.
-				params.Add(parts[0], "")
-			} else {
-				params.Add(parts[0], parts[1])
-			}
-		}
-		if req.URL.RawQuery != "" {
-			req.URL.RawQuery = fmt.Sprintf("%s&%s", req.URL.RawQuery, params.Encode())
-		} else {
-			req.URL.RawQuery = params.Encode()
-		}
-	}
-
-	return transport.Transport.RoundTrip(req)
+type PrometheusExecutor struct {
+	client             apiv1.API
+	intervalCalculator interval.Calculator
 }
 
 //nolint: staticcheck // plugins.DataPlugin deprecated
 func New(provider httpclient.Provider) func(*models.DataSource) (plugins.DataPlugin, error) {
 	return func(dsInfo *models.DataSource) (plugins.DataPlugin, error) {
-		transport, err := dsInfo.GetHTTPTransport(provider)
+		transport, err := dsInfo.GetHTTPTransport(provider, customQueryParametersMiddleware())
+		if err != nil {
+			return nil, err
+		}
+
+		cfg := api.Config{
+			Address:      dsInfo.Url,
+			RoundTripper: transport,
+		}
+
+		client, err := api.NewClient(cfg)
 		if err != nil {
 			return nil, err
 		}
 
 		return &PrometheusExecutor{
 			intervalCalculator: interval.NewCalculator(interval.CalculatorOptions{MinInterval: time.Second * 1}),
-			baseRoundTripperFactory: func(ds *models.DataSource) (http.RoundTripper, error) {
-				return transport, nil
-			},
+			client:             apiv1.NewAPI(client),
 		}, nil
 	}
 }
 
-var (
-	plog         log.Logger
-	legendFormat *regexp.Regexp = regexp.MustCompile(`\{\{\s*(.+?)\s*\}\}`)
-)
-
-func init() {
-	plog = log.New("tsdb.prometheus")
-}
-
-func (e *PrometheusExecutor) getClient(dsInfo *models.DataSource) (apiv1.API, error) {
-	// Would make sense to cache this but executor is recreated on every alert request anyway.
-	transport, err := e.baseRoundTripperFactory(dsInfo)
-	if err != nil {
-		return nil, err
-	}
-
-	promTransport := &prometheusTransport{
-		Transport:             transport,
-		hasBasicAuth:          dsInfo.BasicAuth,
-		username:              dsInfo.BasicAuthUser,
-		password:              dsInfo.DecryptedBasicAuthPassword(),
-		customQueryParameters: dsInfo.JsonData.Get("customQueryParameters").MustString(""),
-	}
-
-	cfg := api.Config{
-		Address:      dsInfo.Url,
-		RoundTripper: promTransport,
-	}
-
-	client, err := api.NewClient(cfg)
-	if err != nil {
-		return nil, err
-	}
-
-	return apiv1.NewAPI(client), nil
-}
-
 //nolint: staticcheck // plugins.DataResponse deprecated
 func (e *PrometheusExecutor) DataQuery(ctx context.Context, dsInfo *models.DataSource,
 	tsdbQuery plugins.DataQuery) (plugins.DataResponse, error) {
 	result := plugins.DataResponse{
 		Results: map[string]plugins.DataQueryResult{},
 	}
 
-	client, err := e.getClient(dsInfo)
-	if err != nil {
-		return result, err
-	}
-
 	queries, err := e.parseQuery(dsInfo, tsdbQuery)
 	if err != nil {
 		return result, err
@@ -145,13 +80,13 @@ func (e *PrometheusExecutor) DataQuery(ctx context.Context, dsInfo *models.DataS
 
 		plog.Debug("Sending query", "start", timeRange.Start, "end", timeRange.End, "step", timeRange.Step, "query", query.Expr)
 
-		span, ctx := opentracing.StartSpanFromContext(ctx, "alerting.prometheus")
+		span, ctx := opentracing.StartSpanFromContext(ctx, "datasource.prometheus")
 		span.SetTag("expr", query.Expr)
 		span.SetTag("start_unixnano", query.Start.UnixNano())
 		span.SetTag("stop_unixnano", query.End.UnixNano())
 		defer span.Finish()
 
-		value, _, err := client.QueryRange(ctx, query.Expr, timeRange)
+		value, _, err := e.client.QueryRange(ctx, query.Expr, timeRange)
 
 		if err != nil {
 			return result, err