Prometheus: Fix body not being included in resource calls if they are POST (#50833)

* Pass on request body

* Fix GETs and add tests

* Fix err handling

* Add comments

* Close response body

* Fix lint maybe

* Fix test

pkg/tsdb/prometheus/client/client.go

@@ -1,8 +1,8 @@
 package client
 
 import (
+	"bytes"
 	"context"
-	"io/ioutil"
 	"net/http"
 	"net/url"
 	"path"
@@ -10,6 +10,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana/pkg/tsdb/prometheus/models"
 )
 
@@ -42,7 +43,7 @@ func (c *Client) QueryRange(ctx context.Context, q *models.Query) (*http.Respons
 	qs.Set("end", formatTime(tr.End))
 	qs.Set("step", strconv.FormatFloat(tr.Step.Seconds(), 'f', -1, 64))
 
-	return c.fetch(ctx, c.method, u, qs)
+	return c.fetch(ctx, c.method, u, qs, nil)
 }
 
 func (c *Client) QueryInstant(ctx context.Context, q *models.Query) (*http.Response, error) {
@@ -60,7 +61,7 @@ func (c *Client) QueryInstant(ctx context.Context, q *models.Query) (*http.Respo
 		qs.Set("time", formatTime(tr.End))
 	}
 
-	return c.fetch(ctx, c.method, u, qs)
+	return c.fetch(ctx, c.method, u, qs, nil)
 }
 
 func (c *Client) QueryExemplars(ctx context.Context, q *models.Query) (*http.Response, error) {
@@ -77,36 +78,51 @@ func (c *Client) QueryExemplars(ctx context.Context, q *models.Query) (*http.Res
 	qs.Set("start", formatTime(tr.Start))
 	qs.Set("end", formatTime(tr.End))
 
-	return c.fetch(ctx, c.method, u, qs)
+	return c.fetch(ctx, c.method, u, qs, nil)
 }
 
-func (c *Client) QueryResource(ctx context.Context, method string, p string, qs url.Values) (*http.Response, error) {
-	u, err := url.ParseRequestURI(c.baseUrl)
+type FetchReq struct {
+	Method      string
+	Url         *url.URL
+	QueryString url.Values
+}
+
+func (c *Client) QueryResource(ctx context.Context, req *backend.CallResourceRequest) (*http.Response, error) {
+	// The way URL is represented in CallResourceRequest and what we need for the fetch function is different
+	// so here we have to do a bit of parsing, so we can then compose it with the base url in correct way.
+	baseUrlParsed, err := url.ParseRequestURI(c.baseUrl)
+	if err != nil {
+		return nil, err
+	}
+	reqUrlParsed, err := url.Parse(req.URL)
 	if err != nil {
 		return nil, err
 	}
 
-	u.Path = path.Join(u.Path, p)
+	baseUrlParsed.Path = path.Join(baseUrlParsed.Path, req.Path)
+	baseUrlParsed.RawQuery = reqUrlParsed.RawQuery
 
-	return c.fetch(ctx, method, u, qs)
+	return c.fetch(ctx, req.Method, baseUrlParsed, nil, req.Body)
 }
 
-func (c *Client) fetch(ctx context.Context, method string, u *url.URL, qs url.Values) (*http.Response, error) {
-	if strings.ToUpper(method) == http.MethodGet {
+func (c *Client) fetch(ctx context.Context, method string, u *url.URL, qs url.Values, body []byte) (*http.Response, error) {
+	// The qs arg seems to be used in some callers of this method, but you can already pass them in the URL object
+	if strings.ToUpper(method) == http.MethodGet && qs != nil {
 		u.RawQuery = qs.Encode()
 	}
-
-	r, err := http.NewRequestWithContext(ctx, method, u.String(), nil)
+	bodyReader := bytes.NewReader(body)
+	request, err := http.NewRequestWithContext(ctx, method, u.String(), bodyReader)
 	if err != nil {
 		return nil, err
 	}
 
+	// This may not be true but right now we don't have more information here and seems like we send just this type
+	// of encoding right now if it is a POST
 	if strings.ToUpper(method) == http.MethodPost {
-		r.Body = ioutil.NopCloser(strings.NewReader(qs.Encode()))
-		r.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+		request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
 	}
 
-	return c.doer.Do(r)
+	return c.doer.Do(request)
 }
 
 func formatTime(t time.Time) string {

pkg/tsdb/prometheus/client/client_test.go

@@ -0,0 +1,83 @@
+package client
+
+import (
+	"context"
+	"io/ioutil"
+	"net/http"
+	"testing"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana/pkg/cmd/grafana-cli/logger"
+	"github.com/stretchr/testify/require"
+)
+
+type MockDoer struct {
+	Req *http.Request
+}
+
+func (doer *MockDoer) Do(req *http.Request) (*http.Response, error) {
+	doer.Req = req
+	return &http.Response{
+		StatusCode: http.StatusOK,
+		Status:     "200 OK",
+	}, nil
+}
+
+func TestClient(t *testing.T) {
+	t.Run("QueryResource", func(t *testing.T) {
+		doer := &MockDoer{}
+		// The method here does not really matter for resource calls
+		client := NewClient(doer, http.MethodGet, "http://localhost:9090")
+
+		t.Run("sends correct POST request", func(t *testing.T) {
+			req := &backend.CallResourceRequest{
+				PluginContext: backend.PluginContext{},
+				Path:          "/api/v1/series",
+				Method:        http.MethodPost,
+				URL:           "/api/v1/series",
+				Headers:       nil,
+				Body:          []byte("match%5B%5D: ALERTS\nstart: 1655271408\nend: 1655293008"),
+			}
+			res, err := client.QueryResource(context.Background(), req)
+			defer func() {
+				if res != nil && res.Body != nil {
+					if err := res.Body.Close(); err != nil {
+						logger.Warn("Error", "err", err)
+					}
+				}
+			}()
+			require.NoError(t, err)
+			require.NotNil(t, doer.Req)
+			require.Equal(t, http.MethodPost, doer.Req.Method)
+			body, err := ioutil.ReadAll(doer.Req.Body)
+			require.NoError(t, err)
+			require.Equal(t, []byte("match%5B%5D: ALERTS\nstart: 1655271408\nend: 1655293008"), body)
+			require.Equal(t, "http://localhost:9090/api/v1/series", doer.Req.URL.String())
+		})
+
+		t.Run("sends correct GET request", func(t *testing.T) {
+			req := &backend.CallResourceRequest{
+				PluginContext: backend.PluginContext{},
+				Path:          "/api/v1/series",
+				Method:        http.MethodGet,
+				URL:           "api/v1/series?match%5B%5D=ALERTS&start=1655272558&end=1655294158",
+				Headers:       nil,
+			}
+			res, err := client.QueryResource(context.Background(), req)
+			defer func() {
+				if res != nil && res.Body != nil {
+					if err := res.Body.Close(); err != nil {
+						logger.Warn("Error", "err", err)
+					}
+				}
+			}()
+			require.NoError(t, err)
+			require.NotNil(t, doer.Req)
+			require.Equal(t, http.MethodGet, doer.Req.Method)
+			body, err := ioutil.ReadAll(doer.Req.Body)
+			require.NoError(t, err)
+			require.Equal(t, []byte{}, body)
+			require.Equal(t, "http://localhost:9090/api/v1/series?match%5B%5D=ALERTS&start=1655272558&end=1655294158", doer.Req.URL.String())
+		})
+	})
+}

pkg/tsdb/prometheus/resource/resource.go

@@ -8,7 +8,6 @@ import (
 	"io"
 	"io/ioutil"
 	"net/http"
-	"net/url"
 	"strings"
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
@@ -133,12 +132,7 @@ func (r *Resource) Execute(ctx context.Context, req *backend.CallResourceRequest
 
 func (r *Resource) fetch(ctx context.Context, client *client.Client, req *backend.CallResourceRequest) (int, []byte, error) {
 	r.log.Debug("Sending resource query", "URL", req.URL)
-	u, err := url.Parse(req.URL)
-	if err != nil {
-		return 500, nil, err
-	}
-
-	resp, err := client.QueryResource(ctx, req.Method, u.Path, u.Query())
+	resp, err := client.QueryResource(ctx, req)
 	if err != nil {
 		statusCode := 500
 		if resp != nil {