Prometheus: Implement Streaming JSON Parser (#48477)

use `prometheusStreamingJSONParser` feature toggle to enable

pkg/tsdb/prometheus/client/cache_test.go

@@ -0,0 +1,135 @@
+package client_test
+
+import (
+	"errors"
+	"io/ioutil"
+	"net/http"
+	"sort"
+	"strings"
+	"testing"
+
+	"github.com/grafana/grafana/pkg/tsdb/prometheus/client"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestCache_GetClient(t *testing.T) {
+	t.Run("it caches the client for a set of auth headers", func(t *testing.T) {
+		tc := setupCacheContext()
+
+		c, err := tc.providerCache.GetClient(headers)
+		require.Nil(t, err)
+
+		c2, err := tc.providerCache.GetClient(headers)
+		require.Nil(t, err)
+
+		require.Equal(t, c, c2)
+		require.Equal(t, 1, tc.clientProvider.numCalls)
+	})
+
+	t.Run("it returns different clients when the headers differ", func(t *testing.T) {
+		tc := setupCacheContext()
+		h1 := map[string]string{"Authorization": "token", "X-ID-Token": "id-token"}
+		h2 := map[string]string{"Authorization": "token2", "X-ID-Token": "id-token"}
+
+		c, err := tc.providerCache.GetClient(h1)
+		require.Nil(t, err)
+
+		c2, err := tc.providerCache.GetClient(h2)
+		require.Nil(t, err)
+
+		require.NotEqual(t, c, c2)
+		require.Equal(t, 2, tc.clientProvider.numCalls)
+	})
+
+	t.Run("it returns from the cache when headers are the same", func(t *testing.T) {
+		tc := setupCacheContext()
+		h1 := map[string]string{"Authorization": "token", "X-ID-Token": "id-token"}
+		h2 := map[string]string{"Authorization": "token", "X-ID-Token": "id-token"}
+
+		c, err := tc.providerCache.GetClient(h1)
+		require.Nil(t, err)
+
+		c2, err := tc.providerCache.GetClient(h2)
+		require.Nil(t, err)
+
+		require.Equal(t, c, c2)
+		require.Equal(t, 1, tc.clientProvider.numCalls)
+	})
+
+	t.Run("it doesn't cache anything when an error occurs", func(t *testing.T) {
+		tc := setupCacheContext()
+		tc.clientProvider.errors <- errors.New("something bad")
+
+		_, err := tc.providerCache.GetClient(headers)
+		require.EqualError(t, err, "something bad")
+
+		c, err := tc.providerCache.GetClient(headers)
+		require.Nil(t, err)
+
+		require.NotNil(t, c)
+		require.Equal(t, 2, tc.clientProvider.numCalls)
+	})
+}
+
+type cacheTestContext struct {
+	providerCache  *client.ProviderCache
+	clientProvider *fakeClientProvider
+}
+
+func setupCacheContext() *cacheTestContext {
+	fp := newFakePromClientProvider()
+	p, err := client.NewProviderCache(fp)
+	if err != nil {
+		panic(err)
+	}
+
+	return &cacheTestContext{
+		providerCache:  p,
+		clientProvider: fp,
+	}
+}
+
+func newFakePromClientProvider() *fakeClientProvider {
+	return &fakeClientProvider{
+		errors: make(chan error, 1),
+	}
+}
+
+type fakeClientProvider struct {
+	headers  map[string]string
+	numCalls int
+	errors   chan error
+}
+
+func (p *fakeClientProvider) GetClient(h map[string]string) (*client.Client, error) {
+	p.headers = h
+	p.numCalls++
+
+	var err error
+	select {
+	case err = <-p.errors:
+	default:
+	}
+
+	var config []string
+	for _, v := range h {
+		config = append(config, v)
+	}
+	sort.Strings(config) //because map
+	res := &http.Response{
+		StatusCode: 200,
+		Header:     http.Header{},
+		Body:       ioutil.NopCloser(strings.NewReader(strings.Join(config, ","))),
+	}
+	c := &fakeClient{res: res}
+	return client.NewClient(c, "GET", "http://localhost:9090/"), err
+}
+
+type fakeClient struct {
+	res *http.Response
+}
+
+func (c *fakeClient) Do(req *http.Request) (*http.Response, error) {
+	return c.res, nil
+}