Graphite: Backend tags autocomplete endpoint (#110772)

* Add lint rules

* Backend decoupling

- Add standalone files
- Add graphite query type
- Add logger to Service
- Create logger in the ProvideService method
- Use a pointer for the HTTP client provider
- Update logger usage everywhere
- Update tracer type
- Replace simplejson with json
- Add dummy CallResource and CheckHealth methods
- Update tests

* Update ConfigEditor imports

* Update types imports

* Update datasource

- Switch to using semver package
- Update imports

* Update store imports

* Update helper imports and notification creation

* Update context import

* Update version numbers and logic

* Copy array_move from core

* Test updates

* Add required files and update plugin.json

* Update core references and packages

* Remove commented code

* Update wire

* Lint

* Fix import

* Copy null type

* More lint

* Update snapshot

* Refactor backend

- Split query logic into separate file
- Move utils to separate file

* Add health-check logic

- Support backend healthcheck if the FF is enabled

* Remove query import support as unneeded

* Add test

* Add util function for decoding responses

* Add events types

* Add resource handler

* Add events handler and generic resource req handler

* Tests

* Update frontend

- Add types
- Update events function to support backend requests

* Lint and typing

* Lint

* Add metrics find endpoint

- Add types
- Add generic response parser
- Add endpoint
- Tests

* Update FE functoin to use backend endpoint

* Lint

* Simplify request

* Update test

* Metrics expand type

* Extract shared logic and add metric expand endpoint

* Update tests

* Call metric expand from backend

* Rename type for clarity

* Add get resource req handler

* Refactor doGraphiteRequest, parseResponse

Update tests

* Migrate functions endpoint to backend

* Support tags autocomplete in backend

- Add tests
- Add types
- Remove unneeded comments

* Add tests

* Review

* Review

* Fix packages

* Format

* Fix merge issues

* Review

* Fix undefined values

* Extract request creation

- Add method for create requests generically with tests
- Replace usage in query method
- Update usages in resource handlers
- Update tests
- Update types

pkg/tsdb/graphite/resource_handler.go

@@ -25,6 +25,7 @@ func (s *Service) newResourceMux() *http.ServeMux {
 	mux.HandleFunc("/metrics/find", handleResourceReq(s.handleMetricsFind, s))
 	mux.HandleFunc("/metrics/expand", handleResourceReq(s.handleMetricsExpand, s))
 	mux.HandleFunc("/functions", handleResourceReq(s.handleFunctions, s))
+	mux.HandleFunc("/tags/autoComplete/tags", handleResourceReq(s.handleTagsAutocomplete, s))
 	return mux
 }
 
@@ -203,6 +204,35 @@ func (s *Service) handleMetricsExpand(ctx context.Context, dsInfo *datasourceInf
 	return metricsExpandResponse, statusCode, nil
 }
 
+func (s *Service) handleTagsAutocomplete(ctx context.Context, dsInfo *datasourceInfo, tagsAutocompleteRequestJson *GraphiteTagsRequest) ([]byte, int, error) {
+	queryParams := map[string]string{
+		"from":      tagsAutocompleteRequestJson.From,
+		"until":     tagsAutocompleteRequestJson.Until,
+		"limit":     fmt.Sprintf("%d", tagsAutocompleteRequestJson.Limit),
+		"tagPrefix": tagsAutocompleteRequestJson.TagPrefix,
+	}
+	req, err := s.createRequest(ctx, dsInfo, URLParams{
+		SubPath:     "tags/autoComplete/tags",
+		Method:      http.MethodGet,
+		QueryParams: queryParams,
+	})
+	if err != nil {
+		return nil, http.StatusInternalServerError, fmt.Errorf("failed to create metrics expand request %v", err)
+	}
+
+	tags, _, statusCode, err := doGraphiteRequest[[]string](ctx, dsInfo, s.logger, req, false)
+	if err != nil {
+		return nil, statusCode, fmt.Errorf("tags autocomplete request failed: %v", err)
+	}
+
+	tagsResponse, err := json.Marshal(tags)
+	if err != nil {
+		return nil, http.StatusInternalServerError, fmt.Errorf("failed to marshal tags autocomplete response: %s", err)
+	}
+
+	return tagsResponse, statusCode, nil
+}
+
 func (s *Service) handleFunctions(ctx context.Context, dsInfo *datasourceInfo, _ *any) ([]byte, int, error) {
 	req, err := s.createRequest(ctx, dsInfo, URLParams{
 		SubPath: "functions",

pkg/tsdb/graphite/resource_handler_test.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -94,7 +95,7 @@ func TestHandleEvents(t *testing.T) {
 			name: "Invalid URL",
 			dsInfo: &datasourceInfo{
 				Id:  1,
-				URL: "ht tp://invalid url", // Invalid URL
+				URL: "ht tp://invalid url",
 			},
 			request:        GraphiteEventsRequest{From: "now-1h", Until: "now"},
 			expectedStatus: http.StatusInternalServerError,
@@ -211,7 +212,7 @@ func TestHandleMetricsFind(t *testing.T) {
 			name: "Invalid URL",
 			dsInfo: &datasourceInfo{
 				Id:  1,
-				URL: "ht tp://invalid url", // Invalid URL
+				URL: "ht tp://invalid url",
 			},
 			request:        GraphiteMetricsFindRequest{Query: "app.grafana.*"},
 			expectedStatus: http.StatusInternalServerError,
@@ -321,7 +322,7 @@ func TestHandleMetricsExpand(t *testing.T) {
 			name: "Invalid URL",
 			dsInfo: &datasourceInfo{
 				Id:  1,
-				URL: "ht tp://invalid url", // Invalid URL
+				URL: "ht tp://invalid url",
 			},
 			request:        GraphiteMetricsFindRequest{Query: "app.grafana.*"},
 			expectedStatus: http.StatusInternalServerError,
@@ -394,6 +395,109 @@ func TestHandleMetricsExpand(t *testing.T) {
 	}
 }
 
+func TestHandleTagsAutocomplete(t *testing.T) {
+	tests := []struct {
+		name          string
+		request       GraphiteTagsRequest
+		responseBody  string
+		statusCode    int
+		expectError   bool
+		errorContains string
+		expectedData  []string
+	}{
+		{
+			name: "successful tags autocomplete request",
+			request: GraphiteTagsRequest{
+				From:      "1h",
+				Until:     "now",
+				Limit:     10,
+				TagPrefix: "app",
+			},
+			responseBody: `["app", "application", "app_name"]`,
+			statusCode:   200,
+			expectedData: []string{"app", "application", "app_name"},
+		},
+		{
+			name:         "tags autocomplete with minimal request",
+			request:      GraphiteTagsRequest{},
+			responseBody: `["tag1", "tag2"]`,
+			statusCode:   200,
+			expectedData: []string{"tag1", "tag2"},
+		},
+		{
+			name: "tags autocomplete with empty response",
+			request: GraphiteTagsRequest{
+				TagPrefix: "nonexistent",
+			},
+			responseBody: `[]`,
+			statusCode:   200,
+			expectedData: []string{},
+		},
+		{
+			name: "tags autocomplete server error - invalid JSON causes marshal error",
+			request: GraphiteTagsRequest{
+				From: "invalid",
+			},
+			responseBody:  `invalid json response`,
+			statusCode:    400,
+			expectError:   true,
+			errorContains: "tags autocomplete request failed",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mockTransport := &mockRoundTripper{
+				respBody: []byte(tt.responseBody),
+				status:   tt.statusCode,
+			}
+
+			dsInfo := &datasourceInfo{
+				HTTPClient: &http.Client{Transport: mockTransport},
+				URL:        "http://graphite.example.com",
+			}
+
+			service := &Service{
+				logger: log.NewNullLogger(),
+			}
+
+			result, statusCode, err := service.handleTagsAutocomplete(context.Background(), dsInfo, &tt.request)
+
+			if tt.expectError {
+				assert.Error(t, err)
+				if tt.errorContains != "" {
+					assert.Contains(t, err.Error(), tt.errorContains)
+				}
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.statusCode, statusCode)
+
+				var tags []string
+				err = json.Unmarshal(result, &tags)
+				assert.NoError(t, err)
+				assert.Equal(t, tt.expectedData, tags)
+			}
+
+			if !tt.expectError {
+				expectedURL := "http://graphite.example.com/tags/autoComplete/tags"
+				assert.Contains(t, mockTransport.lastRequest.URL.String(), expectedURL)
+
+				if tt.request.From != "" {
+					assert.Contains(t, mockTransport.lastRequest.URL.RawQuery, fmt.Sprintf("from=%s", tt.request.From))
+				}
+				if tt.request.Until != "" {
+					assert.Contains(t, mockTransport.lastRequest.URL.RawQuery, fmt.Sprintf("until=%s", tt.request.Until))
+				}
+				if tt.request.Limit != 0 {
+					assert.Contains(t, mockTransport.lastRequest.URL.RawQuery, fmt.Sprintf("limit=%d", tt.request.Limit))
+				}
+				if tt.request.TagPrefix != "" {
+					assert.Contains(t, mockTransport.lastRequest.URL.RawQuery, fmt.Sprintf("tagPrefix=%s", tt.request.TagPrefix))
+				}
+			}
+		})
+	}
+}
 func TestHandleFunctions(t *testing.T) {
 	tests := []struct {
 		name          string

pkg/tsdb/graphite/types.go

@@ -59,3 +59,10 @@ type GraphiteMetricsFindResponse struct {
 type GraphiteMetricsExpandResponse struct {
 	Results []string `json:"results"`
 }
+
+type GraphiteTagsRequest struct {
+	From      string `json:"from"`
+	Until     string `json:"until"`
+	Limit     int    `json:"limit,omitempty"`
+	TagPrefix string `json:"tagPrefix,omitempty"`
+}