Zipkin: Run health check through backend (#96031)

* Zipkin: Run health check through backend

* Mark some errors as downstream

* Update pkg/tsdb/zipkin/zipkin.go

Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>

* Use errors.New where error formatting is not needed

* Remove executable in plugin.json

* Fix joining the path

* Keep logger as global and then create from context

* Close the res body

---------

Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>

pkg/tsdb/zipkin/client.go

@@ -0,0 +1,50 @@
+package zipkin
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana-plugin-sdk-go/backend/log"
+)
+
+type ZipkinClient struct {
+	logger     log.Logger
+	url        string
+	httpClient *http.Client
+}
+
+func New(url string, hc *http.Client, logger log.Logger) (ZipkinClient, error) {
+	client := ZipkinClient{
+		logger:     logger,
+		url:        url,
+		httpClient: hc,
+	}
+	return client, nil
+}
+
+// Services returns list of services
+// https://zipkin.io/zipkin-api/#/default/get_services
+func (z *ZipkinClient) Services() ([]string, error) {
+	services := []string{}
+	u, err := url.JoinPath(z.url, "/api/v2/services")
+	if err != nil {
+		return services, backend.DownstreamError(fmt.Errorf("failed to join url: %w", err))
+	}
+	res, err := z.httpClient.Get(u)
+	if err != nil {
+		return services, err
+	}
+
+	defer func() {
+		if err = res.Body.Close(); err != nil {
+			z.logger.Error("Failed to close response body", "error", err)
+		}
+	}()
+	if err := json.NewDecoder(res.Body).Decode(&services); err != nil {
+		return services, err
+	}
+	return services, err
+}

pkg/tsdb/zipkin/zipkin.go

@@ -0,0 +1,83 @@
+package zipkin
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana-plugin-sdk-go/backend/datasource"
+	"github.com/grafana/grafana-plugin-sdk-go/backend/instancemgmt"
+
+	"github.com/grafana/grafana/pkg/infra/httpclient"
+)
+
+var logger = backend.NewLoggerWith("logger", "tsdb.zipkin")
+
+type Service struct {
+	im instancemgmt.InstanceManager
+}
+
+func ProvideService(httpClientProvider httpclient.Provider) *Service {
+	return &Service{
+		im: datasource.NewInstanceManager(newInstanceSettings(httpClientProvider)),
+	}
+}
+
+type datasourceInfo struct {
+	ZipkinClient ZipkinClient
+}
+
+func newInstanceSettings(httpClientProvider httpclient.Provider) datasource.InstanceFactoryFunc {
+	return func(ctx context.Context, settings backend.DataSourceInstanceSettings) (instancemgmt.Instance, error) {
+		httpClientOptions, err := settings.HTTPClientOptions(ctx)
+		if err != nil {
+			return nil, backend.DownstreamError(fmt.Errorf("error reading settings: %w", err))
+		}
+
+		httpClient, err := httpClientProvider.New(httpClientOptions)
+		if err != nil {
+			return nil, fmt.Errorf("error creating http client: %w", err)
+		}
+
+		if settings.URL == "" {
+			return nil, backend.DownstreamError(errors.New("error reading settings: url is empty"))
+		}
+
+		logger := logger.FromContext(ctx)
+		zipkinClient, err := New(settings.URL, httpClient, logger)
+		return &datasourceInfo{ZipkinClient: zipkinClient}, err
+	}
+}
+
+func (s *Service) getDSInfo(ctx context.Context, pluginCtx backend.PluginContext) (*datasourceInfo, error) {
+	i, err := s.im.Get(ctx, pluginCtx)
+	if err != nil {
+		return nil, err
+	}
+	instance, ok := i.(*datasourceInfo)
+	if !ok {
+		return nil, errors.New("failed to cast datasource info")
+	}
+	return instance, nil
+}
+
+func (s *Service) CheckHealth(ctx context.Context, req *backend.CheckHealthRequest) (*backend.CheckHealthResult, error) {
+	client, err := s.getDSInfo(ctx, backend.PluginConfigFromContext(ctx))
+	if err != nil {
+		return &backend.CheckHealthResult{
+			Status:  backend.HealthStatusError,
+			Message: err.Error(),
+		}, nil
+	}
+	if _, err = client.ZipkinClient.Services(); err != nil {
+		return &backend.CheckHealthResult{
+			Status:  backend.HealthStatusError,
+			Message: err.Error(),
+		}, nil
+	}
+	return &backend.CheckHealthResult{
+		Status:  backend.HealthStatusOk,
+		Message: "Data source is working",
+	}, nil
+}