Backend plugins: Implement support for resources (#21805)

Implements initial support for resources using v0.14.0 of SDK.

Ref #21512

pkg/plugins/backendplugin/backend_plugin.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"net/http"
 
 	"github.com/grafana/grafana-plugin-sdk-go/genproto/pluginv2"
 	"github.com/prometheus/client_golang/prometheus"
@@ -14,7 +15,6 @@ import (
 
 	datasourceV1 "github.com/grafana/grafana-plugin-model/go/datasource"
 	rendererV1 "github.com/grafana/grafana-plugin-model/go/renderer"
-	backend "github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana/pkg/infra/log"
 	"github.com/grafana/grafana/pkg/plugins/backendplugin/collector"
 	"github.com/grafana/grafana/pkg/util/errutil"
@@ -31,7 +31,8 @@ type BackendPlugin struct {
 	client         *plugin.Client
 	logger         log.Logger
 	startFns       PluginStartFuncs
-	diagnostics    backend.DiagnosticsPlugin
+	diagnostics    DiagnosticsPlugin
+	core           CorePlugin
 }
 
 func (p *BackendPlugin) start(ctx context.Context) error {
@@ -61,20 +62,21 @@ func (p *BackendPlugin) start(ctx context.Context) error {
 		}
 
 		if rawDiagnostics != nil {
-			if plugin, ok := rawDiagnostics.(backend.DiagnosticsPlugin); ok {
+			if plugin, ok := rawDiagnostics.(DiagnosticsPlugin); ok {
 				p.diagnostics = plugin
 			}
 		}
 
 		client = &Client{}
 		if rawBackend != nil {
-			if plugin, ok := rawBackend.(backend.BackendPlugin); ok {
-				client.BackendPlugin = plugin
+			if plugin, ok := rawBackend.(CorePlugin); ok {
+				p.core = plugin
+				client.DatasourcePlugin = plugin
 			}
 		}
 
 		if rawTransform != nil {
-			if plugin, ok := rawTransform.(backend.TransformPlugin); ok {
+			if plugin, ok := rawTransform.(TransformPlugin); ok {
 				client.TransformPlugin = plugin
 			}
 		}
@@ -194,6 +196,47 @@ func (p *BackendPlugin) checkHealth(ctx context.Context) (*pluginv2.CheckHealth_
 	return res, nil
 }
 
+func (p *BackendPlugin) callResource(ctx context.Context, req CallResourceRequest) (*CallResourceResult, error) {
+	p.logger.Debug("Calling resource", "path", req.Path, "method", req.Method)
+
+	reqHeaders := map[string]*pluginv2.CallResource_StringList{}
+	for k, v := range req.Headers {
+		reqHeaders[k] = &pluginv2.CallResource_StringList{Values: v}
+	}
+
+	protoReq := &pluginv2.CallResource_Request{
+		Config:  &pluginv2.PluginConfig{},
+		Path:    req.Path,
+		Method:  req.Method,
+		Url:     req.URL,
+		Headers: reqHeaders,
+		Body:    req.Body,
+	}
+	protoResp, err := p.core.CallResource(ctx, protoReq)
+	if err != nil {
+		if st, ok := status.FromError(err); ok {
+			if st.Code() == codes.Unimplemented {
+				return &CallResourceResult{
+					Status: http.StatusNotImplemented,
+				}, nil
+			}
+		}
+
+		return nil, errutil.Wrap("Failed to call resource", err)
+	}
+
+	respHeaders := map[string][]string{}
+	for key, values := range protoResp.Headers {
+		respHeaders[key] = values.Values
+	}
+
+	return &CallResourceResult{
+		Headers: respHeaders,
+		Body:    protoResp.Body,
+		Status:  int(protoResp.Code),
+	}, nil
+}
+
 // convertMetricFamily converts metric family to prometheus.Metric.
 // Copied from https://github.com/prometheus/node_exporter/blob/3ddc82c2d8d11eec53ed5faa8db969a1bb81f8bb/collector/textfile.go#L66-L165
 func convertMetricFamily(pluginID string, metricFamily *dto.MetricFamily, ch chan<- prometheus.Metric, logger log.Logger) {