Use hash of proxy settings as part of datasource instance cache key (#1133)

Author: njvrzm

backend/config.go

@@ -96,6 +96,17 @@ func (c *GrafanaCfg) Equal(c2 *GrafanaCfg) bool {
 	return true
 }
 
+// ProxyHash returns the last four bytes of the PDC client key contents,
+// if present, for use in datasource instance caching
+func (c *GrafanaCfg) ProxyHash() string {
+	if c == nil {
+		return ""
+	}
+	key := c.config[proxy.PluginSecureSocksProxyClientKeyContents]
+	start := max(len(key)-4, 0)
+	return key[start:]
+}
+
 type FeatureToggles struct {
 	// enabled is a set-like map of feature flags that are enabled.
 	enabled map[string]struct{}

backend/datasource/instance_provider.go

@@ -59,12 +59,11 @@ func (ip *instanceProvider) GetKey(ctx context.Context, pluginContext backend.Pl
 		return nil, errors.New("data source instance settings cannot be nil")
 	}
 
-	defaultKey := pluginContext.DataSourceInstanceSettings.ID
-	if tID := tenant.IDFromContext(ctx); tID != "" {
-		return fmt.Sprintf("%s#%v", tID, defaultKey), nil
-	}
+	dsID := pluginContext.DataSourceInstanceSettings.ID
+	proxyHash := pluginContext.GrafanaConfig.ProxyHash()
+	tenantID := tenant.IDFromContext(ctx)
 
-	return defaultKey, nil
+	return fmt.Sprintf("%d#%s#%s", dsID, tenantID, proxyHash), nil
 }
 
 func (ip *instanceProvider) NeedsUpdate(_ context.Context, pluginContext backend.PluginContext, cachedInstance instancemgmt.CachedInstance) bool {

backend/datasource/instance_provider_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana-plugin-sdk-go/backend/instancemgmt"
+	"github.com/grafana/grafana-plugin-sdk-go/backend/proxy"
 	"github.com/stretchr/testify/require"
 )
 
@@ -30,7 +31,43 @@ func TestInstanceProvider(t *testing.T) {
 			},
 		})
 		require.NoError(t, err)
-		require.Equal(t, int64(4), key)
+		require.Equal(t, "4##", key)
+	})
+
+	t.Run("When PDC is configured, datasource cache key should include its (so-called) hash", func(t *testing.T) {
+		cfg := backend.NewGrafanaCfg(map[string]string{
+			proxy.PluginSecureSocksProxyClientKeyContents: "This should work",
+		})
+		key, err := ip.GetKey(context.Background(), backend.PluginContext{
+			DataSourceInstanceSettings: &backend.DataSourceInstanceSettings{ID: 5},
+			GrafanaConfig:              cfg,
+		})
+		require.NoError(t, err)
+		require.Equal(t, "5##work", key)
+	})
+
+	t.Run("When PDC is configured but the key is empty, no problem", func(t *testing.T) {
+		cfg := backend.NewGrafanaCfg(map[string]string{
+			proxy.PluginSecureSocksProxyClientKeyContents: "",
+		})
+		key, err := ip.GetKey(context.Background(), backend.PluginContext{
+			DataSourceInstanceSettings: &backend.DataSourceInstanceSettings{ID: 6},
+			GrafanaConfig:              cfg,
+		})
+		require.NoError(t, err)
+		require.Equal(t, "6##", key)
+	})
+
+	t.Run("When PDC is configured, a too-short key doesn't cause an error", func(t *testing.T) {
+		cfg := backend.NewGrafanaCfg(map[string]string{
+			proxy.PluginSecureSocksProxyClientKeyContents: "doh",
+		})
+		key, err := ip.GetKey(context.Background(), backend.PluginContext{
+			DataSourceInstanceSettings: &backend.DataSourceInstanceSettings{ID: 7},
+			GrafanaConfig:              cfg,
+		})
+		require.NoError(t, err)
+		require.Equal(t, "7##doh", key)
 	})
 
 	t.Run("When both the configuration and updated field of current data source instance settings are equal to the cache, should return false", func(t *testing.T) {