diagnostics: print understandable error

cmd/diag/db/db.go

@@ -61,7 +61,8 @@ var Command = cli.Command{
 func startPrintDBsInfo(cliCtx *cli.Context) error {
 	data, err := DBsInfo(cliCtx)
 	if err != nil {
-		return err
+		util.RenderError(err)
+		return nil
 	}
 
 	dbToPrint := cliCtx.String(DBNameFlag.Name)

cmd/diag/downloader/diag_downloader.go

@@ -63,8 +63,8 @@ func printDownloadStatus(cliCtx *cli.Context) error {
 	data, err := getData(cliCtx)
 
 	if err != nil {
-
-		return err
+		util.RenderError(err)
+		return nil
 	}
 
 	snapshotDownloadStatus := getSnapshotStatusRow(data.SnapshotDownload)
@@ -92,9 +92,8 @@ func printFiles(cliCtx *cli.Context) error {
 	data, err := getData(cliCtx)
 
 	if err != nil {
-		txt := text.Colors{text.FgWhite, text.BgRed}
-		fmt.Printf("%s %s", txt.Sprint("[ERROR]"), "Failed to connect to Erigon node.")
-		return err
+		util.RenderError(err)
+		return nil
 	}
 
 	snapshotDownloadStatus := getSnapshotStatusRow(data.SnapshotDownload)

cmd/diag/stages/stages.go

@@ -34,7 +34,8 @@ func printCurentStage(cliCtx *cli.Context) error {
 
 	err := util.MakeHttpGetCall(cliCtx.Context, url, &data)
 	if err != nil {
-		return err
+		util.RenderError(err)
+		return nil
 	}
 
 	stagesRows := getStagesRows(data.SyncStages)

cmd/diag/util/util.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/http"
 	"os"
+	"strings"
 	"time"
 
 	"github.com/jedib0t/go-pretty/v6/table"
@@ -25,6 +26,9 @@ func MakeHttpGetCall(ctx context.Context, url string, data interface{}) error {
 
 	resp, err := client.Do(req)
 	if err != nil {
+		if strings.Contains(err.Error(), "connection refused") {
+			return fmt.Errorf("it looks like the Erigon node is not running, is running incorrectly, or you have specified the wrong diagnostics URL. If you run the Erigon node with the '--diagnostics.endpoint.addr' or '--diagnostics.endpoint.port' flags, you must also specify the '--debug.addr' flag with the same address and port")
+		}
 		return err
 	}
 
@@ -36,6 +40,10 @@ func MakeHttpGetCall(ctx context.Context, url string, data interface{}) error {
 
 	err = json.Unmarshal(body, &data)
 	if err != nil {
+		if err.Error() == "invalid character 'p' after top-level value" {
+			return fmt.Errorf("diagnostics have not been initialized yet. Please try again in a few seconds")
+		}
+
 		return err
 	}
 
@@ -94,3 +102,8 @@ func RenderUseDiagUI() {
 	txt := text.Colors{text.BgGreen, text.Bold}
 	fmt.Println(txt.Sprint("To get detailed info about Erigon node state use 'diag ui' command."))
 }
+
+func RenderError(err error) {
+	txt := text.Colors{text.FgWhite, text.BgRed}
+	fmt.Printf("%s %s", txt.Sprint("[ERROR]"), err)
+}