vitessio/vitess · error

can't get %v: %v

Error message

can't get %v: %v

What it means

The vtgate HTTP debug API's handleCollection wraps any error from the per-collection getFunc into `can't get <collection>: <err>`. The collection name (e.g. tablets, keyspaces) is preserved so you know which REST resource failed. The wrapped inner error carries the actual cause.

Source

Thrown at go/vt/vtgate/api.go:62

func handleAPI(apiPath string, handlerFunc func(w http.ResponseWriter, r *http.Request) error) {
	servenv.HTTPHandleFunc(apiPrefix+apiPath, func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if x := recover(); x != nil {
				httpErrorf(w, r, "uncaught panic: %v", x)
			}
		}()
		if err := handlerFunc(w, r); err != nil {
			httpErrorf(w, r, "%v", err)
		}
	})
}

func handleCollection(collection string, getFunc func(*http.Request) (any, error)) {
	handleAPI(collection+"/", func(w http.ResponseWriter, r *http.Request) error {
		// Get the requested object.
		obj, err := getFunc(r)
		if err != nil {
			return fmt.Errorf("can't get %v: %v", collection, err)
		}

		// JSON encode response.
		data, err := json.MarshalIndent(obj, "", "  ")
		if err != nil {
			return fmt.Errorf("cannot marshal data: %v", err)
		}
		w.Header().Set("Content-Type", jsonContentType)
		w.Write(data)
		return nil
	})
}

func getItemPath(url string) string {
	// Strip API prefix.
	if !strings.HasPrefix(url, apiPrefix) {
		return ""
	}

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Read the wrapped inner error for the real cause and fix that (bad name, missing object).
2. Verify the collection path parameter (cell/keyspace/tablet) is correct.
3. Check topology connectivity if the underlying error indicates topo failure.

Example fix

// before
curl http://vtgate:15001/api/keyspaces/wrongks/
// after
curl http://vtgate:15001/api/keyspaces/commerce/

resp, err := http.Get(base + "/api/keyspaces/" + ks + "/")
if err != nil || resp.StatusCode != 200 {
    body, _ := io.ReadAll(resp.Body)
    // body contains: can't get <collection>: <inner err>
    log.Warn("vtgate API get failed", "body", string(body))
}

When it happens

Trigger: Requesting a vtgate debug HTTP endpoint like /api/<collection>/ where getFunc fails — e.g. querying /api/tablets/ with a bad tablet filter or an unknown keyspace/cell, causing the underlying lookup to error.

Common situations: Scripts/curl against the vtgate debug API with mistyped collection values or keyspace/cell names; topology temporarily unreachable causing underlying getFunc errors.

Understand the failure class

Background: 'Something went wrong' / 'Request failed (500)' / 'HTTP error! status: 404' — what failed HTTP requests actually mean and how to find the real cause — this error's family across 28 libraries.

Related errors

• cannot marshal data: %v
• invalid health-check path: %q expected path: / or /cell/<ce
• err.Error() (template execute failure)
• err.Error() (Fprintf write failure)
• cells can only be listed, not retrieved

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/4e8d6f81debcd872. Report an issue: GitHub.