cayleygraph/cayley · error

HTTP interface is not supported for this query language

Error message

HTTP interface is not supported for this query language

What it means

ServeQuery dispatches to a query language's registered listener. If the language declares neither an HTTPQuery hook nor a Session factory (l.Session == nil), Cayley cannot execute the query over HTTP and returns this error via errFunc. It means the chosen query language simply has no HTTP interface wired up.

Source

Thrown at server/http/api_v2.go:530

	}
	select {
	case <-ctx.Done():
		errFunc(w, ctx.Err())
		return
	default:
	}
	h, err := api.handleForRequest(r)
	if err != nil {
		errFunc(w, err)
		return
	}
	if l.HTTPQuery != nil {
		defer r.Body.Close()
		l.HTTPQuery(ctx, h.QuadStore, w, r.Body)
		return
	}
	if l.Session == nil {
		errFunc(w, errors.New("HTTP interface is not supported for this query language"))
		return
	}
	ses := l.Session(h.QuadStore)
	var qu string
	if r.Method == "GET" {
		qu = vals.Get("qu")
	} else {
		data, err := readLimit(r.Body)
		if err != nil {
			errFunc(w, err)
			return
		}
		qu = string(data)
	}
	if qu == "" {
		jsonResponse(w, http.StatusBadRequest, "query is empty")
		return
	}

View on GitHub (pinned to 81dcd7d73e)

Solutions

1. Use a supported query language value for HTTP queries (e.g. gremlin/gizmo or sparql) instead of the current one.
2. Check the spelling/case of the query language parameter in the request URL or form values.
3. Verify in the server version's language registry that the language implements HTTPQuery or Session; upgrade Cayley if a newer version adds HTTP support.
4. Execute the query programmatically via the Go API instead of the HTTP endpoint.

Example fix

// before
curl 'http://localhost:64210/v2/query?lang=notalang' --data 'g.V()'
// after
curl 'http://localhost:64210/v2/query?lang=gremlin' --data 'g.V()'

const supported = ["gremlin", "gizmo", "sparql"];
if (!supported.includes(lang)) {
  throw new Error(`query language "${lang}" has no HTTP interface`);
}

When it happens

Trigger: Issuing an HTTP request to /v2/query with a query-language parameter selecting a language whose Listener has no HTTPQuery function and no Session constructor.

Common situations: Typo or unsupported value in the query language parameter of the request; using a query language registered only for internal/programmatic use; version where the language's HTTP support was removed or not yet added.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• no support for HTTP interface for this query language
• request is too large
• request is too large
• invalid quad at index %d. %s
• could not get resource <%s>: %v

AI-assisted analysis of cayleygraph/cayley@81dcd7d73e (2026-09-06). Data as JSON: /api/errors/d8650ff681851ef0. Report an issue: GitHub.