while json unmarshaling result from remote introspection que

Error message

while json unmarshaling result from remote introspection query

What it means

After Dgraph executes the introspection query against the remote GraphQL schema, it reads the body and unmarshals it into introspectedSchema. If the body is not valid JSON in the expected introspection envelope, json.Unmarshal fails and this wrapped error is returned. Usually the remote returned an error page, empty body, or a non-standard introspection response.

Source

Thrown at graphql/schema/remote.go:76

	for k := range headers {
		req.Header.Set(k, headers.Get(k))
	}
	client := &http.Client{Timeout: 5 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err := resp.Body.Close(); err != nil {
			glog.Warningf("error closing body: %v", err)
		}
	}()
	body, err = io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}
	result := &introspectedSchema{}
	return result, errors.Wrapf(json.Unmarshal(body, result),
		"while json unmarshaling result from remote introspection query")
}

const (
	list        = "LIST"
	nonNull     = "NON_NULL"
	inputObject = string(ast.InputObject)
)

const introspectionQuery = `
	query {
	  __schema {
		queryType { name }
		mutationType { name }
		subscriptionType { name }
		types {
		  ...FullType
		}

View on GitHub (pinned to 759e242be6)

Solutions

Test the introspection POST against the remote URL manually (curl) and inspect the raw body
Ensure the remote is a real GraphQL endpoint supporting introspection
Check auth headers in the @custom directive config
Confirm no proxy/CDN is rewriting or blocking the response

Defensive patterns

Strategy: fallback

Validate before calling

const res = await fetch(url, introspectionPost)
try { JSON.parse(await res.text()) } catch { throw new Error('remote introspection response is not valid JSON') }

Try / catch

err := schema.ValidateCustom(dgSchema, gqlSchema)
if err != nil && strings.Contains(err.Error(), "while json unmarshaling result") {
  // manually curl the remote endpoint and inspect the raw body
}

Prevention

Curl the remote with the introspection query before wiring @custom
Confirm content-type is application/json
Check auth headers so the remote doesn't return an error page
Ensure no proxy rewrites the response body

When it happens

Trigger: validateRemoteGraphql calls introspectRemoteSchema, the remote responds (possibly HTTP 200) but the body isn't the expected JSON introspection result — truncated response, HTML error page, or a schema format the introspectedSchema struct doesn't match.

Common situations: Remote endpoint doesn't support the introspection query version Dgraph sends; gateway/CDN intercepting the response; remote requires auth so it returns an HTML/JSON auth error instead of introspection data.

Related errors

AI-assisted analysis of dgraph-io/dgraph@759e242be6 (2026-09-01). Data as JSON: /api/errors/07844d2ad5f5e81b. Report an issue: GitHub.