Fallback Service Using Cloudflare Workers

gistfile1.txt

export default {
    async fetch(request) {
        const primaryUrl = 'https://api.example.com';
        const fallbackUrl = 'https://api2.example.com';

        const url = new URL(request.url);
        const path = url.pathname + url.search;

        // Try primary
        try {
            const response = await fetch(primaryUrl + path, request);

            // If origin responds with a redirect (301/302), return it
            if ([301, 302].includes(response.status)) {
                return new Response(null, {
                    status: response.status,
                    headers: { 'Location': response.headers.get('Location') }
                });
            }

            // Otherwise, return normal response
            if (response.ok) {
                return response;
            }
        } catch (e) {
            console.error('Primary failed:', e);
        }

        // Fallback: try the same logic on secondary
        try {
            const response = await fetch(fallbackUrl + path, request);
            if ([301, 302].includes(response.status)) {
                return new Response(null, {
                    status: response.status,
                    headers: { 'Location': response.headers.get('Location') }
                });
            }
            return response;
        } catch (e) {
            console.error('Fallback failed:', e);
        }

        return new Response('Service unavailable', { status: 503 });
    }
};