refine outbound request caching

src/http/outbound.ts

@@ -103,7 +103,7 @@ export function create_outbound_http_provider(conf: OutboundHttpConfig, logger:
 		if (cached) {
 			const revalidation = response_cache.determine_revalidation_needed(cached);
 
-			if (! revalidation.must_revalidate) {
+			if (! revalidation.should_revalidate) {
 				log.info('serving request from cache (no revalidation required)');
 				result.status = cached.status;
 				result.body = cached.body;
@@ -111,6 +111,10 @@ export function create_outbound_http_provider(conf: OutboundHttpConfig, logger:
 				return Promise.resolve(result);
 			}
 
+			// if (! revalidation.must_revalidate) {
+			// 	// todo: lazy revalidation option
+			// }
+
 			log.info('cached response found, but requires revalidation');
 			Object.assign(req_headers, revalidation.headers);
 		}

src/http/request-cache.ts

@@ -7,6 +7,8 @@ import { parse_cache_headers, ParsedCacheHeaders } from './parse-cache-headers';
 import type { HttpURL } from '../utilities/types';
 import type { HttpResult } from './outbound';
 
+// todo: second implementation that stores to disk / db
+
 export interface RequestCacheConfig {
 	// todo: support for configurable limits:
 	max_records?: number;  // max number of cached responses
@@ -67,6 +69,7 @@ export function create_request_cache_provider(conf: RequestCacheConfig, logger:
 			const { cache_control, etag, date, last_modified } = cached.cache_info;
 
 			const must_revalidate = Boolean(cache_control?.must_revalidate || cache_control?.no_cache);
+			const should_revalidate = must_revalidate || cached.is_stale;
 			const headers: OutgoingHttpHeaders = { };
 
 			if (etag) {
@@ -83,6 +86,7 @@ export function create_request_cache_provider(conf: RequestCacheConfig, logger:
 
 			return {
 				must_revalidate,
+				should_revalidate,
 				headers,
 			};
 		},