Option to respect range during cache streaming

runtime/fastly/builtins/cache-core.cpp

@@ -42,6 +42,7 @@ JS::Result<host_api::CacheLookupOptions> parseLookupOptions(JSContext *cx,
       return JS::Result<host_api::CacheLookupOptions>(JS::Error());
     }
     JS::RootedObject options_obj(cx, &options_val.toObject());
+
     JS::RootedValue headers_val(cx);
     if (!JS_GetProperty(cx, options_obj, "headers", &headers_val)) {
       return JS::Result<host_api::CacheLookupOptions>(JS::Error());
@@ -79,6 +80,20 @@ JS::Result<host_api::CacheLookupOptions> parseLookupOptions(JSContext *cx,
       }
       options.request_headers = host_api::HttpReq(request_handle);
     }
+
+    JS::RootedValue always_use_requested_range_val(cx);
+    if (!JS_GetProperty(cx, options_obj, "always_use_requested_range",
+                        &always_use_requested_range_val)) {
+      return JS::Result<host_api::CacheLookupOptions>(JS::Error());
+    }
+    // always_use_requested_range property is optional
+    if (!always_use_requested_range_val.isUndefined()) {
+      if (!always_use_requested_range_val.isBoolean()) {
+        JS_ReportErrorASCII(cx, "always_use_requested_range must be a boolean");
+        return JS::Result<host_api::CacheLookupOptions>(JS::Error());
+      }
+      options.always_use_requested_range = always_use_requested_range_val.toBoolean();
+    }
   }
   return options;
 }

runtime/fastly/host-api/fastly.h

@@ -871,6 +871,9 @@ int purge_surrogate_key(char *surrogate_key, size_t surrogate_key_len, uint32_t
 
 #define FASTLY_CACHE_LOOKUP_OPTIONS_MASK_RESERVED (1 << 0)
 #define FASTLY_CACHE_LOOKUP_OPTIONS_MASK_REQUEST_HEADERS (1 << 1)
+// Note: SERVICE_ID for internal use only.
+#define FASTLY_CACHE_LOOKUP_OPTIONS_MASK_SERVICE_ID (1 << 2)
+#define FASTLY_CACHE_LOOKUP_OPTIONS_MASK_ALWAYS_USE_REQUESTED_RANGE (1 << 3)
 
 // Extensible options for cache lookup operations currently used for both `lookup` and
 // `transaction_lookup`.

runtime/fastly/host-api/host_api.cpp

@@ -2950,6 +2950,9 @@ Result<CacheHandle> CacheHandle::lookup(std::string_view key, const CacheLookupO
     os.request_headers = opts.request_headers.handle;
     options_mask |= FASTLY_CACHE_LOOKUP_OPTIONS_MASK_REQUEST_HEADERS;
   }
+  if (opts.always_use_requested_range) {
+    options_mask |= FASTLY_CACHE_LOOKUP_OPTIONS_MASK_ALWAYS_USE_REQUESTED_RANGE;
+  }
 
   if (!convert_result(fastly::cache_lookup(reinterpret_cast<char *>(key_str.ptr), key_str.len,
                                            options_mask, &os, &handle),
@@ -2979,6 +2982,9 @@ Result<CacheHandle> CacheHandle::transaction_lookup(std::string_view key,
     os.request_headers = opts.request_headers.handle;
     options_mask |= FASTLY_CACHE_LOOKUP_OPTIONS_MASK_REQUEST_HEADERS;
   }
+  if (opts.always_use_requested_range) {
+    options_mask |= FASTLY_CACHE_LOOKUP_OPTIONS_MASK_ALWAYS_USE_REQUESTED_RANGE;
+  }
 
   if (!convert_result(fastly::cache_transaction_lookup(reinterpret_cast<char *>(key_str.ptr),
                                                        key_str.len, options_mask, &os, &handle),

runtime/fastly/host-api/host_api_fastly.h

@@ -940,6 +940,16 @@ class SecretStore final {
 struct CacheLookupOptions final {
   /// A full request handle, used only for its headers.
   HttpReq request_headers;
+
+  /// When a range is provided to get_body,
+  /// respect the requested range even when the body length is unknown
+  /// (e.g. streaming). If "false", when the body length is unknown,
+  /// the entire body will be returned instead of just the requested range.
+  ///
+  /// The default is "false" to preserve the legacy behavior.
+  /// However, if using ranged get_body, Fastly recommends setting this to "true".
+  /// The default may change in a future release.
+  bool always_use_requested_range;
 };
 
 struct CacheGetBodyOptions final {