674 lines
23 KiB
JavaScript
674 lines
23 KiB
JavaScript
|
'use strict';
|
||
|
|
// rfc7231 6.1
|
||
|
|
const statusCodeCacheableByDefault = new Set([
|
||
|
|
200,
|
||
|
|
203,
|
||
|
|
204,
|
||
|
|
206,
|
||
|
|
300,
|
||
|
|
301,
|
||
|
|
404,
|
||
|
|
405,
|
||
|
|
410,
|
||
|
|
414,
|
||
|
|
501,
|
||
|
|
]);
|
||
|
|
|
||
|
|
// This implementation does not understand partial responses (206)
|
||
|
|
const understoodStatuses = new Set([
|
||
|
|
200,
|
||
|
|
203,
|
||
|
|
204,
|
||
|
|
300,
|
||
|
|
301,
|
||
|
|
302,
|
||
|
|
303,
|
||
|
|
307,
|
||
|
|
308,
|
||
|
|
404,
|
||
|
|
405,
|
||
|
|
410,
|
||
|
|
414,
|
||
|
|
501,
|
||
|
|
]);
|
||
|
|
|
||
|
|
const errorStatusCodes = new Set([
|
||
|
|
500,
|
||
|
|
502,
|
||
|
|
503,
|
||
|
|
504,
|
||
|
|
]);
|
||
|
|
|
||
|
|
const hopByHopHeaders = {
|
||
|
|
date: true, // included, because we add Age update Date
|
||
|
|
connection: true,
|
||
|
|
'keep-alive': true,
|
||
|
|
'proxy-authenticate': true,
|
||
|
|
'proxy-authorization': true,
|
||
|
|
te: true,
|
||
|
|
trailer: true,
|
||
|
|
'transfer-encoding': true,
|
||
|
|
upgrade: true,
|
||
|
|
};
|
||
|
|
|
||
|
|
const excludedFromRevalidationUpdate = {
|
||
|
|
// Since the old body is reused, it doesn't make sense to change properties of the body
|
||
|
|
'content-length': true,
|
||
|
|
'content-encoding': true,
|
||
|
|
'transfer-encoding': true,
|
||
|
|
'content-range': true,
|
||
|
|
};
|
||
|
|
|
||
|
|
function toNumberOrZero(s) {
|
||
|
|
const n = parseInt(s, 10);
|
||
|
|
return isFinite(n) ? n : 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
// RFC 5861
|
||
|
|
function isErrorResponse(response) {
|
||
|
|
// consider undefined response as faulty
|
||
|
|
if(!response) {
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
return errorStatusCodes.has(response.status);
|
||
|
|
}
|
||
|
|
|
||
|
|
function parseCacheControl(header) {
|
||
|
|
const cc = {};
|
||
|
|
if (!header) return cc;
|
||
|
|
|
||
|
|
// TODO: When there is more than one value present for a given directive (e.g., two Expires header fields, multiple Cache-Control: max-age directives),
|
||
|
|
// the directive's value is considered invalid. Caches are encouraged to consider responses that have invalid freshness information to be stale
|
||
|
|
const parts = header.trim().split(/\s*,\s*/); // TODO: lame parsing
|
||
|
|
for (const part of parts) {
|
||
|
|
const [k, v] = part.split(/\s*=\s*/, 2);
|
||
|
|
cc[k] = v === undefined ? true : v.replace(/^"|"$/g, ''); // TODO: lame unquoting
|
||
|
|
}
|
||
|
|
|
||
|
|
return cc;
|
||
|
|
}
|
||
|
|
|
||
|
|
function formatCacheControl(cc) {
|
||
|
|
let parts = [];
|
||
|
|
for (const k in cc) {
|
||
|
|
const v = cc[k];
|
||
|
|
parts.push(v === true ? k : k + '=' + v);
|
||
|
|
}
|
||
|
|
if (!parts.length) {
|
||
|
|
return undefined;
|
||
|
|
}
|
||
|
|
return parts.join(', ');
|
||
|
|
}
|
||
|
|
|
||
|
|
module.exports = class CachePolicy {
|
||
|
|
constructor(
|
||
|
|
req,
|
||
|
|
res,
|
||
|
|
{
|
||
|
|
shared,
|
||
|
|
cacheHeuristic,
|
||
|
|
immutableMinTimeToLive,
|
||
|
|
ignoreCargoCult,
|
||
|
|
_fromObject,
|
||
|
|
} = {}
|
||
|
|
) {
|
||
|
|
if (_fromObject) {
|
||
|
|
this._fromObject(_fromObject);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (!res || !res.headers) {
|
||
|
|
throw Error('Response headers missing');
|
||
|
|
}
|
||
|
|
this._assertRequestHasHeaders(req);
|
||
|
|
|
||
|
|
this._responseTime = this.now();
|
||
|
|
this._isShared = shared !== false;
|
||
|
|
this._cacheHeuristic =
|
||
|
|
undefined !== cacheHeuristic ? cacheHeuristic : 0.1; // 10% matches IE
|
||
|
|
this._immutableMinTtl =
|
||
|
|
undefined !== immutableMinTimeToLive
|
||
|
|
? immutableMinTimeToLive
|
||
|
|
: 24 * 3600 * 1000;
|
||
|
|
|
||
|
|
this._status = 'status' in res ? res.status : 200;
|
||
|
|
this._resHeaders = res.headers;
|
||
|
|
this._rescc = parseCacheControl(res.headers['cache-control']);
|
||
|
|
this._method = 'method' in req ? req.method : 'GET';
|
||
|
|
this._url = req.url;
|
||
|
|
this._host = req.headers.host;
|
||
|
|
this._noAuthorization = !req.headers.authorization;
|
||
|
|
this._reqHeaders = res.headers.vary ? req.headers : null; // Don't keep all request headers if they won't be used
|
||
|
|
this._reqcc = parseCacheControl(req.headers['cache-control']);
|
||
|
|
|
||
|
|
// Assume that if someone uses legacy, non-standard uncecessary options they don't understand caching,
|
||
|
|
// so there's no point stricly adhering to the blindly copy&pasted directives.
|
||
|
|
if (
|
||
|
|
ignoreCargoCult &&
|
||
|
|
'pre-check' in this._rescc &&
|
||
|
|
'post-check' in this._rescc
|
||
|
|
) {
|
||
|
|
delete this._rescc['pre-check'];
|
||
|
|
delete this._rescc['post-check'];
|
||
|
|
delete this._rescc['no-cache'];
|
||
|
|
delete this._rescc['no-store'];
|
||
|
|
delete this._rescc['must-revalidate'];
|
||
|
|
this._resHeaders = Object.assign({}, this._resHeaders, {
|
||
|
|
'cache-control': formatCacheControl(this._rescc),
|
||
|
|
});
|
||
|
|
delete this._resHeaders.expires;
|
||
|
|
delete this._resHeaders.pragma;
|
||
|
|
}
|
||
|
|
|
||
|
|
// When the Cache-Control header field is not present in a request, caches MUST consider the no-cache request pragma-directive
|
||
|
|
// as having the same effect as if "Cache-Control: no-cache" were present (see Section 5.2.1).
|
||
|
|
if (
|
||
|
|
res.headers['cache-control'] == null &&
|
||
|
|
/no-cache/.test(res.headers.pragma)
|
||
|
|
) {
|
||
|
|
this._rescc['no-cache'] = true;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
now() {
|
||
|
|
return Date.now();
|
||
|
|
}
|
||
|
|
|
||
|
|
storable() {
|
||
|
|
// The "no-store" request directive indicates that a cache MUST NOT store any part of either this request or any response to it.
|
||
|
|
return !!(
|
||
|
|
!this._reqcc['no-store'] &&
|
||
|
|
// A cache MUST NOT store a response to any request, unless:
|
||
|
|
// The request method is understood by the cache and defined as being cacheable, and
|
||
|
|
('GET' === this._method ||
|
||
|
|
'HEAD' === this._method ||
|
||
|
|
('POST' === this._method && this._hasExplicitExpiration())) &&
|
||
|
|
// the response status code is understood by the cache, and
|
||
|
|
understoodStatuses.has(this._status) &&
|
||
|
|
// the "no-store" cache directive does not appear in request or response header fields, and
|
||
|
|
!this._rescc['no-store'] &&
|
||
|
|
// the "private" response directive does not appear in the response, if the cache is shared, and
|
||
|
|
(!this._isShared || !this._rescc.private) &&
|
||
|
|
// the Authorization header field does not appear in the request, if the cache is shared,
|
||
|
|
(!this._isShared ||
|
||
|
|
this._noAuthorization ||
|
||
|
|
this._allowsStoringAuthenticated()) &&
|
||
|
|
// the response either:
|
||
|
|
// contains an Expires header field, or
|
||
|
|
(this._resHeaders.expires ||
|
||
|
|
// contains a max-age response directive, or
|
||
|
|
// contains a s-maxage response directive and the cache is shared, or
|
||
|
|
// contains a public response directive.
|
||
|
|
this._rescc['max-age'] ||
|
||
|
|
(this._isShared && this._rescc['s-maxage']) ||
|
||
|
|
this._rescc.public ||
|
||
|
|
// has a status code that is defined as cacheable by default
|
||
|
|
statusCodeCacheableByDefault.has(this._status))
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
_hasExplicitExpiration() {
|
||
|
|
// 4.2.1 Calculating Freshness Lifetime
|
||
|
|
return (
|
||
|
|
(this._isShared && this._rescc['s-maxage']) ||
|
||
|
|
this._rescc['max-age'] ||
|
||
|
|
this._resHeaders.expires
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
_assertRequestHasHeaders(req) {
|
||
|
|
if (!req || !req.headers) {
|
||
|
|
throw Error('Request headers missing');
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
satisfiesWithoutRevalidation(req) {
|
||
|
|
this._assertRequestHasHeaders(req);
|
||
|
|
|
||
|
|
// When presented with a request, a cache MUST NOT reuse a stored response, unless:
|
||
|
|
// the presented request does not contain the no-cache pragma (Section 5.4), nor the no-cache cache directive,
|
||
|
|
// unless the stored response is successfully validated (Section 4.3), and
|
||
|
|
const requestCC = parseCacheControl(req.headers['cache-control']);
|
||
|
|
if (requestCC['no-cache'] || /no-cache/.test(req.headers.pragma)) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (requestCC['max-age'] && this.age() > requestCC['max-age']) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (
|
||
|
|
requestCC['min-fresh'] &&
|
||
|
|
this.timeToLive() < 1000 * requestCC['min-fresh']
|
||
|
|
) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
|
||
|
|
// the stored response is either:
|
||
|
|
// fresh, or allowed to be served stale
|
||
|
|
if (this.stale()) {
|
||
|
|
const allowsStale =
|
||
|
|
requestCC['max-stale'] &&
|
||
|
|
!this._rescc['must-revalidate'] &&
|
||
|
|
(true === requestCC['max-stale'] ||
|
||
|
|
requestCC['max-stale'] > this.age() - this.maxAge());
|
||
|
|
if (!allowsStale) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
return this._requestMatches(req, false);
|
||
|
|
}
|
||
|
|
|
||
|
|
_requestMatches(req, allowHeadMethod) {
|
||
|
|
// The presented effective request URI and that of the stored response match, and
|
||
|
|
return (
|
||
|
|
(!this._url || this._url === req.url) &&
|
||
|
|
this._host === req.headers.host &&
|
||
|
|
// the request method associated with the stored response allows it to be used for the presented request, and
|
||
|
|
(!req.method ||
|
||
|
|
this._method === req.method ||
|
||
|
|
(allowHeadMethod && 'HEAD' === req.method)) &&
|
||
|
|
// selecting header fields nominated by the stored response (if any) match those presented, and
|
||
|
|
this._varyMatches(req)
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
_allowsStoringAuthenticated() {
|
||
|
|
// following Cache-Control response directives (Section 5.2.2) have such an effect: must-revalidate, public, and s-maxage.
|
||
|
|
return (
|
||
|
|
this._rescc['must-revalidate'] ||
|
||
|
|
this._rescc.public ||
|
||
|
|
this._rescc['s-maxage']
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
_varyMatches(req) {
|
||
|
|
if (!this._resHeaders.vary) {
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
|
||
|
|
// A Vary header field-value of "*" always fails to match
|
||
|
|
if (this._resHeaders.vary === '*') {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
|
||
|
|
const fields = this._resHeaders.vary
|
||
|
|
.trim()
|
||
|
|
.toLowerCase()
|
||
|
|
.split(/\s*,\s*/);
|
||
|
|
for (const name of fields) {
|
||
|
|
if (req.headers[name] !== this._reqHeaders[name]) return false;
|
||
|
|
}
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
|
||
|
|
_copyWithoutHopByHopHeaders(inHeaders) {
|
||
|
|
const headers = {};
|
||
|
|
for (const name in inHeaders) {
|
||
|
|
if (hopByHopHeaders[name]) continue;
|
||
|
|
headers[name] = inHeaders[name];
|
||
|
|
}
|
||
|
|
// 9.1. Connection
|
||
|
|
if (inHeaders.connection) {
|
||
|
|
const tokens = inHeaders.connection.trim().split(/\s*,\s*/);
|
||
|
|
for (const name of tokens) {
|
||
|
|
delete headers[name];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
if (headers.warning) {
|
||
|
|
const warnings = headers.warning.split(/,/).filter(warning => {
|
||
|
|
return !/^\s*1[0-9][0-9]/.test(warning);
|
||
|
|
});
|
||
|
|
if (!warnings.length) {
|
||
|
|
delete headers.warning;
|
||
|
|
} else {
|
||
|
|
headers.warning = warnings.join(',').trim();
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return headers;
|
||
|
|
}
|
||
|
|
|
||
|
|
responseHeaders() {
|
||
|
|
const headers = this._copyWithoutHopByHopHeaders(this._resHeaders);
|
||
|
|
const age = this.age();
|
||
|
|
|
||
|
|
// A cache SHOULD generate 113 warning if it heuristically chose a freshness
|
||
|
|
// lifetime greater than 24 hours and the response's age is greater than 24 hours.
|
||
|
|
if (
|
||
|
|
age > 3600 * 24 &&
|
||
|
|
!this._hasExplicitExpiration() &&
|
||
|
|
this.maxAge() > 3600 * 24
|
||
|
|
) {
|
||
|
|
headers.warning =
|
||
|
|
(headers.warning ? `${headers.warning}, ` : '') +
|
||
|
|
'113 - "rfc7234 5.5.4"';
|
||
|
|
}
|
||
|
|
headers.age = `${Math.round(age)}`;
|
||
|
|
headers.date = new Date(this.now()).toUTCString();
|
||
|
|
return headers;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Value of the Date response header or current time if Date was invalid
|
||
|
|
* @return timestamp
|
||
|
|
*/
|
||
|
|
date() {
|
||
|
|
const serverDate = Date.parse(this._resHeaders.date);
|
||
|
|
if (isFinite(serverDate)) {
|
||
|
|
return serverDate;
|
||
|
|
}
|
||
|
|
return this._responseTime;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Value of the Age header, in seconds, updated for the current time.
|
||
|
|
* May be fractional.
|
||
|
|
*
|
||
|
|
* @return Number
|
||
|
|
*/
|
||
|
|
age() {
|
||
|
|
let age = this._ageValue();
|
||
|
|
|
||
|
|
const residentTime = (this.now() - this._responseTime) / 1000;
|
||
|
|
return age + residentTime;
|
||
|
|
}
|
||
|
|
|
||
|
|
_ageValue() {
|
||
|
|
return toNumberOrZero(this._resHeaders.age);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Value of applicable max-age (or heuristic equivalent) in seconds. This counts since response's `Date`.
|
||
|
|
*
|
||
|
|
* For an up-to-date value, see `timeToLive()`.
|
||
|
|
*
|
||
|
|
* @return Number
|
||
|
|
*/
|
||
|
|
maxAge() {
|
||
|
|
if (!this.storable() || this._rescc['no-cache']) {
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Shared responses with cookies are cacheable according to the RFC, but IMHO it'd be unwise to do so by default
|
||
|
|
// so this implementation requires explicit opt-in via public header
|
||
|
|
if (
|
||
|
|
this._isShared &&
|
||
|
|
(this._resHeaders['set-cookie'] &&
|
||
|
|
!this._rescc.public &&
|
||
|
|
!this._rescc.immutable)
|
||
|
|
) {
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (this._resHeaders.vary === '*') {
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (this._isShared) {
|
||
|
|
if (this._rescc['proxy-revalidate']) {
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
// if a response includes the s-maxage directive, a shared cache recipient MUST ignore the Expires field.
|
||
|
|
if (this._rescc['s-maxage']) {
|
||
|
|
return toNumberOrZero(this._rescc['s-maxage']);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// If a response includes a Cache-Control field with the max-age directive, a recipient MUST ignore the Expires field.
|
||
|
|
if (this._rescc['max-age']) {
|
||
|
|
return toNumberOrZero(this._rescc['max-age']);
|
||
|
|
}
|
||
|
|
|
||
|
|
const defaultMinTtl = this._rescc.immutable ? this._immutableMinTtl : 0;
|
||
|
|
|
||
|
|
const serverDate = this.date();
|
||
|
|
if (this._resHeaders.expires) {
|
||
|
|
const expires = Date.parse(this._resHeaders.expires);
|
||
|
|
// A cache recipient MUST interpret invalid date formats, especially the value "0", as representing a time in the past (i.e., "already expired").
|
||
|
|
if (Number.isNaN(expires) || expires < serverDate) {
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
return Math.max(defaultMinTtl, (expires - serverDate) / 1000);
|
||
|
|
}
|
||
|
|
|
||
|
|
if (this._resHeaders['last-modified']) {
|
||
|
|
const lastModified = Date.parse(this._resHeaders['last-modified']);
|
||
|
|
if (isFinite(lastModified) && serverDate > lastModified) {
|
||
|
|
return Math.max(
|
||
|
|
defaultMinTtl,
|
||
|
|
((serverDate - lastModified) / 1000) * this._cacheHeuristic
|
||
|
|
);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
return defaultMinTtl;
|
||
|
|
}
|
||
|
|
|
||
|
|
timeToLive() {
|
||
|
|
const age = this.maxAge() - this.age();
|
||
|
|
const staleIfErrorAge = age + toNumberOrZero(this._rescc['stale-if-error']);
|
||
|
|
const staleWhileRevalidateAge = age + toNumberOrZero(this._rescc['stale-while-revalidate']);
|
||
|
|
return Math.max(0, age, staleIfErrorAge, staleWhileRevalidateAge) * 1000;
|
||
|
|
}
|
||
|
|
|
||
|
|
stale() {
|
||
|
|
return this.maxAge() <= this.age();
|
||
|
|
}
|
||
|
|
|
||
|
|
_useStaleIfError() {
|
||
|
|
return this.maxAge() + toNumberOrZero(this._rescc['stale-if-error']) > this.age();
|
||
|
|
}
|
||
|
|
|
||
|
|
useStaleWhileRevalidate() {
|
||
|
|
return this.maxAge() + toNumberOrZero(this._rescc['stale-while-revalidate']) > this.age();
|
||
|
|
}
|
||
|
|
|
||
|
|
static fromObject(obj) {
|
||
|
|
return new this(undefined, undefined, { _fromObject: obj });
|
||
|
|
}
|
||
|
|
|
||
|
|
_fromObject(obj) {
|
||
|
|
if (this._responseTime) throw Error('Reinitialized');
|
||
|
|
if (!obj || obj.v !== 1) throw Error('Invalid serialization');
|
||
|
|
|
||
|
|
this._responseTime = obj.t;
|
||
|
|
this._isShared = obj.sh;
|
||
|
|
this._cacheHeuristic = obj.ch;
|
||
|
|
this._immutableMinTtl =
|
||
|
|
obj.imm !== undefined ? obj.imm : 24 * 3600 * 1000;
|
||
|
|
this._status = obj.st;
|
||
|
|
this._resHeaders = obj.resh;
|
||
|
|
this._rescc = obj.rescc;
|
||
|
|
this._method = obj.m;
|
||
|
|
this._url = obj.u;
|
||
|
|
this._host = obj.h;
|
||
|
|
this._noAuthorization = obj.a;
|
||
|
|
this._reqHeaders = obj.reqh;
|
||
|
|
this._reqcc = obj.reqcc;
|
||
|
|
}
|
||
|
|
|
||
|
|
toObject() {
|
||
|
|
return {
|
||
|
|
v: 1,
|
||
|
|
t: this._responseTime,
|
||
|
|
sh: this._isShared,
|
||
|
|
ch: this._cacheHeuristic,
|
||
|
|
imm: this._immutableMinTtl,
|
||
|
|
st: this._status,
|
||
|
|
resh: this._resHeaders,
|
||
|
|
rescc: this._rescc,
|
||
|
|
m: this._method,
|
||
|
|
u: this._url,
|
||
|
|
h: this._host,
|
||
|
|
a: this._noAuthorization,
|
||
|
|
reqh: this._reqHeaders,
|
||
|
|
reqcc: this._reqcc,
|
||
|
|
};
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Headers for sending to the origin server to revalidate stale response.
|
||
|
|
* Allows server to return 304 to allow reuse of the previous response.
|
||
|
|
*
|
||
|
|
* Hop by hop headers are always stripped.
|
||
|
|
* Revalidation headers may be added or removed, depending on request.
|
||
|
|
*/
|
||
|
|
revalidationHeaders(incomingReq) {
|
||
|
|
this._assertRequestHasHeaders(incomingReq);
|
||
|
|
const headers = this._copyWithoutHopByHopHeaders(incomingReq.headers);
|
||
|
|
|
||
|
|
// This implementation does not understand range requests
|
||
|
|
delete headers['if-range'];
|
||
|
|
|
||
|
|
if (!this._requestMatches(incomingReq, true) || !this.storable()) {
|
||
|
|
// revalidation allowed via HEAD
|
||
|
|
// not for the same resource, or wasn't allowed to be cached anyway
|
||
|
|
delete headers['if-none-match'];
|
||
|
|
delete headers['if-modified-since'];
|
||
|
|
return headers;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* MUST send that entity-tag in any cache validation request (using If-Match or If-None-Match) if an entity-tag has been provided by the origin server. */
|
||
|
|
if (this._resHeaders.etag) {
|
||
|
|
headers['if-none-match'] = headers['if-none-match']
|
||
|
|
? `${headers['if-none-match']}, ${this._resHeaders.etag}`
|
||
|
|
: this._resHeaders.etag;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Clients MAY issue simple (non-subrange) GET requests with either weak validators or strong validators. Clients MUST NOT use weak validators in other forms of request.
|
||
|
|
const forbidsWeakValidators =
|
||
|
|
headers['accept-ranges'] ||
|
||
|
|
headers['if-match'] ||
|
||
|
|
headers['if-unmodified-since'] ||
|
||
|
|
(this._method && this._method != 'GET');
|
||
|
|
|
||
|
|
/* SHOULD send the Last-Modified value in non-subrange cache validation requests (using If-Modified-Since) if only a Last-Modified value has been provided by the origin server.
|
||
|
|
Note: This implementation does not understand partial responses (206) */
|
||
|
|
if (forbidsWeakValidators) {
|
||
|
|
delete headers['if-modified-since'];
|
||
|
|
|
||
|
|
if (headers['if-none-match']) {
|
||
|
|
const etags = headers['if-none-match']
|
||
|
|
.split(/,/)
|
||
|
|
.filter(etag => {
|
||
|
|
return !/^\s*W\//.test(etag);
|
||
|
|
});
|
||
|
|
if (!etags.length) {
|
||
|
|
delete headers['if-none-match'];
|
||
|
|
} else {
|
||
|
|
headers['if-none-match'] = etags.join(',').trim();
|
||
|
|
}
|
||
|
|
}
|
||
|
|
} else if (
|
||
|
|
this._resHeaders['last-modified'] &&
|
||
|
|
!headers['if-modified-since']
|
||
|
|
) {
|
||
|
|
headers['if-modified-since'] = this._resHeaders['last-modified'];
|
||
|
|
}
|
||
|
|
|
||
|
|
return headers;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Creates new CachePolicy with information combined from the previews response,
|
||
|
|
* and the new revalidation response.
|
||
|
|
*
|
||
|
|
* Returns {policy, modified} where modified is a boolean indicating
|
||
|
|
* whether the response body has been modified, and old cached body can't be used.
|
||
|
|
*
|
||
|
|
* @return {Object} {policy: CachePolicy, modified: Boolean}
|
||
|
|
*/
|
||
|
|
revalidatedPolicy(request, response) {
|
||
|
|
this._assertRequestHasHeaders(request);
|
||
|
|
if(this._useStaleIfError() && isErrorResponse(response)) { // I consider the revalidation request unsuccessful
|
||
|
|
return {
|
||
|
|
modified: false,
|
||
|
|
matches: false,
|
||
|
|
policy: this,
|
||
|
|
};
|
||
|
|
}
|
||
|
|
if (!response || !response.headers) {
|
||
|
|
throw Error('Response headers missing');
|
||
|
|
}
|
||
|
|
|
||
|
|
// These aren't going to be supported exactly, since one CachePolicy object
|
||
|
|
// doesn't know about all the other cached objects.
|
||
|
|
let matches = false;
|
||
|
|
if (response.status !== undefined && response.status != 304) {
|
||
|
|
matches = false;
|
||
|
|
} else if (
|
||
|
|
response.headers.etag &&
|
||
|
|
!/^\s*W\//.test(response.headers.etag)
|
||
|
|
) {
|
||
|
|
// "All of the stored responses with the same strong validator are selected.
|
||
|
|
// If none of the stored responses contain the same strong validator,
|
||
|
|
// then the cache MUST NOT use the new response to update any stored responses."
|
||
|
|
matches =
|
||
|
|
this._resHeaders.etag &&
|
||
|
|
this._resHeaders.etag.replace(/^\s*W\//, '') ===
|
||
|
|
response.headers.etag;
|
||
|
|
} else if (this._resHeaders.etag && response.headers.etag) {
|
||
|
|
// "If the new response contains a weak validator and that validator corresponds
|
||
|
|
// to one of the cache's stored responses,
|
||
|
|
// then the most recent of those matching stored responses is selected for update."
|
||
|
|
matches =
|
||
|
|
this._resHeaders.etag.replace(/^\s*W\//, '') ===
|
||
|
|
response.headers.etag.replace(/^\s*W\//, '');
|
||
|
|
} else if (this._resHeaders['last-modified']) {
|
||
|
|
matches =
|
||
|
|
this._resHeaders['last-modified'] ===
|
||
|
|
response.headers['last-modified'];
|
||
|
|
} else {
|
||
|
|
// If the new response does not include any form of validator (such as in the case where
|
||
|
|
// a client generates an If-Modified-Since request from a source other than the Last-Modified
|
||
|
|
// response header field), and there is only one stored response, and that stored response also
|
||
|
|
// lacks a validator, then that stored response is selected for update.
|
||
|
|
if (
|
||
|
|
!this._resHeaders.etag &&
|
||
|
|
!this._resHeaders['last-modified'] &&
|
||
|
|
!response.headers.etag &&
|
||
|
|
!response.headers['last-modified']
|
||
|
|
) {
|
||
|
|
matches = true;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
if (!matches) {
|
||
|
|
return {
|
||
|
|
policy: new this.constructor(request, response),
|
||
|
|
// Client receiving 304 without body, even if it's invalid/mismatched has no option
|
||
|
|
// but to reuse a cached body. We don't have a good way to tell clients to do
|
||
|
|
// error recovery in such case.
|
||
|
|
modified: response.status != 304,
|
||
|
|
matches: false,
|
||
|
|
};
|
||
|
|
}
|
||
|
|
|
||
|
|
// use other header fields provided in the 304 (Not Modified) response to replace all instances
|
||
|
|
// of the corresponding header fields in the stored response.
|
||
|
|
const headers = {};
|
||
|
|
for (const k in this._resHeaders) {
|
||
|
|
headers[k] =
|
||
|
|
k in response.headers && !excludedFromRevalidationUpdate[k]
|
||
|
|
? response.headers[k]
|
||
|
|
: this._resHeaders[k];
|
||
|
|
}
|
||
|
|
|
||
|
|
const newResponse = Object.assign({}, response, {
|
||
|
|
status: this._status,
|
||
|
|
method: this._method,
|
||
|
|
headers,
|
||
|
|
});
|
||
|
|
return {
|
||
|
|
policy: new this.constructor(request, newResponse, {
|
||
|
|
shared: this._isShared,
|
||
|
|
cacheHeuristic: this._cacheHeuristic,
|
||
|
|
immutableMinTimeToLive: this._immutableMinTtl,
|
||
|
|
}),
|
||
|
|
modified: false,
|
||
|
|
matches: true,
|
||
|
|
};
|
||
|
|
}
|
||
|
|
};
|