feat: add custom ttl and revalidate

README.md

@@ -118,14 +118,38 @@ curl https://myserver.dev/user?force=true # MISS (forcing invalidation)
 ##### cache
 
 Type: `boolean`<br>
-Default: `[keyv](https://github.com/lukechilds/keyv)`
+Default: [`keyv`](https://github.com/lukechilds/keyv)
 
 The cache instance used for backed your pre-calculated server side response copies.
 
 The library delegates in [keyv](https://github.com/lukechilds/keyv), a tiny key value store with [multi adapter support](https://github.com/lukechilds/keyv#official-storage-adapters).
 
 If you don't specify it, a memory cache will be used.
 
+##### ttl
+
+Type: `number`<br>
+Default: `7200000`
+
+Number of milliseconds a cache response is considered fresh.
+
+After this period of time, the cache response should be refreshed.
+
+This value can be specified as well providing it as part of [`.get`](#get) output.
+
+If you don't provide one, this be used as fallback for avoid keep things into cache forever.
+
+##### revalidate
+
+Type: `function`|`number`<br>
+Default: `ttl => ttl / 24`
+
+Number of milliseconds that indicates grace period after response cache expiration for refreshing it in the background. the latency of the refresh is hidden from the user.
+
+You can provide a function, it will receive [`ttl`](#ttl) as first parameter or a fixed value.
+
+The value will be associated with [`stale-while-revalidate`](https://www.mnot.net/blog/2014/06/01/chrome_and_stale-while-revalidate) directive.
+
 ##### get
 
 _Required_<br>
@@ -144,7 +168,7 @@ function get ({ req, res }) {
 The method will received `({ req, res })` and it should be returns:
 
 - **data** `string`: The content to be saved on the cache.
-- **ttl** `number`: The quantity of time in milliseconds the content is considered valid on the cache. Don't specify it means store it forever.
+- **ttl** `number`: The quantity of time in milliseconds the content is considered valid on the cache. Don't specify it means use default [`ttl`](#ttl).
 - **createdAt** `date`: The timestamp associated with the content (`Date.now()` by default).
 
 Any other property can be specified and will passed to `.send`.

index.js

@@ -15,31 +15,47 @@ const getKey = url => {
   return baseKey.replace(origin, '').replace('/?', '')
 }
 
-const setCacheControl = ({ res, createdAt, isHit, ttl, force }) => {
-  // Specifies the maximum amount of time a resource
-  // will be considered fresh in seconds
-  const diff = force ? 0 : createdAt + ttl - Date.now()
-  const maxAge = Math.floor(diff / 1000)
-  res.setHeader(
-    'Cache-Control',
-    `public, max-age=${maxAge}, s-maxage=${maxAge}, stale-while-revalidate=30`
-  )
-  res.setHeader('X-Cache-Status', isHit ? 'HIT' : 'MISS')
-  res.setHeader('X-Cache-Expired-At', prettyMs(diff))
+const toSeconds = ms => Math.floor(ms / 1000)
+
+const createSetCacheControl = ({ revalidate }) => {
+  return ({ res, createdAt, isHit, ttl, force }) => {
+    // Specifies the maximum amount of time a resource
+    // will be considered fresh in seconds
+    const diff = force ? 0 : createdAt + ttl - Date.now()
+    const maxAge = toSeconds(diff)
+    res.setHeader(
+      'Cache-Control',
+      `public, max-age=${maxAge}, s-maxage=${maxAge}, stale-while-revalidate=${toSeconds(
+        revalidate(ttl)
+      )}`
+    )
+    res.setHeader('X-Cache-Status', isHit ? 'HIT' : 'MISS')
+    res.setHeader('X-Cache-Expired-At', prettyMs(diff))
+  }
 }
 
-module.exports = ({ cache = new Keyv(), get, send } = {}) => {
+module.exports = ({
+  cache = new Keyv(),
+  get,
+  send,
+  revalidate = ttl => ttl / 24,
+  ttl: defaultTtl = 7200000
+} = {}) => {
   assert(get, 'get required')
   assert(send, 'send required')
 
+  const setCacheControl = createSetCacheControl({
+    revalidate: typeof revalidate === 'function' ? revalidate : () => revalidate
+  })
+
   return async ({ req, res, ...opts }) => {
     const hasForce = Boolean(req.query ? req.query.force : parse(req.url).force)
     const url = urlResolve('http://localhost', req.url)
     const key = getKey(url)
     const cachedResult = await cache.get(key)
     const isHit = cachedResult && !hasForce
 
-    const { ttl, createdAt = Date.now(), data, ...props } = isHit
+    const { ttl = defaultTtl, createdAt = Date.now(), data, ...props } = isHit
       ? cachedResult
       : await get({ req, res, ...opts })
 

test/index.js

@@ -19,6 +19,53 @@ test('required props', t => {
   t.throws(() => cacheableResponse({ get: true }), AssertionError, 'send is required')
 })
 
+test('default ttl and revalidate', async t => {
+  const url = await createServer({
+    get: ({ req, res }) => ({ data: { foo: 'bar' } }),
+    send: ({ data, headers, res, req, ...props }) => res.end('Welcome to Micro')
+  })
+  const { headers } = await got(`${url}/kikobeats`)
+  t.is(headers['cache-control'], 'public, max-age=7200, s-maxage=7200, stale-while-revalidate=300')
+})
+
+test('custom ttl', async t => {
+  const url = await createServer({
+    get: ({ req, res }) => ({ data: { foo: 'bar' }, ttl: 86400000 }),
+    send: ({ data, headers, res, req, ...props }) => res.end('Welcome to Micro')
+  })
+  const { headers } = await got(`${url}/kikobeats`)
+  t.is(
+    headers['cache-control'],
+    'public, max-age=86400, s-maxage=86400, stale-while-revalidate=3600'
+  )
+})
+
+test('custom revalidate', async t => {
+  const url = await createServer({
+    revalidate: ttl => ttl * 0.8,
+    get: ({ req, res }) => ({ data: { foo: 'bar' }, ttl: 86400000 }),
+    send: ({ data, headers, res, req, ...props }) => res.end('Welcome to Micro')
+  })
+  const { headers } = await got(`${url}/kikobeats`)
+  t.is(
+    headers['cache-control'],
+    'public, max-age=86400, s-maxage=86400, stale-while-revalidate=69120'
+  )
+})
+
+test('custom fixed revalidate', async t => {
+  const url = await createServer({
+    revalidate: 300000,
+    get: ({ req, res }) => ({ data: { foo: 'bar' }, ttl: 86400000 }),
+    send: ({ data, headers, res, req, ...props }) => res.end('Welcome to Micro')
+  })
+  const { headers } = await got(`${url}/kikobeats`)
+  t.is(
+    headers['cache-control'],
+    'public, max-age=86400, s-maxage=86400, stale-while-revalidate=300'
+  )
+})
+
 test('MISS for first access', async t => {
   const url = await createServer({
     get: ({ req, res }) => {