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apicache.js
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apicache.js
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var url = require('url')
var MemoryCache = require('./memory-cache')
var pkg = require('../package.json')
var t = {
ms: 1,
second: 1000,
minute: 60000,
hour: 3600000,
day: 3600000 * 24,
week: 3600000 * 24 * 7,
month: 3600000 * 24 * 30,
}
var instances = []
var matches = function(a) {
return function(b) {
return a === b
}
}
var doesntMatch = function(a) {
return function(b) {
return !matches(a)(b)
}
}
var logDuration = function(d, prefix) {
var str = d > 1000 ? (d / 1000).toFixed(2) + 'sec' : d + 'ms'
return '\x1b[33m- ' + (prefix ? prefix + ' ' : '') + str + '\x1b[0m'
}
function getSafeHeaders(res) {
return res.getHeaders ? res.getHeaders() : res._headers
}
function ApiCache() {
var memCache = new MemoryCache()
var globalOptions = {
debug: false,
defaultDuration: 3600000,
enabled: true,
appendKey: [],
jsonp: false,
redisClient: false,
headerBlacklist: [],
statusCodes: {
include: [],
exclude: [],
},
events: {
expire: undefined,
},
headers: {
// 'cache-control': 'no-cache' // example of header overwrite
},
trackPerformance: false,
respectCacheControl: false,
}
var middlewareOptions = []
var instance = this
var index = null
var timers = {}
var performanceArray = [] // for tracking cache hit rate
instances.push(this)
this.id = instances.length
function debug(a, b, c, d) {
var arr = ['\x1b[36m[apicache]\x1b[0m', a, b, c, d].filter(function(arg) {
return arg !== undefined
})
var debugEnv = process.env.DEBUG && process.env.DEBUG.split(',').indexOf('apicache') !== -1
return (globalOptions.debug || debugEnv) && console.log.apply(null, arr)
}
function shouldCacheResponse(request, response, toggle) {
var opt = globalOptions
var codes = opt.statusCodes
if (!response) return false
if (toggle && !toggle(request, response)) {
return false
}
if (codes.exclude && codes.exclude.length && codes.exclude.indexOf(response.statusCode) !== -1)
return false
if (codes.include && codes.include.length && codes.include.indexOf(response.statusCode) === -1)
return false
return true
}
function addIndexEntries(key, req) {
var groupName = req.apicacheGroup
if (groupName) {
debug('group detected "' + groupName + '"')
var group = (index.groups[groupName] = index.groups[groupName] || [])
group.unshift(key)
}
index.all.unshift(key)
}
function filterBlacklistedHeaders(headers) {
return Object.keys(headers)
.filter(function(key) {
return globalOptions.headerBlacklist.indexOf(key) === -1
})
.reduce(function(acc, header) {
acc[header] = headers[header]
return acc
}, {})
}
function createCacheObject(status, headers, data, encoding) {
return {
status: status,
headers: filterBlacklistedHeaders(headers),
data: data,
encoding: encoding,
timestamp: new Date().getTime() / 1000, // seconds since epoch. This is used to properly decrement max-age headers in cached responses.
}
}
function cacheResponse(key, value, duration) {
var redis = globalOptions.redisClient
var expireCallback = globalOptions.events.expire
if (redis && redis.connected) {
try {
redis.hset(key, 'response', JSON.stringify(value))
redis.hset(key, 'duration', duration)
redis.expire(key, duration / 1000, expireCallback || function() {})
} catch (err) {
debug('[apicache] error in redis.hset()')
}
} else {
memCache.add(key, value, duration, expireCallback)
}
// add automatic cache clearing from duration, includes max limit on setTimeout
timers[key] = setTimeout(function() {
instance.clear(key, true)
}, Math.min(duration, 2147483647))
}
function accumulateContent(res, content) {
if (content) {
if (typeof content == 'string') {
res._apicache.content = (res._apicache.content || '') + content
} else if (Buffer.isBuffer(content)) {
var oldContent = res._apicache.content
if (typeof oldContent === 'string') {
oldContent = !Buffer.from ? new Buffer(oldContent) : Buffer.from(oldContent)
}
if (!oldContent) {
oldContent = !Buffer.alloc ? new Buffer(0) : Buffer.alloc(0)
}
res._apicache.content = Buffer.concat(
[oldContent, content],
oldContent.length + content.length
)
} else {
res._apicache.content = content
}
}
}
function makeResponseCacheable(req, res, next, key, duration, strDuration, toggle) {
// monkeypatch res.end to create cache object
res._apicache = {
write: res.write,
writeHead: res.writeHead,
end: res.end,
cacheable: true,
content: undefined,
}
// append header overwrites if applicable
Object.keys(globalOptions.headers).forEach(function(name) {
res.setHeader(name, globalOptions.headers[name])
})
res.writeHead = function() {
// add cache control headers
if (!globalOptions.headers['cache-control']) {
if (shouldCacheResponse(req, res, toggle)) {
res.setHeader('cache-control', 'max-age=' + (duration / 1000).toFixed(0))
} else {
res.setHeader('cache-control', 'no-cache, no-store, must-revalidate')
}
}
res._apicache.headers = Object.assign({}, getSafeHeaders(res))
return res._apicache.writeHead.apply(this, arguments)
}
// patch res.write
res.write = function(content) {
accumulateContent(res, content)
return res._apicache.write.apply(this, arguments)
}
// patch res.end
res.end = function(content, encoding) {
if (shouldCacheResponse(req, res, toggle)) {
accumulateContent(res, content)
if (res._apicache.cacheable && res._apicache.content) {
addIndexEntries(key, req)
var headers = res._apicache.headers || getSafeHeaders(res)
var cacheObject = createCacheObject(
res.statusCode,
headers,
res._apicache.content,
encoding
)
cacheResponse(key, cacheObject, duration)
// display log entry
var elapsed = new Date() - req.apicacheTimer
debug('adding cache entry for "' + key + '" @ ' + strDuration, logDuration(elapsed))
debug('_apicache.headers: ', res._apicache.headers)
debug('res.getHeaders(): ', getSafeHeaders(res))
debug('cacheObject: ', cacheObject)
}
}
return res._apicache.end.apply(this, arguments)
}
next()
}
function sendCachedResponse(request, response, cacheObject, toggle, next, duration) {
if (toggle && !toggle(request, response)) {
return next()
}
var headers = getSafeHeaders(response)
Object.assign(headers, filterBlacklistedHeaders(cacheObject.headers || {}), {
// set properly-decremented max-age header. This ensures that max-age is in sync with the cache expiration.
'cache-control':
'max-age=' +
Math.max(
0,
(duration / 1000 - (new Date().getTime() / 1000 - cacheObject.timestamp)).toFixed(0)
),
})
// only embed apicache headers when not in production environment
if (process.env.NODE_ENV !== 'production') {
Object.assign(headers, {
'apicache-store': globalOptions.redisClient ? 'redis' : 'memory',
'apicache-version': pkg.version,
})
}
// unstringify buffers
var data = cacheObject.data
if (data && data.type === 'Buffer') {
data =
typeof data.data === 'number' ? new Buffer.alloc(data.data) : new Buffer.from(data.data)
}
// test Etag against If-None-Match for 304
var cachedEtag = cacheObject.headers.etag
var requestEtag = request.headers['if-none-match']
if (requestEtag && cachedEtag === requestEtag) {
response.writeHead(304, headers)
return response.end()
}
response.writeHead(cacheObject.status || 200, headers)
return response.end(data, cacheObject.encoding)
}
function syncOptions() {
for (var i in middlewareOptions) {
Object.assign(middlewareOptions[i].options, globalOptions, middlewareOptions[i].localOptions)
}
}
this.clear = function(target, isAutomatic) {
var group = index.groups[target]
var redis = globalOptions.redisClient
if (group) {
debug('clearing group "' + target + '"')
group.forEach(function(key) {
debug('clearing cached entry for "' + key + '"')
clearTimeout(timers[key])
delete timers[key]
if (!globalOptions.redisClient) {
memCache.delete(key)
} else {
try {
redis.del(key)
} catch (err) {
console.log('[apicache] error in redis.del("' + key + '")')
}
}
index.all = index.all.filter(doesntMatch(key))
})
delete index.groups[target]
} else if (target) {
debug('clearing ' + (isAutomatic ? 'expired' : 'cached') + ' entry for "' + target + '"')
clearTimeout(timers[target])
delete timers[target]
// clear actual cached entry
if (!redis) {
memCache.delete(target)
} else {
try {
redis.del(target)
} catch (err) {
console.log('[apicache] error in redis.del("' + target + '")')
}
}
// remove from global index
index.all = index.all.filter(doesntMatch(target))
// remove target from each group that it may exist in
Object.keys(index.groups).forEach(function(groupName) {
index.groups[groupName] = index.groups[groupName].filter(doesntMatch(target))
// delete group if now empty
if (!index.groups[groupName].length) {
delete index.groups[groupName]
}
})
} else {
debug('clearing entire index')
if (!redis) {
memCache.clear()
} else {
// clear redis keys one by one from internal index to prevent clearing non-apicache entries
index.all.forEach(function(key) {
clearTimeout(timers[key])
delete timers[key]
try {
redis.del(key)
} catch (err) {
console.log('[apicache] error in redis.del("' + key + '")')
}
})
}
this.resetIndex()
}
return this.getIndex()
}
function parseDuration(duration, defaultDuration) {
if (typeof duration === 'number') return duration
if (typeof duration === 'string') {
var split = duration.match(/^([\d\.,]+)\s?(\w+)$/)
if (split.length === 3) {
var len = parseFloat(split[1])
var unit = split[2].replace(/s$/i, '').toLowerCase()
if (unit === 'm') {
unit = 'ms'
}
return (len || 1) * (t[unit] || 0)
}
}
return defaultDuration
}
this.getDuration = function(duration) {
return parseDuration(duration, globalOptions.defaultDuration)
}
/**
* Return cache performance statistics (hit rate). Suitable for putting into a route:
* <code>
* app.get('/api/cache/performance', (req, res) => {
* res.json(apicache.getPerformance())
* })
* </code>
*/
this.getPerformance = function() {
return performanceArray.map(function(p) {
return p.report()
})
}
this.getIndex = function(group) {
if (group) {
return index.groups[group]
} else {
return index
}
}
this.middleware = function cache(strDuration, middlewareToggle, localOptions) {
var duration = instance.getDuration(strDuration)
var opt = {}
middlewareOptions.push({
options: opt,
})
var options = function(localOptions) {
if (localOptions) {
middlewareOptions.find(function(middleware) {
return middleware.options === opt
}).localOptions = localOptions
}
syncOptions()
return opt
}
options(localOptions)
/**
* A Function for non tracking performance
*/
function NOOPCachePerformance() {
this.report = this.hit = this.miss = function() {} // noop;
}
/**
* A function for tracking and reporting hit rate. These statistics are returned by the getPerformance() call above.
*/
function CachePerformance() {
/**
* Tracks the hit rate for the last 100 requests.
* If there have been fewer than 100 requests, the hit rate just considers the requests that have happened.
*/
this.hitsLast100 = new Uint8Array(100 / 4) // each hit is 2 bits
/**
* Tracks the hit rate for the last 1000 requests.
* If there have been fewer than 1000 requests, the hit rate just considers the requests that have happened.
*/
this.hitsLast1000 = new Uint8Array(1000 / 4) // each hit is 2 bits
/**
* Tracks the hit rate for the last 10000 requests.
* If there have been fewer than 10000 requests, the hit rate just considers the requests that have happened.
*/
this.hitsLast10000 = new Uint8Array(10000 / 4) // each hit is 2 bits
/**
* Tracks the hit rate for the last 100000 requests.
* If there have been fewer than 100000 requests, the hit rate just considers the requests that have happened.
*/
this.hitsLast100000 = new Uint8Array(100000 / 4) // each hit is 2 bits
/**
* The number of calls that have passed through the middleware since the server started.
*/
this.callCount = 0
/**
* The total number of hits since the server started
*/
this.hitCount = 0
/**
* The key from the last cache hit. This is useful in identifying which route these statistics apply to.
*/
this.lastCacheHit = null
/**
* The key from the last cache miss. This is useful in identifying which route these statistics apply to.
*/
this.lastCacheMiss = null
/**
* Return performance statistics
*/
this.report = function() {
return {
lastCacheHit: this.lastCacheHit,
lastCacheMiss: this.lastCacheMiss,
callCount: this.callCount,
hitCount: this.hitCount,
missCount: this.callCount - this.hitCount,
hitRate: this.callCount == 0 ? null : this.hitCount / this.callCount,
hitRateLast100: this.hitRate(this.hitsLast100),
hitRateLast1000: this.hitRate(this.hitsLast1000),
hitRateLast10000: this.hitRate(this.hitsLast10000),
hitRateLast100000: this.hitRate(this.hitsLast100000),
}
}
/**
* Computes a cache hit rate from an array of hits and misses.
* @param {Uint8Array} array An array representing hits and misses.
* @returns a number between 0 and 1, or null if the array has no hits or misses
*/
this.hitRate = function(array) {
var hits = 0
var misses = 0
for (var i = 0; i < array.length; i++) {
var n8 = array[i]
for (j = 0; j < 4; j++) {
switch (n8 & 3) {
case 1:
hits++
break
case 2:
misses++
break
}
n8 >>= 2
}
}
var total = hits + misses
if (total == 0) return null
return hits / total
}
/**
* Record a hit or miss in the given array. It will be recorded at a position determined
* by the current value of the callCount variable.
* @param {Uint8Array} array An array representing hits and misses.
* @param {boolean} hit true for a hit, false for a miss
* Each element in the array is 8 bits, and encodes 4 hit/miss records.
* Each hit or miss is encoded as to bits as follows:
* 00 means no hit or miss has been recorded in these bits
* 01 encodes a hit
* 10 encodes a miss
*/
this.recordHitInArray = function(array, hit) {
var arrayIndex = ~~(this.callCount / 4) % array.length
var bitOffset = (this.callCount % 4) * 2 // 2 bits per record, 4 records per uint8 array element
var clearMask = ~(3 << bitOffset)
var record = (hit ? 1 : 2) << bitOffset
array[arrayIndex] = (array[arrayIndex] & clearMask) | record
}
/**
* Records the hit or miss in the tracking arrays and increments the call count.
* @param {boolean} hit true records a hit, false records a miss
*/
this.recordHit = function(hit) {
this.recordHitInArray(this.hitsLast100, hit)
this.recordHitInArray(this.hitsLast1000, hit)
this.recordHitInArray(this.hitsLast10000, hit)
this.recordHitInArray(this.hitsLast100000, hit)
if (hit) this.hitCount++
this.callCount++
}
/**
* Records a hit event, setting lastCacheMiss to the given key
* @param {string} key The key that had the cache hit
*/
this.hit = function(key) {
this.recordHit(true)
this.lastCacheHit = key
}
/**
* Records a miss event, setting lastCacheMiss to the given key
* @param {string} key The key that had the cache miss
*/
this.miss = function(key) {
this.recordHit(false)
this.lastCacheMiss = key
}
}
var perf = globalOptions.trackPerformance ? new CachePerformance() : new NOOPCachePerformance()
performanceArray.push(perf)
var cache = function(req, res, next) {
function bypass() {
debug('bypass detected, skipping cache.')
return next()
}
// initial bypass chances
if (!opt.enabled) return bypass()
if (
req.headers['x-apicache-bypass'] ||
req.headers['x-apicache-force-fetch'] ||
(opt.respectCacheControl && req.headers['cache-control'] == 'no-cache')
)
return bypass()
// REMOVED IN 0.11.1 TO CORRECT MIDDLEWARE TOGGLE EXECUTE ORDER
// if (typeof middlewareToggle === 'function') {
// if (!middlewareToggle(req, res)) return bypass()
// } else if (middlewareToggle !== undefined && !middlewareToggle) {
// return bypass()
// }
// embed timer
req.apicacheTimer = new Date()
// In Express 4.x the url is ambigious based on where a router is mounted. originalUrl will give the full Url
var key = req.originalUrl || req.url
// Remove querystring from key if jsonp option is enabled
if (opt.jsonp) {
key = url.parse(key).pathname
}
// add appendKey (either custom function or response path)
if (typeof opt.appendKey === 'function') {
key += '$$appendKey=' + opt.appendKey(req, res)
} else if (opt.appendKey.length > 0) {
var appendKey = req
for (var i = 0; i < opt.appendKey.length; i++) {
appendKey = appendKey[opt.appendKey[i]]
}
key += '$$appendKey=' + appendKey
}
// attempt cache hit
var redis = opt.redisClient
var cached = !redis ? memCache.getValue(key) : null
// send if cache hit from memory-cache
if (cached) {
var elapsed = new Date() - req.apicacheTimer
debug('sending cached (memory-cache) version of', key, logDuration(elapsed))
perf.hit(key)
return sendCachedResponse(req, res, cached, middlewareToggle, next, duration)
}
// send if cache hit from redis
if (redis && redis.connected) {
try {
redis.hgetall(key, function(err, obj) {
if (!err && obj && obj.response) {
var elapsed = new Date() - req.apicacheTimer
debug('sending cached (redis) version of', key, logDuration(elapsed))
perf.hit(key)
return sendCachedResponse(
req,
res,
JSON.parse(obj.response),
middlewareToggle,
next,
duration
)
} else {
perf.miss(key)
return makeResponseCacheable(
req,
res,
next,
key,
duration,
strDuration,
middlewareToggle
)
}
})
} catch (err) {
// bypass redis on error
perf.miss(key)
return makeResponseCacheable(req, res, next, key, duration, strDuration, middlewareToggle)
}
} else {
perf.miss(key)
return makeResponseCacheable(req, res, next, key, duration, strDuration, middlewareToggle)
}
}
cache.options = options
return cache
}
this.options = function(options) {
if (options) {
Object.assign(globalOptions, options)
syncOptions()
if ('defaultDuration' in options) {
// Convert the default duration to a number in milliseconds (if needed)
globalOptions.defaultDuration = parseDuration(globalOptions.defaultDuration, 3600000)
}
if (globalOptions.trackPerformance) {
debug('WARNING: using trackPerformance flag can cause high memory usage!')
}
return this
} else {
return globalOptions
}
}
this.resetIndex = function() {
index = {
all: [],
groups: {},
}
}
this.newInstance = function(config) {
var instance = new ApiCache()
if (config) {
instance.options(config)
}
return instance
}
this.clone = function() {
return this.newInstance(this.options())
}
// initialize index
this.resetIndex()
}
module.exports = new ApiCache()