| 1 | "use strict"
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| 2 |
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| 3 | const GET = "GET"
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| 4 | const healthzUrl = "/healthz"
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| 5 |
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| 6 | class Healthz {
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| 7 | constructor(logger, app, options={}) {
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| 8 | let checkInterval = 10000
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| 9 | if (arguments.length === 2) {
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| 10 | options = app
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| 11 | app = null
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| 12 | }
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| 13 |
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| 14 | checkInterval = options.checkInterval
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| 15 |
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| 16 | this.logger = logger
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| 17 | this.watchers = []
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| 18 | this.checkInterval = checkInterval
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| 19 | this.state = {}
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| 20 | this.app = app
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| 21 | this.timer = null
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| 22 | this.onStop = null
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| 23 | }
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| 24 |
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| 25 | registerWatcher(name, watcherFn, {required, defaultIsOk}) {
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| 26 | this.watchers.push({
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| 27 | state: {},
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| 28 | name, watcherFn,
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| 29 | isOk: !!defaultIsOk,
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| 30 | required: !!required
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| 31 | })
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| 32 | }
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| 33 |
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| 34 | async start(app=null) {
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| 35 | if (app) {
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| 36 | this.app = app
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| 37 | }
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| 38 |
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| 39 | this._loop()
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| 40 | }
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| 41 |
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| 42 | async stop() {
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| 43 | return new Promise((resolve) => {
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| 44 | this.onStop = () => {
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| 45 | this.watchers.map((watcher) => watcher.isOk = false)
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| 46 | resolve()
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| 47 | }
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| 48 |
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| 49 | if (this.timer || this.timer === null) {
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| 50 | clearTimeout(this.timer)
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| 51 | this.onStop()
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| 52 | }
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| 53 | })
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| 54 | }
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| 55 |
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| 56 | async whenOk() {
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| 57 | if (this.status.isOk) return
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| 58 | await this._waitForOk()
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| 59 | }
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| 60 |
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| 61 | get handler() {
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| 62 | return this._handler.bind(this)
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| 63 | }
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| 64 |
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| 65 | get middleware() {
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| 66 | return this._middleware.bind(this)
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| 67 | }
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| 68 |
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| 69 | get status() {
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| 70 | let sumIsOk = true
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| 71 | let detailed = {}
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| 72 |
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| 73 | this.watchers.forEach(({name, isOk, required}) => {
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| 74 | detailed[name] = isOk
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| 75 | if (required && !isOk) {
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| 76 | sumIsOk = false
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| 77 | this.logger.error(`${name} not OK`)
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| 78 | }
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| 79 | })
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| 80 |
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| 81 | return {isOk: sumIsOk, detailed}
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| 82 | }
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| 83 |
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| 84 | async _middleware(ctx, next) {
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| 85 | let {method, url} = ctx.request
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| 86 |
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| 87 | if (method === GET && url === healthzUrl) {
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| 88 | await this._handler(ctx)
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| 89 | } else {
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| 90 | await next()
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| 91 | }
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| 92 | }
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| 93 |
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| 94 | async _handler(ctx) {
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| 95 | let {isOk, detailed} = this.status
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| 96 |
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| 97 | ctx.body = detailed
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| 98 | ctx.status = isOk ? 200 : 500
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| 99 | }
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| 100 |
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| 101 | async _waitForOk() {
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| 102 | return this._promiseWaitForOk = this._promiseWaitForOk || new Promise(resolve => this._resolveOk = resolve).finally(() => {
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| 103 | this._promiseWaitForOk = null
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| 104 | this._resolveOk = () => {}
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| 105 | })
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| 106 | }
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| 107 |
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| 108 | async _loop() {
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| 109 | this.logger.trace("Loop...")
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| 110 | this.timer = null
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| 111 | await this._executeWatchers()
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| 112 |
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| 113 | if (this._promiseWaitForOk && this.status.isOk) {
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| 114 | this._resolveOk()
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| 115 | }
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| 116 |
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| 117 | if (this.onStop) {
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| 118 | this.logger.debug("Stopping...")
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| 119 | this.onStop()
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| 120 | } else {
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| 121 | let interval = Math.round(this.checkInterval + Math.random() * this.checkInterval / 2)
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| 122 | this.logger.trace(`Scheduling in ${interval}ms...`)
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| 123 | this.timer = setTimeout(this._loop.bind(this), interval)
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| 124 | }
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| 125 | }
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| 126 |
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| 127 | async _executeWatchers() {
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| 128 | return Promise.all(this.watchers.map((watcher) => {
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| 129 | return new Promise(resolve => {
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| 130 | if (watcher.running) {
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| 131 | resolve(watcher.isOk = false)
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| 132 | }
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| 133 | const timeout = setTimeout(() => resolve(watcher.isOk = false), 1000)
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| 134 | watcher.running = true
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| 135 | watcher.watcherFn
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| 136 | .call(watcher.state, this.logger, this.app)
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| 137 | .then(isOk => {
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| 138 | clearTimeout(timeout)
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| 139 | resolve(watcher.isOk = isOk)
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| 140 | })
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| 141 | .catch(() => resolve(watcher.isOk = false))
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| 142 | .finally(() => watcher.running = false)
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| 143 | })
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| 144 | }))
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| 145 | }
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| 146 | }
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| 147 |
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| 148 | module.exports = Healthz
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