fix: close/open websocket on freeze/resume events (#1195)

* fix: close/open websocket on freeze/resume events

attempt to address #14

* fix unit tests

bin/browser-shim.js

@@ -0,0 +1,9 @@
+// browser shims that run in node, so that page-lifecycle won't error
+global.self = global
+global.document = {
+  visibilityState: 'visible',
+  hasFocus: () => true,
+  wasDiscarded: false
+}
+global.addEventListener = () => {}
+global.removeEventListener = () => {}

package.json

@@ -28,7 +28,7 @@
     "testcafe": "run-s testcafe-suite0 testcafe-suite1",
     "testcafe-suite0": "cross-env-shell testcafe --hostname localhost --skip-js-errors -c 4 $BROWSER tests/spec/0*",
     "testcafe-suite1": "cross-env-shell testcafe --hostname localhost --skip-js-errors $BROWSER tests/spec/1*",
-    "test-unit": "mocha -r esm tests/unit/",
+    "test-unit": "mocha -r esm -r bin/browser-shim.js tests/unit/",
     "wait-for-mastodon-to-start": "node -r esm bin/wait-for-mastodon-to-start.js",
     "wait-for-mastodon-data": "node -r esm bin/wait-for-mastodon-data.js",
     "deploy-prod": "DEPLOY_TYPE=prod ./bin/deploy.sh",

src/routes/_api/TimelineStream.js

@@ -1,6 +1,7 @@
 import { paramsString } from '../_utils/ajax'
 import noop from 'lodash-es/noop'
-import { importWebSocketClient } from '../_utils/asyncModules'
+import WebSocketClient from '@gamestdio/websocket'
+import lifecycle from 'page-lifecycle/dist/lifecycle.mjs'
 
 function getStreamName (timeline) {
   switch (timeline) {
@@ -46,27 +47,60 @@ function getUrl (streamingApi, accessToken, timeline) {
 
 export class TimelineStream {
   constructor (streamingApi, accessToken, timeline, opts) {
-    let url = getUrl(streamingApi, accessToken, timeline)
-    importWebSocketClient().then(WebSocketClient => {
-      if (this.__closed) {
-        return
-      }
-      const ws = new WebSocketClient(url, null, { backoff: 'exponential' })
-      const onMessage = opts.onMessage || noop
-
-      ws.onopen = opts.onOpen || noop
-      ws.onmessage = e => onMessage(JSON.parse(e.data))
-      ws.onclose = opts.onClose || noop
-      ws.onreconnect = opts.onReconnect || noop
-
-      this._ws = ws
-    })
+    this._streamingApi = streamingApi
+    this._accessToken = accessToken
+    this._timeline = timeline
+    this._opts = opts
+    this._onStateChange = this._onStateChange.bind(this)
+    this._setupWebSocket()
+    this._setupLifecycle()
   }
 
   close () {
-    this.__closed = true
+    this._closed = true
+    this._closeWebSocket()
+    this._teardownLifecycle()
+  }
+
+  _closeWebSocket () {
     if (this._ws) {
       this._ws.close()
+      this._ws = null
+    }
+  }
+
+  _setupWebSocket () {
+    const url = getUrl(this._streamingApi, this._accessToken, this._timeline)
+    const ws = new WebSocketClient(url, null, { backoff: 'exponential' })
+
+    ws.onopen = this._opts.onOpen || noop
+    ws.onmessage = this._opts.onMessage ? e => this._opts.onMessage(JSON.parse(e.data)) : noop
+    ws.onclose = this._opts.onClose || noop
+    ws.onreconnect = this._opts.onReconnect || noop
+
+    this._ws = ws
+  }
+
+  _setupLifecycle () {
+    lifecycle.addEventListener('statechange', this._onStateChange)
+  }
+
+  _teardownLifecycle () {
+    lifecycle.removeEventListener('statechange', this._onStateChange)
+  }
+
+  _onStateChange (event) {
+    if (this._closed) {
+      return
+    }
+    // when the page enters or exits a frozen state, pause or resume websocket polling
+    if (event.newState === 'frozen') { // page is frozen
+      console.log('frozen')
+      this._closeWebSocket()
+    } else if (event.oldState === 'frozen') { // page is unfrozen
+      console.log('unfrozen')
+      this._closeWebSocket()
+      this._setupWebSocket()
     }
   }
 }

src/routes/_store/LocalStorageStore.js

@@ -1,6 +1,6 @@
 import { Store } from 'svelte/store'
 import { safeLocalStorage as LS } from '../_utils/safeLocalStorage'
-import { importPageLifecycle } from '../_utils/asyncModules'
+import lifecycle from 'page-lifecycle/dist/lifecycle.mjs'
 
 function safeParse (str) {
   return !str ? undefined : (str === 'undefined' ? undefined : JSON.parse(str))
@@ -31,14 +31,12 @@ export class LocalStorageStore extends Store {
       })
     })
     if (process.browser) {
-      importPageLifecycle().then(lifecycle => {
       lifecycle.addEventListener('statechange', e => {
         if (e.newState === 'passive') {
           console.log('saving LocalStorageStore...')
           this.save()
         }
       })
-      })
     }
   }
 

src/routes/_utils/asyncModules.js

@@ -4,14 +4,6 @@ export const importTimeline = () => import(
   /* webpackChunkName: 'Timeline' */ '../_components/timeline/Timeline.html'
   ).then(getDefault)
 
-export const importPageLifecycle = () => import(
-  /* webpackChunkName: 'page-lifecycle' */ 'page-lifecycle/dist/lifecycle.mjs'
-  ).then(getDefault)
-
-export const importWebSocketClient = () => import(
-  /* webpackChunkName: '@gamestdio/websocket' */ '@gamestdio/websocket'
-  ).then(getDefault)
-
 export const importVirtualList = () => import(
   /* webpackChunkName: 'VirtualList.html' */ '../_components/virtualList/VirtualList.html'
   ).then(getDefault)

webpack/server.config.js

@@ -3,11 +3,14 @@ const config = require('sapper/config/webpack.js')
 const pkg = require('../package.json')
 const { mode, dev, resolve, inlineSvgs } = require('./shared.config')
 
+const serverResolve = JSON.parse(JSON.stringify(resolve))
+serverResolve.alias['page-lifecycle/dist/lifecycle.mjs'] = 'lodash-es/noop' // page lifecycle fails in Node
+
 module.exports = {
   entry: config.server.entry(),
   output: config.server.output(),
   target: 'node',
-  resolve,
+  resolve: serverResolve,
   externals: Object.keys(pkg.dependencies),
   module: {
     rules: [