hung window cleanup, improved code docs. Fixes #163 (#165)

* hung window cleanup, improved code docs. Fixes #163

* document units for timed constants #163

lib/exportJob.js

@@ -19,17 +19,70 @@ const logger = debug('electronpdf:')
 const wargs = require('./args')
 
 // CONSTANTS
+/** Used to calculate browser dimensions based on PDF size */
 const HTML_DPI = 96
+/** Interval for which to check for hung windows, in milliseconds */
+const HUNG_WINDOW_CLEANUP_INTERVAL = process.env.ELECTRONPDF_WINDOW_CLEANUP_INTERVAL || 1000 * 30 /* seconds */
+/** How long a window can remain open before it is terminated, in milliseconds */
+const HUNG_WINDOW_THRESHOLD = process.env.ELECTRONPDF_WINDOW_LIFE_THRESHOLD || 1000 * 60 * 5 /* minutes */
+/** Used to determine browser size using a Micron -> Inch -> Pixel conversion */
 const MICRONS_INCH_RATIO = 25400
-const MAX_EVENT_WAIT = 10000
+/** When a ready event option is set, this is the default timeout.  It is overridden by the wait option */
+const MAX_READY_EVENT_WAIT = 10000
+/** The event name for which Electron IPC is done over */
 const IPC_MAIN_CHANNEL_RENDER = 'READY_TO_RENDER'
-const eventPrefix = 'job.render.'
+/** Prepended to events emitted during rendering */
+const RENDER_EVENT_PREFIX = 'job.render.'
 
 const DEFAULT_OPTIONS = {
   closeWindow: true,
   inMemory: false
 }
 
+// Window Cache - Keep track of all windows created, and if any get stuck close
+// them
+const windowCache = {}
+/**
+ * When a job creates a window it invoks this method so any memory leaks
+ * due to hung windows are prevented.  This can happen if an uncaught exception
+ * occurs and job.destroy() is never invoked.
+ * @param job
+ */
+function registerOpenWindow (job) {
+  const w = job.window
+  windowCache[w.id] = {job: job, window: w, lastUsed: Date.now()}
+}
+/**
+ * Anytime a window is used this function should be invoked to update
+ * the lastUsed property in the window cache
+ * @param id
+ */
+function touchWindow (id) {
+  windowCache[id].lastUsed = Date.now()
+}
+
+function cleanupHungWindows () {
+  const now = Date.now()
+  const hungWindows = _.filter(windowCache,
+    e => now - e.lastUsed > HUNG_WINDOW_THRESHOLD)
+  logger(`checking hung windows.  total windows: ${_.size(windowCache)}`)
+  _.forEach(hungWindows, e => {
+    const windowContext = {
+      id: e.window.id,
+      lifespan: now - e.lastUsed
+    }
+    e.job.emit('window.termination', windowContext)
+    delete windowCache[e.window.id]
+    e.job.destroy()
+  })
+}
+
+setInterval(cleanupHungWindows, HUNG_WINDOW_CLEANUP_INTERVAL)
+
+/**
+ * A job should be created to process a given export opreation for one or more
+ * resources and a set of output options.
+ */
 class ExportJob extends EventEmitter {
 
   /**
@@ -84,20 +137,20 @@ class ExportJob extends EventEmitter {
   /**
    * Render markdown or html to pdf
    */
-  render (window) {
-    this.emit(`${eventPrefix}start`)
+  render () {
+    this.emit(`${RENDER_EVENT_PREFIX}start`)
 
     const win = this._launchBrowserWindow()
     this.window = win
+    registerOpenWindow(this)
 
     // TODO: Check for different domains, this is meant to support only a single origin
     const firstUrl = this.input[0]
     this._setSessionCookies(this.args.cookies, firstUrl, win.webContents.session.cookies)
 
     const windowEvents = []
     // The same listeners can be used for each resource
-    this._passThroughEvents(win, eventPrefix)
-
+    this._passThroughEvents(win, RENDER_EVENT_PREFIX)
     this.input.forEach((uriPath, i) => {
       windowEvents.push((pageDone) => {
         this._initializeWindowForResource()
@@ -114,7 +167,7 @@ class ExportJob extends EventEmitter {
     async.series(windowEvents, (err, results) => {
       if (this.options.closeWindow) {
         win.close()
-        this.emit(`${eventPrefix}window.close`)
+        this.emit(`${RENDER_EVENT_PREFIX}window.close`)
       }
       /**
        * PDF Generation Event - fires when all PDFs have been persisted to disk
@@ -123,7 +176,7 @@ class ExportJob extends EventEmitter {
        * @property {String} results - array of generated pdf file locations
        * @property {Object} error - If an error occurred, null otherwise
        */
-      this.emit(`${eventPrefix}complete`, {results: results, error: err})
+      this.emit(`${RENDER_EVENT_PREFIX}complete`, {results: results, error: err})
       this.emit('job-complete', {results: results, error: err}) // Deprecated
     })
   }
@@ -237,6 +290,7 @@ class ExportJob extends EventEmitter {
    * @private
    */
   _initializeWindowForResource () {
+    touchWindow(this.window.id)
     // Reset the generated flag for each input URL because this same job/window
     // can be reused in this scenario
     this.generated = false
@@ -299,7 +353,8 @@ class ExportJob extends EventEmitter {
   }
 
   /**
-   * Inpects this.args and sets the window size based on the pageSize and orientation
+   * Inpects this.args and sets the window size based on the pageSize and
+   * orientation
    * @private
    */
   _setWindowDimensions () {
@@ -401,7 +456,7 @@ class ExportJob extends EventEmitter {
     if (this.args.disableCache) {
       loadOpts.extraHeaders += 'pragma: no-cache\n'
     }
-    this.emit(`${eventPrefix}loadurl`, { url: url })
+    this.emit(`${RENDER_EVENT_PREFIX}loadurl`, { url: url })
     window.loadURL(wargs.urlWithArgs(url, {}), loadOpts)
   }
 
@@ -454,7 +509,7 @@ class ExportJob extends EventEmitter {
 
     // Don't let a ready event hang, set a max timeout interval
     const f = this._cancelReadyEvent.bind(this, eventName, ipcListener, generateFunction)
-    const maxWait = this.args.outputWait > 0 ? this.args.outputWait : MAX_EVENT_WAIT
+    const maxWait = this.args.outputWait > 0 ? this.args.outputWait : MAX_READY_EVENT_WAIT
     const timeout = setTimeout(f, maxWait)
 
     // clear the timeout as soon as we get the ready event from the browser
@@ -464,11 +519,13 @@ class ExportJob extends EventEmitter {
   }
 
   /**
-   * Invoked when a ready event has not been received before the max timeout is reached
+   * Invoked when a ready event has not been received before the max timeout is
+   * reached
    * @param eventName The eventName provided by the client
-   * @param ipcListener The ipcMain listener waiting for the IPC_MAIN_CHANNEL_RENDER
-   * event from the renderer process
-   * @param generateFunction A callback function to invoke to capture the window
+   * @param ipcListener The ipcMain listener waiting for the
+   *   IPC_MAIN_CHANNEL_RENDER event from the renderer process
+   * @param generateFunction A callback function to invoke to capture the
+   *   window
    * @private
    */
   _cancelReadyEvent (eventName, ipcListener, generateFunction) {
@@ -531,7 +588,7 @@ class ExportJob extends EventEmitter {
        */
       this.emit('window.observer.timeout', {})
       generateFunction()
-    }, MAX_EVENT_WAIT)
+    }, MAX_READY_EVENT_WAIT)
 
     this.readyEventObserver(customEventDetail).then(() => {
       /**