core/local: SyncDir helpers (#1272)

core/local: Extract syncDir from Local & Watchers

- DRY
- 1 method less in Watcher interface & subclasses
- Local doesn't need LocalWatcher anymore to ensure sync dir exists
- AtomWatcher module doesn't use fs-extra anymore

core/local: Manage syncDir interval check in Local

- So we don't need to do it for each watcher subclass (DRY)
- AtomWatcher doesn't need syncDir anymore.

core/local/atom_watcher.js

@@ -1,6 +1,5 @@
 /* @flow */
 
-const fse = require('fs-extra')
 const Promise = require('bluebird')
 
 const checksumer = require('./checksumer')
@@ -26,7 +25,6 @@ module.exports = class AtomWatcher {
   syncPath: string
   events: EventEmitter
   checksumer: Checksumer
-  ensureDirInterval: *
   running: Promise<void>
   _runningResolve: ?Function
   _runningReject: ?Function
@@ -46,17 +44,8 @@ module.exports = class AtomWatcher {
     this.source = new LinuxSource(syncPath, identifier)
   }
 
-  ensureDirSync () {
-    // This code is duplicated in local/index#start
-    if (!fse.existsSync(this.syncPath)) {
-      this.events.emit('syncdir-unlinked')
-      throw new Error('Syncdir has been unlinked')
-    }
-  }
-
   start () {
     log.debug('starting...')
-    this.ensureDirInterval = setInterval(this.ensureDirSync.bind(this), 5000)
     this.running = new Promise((resolve, reject) => {
       this._runningResolve = resolve
       this._runningReject = reject
@@ -72,7 +61,6 @@ module.exports = class AtomWatcher {
       this._runningResolve()
       this._runningResolve = null
     }
-    clearInterval(this.ensureDirInterval)
     this.source.stop()
   }
 }

core/local/chokidar_watcher.js

@@ -14,6 +14,7 @@ const LocalEventBuffer = require('./event_buffer')
 const logger = require('../logger')
 const metadata = require('../metadata')
 const {sameDate, fromDate} = require('../timestamp')
+const syncDir = require('./sync_dir')
 
 /*::
 import type { Metadata } from '../metadata'
@@ -60,7 +61,6 @@ module.exports = class LocalWatcher {
   checksumer: Checksumer
   watcher: any // chokidar
   buffer: LocalEventBuffer<ChokidarEvent>
-  ensureDirInterval: *
   pendingChanges: LocalChange[]
   running: Promise<void>
   _runningResolve: ?Function
@@ -90,21 +90,11 @@ module.exports = class LocalWatcher {
     })
   }
 
-  ensureDirSync () {
-    // This code is duplicated in local/index#start
-    if (!fs.existsSync(this.syncPath)) {
-      this.events.emit('syncdir-unlinked')
-      throw new Error('Syncdir has been unlinked')
-    }
-  }
-
   // Start chokidar, the filesystem watcher
   // https://github.com/paulmillr/chokidar
   start () {
     log.debug('Starting...')
 
-    this.ensureDirInterval = setInterval(this.ensureDirSync.bind(this), 5000)
-
     this.watcher = chokidar.watch('.', {
       // Let paths in events be relative to this base path
       cwd: this.syncPath,
@@ -174,7 +164,7 @@ module.exports = class LocalWatcher {
 
     if (this.initialScan) this.initialScan.flushed = true
     this.events.emit('buffering-end')
-    this.ensureDirSync()
+    syncDir.ensureExistsSync(this)
     this.events.emit('local-start')
 
     let events = rawEvents.filter((e) => e.path !== '') // @TODO handle root dir events
@@ -374,7 +364,6 @@ module.exports = class LocalWatcher {
       this._runningResolve()
       this._runningResolve = null
     }
-    clearInterval(this.ensureDirInterval)
     this.buffer.switchMode('idle')
     if (force) return Promise.resolve()
     // Give some time for awaitWriteFinish events to be managed

core/local/index.js

@@ -16,6 +16,7 @@ const sentry = require('../sentry')
 const watcher = require('./watcher')
 const measureTime = require('../perftools')
 const { withContentLength } = require('../file_stream_provider')
+const syncDir = require('./sync_dir')
 
 bluebird.promisifyAll(fs)
 
@@ -43,6 +44,7 @@ module.exports = class Local /*:: implements Side */ {
   pouch: Pouch
   events: EventEmitter
   syncPath: string
+  syncDirCheckInterval: IntervalID
   tmpPath: string
   watcher: Watcher
   other: FileStreamProvider
@@ -73,12 +75,14 @@ module.exports = class Local /*:: implements Side */ {
 
   // Start initial replication + watching changes in live
   start () {
-    this.watcher.ensureDirSync()
+    syncDir.ensureExistsSync(this)
+    this.syncDirCheckInterval = syncDir.startIntervalCheck(this)
     return this.watcher.start()
   }
 
   // Stop watching the file system
   stop () {
+    clearInterval(this.syncDirCheckInterval)
     return this.watcher.stop()
   }
 

core/local/sync_dir.js

@@ -0,0 +1,32 @@
+/* @flow */
+
+var fs = require('fs')
+
+/*::
+import type EventEmitter from 'events'
+*/
+
+module.exports = {
+  ensureExistsSync,
+  startIntervalCheck
+}
+
+/** Make sure syncPath actually exists.
+ *
+ * In case it doesn't, emit 'syncdir-unlinked' and throws.
+ * Any other error occuring during the check will be thrown too.
+ */
+function ensureExistsSync ({syncPath, events} /*: {syncPath: string, events: EventEmitter} */) /*: void */ {
+  if (!fs.existsSync(syncPath)) {
+    events.emit('syncdir-unlinked')
+    throw new Error('Syncdir has been unlinked')
+  }
+}
+
+/** Start regularly checking that syncPath actually exists.
+ *
+ * Caller should stop the regular check at some point with clearInterval().
+ */
+function startIntervalCheck (context /*: {syncPath: string, events: EventEmitter} */) /*: IntervalID */ {
+  return setInterval(() => ensureExistsSync(context), 5000)
+}

core/local/watcher.js

@@ -16,7 +16,6 @@ export interface Watcher {
   running: Promise<*>,
   start (): Promise<*>,
   stop (force: ?bool): Promise<*>,
-  ensureDirSync (): void,
 }
 */