Ember.js Network Request Retries

application-adapter.coffee

ApplicationAdpater = DS.ActiveModelAdapter.extend
  synchronizer: Em.inject.service()
  ajax: (url, type, options) ->
    hash = @ajaxOptions(url, type, options)
    # set up hash.success & hash.error callbacks normally
    @get('synchronizer').handleRequest(hash)

application-route.coffee

afterModel: (resolvedModel) ->
# Load from local storage
@get('synchronizer.syncQueue').loadStateFromPersistentStorage(user.get('id')).then (entries) ->
  if entries.length > 0
    # Re-populate queue
    @get('synchronizer.syncQueue').replaceWithEntries(entries)
    # start syncing
    @get('synchronizer').startSync()

storage-service.coffee

StorageService = Em.Object.extend
  init: ->
    @set 'maxOrder', 0
    @set 'localForage', localforage
    @populateMaxOrder()
 
  # The request order is determined by what already exists in local storage
  populateMaxOrder: ->
    new Em.RSVP.Promise (resolve, reject) =>
      @get('localForage').iterate (value, key, index) =>      
        if @get('maxOrder') < value.order 
        @set 'maxOrder', value.order
        return
    modelJson = @get('syncModelRepository').jsonForModel entry.get('model')
    serialized = {
      id: @idForEntry(entry) # Generate UUID to identify entry
      order: @get('maxOrder') + 1
      queueEntry: @get('syncQueueEntryRepository').jsonForEntry(entry) # Serialize entry for storage
      model: modelJson
    }
    new Em.RSVP.Promise(resolve, reject) =>
      @get('localforage').setItem(@idForEntry(entry), serialized).then (value) =>
        resolve(value)
      , (err) =>
        reject(err)

sync-queue.coffee

SyncQueue = Em.Object.extend
  init: ->
    @set 'queue', []
  pushEntry: (entry) ->
    @get('queue').pushObject(entry)
    @get('storageService').pushEntry(entry)

synchronizer.coffee

Synchronizer = Em.Object.extend
  handleRequest: (opts) ->
    # Create an object that describes the request
    @get('syncQueueEntryRepository').entryForJqueryOpts(opts).then (entry) =>
      # Push that object into local storage
      @get('syncQueue').pushEntry(entry).finally =>
        # Tell the application that the request was successful
        opts.success({}, "success", entry)
        
  processRequests: ->
    entry = @get('syncQueue.firstObject')
    if entry?
      # deserialize entry into request
      opts = @get('syncQueueEntryRepository').jqueryOptsForEntry(entry)
    
      # Make the request
      Ember.$.ajax(opts).then (result) =>
        # Success case
        Em.run =>
          # Request was successful, so remove that entry
          @get('syncQueue').removeEntry(entry).then (val) =>
            # Push resulting objects into the Store
            @handleResponse(result, entry)
            # Process the next request
            Em.run.once @, 'processRequest'
      , if ((not jqXHR.readyState?) or jqXHR.readyState == 0)
          # Connectivity problem -- keep retrying
          Em.run =>
            # Update a retry timer
            @_backoffRetrySyncTime()
            # Re-run the request after the backoff has ended
            Ember.run.later @, 'processRequest', @get('retrySyncInSeconds') * 1000