{"id":6237,"date":"2019-01-09T11:23:58","date_gmt":"2019-01-09T19:23:58","guid":{"rendered":"https:\/\/www.couchbase.com\/blog\/?p=6237"},"modified":"2025-06-13T19:58:19","modified_gmt":"2025-06-14T02:58:19","slug":"background-sync-couchbase-mobile-ios","status":"publish","type":"post","link":"https:\/\/www.couchbase.com\/blog\/background-sync-couchbase-mobile-ios\/","title":{"rendered":"Background data sync with Couchbase Mobile on iOS: Tutorial"},"content":{"rendered":"

One of the key features of Couchbase Mobile<\/a> data platform is the ability to sync data across the Couchbase Lite<\/a> enabled mobile clients and the Sync Gateway<\/a>. The ability to run apps in the background is typical in the mobile application life cycle on iOS<\/a>, Android<\/a> and .Net<\/a> platforms and has several uses, for instance, to reduce initial sync\/startup costs by ensuring that the app is launched with the latest data.<\/p>\n

In this post, we will introduce you to a simple tutorial that discusses how you can use iOS Background App Refresh<\/a> capability to sync data when in the background. While the tutorial itself is iOS specific, concepts discussed here apply to all of the supported Couchbase Lite platforms.<\/p>\n

Introduction<\/h2>\n

Every mobile platform has its own implementation of app backgrounding. In some instances, they may even vary with version of the OS. For instance, among the various options, you have Background Services<\/a> on Android, Background App Refresh<\/a> on iOS and Background Tasks<\/a> on UWP apps . For these reasons, with some exceptions, backgrounding support is an app level concern and is not built into Couchbase Lite. In other words, the mobile app will have to support the platform\u2019s built-in backgrounding capability and then invoke Couchbase Mobile\u2019s data sync capabilities whenever it gets the opportunity to execute in the background.<\/p>\n

It is to be noted that on some platforms, the system uses its discretion to terminate the app when it is in the background. Hence, there are no guarantees that the app will even have an opportunity to run in the background.<\/p>\n

Backgrounding Options in iOS<\/h2>\n

Background Task<\/h3>\n

Everytime the app is pushed into the background, Couchbase Lite will use the iOS Background Task<\/a> capability to wrap up ongoing sync before going into idle mode. With the Background Task capability, the system provides the app with a finite amount of time to run in the background to perform critical tasks before suspending it.<\/p>\n

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Silent Notifications<\/h3>\n

In this mode, your backend system can be configured to send out silent push notifications<\/a> to your apps whenever there is data available to be synced by the clients. Silent push notifications are like regular push notifications except that the end user is not notified. Instead, your app is notified and given the oppportunity to handle the notification. When your app is woken up in this mode, it can do a one-shot replication to sync and pending changes with the remote server.
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Background App Refresh<\/h3>\n

Background App Refresh<\/a> lets your app run periodically in the background so that it can update its content. Over time, the system learns the usage of your app , will wake up your app at appropriate times and give it some finite amount of time to execute. When your app is woken up in this mode, it can do a one-shot replication to sync and pending changes with the remote server.
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Tutorial<\/h2>\n

The tutorial introduced in this post uses Background App Refresh mode and is available here<\/a><\/strong>. In this tutorial, you will learn how to –<\/p>\n