Gaia/System/Updates/Apps

App Updates: Overview

Introduction

Apps can be divided into three categories, each with their own update policies.

• Core apps
• Pre-installed 3rd party apps
• User-installed apps

Core apps

About

• Are all packaged apps
• Are pre-installed with the OS
• Are not user-removable
• Will survive a factory reset
  • We ensure that Core apps are available after a factory reset by storing them in the System partition, in /system/b2g/webapps, instead of the usual /data/local/webapps.

Updates

• Core apps updates are bundled with Gecko updates, and are therefore governed by Gecko update policies.

Pre-installed third party apps

About

• These are 3rd party apps that come bundled with the phone.
• Are governed by same rules as User-installed apps.

Updates

• Are governed by same rules as User-installed apps.

Open questions

• Can these be uninstalled by the user
• What happens with these on a factory reset? Are they removed if installed? Re-spawn if uninstalled?

User-installed apps

About

• Can be packaged or non-packaged
  • Differences between packaged and non-packaged apps should generally not be surfaced to the user.
  • For both types, we ensure that they stay up-to-date by checking for new versions at regular intervals.
• Updates are not be free and will incur data charges when on the carrier’s network.

Non-packaged app updates

• Non-packaged apps can specify the location of an offline-cache manifest to be loaded at install time. This offline-cache is subsequently updated.
• Update availability is checked by polling the developer website.
• We don't yet have the ability to tell a packaged app that an update is available.

Package apps

See section below.

Answered questions

• Can the user inspect permissions enumerated in the app at the time of installation? Should we let the user know if an update expands the list of permissions?
• Do we need to have a mechanism for pushing extra-critical updates?
• Should we inform users about how big updates will be before downloading them?
  • For un-packaged apps we generally can't tell how big an update is going to be. We could implement mechanisms for doing estimates, but we don't have anything right now
  • For packaged apps we could implement such a mechanism, but it depends on the protocols we use (see below):
  • What protocol should we use for detecting that an app update is available and downloading the update? This is a question we need to hammer out with the store people and the AMO people who have a lot of experience with updates for addons. The last two solutions involve new server-side APIs to be defined, but could potentially be more efficient. Three possibilities which have been discussed:
    • Check if the HTTP Etag of the package has changed by sending a conditional HTTP request with a If-None-Match header. This is what the work-in-progresss implementation in bug 772364 is doing.
    • Group all the applications by store, and send to each store the list to check with ones to update. This could also return hashes for the new packages which could be safely downloaded from mirrors.
    • If the user has authentication credentials with a store, use a store specific api to get a list of updated applications.

mozApps API Changes

To support the previously described behaviour, we need a couple of additions to the content facing mozApps API, on the Application object:

• Add a |readonly boolean removable| property.
• Add a |DOMEventListener onupdated| event listener to be notified when an application has been updated. This let a dashboard update any displayed item that could have changed (icon, application name, etc.)

Packaged Apps

Users

• Limited access to wifi
• Rarely roaming
• Off-by-default data connections
• SIM card swapping
• Expensive data
• Mental models are "installed" vs "not-installed"

Technical parameters

• Can poll Marketplace for update, or push update to user.
• Marketplace will know installed version #.
• We can download and install updates while current version is running. New version is then available on app restart
• Low risk of new versions breaking old.

Developers

• Web devs are used to their users being on latest version. Makes development easier.
• Long term, we want world where as many users as possible are always on newest app versions. Great for security, development, etc.

Challenge

• Our long term vision depends on ubquitious, fast, affordable connectivity. But those conditions do not exist in initial launch markets. It may be a challenge convincing users to use and update apps if data connectivity is a requirement.

Design principles

• Low-friction. Minimize user interruptions, connection speed impacts, etc.
• Free. Avoid user charges.
• Safe. Minimize changes and consequences of failed updates.
• Patient. Support backwards compatibility for users who cannot update.
• Friendly. Avoid presenting users with excess technical details.

User-facing Steps

• Inform
• Request confirmation
• Show Process
• Confirm success / failure
• Prompt for new permissions at next run

Potential tactics (v2?)

• Batch process updates?
  • Poll Marketplace(s) for list of all available updates, and A) present menu to user with Update Individual and Update All options, and/or B) download automatically.
• Poll less frequently, depending on connection type?
• Poll less frequently, depending on frequency of app use?
• Update all apps automatically with Gecko+Gaia atomic updates?
• Enable users to opt-out? eg: "Don't remind me again"?
• Enable users to specify per-app update permissions? eg: app by app silent update?
• Incentivize updates? "Update for free credits"
• Allow users to set global update preferences?

Questions:

• Can/should apps tell inform users of available updates?
• Package apps: require full .ZIP contents update every single time?
• Marketplace maintains receipts of transactions and can be used as update channel?
• Can users defer updates and still use app? Sounds like this will be up to app devs to ensure on app-by-app basis?
• How often will packaged apps be updated? It could get obnoxious if I am constantly being pinged by the app to update.
• Do we have strategies to reduce file sizes? ala Binary diffs in Gecko+Gaia updates?