App Updates
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.
Packaged app updates
- Update availability is checked by polling the store to see whether a new package available.
- We also have the ability to tell the app that an update is available.
Deferred download
- We have the ability to download and install app updates while the previous versions are running. The new version is made available on app restart.
Open questions
- How often should we check for app update?
- Once a day, only on WiFi?
- Does the frequency of usage affect how often we check for app updates?
- Does being on 3G/Edge affect when we check for app updates?
- What should we tell the user when an app update is detected?
- What should we tell the user when an app update is detected while the app is running, or should we rely on the app to do so? (note that while we can inform a running app about an update being available, we can't detect if the app is actually doing anything useful with that information)
- Should we behave differently if the user is on 3G/Edge connection when we detect that an update is available?
- 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.
- Should we enable batch download of updates?
- Should we indicate download+install progress to user?
- Should we surface "this app has been updated" information to user?
- Do we create user configuration options? eg:
- Download and install apps in background.
- How do we ensure backwards compatibility for apps that cannot update? eg: User is on Edge connection and rarely accesses via WiFi. Would their apps stop working once they are out of date?
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.)
Open questions:
- Do we also need an event signaling that an update is available?
- Do we also need an event signaling that an update has been downloaded?