WorkManager Side Effects: A Follow-Up
About two months ago, I wrote about how
WorkManager has side effects.
Notably, it triggers the system to send ACTION_PACKAGE_CHANGED broadcasts
to your app. At best, those broadcasts might confuse your code that is expecting
those broadcasts to be sent for other reasons, such as components that you are enabling
or disabling yourself. At worst, we wind up in an infinite loop, if you try scheduling
work as part of handling such a broadcast��� which includes scheduling work from
onUpdate() of an AppWidgetProvider.
I argued that WorkManager should provide options to avoid or manage that side effect.
Google disagreed.
This side effect, and any others, seem to be undocumented. Apparently, blog posts
from balding authors suffices.
So, you need to be a bit careful about your use of WorkManager:
If your app responds to ACTION_PACKAGE_CHANGED broadcasts, directly or indirectly,
it may not be safe to schedule work there, lest you wind up in the infinite loop
scenario that I described in my earlier post.
If your app responds to ACTION_BATTERY_OK, ACTION_BATTERY_LOW,
ACTION_POWER_CONNECTED, ACTION_POWER_DISCONNECTED, ACTION_DEVICE_STORAGE_LOW,
ACTION_DEVICE_STORAGE_OK, CONNECTIVITY_CHANGE, ACTION_TIME_SET, or
ACTION_TIMEZONE_CHANGED, bear in mind that WorkManager has receivers for
those broadcasts in your app. These are all disabled at the outset, but presumably
WorkManager has code to enable them based on certain conditions, such as certain
constraints that you set in your work requests. Be careful about scheduling
work with WorkManager on those broadcasts as well.
If your app responds to ACTION_BOOT_COMPLETED broadcasts, bear in mind that WorkManager
also depends on this broadcast. Your respective receivers might be invoked
in any order. It may not be safe to schedule work here, as WorkManager might
assume that its own ACTION_BOOT_COMPLETED receiver has completed its work by
the time you try scheduling new work. While I would not expect an infinite
loop scenario, this is the sort of edge case that requires a lot of testing to
ensure everything will work as expected.
WorkManager has a ContentProvider that it bakes into your app as well.
While scheduling your own work from onCreate() of a ContentProvider would
be rather odd, it���s possible that somebody might want to do that. Be careful,
as WorkManager may not be fully ready for operation at that point. Note that,
last time I tested it, all ContentProvider instances are created before
onCreate() of Application, so probably it is safe to schedule work there.
There may be other edge and corner cases beyond these. So, while WorkManager
is nice, make sure that you thoroughly test your use of it.
