Periodic task concurrency issue with foreground app - windows-phone-7

I am developing a Windows Phone 8 app that would have a live flip tile. I will be creating a scheduled agent (periodic task not resource intensive) which will update the live tile using local data.
The whole app does not connect to the internet in any way, it uses only local data. So push notifications are out of the question.
I need to update the live tile from the background agent and/or from the foreground app when it's launched whichever happens first.
However how can I ensure the foreground app and the background agent do not step on each other's toes? I have two main options to do this :
Use a mutex (AFAIK the background agent runs in a different process so locks (monitor that is) is out of the question). But I'm afraid it would have a high performance cost (obtaining and releasing the mutex, that is).
When the foreground app starts I would always remove the agent, do its work and reschedule the agent back. Theferore there would not be any chance of overlapping between the foreground app and the background agent, BUT the whole add/remove agent could also be lengthy and, furthemore, the user might close the app after this removed the agent but before it added it back.
I am really torn between these two approaches and can't tell which would be best.
PS : You can't reschedule an agent from the agent's own code, right?

Mutex
The mutex option is officially recommended by the MSDN documentation for both Windows Phone 7 and 8.
I have used this option and experienced no noticeable performance problems when sharing data between the Background Agent and Foreground App, and I target WP7.1 and test on 1st and 2nd generation WP7 devices (LG E900 and Lumia 800).
Obviously, when using mutex, the key is to lock the resource for as short a time as possible. And when trying to acquire a lock on a resource in a Background Agent, the timeout feature of WaitHandle.WaitOne is very useful as the Background Agent only has 25 seconds to run.
NOTE: If you are targeting Windows Phone 8 only, or via a 2nd project/binary then a different approach (named events for inter-process-communication) is available. Peter Torr wrote about it on the official Windows Phone Developer blog.
Enabled/Disable Background Agent
The second approach you mention is riskier because the we don't know what guarantees the OS gives for adding or removing of the Background Agent - what happens if removal if not instant? what happens if a newly renewed Background Agent fires while to Foreground App is running? etc.
Agent Renewal
Background Agents cannot renew themselves - once added, they will run for a maximum of two weeks unless renewed by the Foreground App. This will prevent Background Agents running for apps the user no longer uses.

Related

How to activate / enable the process notification feature in API Monitor?

API Monitor has a feature to automatically watch for a new process starting and ask if you want to monitor it. However I have not been able to get this to actually work. The only option in the program I can find which seems to be related is the File menu "Pause Process Notifications" option. However, this is disabled which gives me the impressions that it can't be turned off but also that it is supposed to work automatically "out of the box". But whenever I start a new process, nothing happens.
Specifically I'm referring to the feature described here:
Process Notification
API Monitor intercepts process creation and allows you to select the
process for monitoring. Each time a process is created by the system,
a notification window is displayed with options to monitor, skip or
terminate the process. This is especially useful for monitoring
processes with a short lifespan or processes that are automatically
launched in the background. Process Notification can also be used to
monitor applications such as consent.exe (UAC prompt), which run on a
different desktop.
The following screenshot shows an example of the Process Notification
window that is displayed when launching an application that requires
elevation
I've tried both the 32-bit and 64-bit versions of API Monitor (Version 2.0 Alpha-r13) running both as regular user and as admin; makes no difference.
How can this feature be activated?
The specific reason I'd like to use this feature is that I have process A which starts process B, and it is B I need to monitor. A and B each run for only a few seconds so I can't manually get it to monitor fast enough.
Finally after reading through API Monitor forums I found some information. Unfortunately (for now at least) it seems the answer is that this feature no longer works (since Windows 8.1).
As posted on http://www.rohitab.com/discuss/topic/40418-process-notification-on-81/?p=10093378
rohitabPosted 11 October 2013 - 03:38 AM
Due to security related changes in Windows 8.1, the Process
Notifications feature of API Monitor does not work. I will try to
resolve this issue as soon as possible and post a hotfix.
But a later update in 2014 indicated that it hadn't been fixed yet, and seems not to have been since then either.
It was implied that running in a Windows 7 (or 8.0?) virtual machine might be a workaround, or obviously finding another tool which has this capability.

UWP apps running background tasks when the app is closed

I want to run a background task for every 10 mins.As the UWP app will not always be opened.Is there a way to run a background task even when the app is closed(Not Running State)?
If the answer is NO,
Is there any another way other than Windows Services?
You can create BackgroundTask which run at the most every 15 minutes not less than that in UWP apps. for more details you can check this source.
Is there a way to run a background task even when the app is
closed(Not Running State)?
According to this document:
You can use background tasks to provide functionality when your app is
suspended or not running.
The 'not running' state in UWP is described in more detail here. It reads:
An app could be in this state because it hasn't been launched since
the last time the user rebooted or logged in. It can also be in this
state if it was running but then crashed, or because the user closed
it earlier.
This implies that the app simply needs to run once after installation to be able to successfully register a background task, which can then run even after your app is closed.
I want to run a background task for every 10 mins
Not sure I'm interpreting this correctly but I assume you mean you want to run some bit of code every 10 mins while your app is not running. Well there are two way that I can think of to achieve this.
Method 1:
While background tasks are meant to be very short-lived tasks, they may even be made to run indefinitely if:
extendedBackgroundTaskTime capability is added as a restricted
capability in your app's manifest file
Using this technique along with a simple timer mechanism would achieve the desired result.
Method 2 (more complicated but keeps background tasks short-lived):
Setup a DatagramSocket to a remote server which sends some data every 10 mins and register your background task with a SocketActivityTrigger.

Running profiler on a background agent

My background agent is hitting the 6MB memory limit, and I'd like to understand what objects are being allocated.
In principle I can do this using the Visual Studio Windows Phone Performance Analysis tool, however I don't see how I can run this on a background agent, only on the main app.
Anyone know how to run the Visual Studio Windows Phone Performance Analysis tool on a background agent?
If you are just trying to get the background agent to run while you are profiling you can use ScheduledActionService.LaunchForTest like in this question. And here it is noted that it can still take a while before the agent runs.
If you want to test just the background agent outside of the rest of the app I haven't seen a good way to do it. However I would make a make an empty app and have it manually run the background agent functionality. Then you can profile that and it should work well enough.
Additionally here are some links about keeping your memory consumption down in background agents that you might find helpful:
Wp7.5 Mango–Background Agents - Chris Sainty (of gReadie fame)
Optimizing memory consumption for WP7 Background Agents - Oliver Weichhold

Using timed events in BlackBerry

is it possible to fire up an event at a specified time interval in BlackBerry? I'm looking for something similar to AlarmManager class in Android (if anyone is familiar with it).
The goal is to is to run some code, even when the application is not in foreground and without it gaining foreground "focus". Preferably it should be possible to fire the event even if the app was killed by system or by phone reboot (I do not know the details about killing apps at this OS, I'm beginning development now).
I would prefer not to write a background process for this task as it is going to be fired every few hours (I think it would be a waste of battery to use a background task for a simple alarm-like event).
I've looked around a lot, but I cannot find any satisfying solution.
cheers,
kajman
The Timer and TimerTask classes are useful for running a task on a schedule. Take a look at the APIs here:
http://www.blackberry.com/developers/docs/7.0.0api/java/util/Timer.html
The Timer will create its own Thread and sleep until it has a task to run. It would involve having a background task running but it wouldn't be using an CPU or battery if it is just waiting.
If you don't want a Thread running all of the time you can use the ApplicationManager class to schedule your application to start later.
You can also configure your app to run on start up. The OS generally won't kill your apps unless you have a coding error. RIM refers to this as the Always-On Experience in their Super App document:
http://docs.blackberry.com/en/developers/deliverables/23567/Always_on_1380986_11.jsp#Keeping_the_app_running_1381022_11

Timer applications running under lock on Windows Phone 7

Under the current Windows Phone 7 Application Certification Requirements (pdf) applications running under lock must "stop any ... active timers" (section 6.3.1). However looking out on Marketplace there are a number of timer/stopwatch apps claiming to run under lock and also allow lock to be disabled in their settings. How are these apps certified or is there some loosening on the restrictions by Microsoft if the app allows the user to make that decision?
Also some of these apps also suggest they continue even when the app is exited or when the device off. Is it the case that they are not truly running under these circumstances, i.e. the timers either start where they left off when reactivated, or perhaps use the OS time to work out the time elapsed between tombstoning and reactivation? In these circumstance I also presume it is not possible for the app to notify the user when the timer completes?
6.3.1 requires apps to offer the ability to prevent the app from running under a lock screen.
Apps can run under a lock screen by disabling ApplicationIdleDetectionMode.
You can keep track of time while the device is off using the OS time as you note. Peter Torr demoed this with tombstoning state in his WPH305 Tech Ed 2010 Talk.. refer 28 minutes in.
You presume correct that there is no ability to notify the user using client APIs on a timer. The closest you'll get to this is notifications which entails network communication and presumes connectivity.

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