Custom Tasks time interval issue when forceAlarmManager is set to false

[vtoupet]

Your Environment

• Plugin version: 4.1.7
• Platform: Android
• OS version: Android 13
• Device manufacturer / model: Google Pixel 5a
• React Native version (react-native -v): 0.70.5
• Plugin config:

The basic BackgroundFetch is configure in a useEffect at startup only:

const initBackgroundFetch = async () => {
      const onEvent = async (taskId) => {
        console.log('[BackgroundFetch] task: ', taskId);
        if (taskId == 'MyCustomTask1')
          await updateWidget1();
        } else if (taskId == 'MyCustomTask2') {
          await updateWidget2();
        }
        BackgroundFetch.finish(taskId);
      };
      const onTimeout = async (taskId) => {
        console.warn('[BackgroundFetch] TIMEOUT task: ', taskId);
        BackgroundFetch.finish(taskId);
      };
      let status = await BackgroundFetch.configure(
        {
          enableHeadless: true,
          minimumFetchInterval: 15,
          startOnBoot: true,
          stopOnTerminate: false,
          requiredNetworkType: BackgroundFetch.NETWORK_TYPE_ANY,
        },
        onEvent,
        onTimeout,
      );

      console.log('[BackgroundFetch] configure status: ', status);
    };

on index.js, the headless task is properly registered.

The problem comes from custom tasks. When a task is scheduled like this:

BackgroundFetch.scheduleTask(
{
  taskId: 'MyCustomTask1',
  enableHeadless: true,
  minimumFetchInterval: 15,
  startOnBoot: true,
  stopOnTerminate: false,
  forceAlarmManager: false,
  requiredNetworkType: BackgroundFetch.NETWORK_TYPE_ANY,
},

I get this from logcat output:

01-19 15:13:46.181 20764 20764 D TSBackgroundFetch: - registerTask: MyCustomTask1
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch: {
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "taskId": "MyCustomTask1",
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "isFetchTask": false,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "minimumFetchInterval": 15,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "stopOnTerminate": false,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "requiredNetworkType": 1,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "requiresBatteryNotLow": false,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "requiresCharging": false,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "requiresDeviceIdle": false,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "requiresStorageNotLow": false,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "startOnBoot": true,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "jobService": "com.transistorsoft.rnbackgroundfetch.HeadlessTask",
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "forceAlarmManager": false,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "periodic": true,
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch:   "delay": -1
01-19 15:13:46.181 20764 20764 D TSBackgroundFetch: }
**01-19 15:13:46.181 20764 20764 W JobInfo : Requested interval -1ms for job -1796060099 is too small; raising to +15m0s0ms
01-19 15:13:46.181 20764 20764 W JobInfo : Requested flex -1ms for job -1796060099 is too small; raising to +5m0s0ms**

Expected Behavior

I would expect to see 15 minutes as the requested interval in JobInfo

Actual Behavior

Instead of using minimumFetchInterval value to configure the interval, it is using the delay which is incorrect when forceAlarmManager is set to false.

I think the problem comes from the transistor-background-fetch library: this line: long interval = (config.isFetchTask()) ? (TimeUnit.MINUTES.toMillis(config.getMinimumFetchInterval())) : config.getDelay();

[christocracy]

scheduleTask does not have an option minimumFetchInterval. That is for the built-in, recurring fetch task.

scheduleTask uses delay.

[vtoupet]

There is nothing preventing the usage of minimumFetchInterval with scheduleTask. The underlying java method expect a BackgroundFetchConfig object and uses more or less the same mechanism as the configure method.

I think that would be great to be able to create custom tasks that can benefit from the JobService for Android SDK >= LOLLiPOP. It would require minimal changes when computing interval value in BGTask class. Something like the following (in the function schedule of the BGTask class):

long interval = 0;
if (config.isFetchTask() || (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && !config.getForceAlarmManager())) {
  interval = TimeUnit.MINUTES.toMillis(config.getMinimumFetchInterval());
} else {
  interval = config.getDelay();
} 

What do you think?

[christocracy]

There is nothing preventing the usage of minimumFetchInterval with scheduleTask

It doesn't make sense to use the word "minimumFetchInterval" with the method scheduleTask. scheduleTask uses delay.

Anyway, it's not necessary since scheduleTask already uses JobScheduler by default. It only uses AlarmManager when configured with forceAlarmManager: true.

[christocracy]

The config option is named forceAlarmManager to communicate to the developer that JobScheduler is the implied default and you must "force" the SDK to use AlarmManager.

[vtoupet]

Ok, I get it, thanks @christocracy.

2 other things (let me know if you want me to create other issues).

• It is hard to test because we don't know the JobId of custom task (it would be great to add a debug log in the logcat)
• the scheduleTask does not cancel (there is a comment in your code). What happens when we update the config of the same taskId without cancelling?

[christocracy]

Your last two points are fair. Go ahead and post two separate issues for those.

[christocracy]

btw, if you are using Typescript, the linter should flag using minimumFetchInterval with the method scheduleTask, which accepts TaskConfig

https://github.com/transistorsoft/react-native-background-fetch/blob/8a3ba2288200e07ef3e7d291d0de8ffd366c78cf/index.d.ts#L54-L71

[vtoupet]

I actually don't use scheduleTask in react-native side but rather in the Java side (from a pure Java Android widget configuration screen). So I am using this instead:

BackgroundFetchConfig.Builder config = new BackgroundFetchConfig.Builder();
config.setTaskId(taskId);
config.setIsFetchTask(false);
config.setDelay(TimeUnit.MINUTES.toMillis(interval));
config.setPeriodic(true);
config.setStartOnBoot(true);
config.setStopOnTerminate(false);
config.setJobService(JOB_SERVICE_CLASS);
config.setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY);
BackgroundFetch adapter = getAdapter(context);
adapter.scheduleTask(config.build());

But my application is react-native. It's not conventional. I did not introduce it to you like this as you would have probably told me that t is out of the scope of this library ;-)

[vtoupet]

Your last two points are fair. Go ahead and post two separate issues for those.

Do you want me to create the issues in this repository or the native one (https://github.com/transistorsoft/transistor-background-fetch)

[christocracy]

Native one. The native lib is common to this RN version in addition to the Cordova, Capacitor and Flutter versions.