Android Worker Max Retries

Background : While working with WorkManager on Android if there is a handled exception within doWork() we can ask the WorkManager to retry the work and consequently the doWork() will get executed again .

So when will the work get executed again ? Back-Off Policy (as long as Work Constraints are met)

Use case : The work kept on retrying on every interval (indefinitely) as computed through the Back-Off Policy. I wanted to make sure that after five retries the work fails and we log that failure appropriately.

I also wanted to make sure all unit and integration tests passed.

Solution:

Even though there is no direct API to set Max retries (to five in my case) there is a method in WorkParameters getRunAttemptCount() . This “Gets the current run attempt count for this work. Note that for periodic work, this value gets reset between periods.”

Note that runAttemptCount starts from 0

Sample CoroutineWorker doWork method -

override suspend fun doWork(): Result {
        return if (runAttemptCount < 5) { // runAttemptCount starts from 0
            try {
                // do long running work
            } catch (ex: IOException) {
                Result.retry()
            }
            Result.success()
        } else {
            Result.failure()
        }
    }

Testing :

use TestListenableWorkerBuilder to test CoroutineWorker implementations, as the work-testing artifact uses Dispatchers.Default rather than your worker implementation’s CoroutineDispatcher

Unit Tests for coroutine worker with MAX_RETRIES

@Test
fun testWorkerSucceedsIfRunAttemptIsLessThanMax() {
    val worker = TestListenableWorkerBuilder<LongRunningWorker>(
        context = ApplicationProvider.getApplicationContext(),
        runAttemptCount = MAX_RETRIES - 1
    ).build()
    runBlocking {
        val result = worker.doWork()
        assertThat(result, `is`(ListenableWorker.Result.Success()))
    }

}

@Test
fun testWorkerFailsIfRunAttemptIsAtMax() {
    val worker = TestListenableWorkerBuilder<LongRunningWorker>(
        context = ApplicationProvider.getApplicationContext(),
        runAttemptCount = MAX_RETRIES
    ).build()
    runBlocking {
        val result = worker.doWork()
        assertThat(result, `is`(ListenableWorker.Result.Failure()))
    }
}

Sample Code on Git

https://github.com/ChaitanyaDuse/WorkManagerSamples

Resources

Define work requests | Android Developers

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