IssueTracker

So you can do this now by doing something like:

@Suppress("UNCHECKED_CAST")
class DelegateWorker: Worker() {
    companion object {
        const val DELEGATE_WORKER_NAME = "DELEGATE_WORKER_NAME"
        const val PERIOD = "PERIOD" // in minutes.
    }

    override fun doWork(): Result {
        val delegateName = inputData.getString(DELEGATE_WORKER_NAME) ?: return Result.FAILURE
        val delegateKlass = Class.forName(delegateName) as? Class<out Worker> ?: return Result.FAILURE
        val period = inputData.getLong(PERIOD, 15)
        // build your worker with the constraints you want.
        val request = PeriodicWorkRequest.Builder(delegateKlass, period, TimeUnit.MINUTES)
                .setInputData(inputData)
                .build()
        WorkManager.getInstance()
                .enqueue(request)

        return Result.SUCCESS
    }
}

class PeriodicWorker: Worker() {
    override fun doWork(): Result {
        // Do some periodic work
        return Result.SUCCESS
    }
}

// You want to delay the PeriodicWorker. You can use initial delay on the DelegateWorker, which in
// turn enqueue's PeriodicWorker.

val data = mapOf(DelegateWorker.DELEGATE_WORKER_NAME to PeriodicWorker::class.java.name).toWorkData()
val delayedPeriodicWorkRequest = OneTimeWorkRequestBuilder<DelegateWorker>()
        .setInitialDelay(10, TimeUnit.SECONDS)
        .build()

WorkManager.getInstance()
    .enqueue(delayedPeriodicWorkRequest)

The idea is to create a OneTimeWorkRequest with an initial delay, which in turn calls an enqueue() on the PeriodicWorkReqeust.

This looks like a hack, instead of just adding setInitialDelay method on the periodic worker that will just run once.

I have tried going the route of the OneTimeWorkRequest with an initial delay that triggers a PeriodicWorkRequest but it doesn't seem to work. It would be much nicer to be able to add a simple delay to the first occurence.

#3: This is exactly what an internal implementation would look like because the backing JobScheduler does not support initial delays on periodic work.  I realize that WorkManager doing it for you is nicer, which is why this feature request is still open, but it may take us some time to get to it.

#4: Please file a separate bug if that doesn't work for you.

#5: How could I debug the behaviour of this chain of Work?

Use logcat, or use the various getStatus methods to see what's going on.  File a bug with a bugreport and sample code that results in the problem.

It would be nice to see setInitialDelay() on PeriodicWorkRequest.Builder in the next version, Thanks

Just a "+1" "me too" to add another voice to this... would make so much sense to be able to have setInitialDelay() on PeriodicWorkRequest.Builder

Android must list down the challenges of Periodic Work request  in there documents, I am  tracking Work Manager since it was alpha.Here are the limitations of Priodic Work request:
1. Periodic work request does not support setInitialDelay.
2. Periodic Work request does not support the Chining.

Both of these items are listed in the official documentation for PeriodicWorkRequest: https://developer.android.com/reference/androidx/work/PeriodicWorkRequest

"Periodic work has a minimum interval of 15 minutes and it cannot have an initial delay."
"Periodic work cannot be part of a chain or graph of work."

Still not supported...
I feel that many people need it...would make so much sense to be able to have setInitialDelay() on PeriodicWorkRequest.Builder

Setting a flex period effectively delays a PeriodicWorkRequest.

+1 from me too, with an extra option to limit the number of repeats, for example, run a periodic job daily for 7 days and then stop.

+1 for setInitailDelay() and limitNumberOfFires() for Periodic work request!

What is the best solution for now to setInitailDelay() ?

You can use a PeriodicWorkRequest.Builder with a flex Period as suggested in #13.
This behaviour is documented: https://developer.android.com/reference/androidx/work/PeriodicWorkRequest.Builder#PeriodicWorkRequest.Builder(java.lang.Class%3C?%20extends%20androidx.work.ListenableWorker%3E,%20long,%20java.util.concurrent.TimeUnit,%20long,%20java.util.concurrent.TimeUnit)

The call creates a PeriodicWorkRequest to run periodically once within the flex period of every interval period.

What I mean by setInitailDelay() is the delay before the first run then a fixed periodic delay.

Project: platform/frameworks/support
Branch: androidx-master-dev

commit 25dc21990f5b0d606f3141b9120516b880599b6c
Author: Rahul Ravikumar <rahulrav@google.com>
Date:   Mon Apr 29 10:27:18 2019

    Add support for initialDelays for PeriodicWorkRequests.
   
    Test: Additional WorkSpecTest unit tests.
    Integration tests on API 23, and API 21.
   
    Fixes: b/111404867
   
    Change-Id: I9eae1c7cf527c231b831f22c6a2d10089d6a63c9

M       work/integration-tests/testapp/src/main/java/androidx/work/integration/testapp/MainActivity.java
M       work/integration-tests/testapp/src/main/res/layout/activity_main.xml
M       work/integration-tests/testapp/src/main/res/values/strings.xml
M       work/workmanager/api/2.1.0-alpha01.txt
M       work/workmanager/api/current.txt
M       work/workmanager/src/androidTest/java/androidx/work/WorkSpecTest.java
M       work/workmanager/src/main/java/androidx/work/OneTimeWorkRequest.java
M       work/workmanager/src/main/java/androidx/work/WorkRequest.java
M       work/workmanager/src/main/java/androidx/work/impl/WorkerWrapper.java
M       work/workmanager/src/main/java/androidx/work/impl/background/systemjob/SystemJobScheduler.java
M       work/workmanager/src/main/java/androidx/work/impl/model/WorkSpec.java

https://android-review.googlesource.com/953484
https://goto.google.com/android-sha1/25dc21990f5b0d606f3141b9120516b880599b6c

still can't rely on it :(
I calculate millis to midnight and schedule a daily backup with PeriodicWorkRequest (should happen each 24h), and it just won't fire up the Worker.
When I remove setInitialDelay() call, PeriodicWorkRequest - it works!

classic