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Android Things - UpdatePolicy not applied

I'm programming an update interface in my Android Things project. I can do manual update, with an user input. But I'm trying to schedule an auto-update every night at midnight. I want to use a custom UpdatePolicy with a deadline but I failed to use it.
I tried this in the onCreate method in my activity :
mUpdateManager.setPolicy(
new UpdatePolicy.Builder()
.setPolicy(POLICY_APPLY_AND_REBOOT)
.setUpdateDeadline(10, TimeUnit.SECONDS)
.build());
But there isn't any update after 10 seconds.
Maybe, I don't understand the deadline.
Do I use it wrong ?

The deadline has nothing to do with when an update check is performed. The usual schedule of update checks is
once shortly after boot
once every 5 hours (approximately) thereafter
(These times are not exact for reasons that aren't relevant to this discussion.)
The deadline reflects how long the device will let an available update sit without being applied before the device will force it to apply and reboot. The device doesn't know about an available update until it performs a check, so you could be waiting up to 5 hours for that.
The deadline is meant to operate on a longer timescale (for instance, 5 days, a week, etc). This is useful as a fallback in case there's some kind of bug with the update scheduler, or in case you allow users to postpone the update but don't want them to be able to do that forever.
To achieve what you want, you should schedule (using WorkManager, JobScheduler, etc) a task that runs at midnight each day and calls UpdateManager.performUpdateNow(UpdatePolicy.POLICY_APPLY_AND_REBOOT)
TL,DR: Update checks are very much a background thing. If you care about timing at all, use UpdateManager.performUpdateNow, but no more than once every 5 hours.

Spring Boot - check if target date is reached for objects

I don't know if it's a real question or not... But i'd like to know how some of you will approach this...
I have a Spring Boot application.
Then I have a Interruttore.class, which has, among others this field timeoutDatewhich is a Date.
In the app, various instances of this class are used. The timeoutDate field can be updated, for every single object, by various factors. I need to know when the actual date reaches the timeutDate.
In a very simple (and not optimized) way i would have created a #Scheduled task, but the delay will be too short and i don't like it, how can i do?

In a very simple (and not optimized) way i would have created a
#Scheduled task, but the delay will be too short and i don't like it,
how can i do?
Why too short ?
You can use the delay you wish.
#Scheduled(fixedDelay=50000) // 50 secs
#Scheduled(fixedDelay=1000) // 1 secs

Look at the documentation for Spring's various task scheduling APIs: http://docs.spring.io/spring/docs/current/spring-framework-reference/html/scheduling.html
You have plenty of choices. I think the "not optimised" idea you might have is to schedule a repeating task which searches your beans to find the expired ones. That would indeed be inefficient for large numbers of beans.
You could simply create a scheduled task for each bean with a timeoutDate, created at the same time as that bean, and when its timeoutdate is updated (Spring AOP could help with this).
Alternatively you could keep a list of beans, sorted by timeout date. Schedule a task for the time of the earliest expiry. It reaps that bean and any others who's time is past, then schedules a new task for the time of the next expiry.
If you do this, you need to make sure that:
- it handles new objects added to the list (perhaps with an expiry date earlier than the currently scheduled cull)
- it handles the case where an object is removed for a reason other than a timeout
(Unless neither of those things can happen -- in which case don't worry about it!)

You can use Quartz or Jesque(redis). Whatever task needs to be executed, you can schedule that task at that time.
If this time value can be updated anytime, you can cancel(unschedule) the previously scheduled task(using task identifiers or keys) and reschedule it with the updated time.

schedule event run after 2 hour

My app is an Android app for booking tables.so the app directly communicating with the server.I need to call a specific event that is generated by the Android app.say an item is purchased by the Android app, so I need to hold that item for 2 hour so no one can use that item.i'm thinking change the flag inside the database to not available. After the use that is after 2 hour I need to release the item for the other users.
I know from trigger will done the job but is it possible to delete the crown trigger from the table and remove the scheduling.

Why would you hold/release like that? It doesn't seem robust... if there's some kind of communication error, the bike could get hung up permanently. I would run something based off timestamps and calculate the bike's availability in realtime based on the date. These calculations are going to be cheap to do.

If you want to handle this on the client side then you have to do it using AlarmManager, schedule an event to make an api call or just release it locally. But as u said cron job will be a better way to do it where u update the db after 2 hrs.

If you want to run particular Rest API
, after every 2 hr , You can either set Repeating ALARM , or you can user Timer and Timer Task
OR
If you want to just notify the user after 2 hr,
Then you can use cron-trigger with cloud messaging like FCM (firebase clod messaging )

EJB timer performance

I am trying to decide if use a java-ee timer in my application or not. The server I am using is Weblogic 10.3.2
The need is: After one hour of a call to an async webservice from an EJB, if the async callback method has not been called it is needed to execute some actions. The information regarding if the callback method has been called and the date of the execution of the call is stored in database.
The two possibilities I see are:
Using a batch process that every half hour looks for all the calls that have been more than one hour without response and execute the needed actions.
Create a timer of one hour after every single call to the ws and in the #Timeout method check if the answer has come and if it has not, execute the required actions.
From a pure programming point of view, it looks easier and cleaner the second one, but I am worry of the performance issues I could have if let's say there are 100.000 Timer created at a single moment.
Any thoughts?

You would be better off having a more specialized process. The real problem is the 100,000 issue. It would depend on how long your actions take.
Because its easy to see that each second, the EJB timer would fire up 30 threads to process all of the current pending jobs, since that's how it works.
Also timers are persistent, so your EJB managed timer table will be saving and deleting 30 rows per second (60 total), this is assuming 100K transactions/hour.
So, that's an lot of work happening very quickly. I can easily see the system simply "falling behind" and never catching up.
A specialized process would be much lighter weight, could perhaps batch the action calls (call 5 actions per thread instead of one per thread), etc. It would be nice if you didn't have to persist the timer events, but that is what it is. You could almost easily simply append the timer events to a file for safety, and keep them in memory. On system restart, you can reload that file, and then roll the file (every hour create a new file, delete the older file after it's all been consumed, etc.). That would save a lot of DB traffic, but you could lose the transactional nature of the DB.
Anyway, I don't think you want to use the EJB Timer for this, I don't think it's really designed for this amount of traffic. But you can always test it and see. Make sure you test restarting your container see how well it works with 100K pending timer jobs in its table.

All depends of what is used by the container. e.g. JBoss uses Quartz Scheduler to implement EJB timer functionality. Quartz is pretty good when you have around 100 000 timer instances.

#Pau: why u need to create a timer for every call made...instead u can have a single timer thread created at start up of application which runs after every half-hour(configurable) period of time and looks in your Database for all web services calls whose response have not been received and whose requested time is past 1 hour. And for selected records, in for loop, it can execute required action.
Well above design may not be useful if you have time critical activity to be performed.
If you have spring framework in your application, you may also look up its timer services.http://static.springsource.org/spring/docs/1.2.9/reference/scheduling.html

Maybe you could use some of these ideas:
Where I'm at, we've built a cron-like scheduler which is powered by a single timer. When the timer fires the system checks which crons need to run using a Quartz CronTrigger. Generally these crons have a lot of work to do, and the way we handle that is each cron spins its individual tasks off as JMS messages, then MDBs handle the messages. Currently this runs on a single Glassfish instance and as our task load increases, we should be able to scale this up with a cluster so multiple nodes are processing the jms messages. We balance the jms message processing load for each type of task by setting the max-pool-size in glassfish-ejb-jar.xml (also known as sun-ejb-jar.xml).
Building a system like this and getting all the details right isn't trivial, but it's proving really effective.

How to trigger alerts based upon timestamps in database?

Scenario:
There's a task-manager application that allows its users to create tasks and associate a timestamp with it.
Goal:
The application is supposed to send email alerts to the users at the time when any of their tasks are due.
Question:
If there's a function in the application sendEmailAlerts, which queries database, fetches all those tasks which are due now, and send their creators alerts; is it possible to trigger this function exactly at the moment when a task is due?
The approach that I have in mind is to use a Quartz job, that would run every x minutes and invoke sendEmailAlerts. But this approach doesn't seem very efficient. Is there any better way of doing it?
Thank you for your help.

You could use SQL Server Agent to create a job to execute at a specified time, although in this scenario i don't think it's optimal to create x jobs for x alerts.