Clowder supports scheduling of repetitive tasks by executing a job registered in MongoDB jobs Collection. The only implemented job as of August 2016 is EmailDigest triggered by setting an e-mail option in user's profile page as seen in Figure below. Selecting hourly, daily or monthly option in the pull down menu creates a job called Digest('userId') in the database which is then executed at pre-defined times, currently at the top of an hour (hourly), at 7:00 am (daily) or every Monday at 7:00 am (weekly). 

Implementation

A jobTimer in the Clowder calls JobsScheduler.runScheduledJobs() every minute. This is done from Akka.system().scheduler.schedule in app/Global.
This time is then split into minute, hour, day_of_week, day_of_month variables in the JobsScheduler (app/models/JobsScheduler.scala) for further use in the code and for jobs’ execution and maintenance.
The time variables are compared with a set of integers stored in every job object in the MongoDB Collection (jobs). In other words the time comparison is done by integer equality. A job gets fired hourly when minute=minutejob if no other values of hour, day_of_week, day_of_month are defined. Similarly, the job gets executed with minutes and hours set (daily) when  minute=minutejob and hour=hourjob (no other values of day_of_week, day_of_month are defined) etc. Note that there is no verification of time inserted in the system, nor there is time/date object comparison.

A job model in Clowder is called TimerJob (app/models/TimerJob.scala). A programmer can create different job schema but the TimerJob is sufficient for the most repetitive tasks.
A full time, or only subset of it is set in the TimerJob with minute (0-59), hour (0-23), day_of_week (1-7 for Monday-Sunday) and day_of_month (1-31) precision. An option frequency is meant to be ‘hourly’, ‘daily’, ‘weekly’, ‘monthly’ but can be any descriptive string. The lastJobTime field is useful for  getting the time interval since the last job call (set by scheduler.updateLastRun(‘jobName’)). Additionally, parameters can be used for any object id, function is a string describing action (e.g. EmailDigest).

Creating and calling a new timer job

Create and update job

  1. A new TimerJob job is created and set in the MongoDB Collection by newly coded functions in app/services/ScheduleService and app/services/mongoldb/MongoDBSchedulerService.scala called for example  updateMyJob():

    def updateMyJob(id: UUID, name: String, setting: String)

    and

    def updateMyJob(id: UUID, name: String, setting: String) = {
  if (jobExists(name) == false) {
      Jobs.insert(new TimerJob(name, None, None, None, None, Option(‘function’), Option(id), None, Option(new Date())))
  }
  if (setting == "hourly"){
    updateJobTime(name, Option(0), None, None, Option(setting))
  }
  else if (setting == "daily"){
    updateJobTime(name, Option(0), Option(7), None, Option(setting))
  }
  else if (setting == "weekly"){
    updateJobTime(name, Option(0), Option(7), Option(1), Option(setting))
  }
  else {
    deleteJob(name)
  }
}

    This is similar to a function updateEmailJob() already implemented in the Clowder where  updateJobTime(name, Option(0), Option(7), Option(1), Option(setting)) refers tot the time set to minute=0, hour=7 and day_of_week=1 (Monday) in the database as mentioned above. When Clowder time matches the values the job is returned from the database and Action is fired.
    You can either change time directly in the code or pass the time values from a Play template as additional parameters such as:

    def updateMyJob(id: UUID, name: String, setting: String, minute: Integer)= {
    updateJobTime(name, Option(minute), None, None, Option(setting))
}

  2. from the Play request or directly in Scala on the server side call your job update:
    scheduler.updateMyJob(id, name, setting)
    here the id is a parameters id (parameters: Option[UUID], see TimerJob model), name is the job's name and settings are used to  distinguish time frequency (from options of pull down menus for example - hourly, weekly etc.)

Call and get job

  1. Create function getMyJobs() in app/models/JobsScheduler.scala to get your job (TimerJob) at a certain time

    def getMyJobs (minute: Integer, hour: Integer, day_of_week: Integer) = {
   var myJobs = scheduler.getJobByTime(minute, hour, day_of_week)
   myJobs
}

    and register it with runScheduledJobs()

    var myJobs = getMyJobs(minute.toInt, hour.toInt, day_of_week.toInt)
myAction.myActionJob(myJobs)

  2. Create a new class myAction.scala for example in a package models (see models/Event.scala as an example)

    package models

import java.util.Date
import services.SchedulerService
import services.DI

object myAction {
val scheduler: SchedulerService =  DI.injector.getInstance(classOf[SchedulerService])
val objects: ObjectService =  DI.injector.getInstance(classOf[ObjectService])
 /**
  * ‘Do something’ for each job returned by getMyJobs
  */
 def myActionJob(listJob: List[TimerJob]) = {
   for (job <- listJob){
     job.parameters match {
       case Some(id) => {
         objects.findById(id) match {
           case Some(object) => {
             job.lastJobTime match {
               case Some(date) => {
                 ‘Do something’
               }
               case None => Logger.debug("LastJobTime not found")
             }
           }
           case None => Logger.debug(“Object not found")
         }
         scheduler.updateLastRun(‘jobName’) //sets job’s name for example ”myJob[“ + id + "]")
       }
       case None => Logger.debug("Parameters not found")
     }
   }
 }

    The ObjectService  above, for example called UserService in the case of sending email digest and the user id was used as a parameter in the TimerJob and MongoDB job objects.

  3. implement 'Do something' in myActionJob() (smile)

Note

The day_of_month variable is part of the TimerJob model but it is not used in the scheduler.getJobByTime()
Adding it is straightforward:

Testing

  1. Disable scheduler.updateLastRun(‘jobName’) in myAction.scala (or in models/Event.scala for sending email digests) by commenting it out. Your events (followed objects for example) will become 'permanent' and the timer job will always execute since there is no update of the lastJobTime variable in the MongoDB job object. Don't forget to enable the updateLastRun() when you are done debugging.

  2. Set the time variables in getJobByTime() in app/services/mongoldb/MongoDBSchedulerService.scala to those saved in the MongoDB job object. The job action will fire every minute since the integer equality is always true. For example for the pre-defined e-mail times (minute=0, hour=7 and day_of_week=1) set getJobByTime()

    def getJobByTime(minute: Integer, hour: Integer, day_of_week: Integer, day_of_month: Integer): List[TimerJob] ={
    val jobs = Jobs.find(
      $and(
        $or($and("day_of_week" $exists true, MongoDBObject("day_of_week" -> 1)), "day_of_week" $exists false),
        $or($and("hour" $exists true, MongoDBObject("hour" -> 7)), "hour" $exists false),
        $or($and("minute" $exists true, MongoDBObject("minute" -> 0)), "minute" $exists false)
      )
    )

    Again, don't forget to reverse changes when you are done debugging.

  3. Testing e-mail digest