I need to execute a call to a particular method daily or more, considering that the app may and the machine may reboot.
I saw examples where they just put the thread to sleep but I need persistance, managing system rebooting.
I have to be sure that if I switch off my machine when I reboot it reprises task execution.
I found schedulers as cron4j and quartz but don't get if it's possible, and if it is, how to do that.
With Quartz you will only need to configure it with a persistent job store implementation and that is pretty much all there is to it. I suggest that you read through the Quartz scheduler tutorial, especially the chapter that describes Quartz job stores.
Related
I am using quartz to schedule jobs to be executed daily as a part of a much larger web application. However, after a couple of days, the administrator would like to stop the execution of a particular job (maybe because it is no longer needed). How do I go about doing this? I read the api docs for the Scheduler and it has a method called interrupt(JobKey jobkey) but that method would work only with the same instance of the scheduler that was used to schedule the job.
interrupt(JobKey jobKey)
Request the interruption, within this Scheduler instance, of all
currently executing instances of the identified Job, which must be an
implementor of the InterruptableJob interface.
Is there anyway of getting the instance of an existing scheduler? Or maybe use singletons?
Should definitely use a singleton instance of your scheduler. I recommend the use of an IoC container to manage this in a clean and efficient way.
I have looked at the documentation on both, but am not sure what's the best choice for a given application. I have looked closer at celery, so the example will be given in those terms.
My use case is similar to this question, with each worker loading a large file remotely (one file per machine), however I also need workers to contain persistent objects. So, if a worker completes a task and returns a result, then is called again, I need to use a previously created variable for the new task.
Repeating the object creation at each task call is far too wasteful. I haven't seen a celery example to lead me to believe this is possible, I was hoping to use the worker_init signal to accomplish this.
Finally, I need a central hub to keep track of what all the workers are doing. This seems to imply a client-server architecture rather than the one provided by Celery, is this correct? If so, would IPython Parallel be a good choice given the requirements?
I'm currently evaluating Celery vs IPython parallel as well. Regarding a central hub to keep track of what the workers are doing, have you checked out the Celery Flower project here? It provides a webpage that allows you to view the status of all tasks in the queue.
I'd like to move my scheduled tasks into workflows so I can better monitor their execution. Currently I'm using a Window's scheduled task to call a web service that starts the process. Is there a facility that you use to schedule execution of a sequence so that it occurs every N minutes?
My optimal solution would:
Easy to configure
Provide useful feedback on errors
Be 'fire and forget'
PS - Trying out AppFabric for Windows Server if that adds any options.
The most straightforward way I know of would be to make an executable for each workflow (could be console or windows app), and have it host the workflow through code.
This way you can continue to use scheduled tasks to manage the tasks, the main issue is feedback/monitoring the process. For this you could output to console, write to the event log, or even have a more advanced visualisation with a windows app - although you'd have to write this yourself (or google for something!). This MS Workflow Monitoring sample might be of interest, haven't used it myself.
Similar deal with errors, although writing to the event log would be the normal course of action in this case.
I'm not aware of any other hosts for WF, aside from things like Dynamics CRM, but that won't help you with what you're trying to do.
You need to use a scheduler. Either roll your own, use AppFabic as mentioned or use Quartz.NET:
http://quartznet.sourceforge.net/
If you use Quartz, it's either roll your own service host or use the ready-made one and configure it using xml. I rolled my own and it worked fine.
Autorun is another free option... http://autorun.codeplex.com/
I have a building block which sets up a Quartz job to send out emails every morning. The job is fired three times every morning instead of once. We have a hosted instance of Blackboard, which I am told runs on three virtual servers. I am guessing this is what is causing the problem, as the building block was previously working fine on a single server installation.
Does anyone have Quartz experience, or could suggest how one might prevent the job from firing multiple times?
Thanks,
You didn't describe in detail how your Quartz instance(s) are being instantiated and started, but be aware that undefined behavior will result if you run multiple Quartz instances against the same job store database at the same time, unless you enable clustering (see http://www.quartz-scheduler.org/docs/configuration/ConfigJDBCJobStoreClustering.html).
I guess I'm a little late responding to this, but we have a similar sort of scenario with our application. We have 4 servers running jobs, some of which can run on multiple servers concurrently, and some should only be run once. As Will's response said, you can look into the clustering features of Quartz.
Our approach was a bit different, as we had a home-grown solution in place before we switched to Quartz. Our jobs utilize a database table that store the cron triggers and other job information, and then "lock" the entry for a job so that none of the other servers can execute it. This keeps jobs from running multiple-times on the servers, and has been fairly effective so far.
Hope that helps.
I had the same issue before but I discovered that I was calling scheduler.scheduleJob(job, trigger); to update the job data while the job is running which is randomly triggered the job 5-6 times each run. I had to use the following to update the job data without updating the trigger scheduler.addJob(job, true);
I have several web-servers and need them to use Quartz. The clustering feature of Quartz would be ideal, but it requires that the servers clocks are in complete sync. They have a very scary warning about this:
Never run clustering on separate machines, unless their clocks are synchronized using some form of time-sync service (daemon) that runs very regularly (the clocks must be within a second of each other).
I cannot guarantee complete clock synchronization, so instead of using the clustering feature I was thinking to have a single Quartz instance (with a stand-by for fail-over). Having a single instance executing jobs is not a problem, but I still need all of the web servers to be able to schedule jobs.
Can I directly add jobs into the JDBCJobStore from the web servers, and will they be picked up by the (non-clustered) Quartz server? I would be doing this by creating schedule instances in the web servers to add jobs. These instances would never be started, just used to access the JobStore.
Wrote a test program that creates a "non-clustered" Quartz scheduler using the same JobStore as the "real" scheduler (also non-clustered), and schedules jobs. After a few seconds, these jobs do get executed, so it seems to work.
Update: I cross-posted this question to the Quartz forum, and got the answer that this should work. In a related question they state that
The jobs can be inserted into that database by another process by:
1- using the rmi features of quartz from another process, and using the quartz API
2- instantiating a scheduler within another process (e.g. webapp), also pointing it to the same database, but NOT start()ing that scheduler instace, and the using the quartz api to schedule jobs.