I am planning to have a large collection containing items that need to be processed by a Quartz/cron job. So the cron job will set to run periodically and access mongodb to find the 5 oldest items and process them.
This would be ok for a single server running the cron job. But, later on if i run 2 servers each running the same cron job, I fear that the 2 cron jobs may run at same time and grab 5 same items which may lead to race condition issues.
What is the best practice to avoid this problem?
I'm thinking of putting logic to each job to grab the 5 oldest items that have PENDING status, then immediately change the status to PROCESSED so that other jobs cannot process them. Do you think this will work?
The same issue I got using quartz scheduler.
You have to involved data base. I am sharing the GitHub link so you can follow the given code.
https://github.com/faizakram/Spring_MongoDb_Quartz_Cluster
Any confusions please comment so I can improve my way to understand
Thanks
Related
I did an application to do some testing on network nodes like ping test, retrieve disk space ans so on.
I use a scheduled batchlet to run the actions but I wonder if it is the rigth use of batchlet?
Does an EJB timer should be more relevant? Also, when I run a batchlet, my glassfish server keeps a log of the batch job and I don't necessary need it (especially with the amount of batch jobs genereted during a day).
If I need to run some job in the same schedule time, I think batchled can do it but EJB timer too?
Could you give me your input on the rigth way to achieve this?
Thanks,
Ersch
This isn't a question with a clear answer, but there is a bit of a cost in factoring your application as a batch job, and I would look at what I'm getting to see if it's worth doing so.
So you're thinking about a job consisting of a single Batchlet step. Well, there'd be nothing gained from "restart" functions, neither at the failing step within a job nor leveraging checkpoints within a chunk step. The batchlet programming model is quite simple... even if you really like #BatchProperty you'd have to deal with an XML now to do so.
This only starts to get more interesting if you want to start, view, and manage these executions along with the rest of your batch jobs. This might be because you're working with an implementation that offers some kind of implementation-specific add-on function. An example of this could be an integration with external scheduler software, allowing jobs to be scheduled by it. At the other extreme, if you found value in having a persisted record of all your batch job executions in one place (the job repository, usually a persistent DB), then that could also make this worthwhile for you.
But if you don't care for any of that, then an EJB timer could be the way to go instead.
Using an EJB timer is appropriate when your task executes in an eye blink (or thereabouts).
Otherwise use the batching mechanism.
Long running tasks executed from EJB timers can be problematical because they execute in transactions which normally time out after a short period of time. Increasing this transaction time out also increases the chances of database and perhaps other resource locks which can impact normal operation of your application.
I've got a Spring Web application that's running on two different instances.
The two instances aren't aware of each other, they run on distinct servers.
That application has a scheduled Quartz job but my problem is that the job shouldn't execute simultaneously on the instances, as its a mail sending job, it could cause duplicate emails being sent.
I'm using RAMJobStore and JDBCJobStore is not an option for me due to the large number of tables it requires.(I cant afford to create many tables due to internal restriction)
The solutions I thought about:
-creating a single control table, that has to be checked everytime a job starts (with repeatable read isolation level to avoid concurrency issues) The problem is that if the server is killed, the table might be left in a invalid state.
-using properties to define a single server to be the job running server. Problem is that if that server goes down, jobs will stop running
Has anyone ever experienced this problem and do you have any thoughts to share?
Start with the second solution (deactivate qartz on all nodes except one). It is very simple to do and it is safe. Count how frequently your server goes down. If it is inacceptable then try the first solution. The problem with the first solution is that you need a good skill in mutithreaded programming to implement it without bugs. It is not so simple if multithreading is not your everyday task. And a cost of some bug in your implementation may be bigger than actual profit.
I have a Java/Database project in Netbeans that I would like to run once a day at a set time. I am using Derby for the database driver. I am trying to automate a process.
How can I 'schedule' this program to run at specified times?
How can I customize this to keep running until a certain criteria is met?
Say my criteria is that It has to populate 500 rows in the database. (So say at the scheduled time it runs it can only populate 400 rows, then maybe 2 hours later it tries running again to fill the last 100 rows)
Lastly, what are the best practices of automation and scheduled tasks?
How can I 'schedule' this program to run at specified times?
This can be done one of two ways, depending on your operating system - write a job that kicks off the java program at the intervals you need. You may then hook up the job to be started off on start up.
In Linux you can accomplish this with a cron job or so. On windows you may refer to this http://support.microsoft.com/kb/308569.
You may also program the scheduler into your java program using http://quartz-scheduler.org or http://www.sauronsoftware.it/projects/cron4j/ .
How can I customize this to keep running until a certain criteria is met?
This is perhaps best established from within your program, although it is hard to give you directions without much info.
Lastly, what are the best practices of automation and scheduled tasks?
Depending on your application architecture, scheduling and automation can be handled either from within the app or get support from the operating system. The criteria depends on how much control the application needs, which platform makes scheduling easy etc.
Hope this helps.
Quartz is a scheduling project for Java. I have used it in many projects and find it to be very intuitive.
It may be a little over the top for what your after but worth a look anyway.
You can make use of Timer for scheduling the events & the events/task must be implemented using TimerTask
I am working on an application in which I want multiple tasks to be executed simultaneously.
I also want to be able to keep track of the number of such tasks being run in parallel, and sometimes add yet another task to be processed in parallel, in addition to the current set of tasks already being processed.
One more thing- I want to do the above, not only in a desktop app, but also in a cloud app, in which I initialise another virtual machine running Tomcat, and then repeat all of the above in that instance.
What is the best way to do this? If you can point me to the correct theory/guides on this subject, that would be great, although code samples are also welcome.
Concurrency is a huge topic in Java, please take your time for it
Lesson: Concurrency
Concurrency in a Java program is accomplished by starting your own Threads. Multiple processes can only be realized with multiple JVMs. When you are done with the basics, you want to take a look at Executors. They will help to implement your application in a structured way since they abstract from Threads to Tasks.
I don't know how much time you have planned for this, but if you are really at the start, get Java Concurrency in Practice, read it and write a kick-ass concurrent Java application.
Raising the whole thing to a distributed level is a whole other story. You cannot tackle that all at once.
Wow... What a series of steps. Start by extending Runnable, then using Thread to run and manage your Jobs. After that, you can get into Tomcat.
I have a general question related to the quartz scheduling framework:
I need to perform a task after a fixed amount of time after a user registration. For the sake of simplicity let's say exactly 1 hour after registration of a user in my system. The job MUST be done, even if the system is restarting during this one hour the task must be remembered and it MUST be performed later if my system is down at the usual time.
Is this something where I can or where I would use Quartz? I looked at persistent jobs which looks quite promising but I am not sure if this will still work out for 1000 jobs a day. Furthermore, I am not sure about the performance implications. Maybe someone can help me with information here.
If Quartz is not the right choice, which other ways/frameworks do you see for this issue? My application is a Java 6/Spring 3 based Web-App.
Thanks for your help!
We are using quartz persisted job store successfully in our production environment for a SaaS platform application where 100s of jobs are running.