CODEWITHSUNDEEP
jpaplayframework
Joshua Gunder
Joshua Gunder

Reputation: 245

Play Model save function isn't actually writing to the database

I have a play model called "JobStatus" and it's just got one property, an enum with a JobState, (Running/notRunning).

The class extends model and is implemented as a singleton. You call it's getInstance() method to get the only record in the underlying table.

I have a job that runs every month and in the job I will toggle the state of the JobStatus object back and forth at various times and call .save().

I've noticed it isn't actually saving.

When the job starts off, it's first line of code is 

JobStatus thisJobStatus = jobStatus.getInstance();
...// exit if already running

thisJobStatus.JobState = JobState.Running;
thisJobStatus.save()

then when the job is done it will change the status back to NotRunning and save again.

The issue is that when I look in the MySql database the actual record value is never changed.

This causes a catastrophic failure because when other nodes try to run the job they check the state and since they're seeing it as NotRunning, they all try to run the job also.

So my clever scheme for managing job state is failing because the actual value isn't getting commited to the DB.

How do I force Play to write to the DB right away when I call .save() on a model?

Thanks Josh

Upvotes: 3

Views: 503

Answers (2)

Tommi
Tommi

Reputation: 8608

I suppose you want to mark your job as "running" pretty much as the first thing when the job starts? In that case, you shouldn't have any other ongoing database statements yet...

To commit your changes in the database immediately (instead of after the job has ended), add the following commands after the thisJobStatus.save(); method call:

JPA.em().flush();
JPA.em().getTransaction().commit();

Additionally, since you're using MySQL, you might want to lock the row immediately upon retriveval using the SELECT ... FOR UPDATE clause. (See MySQL Reference Manual for more information.) Of course, you wouldn't want to have that in your getInstance() method, otherwise every fetch operation would lock the record.

Upvotes: 0

emt14
emt14

Reputation: 4896

try adding this to your JobStatus and call it after save.

public static void commit(){
    JobStatus.em().getTransaction().commit();
    JobStatus.em().getTransaction().begin();
    JobStatus.em().flush();
    JobStatus.em().clear();
}

Upvotes: 3

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