mysql database update possible timing issue I have a strange situation.
I have a cronjob running queue tasks one after the other. I have a delay of 1s between the tasks.

After a task is run, it sets processed=1, and continues with the next one, that has processed=0.

I have some situations where a task is executed twice. This means that processed=1 was set, but when we read again for processed=0, it finds it.

I use PHP, and ->execute(). Is it possible changes in the database not to be reflected immediately for some reasons?
The issue was that since the queue run for 1 minute, there were cases that one cronjob was not finished yet, and another was starting. So they were processing the same tasks from the database.

The solution is to run cronjob using flock(), thus making sure that only 1 is run:

* * * * * /usr/bin/flock -n /tmp/fcj.lockfile /usr/local/bin/frequent_cron_job