> > Are you sure? > My (possibly flawed) understanding is that if you can make the change in > a single transaction, no-one else can see what is happening until it is > committed. Effectively that would be an instantaneous change. > Depending on your data architecture you might need to make some parts > read-only for the 30 minutes prior to committing.
The transaction can be atomic if it is a database such as PostgreSQL that offers DDL changes in a transaction. The issue is that rather than updating the code for the web application in place, and then running migrations, my CI/CD pipeline will instead bring up an entirely new set of servers. This makes a more isolated change to the environment, and deployment also will take care of OS patching and such, but the old web servers will still be online and querying the database. They may will be querying a column that no longer exists, which is a form of "Read after Write" synchronization problem. I think with an alternative CI/CD, in the cloud or elsewhere, this would not be an issue. -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscr...@googlegroups.com. To post to this group, send email to django-users@googlegroups.com. Visit this group at https://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/CAFzonYbMEJ4k43%2BjxnSOojOgTMO9Y6%3Dc5W2DCrCWrNnsRMuEeQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
