CODEWITHSUNDEEP
djangodatabasetransactionsrollback
sulimmesh
sulimmesh

Reputation: 763

Use atomic blocks with error handling in Django

I have a Django 1.9 application that is running a section of code where changes are made to the database based on the results of queries to certain remote APIs. For instance, this might be data about commits, file changes, reviewers, pull requests, etc. that I want to save as entities in my database. 

commit_data = commit_API_client.get_commit_info(argument1, argument2)
new_commit = models.Commit.Create(**commit_data)

#if the last API failed, this will fail
#I will need to run this again to get these files, so I need
#to get the commit all over again, too
files = file_API_client.get_file_info(new_commit.id)
new_files = models.Files.Create(**files)

#do some more stuff here

It's very possible that one of the few APIs I'm calling will return some error instead of valid data. I essentially need to make this section into a single atomic transaction so that if there are no errors returned from the HTTP requests, I commit all the changes to the database. Otherwise, I might lose some data if 2 APIs return correctly, but the 3rd doesn't.

I saw that Django supports commit hooks for database transactions, but I was wondering if that would applicable to this situation and how I would go about implementing that.

Upvotes: 2

Views: 1470

Answers (1)

Kevin Christopher Henry
Kevin Christopher Henry

Reputation: 49012

If you want to make that into an atomic operation, just wrap it in transaction.atomic(). If any of your code raises an exception the whole block will roll back. If you're only doing reads from the remote API that should work fine. A typical pattern is:

def my_function():
    try:
        with transaction.atomic():
            # Do your work here
            pass
    except Exception:
        # Do some error handling
        pass

Django does have an on_commit hook, but that isn't really applicable here. Its purpose is to run some code after a transaction has completed successfully. For example, you might use it to write some log data to a remote API if the transaction was successful.

Upvotes: 6

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