I have two Django Projects that have different use cases. There are reached using different domains. They are hosted in two different servers. Also each Django project has it's own database.
Now, both the projects have some models and some business logic common between them. I don't want to duplicate the code and data which shall be chaotic going forward. Also, I want the models and code (business logic) to be in sync (when models/code is altered).
Can anyone guide me towards a pattern that can help me attain the required architecture: 2 separate projects with common models and business logic.
Thanks in advance.
I've done this before. You will have to move the shared models and business into a new python package (better if you can create a django app that encapsulates these models), in a separate directory.
Add this directory to your python path (the one that contains the package, not the package itself) and you should be able to use this code from within your projects.
The only downside to this is having to configure PYTHON_PATH in your servers or having to copy manually this package into your runtimes
Related
I've been reading through related articles regarding using same database for multiple django projects however, I have not been able to come up with a fix yet.
I've tried relative and absolute pathing when importing but it gives "attempted relative import beyond top-level package" error when I try to access parent directory.
Project 1 gets the users to write to database by filling in a form and Project 2 retrieves data written in by users from database.
I'm using Postgresql for database. I've tried writing exactly same models.py for both projects but it seems like in database they appear as separate relations/tables. E.g. for table named school in both models.py, it would look like project1_school and project2_school in Postgres database.
Is there a way to write to and read from same tables of same database?
Thank you so much in advance.
I think that you might be confuse with the difference between Projects and Applications.
Projects vs. apps
What’s the difference between a project and an app? An app is a Web application that does something – e.g., a Weblog system, a database of public records or a small poll app. A project is a collection of configuration and apps for a particular website. A project can contain multiple apps. An app can be in multiple projects.
Writing your first Django app, part 1
So in you particular case, I would say that your actual projects, both of them, could be applications of one project. The main reason, why I think this is a better approach, is that both are gonna use the same data, one application writes while the other retrieve it. One could even argue that they actually could be the same application. But this may depend on many factors of your business.
BTW, is really hard for me to imagine a situation where it would be a good idea to have two projects using the same database. Even if both projects need to share data, I would not think in using on database. I would try to solve it at an application level. But I you need for some reason to share information at database level, there are tools to connect both databases.
Our product has a restful API and a server rendered app (the CMS). Both share the database. Both are written in django
The fields and the models needed in both are not mutually exclusive, there are some only particular to the API, some particular to the CMS, and some which are common.
My question is if I run migrations on one of the repos will they try to drop the fields that aren't present in the models of that particular repo, and needed by the other. Will running the migrations individually in both repos keep the database up to date and not pose a problem.
The only other valid option IMHO (besides merging projects) is turning off automation of Django migrations on common models (Meta.managed = False) and taking table creation & versioning into your own hands. You still can write migration scripts using django.db.migrations but makemigrations command won't do anything for these tables.
This was solved by using a schema migration tool external to Django's own. We use
yoyo migrations to migrate our schema now.
Will running the migrations individually in both repos keep the database up to
date and not pose a problem.
Unfortunately, no. As you suspected, changes in one will attempt to override the other.
The easiest thing to do is merge the two projects into one so this problem goes away entirely.
If this isn't an option, can the code be organised in such a way that both projects share the same models.py files? You could do this by perhaps having the models.py files and migrations folders only exist in one project. The second project could have a symlink across to each models.py file it uses. The trick (and the difficult part) will be to make sure you never create migrations for the app which uses the symlinks.
I think the best things to do would be to have one repo that contains all the fields. This project will be responsible to apply the migrations.
In the other projects, you'll need a db_router containing a function allow_migrate which will return False on your model classes.
Also having different db user with different db permissions can prevent from altering the tables.
I have two a django site, on some of the pages data is coming from a postgresql database. Another set of pages are connected to a sqlite database. The tables are from two different sources so I cannot merge them but I need to merge them in one django site. What is the best practice for this:
should I merge the two in a django application so modifiying model.py,views.. or I should put them into different django applications with different models, view ?
You can merge two apps into one instance, but then you won't be able to use default session and auth modules from django with models of one of it.
Good solution is to merge it into one project (so two apps can share some code and maybe some settings) but run it as 2 separate instances with 2 different settings loaded.
Also: you can just merge two databases, even if they are using different engines. Django has built in dumpdata and loaddata manage commands, you can use it to move data from one database to another.
I'm getting set up with proper distribution version control (yes, overdue) on a large Django environment with lot's of reusable apps and lot's of projects.
What's the right way to do this?
Clone each app you need within each project, to allow you to make changes to the app without worrying about breaking anything.
Have one copy of each version controlled application to avoid having multiple copies of the code, each in its own repository.
Or is there a better way?
Thanks.
Edit for clarity: These are in house apps that are reused from project to project.
In my opinion the best practice is to keep all your apps as one library/package. You can have versions/snapshots (e.g. tags in hg) and branches and you should definitely create and configure setup.py file.
If the app are reusables, you must create a egg in pypi. These have releases. For each project, you could use one or the other releases.
See for example this package.
To deploy the projects both in local as in the server, you can use buildout (very recomended)
I am about to start a django project, where I need a base deployment, lets say just for admins initially. Later admins can add instances of my main public site.
Now, one instance will, obviously be separated by dynamic sub-domains. I need to capture sub-domains from requests, and compute accordingly. It has its own base templates, static files, etc (easiest part). It would have set of feature apps (common for all instances, but not the data in their models). And I am thinking of using Django1.2's multiple database support, and try to get one db per instance (* adding dynamically :( , if that is feasible, It will include dynamic db/model creations*). Or I can go for adding an instance foreign_key in all feature apps models, to separate them instant-wise.
If my instances were known prior to deployment, I would have used multiple database support easily by capturing the sub-domains and diverting my ORM calls to concerned db. But, that is not the case. Those has to be dynamic (added as need arises).
Now before I give it a try, to get solution/rid of delusions about it, I would want experts of SO to think about it. I would appreciate the suggestions, insights and of-course criticism.
I can make it community wiki, if suggested. Thanks guys.
Shouldn't you just run a separate Django instance in a each their Apache VirtuaHost? Then, you can have a Django settings file for each instance and they can each point at their proper database. This also simplifies your code because you don't need to map subdomain names to databases inside your views. As a real bonus, your code gets re-usable because it doesn't depend on your complex setup.
Ususally you can do instances of your app with the sites framework.