How to perform a DB migration from outside the app where DB is defined?

[Lisandro]

Hey there! 

I have several web2py apps running, and one of them acts as the main one, taking care of mantainance and upgrading the apps when needed. Sometimes the upgrade requires a database migration.

All the process is controlled by the main app, which takes the app that needs to be upgraded and does this:

1) Puts the app in maitenance mode (this is, returns http 503 to any requests that doesn't come from localhost)

2) Upgrades the app's code.

3) Sets migrate=True

4) Uses requests module to perform a GET so the migration is done in the database app.

5) Sets migrate=False

6) Reactivates the app to serve any request.

The problem I'm facing with this technique is that some migrations take a lot of time (sometimes because there is a lot of changes, some other times because it's a small change in a really big database). In this cases, using requests to perform a GET isn't ideal because it hits the timeout (a normal timeout set for any http request).

Is there any way to perform the database migration from outside the app where the database is defined that doesn't involve using http requests?

Thanks in advance!

Warm regards,

Lisandro

[Carlos Correia]

Às 11:34 de 28/11/23, Lisandro escreveu:

Hey there! 

I have several web2py apps running, and one of them acts as the main one, taking care of mantainance and upgrading the apps when needed. Sometimes the upgrade requires a database migration.

All the process is controlled by the main app, which takes the app that needs to be upgraded and does this:

1) Puts the app in maitenance mode (this is, returns http 503 to any requests that doesn't come from localhost)

2) Upgrades the app's code.

3) Sets migrate=True

4) Uses requests module to perform a GET so the migration is done in the database app.

5) Sets migrate=False

6) Reactivates the app to serve any request.

The problem I,

'm facing with this technique is that some migrations take a lot of time (sometimes because there is a lot of changes, some other times because it's a small change in a really big database). In this cases, using requests to perform a GET isn't ideal because it hits the timeout (a normal timeout set for any http request).

Is there any way to perform the database migration from outside the app where the database is defined that doesn't involve using http requests?

Thanks in advance!

Warm regards,

Lisandro

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Hi,

With complex databases I recomend using a SQL script or executing the required SQL commands from Web2py, via db.executesql(), in particular in the case theres is also data changes associated.

Regards,

Carlos Correia
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[Lisandro]

Ok great! Thanks for the advice.

I already made the changes so I already don't depend on having to make a request with migrate=True.

I tested it and it works ok: from my main application I connect to the secondary app's database and I use .executesql() to make the changes I need before upgrading the app's code.

One more question: should I run the app once with fake_migrate=True? 

After manually performing the database migration and updating the app's code, it works great. I mean, the database migration involved creating and deleting some table fields, those changes were made using .executesql(). After that, I updated the app's code, including models/db.py which already has those changes in its definitions. At this point, although the application works great, the files inside /databases/ folder are not up to date. So, should I run the app one with fake_migrate=True? Or I don't need it anymore as I'm going to perform manually database migrations from now on?

Thanks in advance!

Best regards,

Lisandro