Moodle in English: Urgent: Downgrading from 4.0dev (Build: 20210108) to a stable version of Moodle.

Urgent: Downgrading from 4.0dev (Build: 20210108) to a stable version of Moodle.

by Stephen Jenkins - Saturday, February 6, 2021, 3:58 AM

I posted a brief synopsis a few weeks ago, but to recap. I have accidentally "upgraded" a production Moodle site to 4.0dev (Build: 20210108) - which is throwing tons of cache errors and basically has to be babysat, going down often with session writing errors, caching errors, etc - often resulting in the client getting the too many redirects error upon trying to login.

This happened because of what I can only understand to be mislabeled files from Moodle, I went to upgrade to the "latest version" - and I was given 4.0dev (Build: 20210108). Yes, it's totally my fault still, no I don't have backups - it was some time before realize the issue and my backups had been overwritten.

I know that's "officially" not possible to downgrade versions, but a few people mentioned that it may just be a matter of editing a few things in the database and then installing the version of Moodle I would like, clearing caches, and seeing if that works.

Would any developer, either here, or working together be wiling to help me navigate this process? I am reasonably tech savvy, I am comfortable using mysqladmin, etc, and follow directions very well, I just need to know where to start and which things need changed in order for me to be able to revert.

The alternative is to stay on the Dev path and deal with things as the break until November which seems like a nightmare.

Would really really appreciate any help I can get, very hopeful that I can downgrade somehow.

Re: Urgent: Downgrading from 4.0dev (Build: 20210108) to a stable version of Moodle.

by Davo Smith - Saturday, February 6, 2021, 4:42 AM

A few thoughts (these may well not be the complete solution, but may be a starting point).

First you need to know what has changed in terms of database structures - I suggest you (separately) create a clean install of Moodle 3.10 and Moodle 4.0 (dev) and then export the database structures as SQL files, then do a diff. That should give you a starting point in trying to figure out how much the database structures have changed. You should revert all changes, but you _may_, in theory, be able to get away with some of the differences.

You'll also want to find all the upgrade.php files in the code and look at each of them to see what changes are made in there (this should match the differences you observe between the two databases).

Next you'll need to change the main Moodle version number in the database (mdl_config - search for 'version' and change it to match the version number in Moodle 3.10, version.php), you will also need to reset the version number for lots of plugins (they will be in mdl_config_plugins, called 'version' and will need resetting back to the version number that plugin had in Moodle 3.10). It is possible to write a script that checks for version number mismatches and resets all of them (I don't have a copy of my script to hand, but it is based on the checks that Moodle itself does to show an error about plugins that have a higher version number in the database than in the code).

After that, you could try purging all the caches and seeing what happens.

I will guarantee that this will take a lot of work to do and you should also assume you will have ongoing problems (which may even persist after the official upgrade in 6 months time, as there is a chance that some of the data will be irrevocably confused in this process).

Needless to say, make sure your site is offline throughout the whole process, make sure you have full backups from the start of the process.

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Re: Urgent: Downgrading from 4.0dev (Build: 20210108) to a stable version of Moodle.

by Stephen Jenkins - Sunday, February 7, 2021, 6:49 AM

Davo, I have spent the last 24 hours planning this operation, and incredibly I have been successful up to this point:

"you will also need to reset the version number for lots of plugins "

There are 414 Plug-ins that "need attention" - I believe they simply need the version correctly, like you said.

Could you share your script/process? OR do you think I could just replace that table with the table of a fresh install that has the same version that I'm running?

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Re: Urgent: Downgrading from 4.0dev (Build: 20210108) to a stable version of Moodle.

by Davo Smith - Sunday, February 7, 2021, 11:30 PM

Sounds like you have already solved this problem, but in case it helps anyone else out, I've attached my script for handling "Cannot downgrade plugin" errors by forcing the version numbers.

It is not something you should be doing on a production site (you should be looking very carefully at exactly what was changed, before messing with version numbers - it can leave the database structure and code in a state where they don't work together), but it is quite handy when switching between development branches with different custom plugins that are being worked on.

To use: drop the script into your path (and mark it as executable), or put it in the root directory of the Moodle code. On the command line, from the Moodle code root directory, you should just be able to type 'downgradefix.php'. If that doesn't work, then remove the first line of the script (the '#!/usr/bin/php' line) and run it via: 'php downgradefix.php'.

No warranties are provided with this script, it is not recommended that you get into a situation where you need to use it, but it is there if it is of use.

downgradefix.php

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Re: Urgent: Downgrading from 4.0dev (Build: 20210108) to a stable version of Moodle.

by Colin Fraser - Saturday, February 6, 2021, 9:21 AM

Another thing you may add to the list of possible things to do is to create a test Moodle. Whenever you do anything to your Moodle do it there first. From minor changes to complete upgrades. Have a few dummy users with courses, be able to log in as any user, do things testing it out BEFORE you do anything to your production site. I don't know how many times this simple exercise in patience has save my bacon. My clients think I am a real Moodle guru, how little they understand..

Just they ask for something, or I give them an upgrade, it all works perfectly, every time, no fuss. Absolutely minimum downtime then. Also, TBH, they don't ever ask for much beyond an out of the box Moodle with a few additional plugins, which make it so much easier for me.

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Re: Urgent: Downgrading from 4.0dev (Build: 20210108) to a stable version of Moodle.

by Michael Milette - Wednesday, February 10, 2021, 6:26 PM

Hi Stephen,

Depending on the complexity of your Moodle site, another option might be to backup all of your courses including users, blocks, etc. and restore them all into a new instance of Moodle. Still a lot of work and you may need to manually deal with missing information like glossaries which are not included in course backups but can be exported and re-imported.

The Moosh command line tool may be helpful in bulk backing up and restoring your courses.

I see you do have a backup system in place but this might benefit others reading too: Implement an automated backup system for your Moodle site. It would have been much easier to restore a site from a full backup (application, moodledata and SQL database). Always make an extra full backup of your Moodle site just before making any application file changes (in climaintenance mode). I know it can be a pain and extends your maintenance period but you can never be 100% sure that a change won't be disastrous, even if it seemed to work perfectly in your development/test environment. It is also a good idea to periodically test your backup, changes (always) and restore process on a copy of your Moodle site just to make sure the backups are working properly. Disaster recovery plans are worth your time, money and effort. The only time you should skip all this is if you are ready and willing to lose it all.

Good luck! I hope it all works out for you.

Michael Milette

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Urgent: Downgrading from 4.0dev (Build: 20210108) to a stable version of Moodle.