At times you have to make hard decisions and this has been one of those. We have decided to remove Mongo support from Keycloak. The primary motivation behind this decision is that we simply don't have the resources to maintain and further develop the back-end for both relational databases and Mongo. Further, there are some fundamental issues with our current use of Mongo that would require a large amount of work to become fully production ready. This primarily boils down to the lack of ACID transactions in Mongo.
We hope that this decision won't result in too much trouble for those of you that are currently using Mongo as the back-end for Keycloak. It should be relatively painless to migrate to a relational database with our export/import feature. If you do run into issues with this please let us know on the mailing list and we will do whatever we can to help make the transition as smooth as possible.
If anyone from the community would like to take over the Mongo support and maintain it as a separate extension please let us know. We can help with extracting the code and work together in making it easy to install it as an extension.
Migrating from Mongo to relational database
First step is to export the full database. You can do this by stopping the Keycloak server and running:
bin/standalone.sh -Dkeycloak.migration.action=export -Dkeycloak.migration.provider=dir -Dkeycloak.migration.dir=backup
This will export all data from Mongo to JSON files within the directory backup. For full details refer to the Server Administration Guide.
Next step is to install a relational database and configure it in Keycloak. Take your pick we support quite a few. For full details refer to the Server Installation Guide.
Once you have the relational database ready and configured, you can start Keycloak and import the data exported from Mongo. To do this run Keycloak with:
bin/standalone.sh -Dkeycloak.migration.action=import -Dkeycloak.migration.provider=dir -Dkeycloak.migration.dir=backup
Hopefully you're now up and running with all your realms and users migrated to the relational database. If not, let us know on the user mailing list and we'll help you out as soon as possible.