[keycloak-dev] Keycloak with CockroachDB

[Stian Thorgersen]

On Tue, 6 Nov 2018 at 17:34, Poiffaut Romain <romain.poiffaut at elca.ch>
wrote:

> CockroachDB is a normal ACID relational SQL database which uses the
> PostgreSQL driver. The modifications that were necessary are due to the
> client retry mechanism for conflicting transactions. From our point of view
> (or perhaps more correctly, for our use cases), its advantages over the
> currently supported databases for cloud deployment would be sufficient to
> have it included in the core.
>

The issue is if support for CockroachDB is added directly to Keycloak and
not maintained as an extension it becomes our responsibility to maintain
and support it, which we simply don't have capacity to do.


>
>
> However, if you’re willing to introduce changes that allow us to maintain
> the integration of CockroachDB as a module/extension, we would more than
> willing to shift our code to make it a separate extension. In this manner,
> CockroachDB would be usable with Keycloak for anyone who wishes to benefit
> its use, and if you later decide that it would be beneficial to maintain it
> in the core, the work to integrate it should be quite low.
>

I would love to get to a point to make it easier to properly have community
maintained extensions to Keycloak. That is a great way to provide
additional features and capabilities that we do not have the capacity to
maintain within the core Keycloak team. So I'm absolutely open to
discussions around how this can be improved and simplified.


>
>

>
> I’ll try out your suggestions for lessening the dependency to the code,
> and I’d be happy to discuss the changes that need to be done to make it a
> drop-in extension.
>
>
>
>
>
> *De :* Stian Thorgersen <sthorger at redhat.com>
> *Envoyé :* lundi 5 novembre 2018 20:20
> *À :* Poiffaut Romain <romain.poiffaut at elca.ch>
> *Cc :* keycloak-dev <keycloak-dev at lists.jboss.org>
> *Objet :* Re: [keycloak-dev] Keycloak with CockroachDB
>
>
>
> CockroachDB is not something we will consider including in the core code
> base at the moment. It is a very high overhead supporting multiple DB and
> something like CockroachDB that is less like a traditional relational DB
> will be too much effort for us to consider at this stage.
>
>
>
> I would suggest that you maintain this as a separate extension, but we can
> discuss how that can be done. What changes are needed to make this into a
> drop-in extension that doesn't require a forked Keycloak build for instance.
>
> On Fri, 2 Nov 2018 at 09:56, Poiffaut Romain <romain.poiffaut at elca.ch>
> wrote:
>
> Hello,
>
> For the Cloudtrust project (https://github.com/cloudtrust), I have
> investigated the feasibility of supporting CockroachDB in Keycloak.
>
> I have created a fork based on Keycloak 3.4.3 (it was the latest version
> when I started on this) working with CockroachDB 2.0.2. It is now working
> with this DB, and passes all unit tests. Some resilience tests have also
> been performed to validate the whole integration.
> Address of the repo :
> https://github.com/cloudtrust/keycloak/tree/cockroach-db
>
> For those who might be interested, here are some details:
>
> CockroachDB is a multi-master SQL database designed to run in the cloud
> and being resilient to failures (https://www.cockroachlabs.com/).
> This database has a lot of very interesting properties such as being
> lockless, distributed and supporting serializable isolation.
> CockroachDB introduces the notion of SAVEPOINT. As this DB is lockless, a
> transaction may fail due to a concurrent transaction. In such case, we can
> rollback to the SAVEPOINT and retry the transaction. Retrying transactions
> has the benefit of increasing their priority each time they are retried,
> thus increasing their likelihood to succeed. (More detailed information are
> available in their very good documentation (e.g.
> https://www.cockroachlabs.com/docs/stable/transactions.html#client-side-transaction-retries,
>
> https://www.cockroachlabs.com/blog/how-cockroachdb-distributes-atomic-transactions/,
>
> https://www.cockroachlabs.com/blog/serializable-lockless-distributed-isolation-cockroachdb/
> ))
>
> So even if CockroachDB uses PostgreSQL driver to communicate with the DB,
> one of the challenges was to add an automatic transaction retry mechanism
> with the smallest impact on Keycloak.
> Thanks to the architecture of Keycloak, this mechanism can be added in
> KeycloakSessionServletFilter with a very limited impact.
>
>
>
> This can be achieved with a custom KeycloakTransaction wrapper instead.
> That way you do not need to modify Keycloak source code.
>
>
>
>
> A second challenge is due to the rollbackOnly mechanism implemented in
> Keycloak and Hibernate: after a rollback, a transaction cannot be used
> anymore.
> The retry operation must be performed in the same transaction to increase
> its priority.
> Thus the rollbackOnly mechanism is disabled/bypassed in order to keep the
> transaction active even after a rollback is issued.
> As suggested by CockroachDB, we replace the default Hibernate transaction
> coordinator class to a custom one (
> https://github.com/cockroachdb/hibernate-savepoint-fix).
> Moreover, we mainly modify JpaKeycloakTransaction so that if the
> transaction fails to commit due to retryable transaction error, we disable
> the rollbackOnly mechansim to able to retry the transaction.
>
>
>
> We could add an option to the connection provider to allow setting a
> custom transaction coordinator.
>
>
>
>
> CockroachDB does not support addition of some constraints (e.g. primary
> keys) after table creation.
> To circumvent this limitation, we can create a new table, migrate the
> data, delete the old table, rename the new table with the correct name.
> As CockroachDb was not supported by Keycloak until now, we didn’t adapt
> all existing liquibase scripts. We decided to create a new liquibase script
> which creates the whole database schema for the current version.
> This current limitation is being discussed and will be fixed in future
> release (https://github.com/cockroachdb/cockroach/issues/19141).
>
>
>
> Not sure how to handle this. If you need to modify Liquibase scripts that
> pretty much leaves you with having to maintain your own "duplicates".
>
>
>
>
> Some tests have also been slightly adapted to support SERIALIZABLE
> isolation, so other DBs configured with such level can also benefit from
> this adaptation (i.e. PostgreSQL)
>
> These challenges have been solved and our forked version of Keycloak is
> now compatible with CockroachDB, but it currently is at the cost of
> breaking the usage of standard databases.
> Our company is really interested to add the support of this DB into
> Keycloak and to provide it to the community.
> The next steps now would be to migrate our fork to the latest version of
> Keycloak and add the support of this DB without breaking support of the
> others and we would be happy to discuss it.
>
>
> Cheers,
> Romain Poiffaut
>
> _______________________________________________
> keycloak-dev mailing list
> keycloak-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/keycloak-dev
>
>