[keycloak-dev] Access datasource from a CLI

[Marko Strukelj]

On Wed, Oct 21, 2015 at 5:57 PM, Stan Silvert <ssilvert at redhat.com> wrote:

> On 10/21/2015 11:14 AM, Marko Strukelj wrote:
>
>> I haven't taken a very close look at Swarm yet, but I assumed you start
>> Wildfly embedded in the same JVM as your Main class. If that is the case,
>> then there should be no problem communicating with any kind of deployed
>> component via heap directly - just lookup some singleton ...
>>
> Classloading constraints are what you usually run up against.  You can't
> use your own version of a class that was loaded from a different
> classloader.  I don't think Swarm helps you get around that, but just
> assumes you will access the WAR in the usual way through an HTTP port.  But
> I could be wrong as I haven't worked with Swarm either.
>
> Here is an explanation of the problem based on an old version of JBoss:
>
> https://docs.jboss.org/jbossas/docs/Server_Configuration_Guide/4/html/JBoss_JMX_Implementation_Architecture-Class_Loading_and_Types_in_Java.html
>
> With jboss-modules, it's easier to get around these problems, but you
> still run into the isolation built into the container itself, especially in
> the case of a WAR.


CLI running in the same JVM as Wildfly would get bootstrapped through
jboss-modules, and would package it's classes as a jboss module. It can
then deploy additional 'in-container' logic that needs actual access to
datasources via many different mechanisms. It can be a .jar containing a
SLSB, a .war, a .sar, a POJO (via pojo subsystem), it can be a custom
subsystem that gets installed ... In every of these cases it can then have
access to resource objects bound to java:jboss JNDI space ... And in every
of these cases it uses shared types loaded via dependencies on
jboss-modules.



>> If that is not the case, then we would need some kind of interprocess
>> communication going. With shell the roles of who connects where could also
>> be reversed, and a started up Wildfly instance could have a service
>> connecting out to local port bound by our CLI rather than the other way
>> around.
>>
> I don't think the direction of the connection matters so much as the fact
> that you need a serialized format to issue commands to a foreign container.
>
> Or, as I mentioned, you need the CLI to actually live inside the container.


CLI needs to be able to execute its logic inside the container in order to
harness the datasources, but the UI part that takes care of getting the
inputs and displaying the outputs - e.g. CraSH, does not have to be inside
the container.

I don't know what you mean by 'serialized format to issue commands to a
foreign container', but if it means taking care of UI interaction, CraSH
looks pretty decent CLI, easy to extend with custom commands.
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