[keycloak-dev] User apps and HttpClient

[Marko Strukelj]

We package examples with jboss-deployment-structure.xml that looks like this:


    <jboss-deployment-structure>
        <deployment>
            <dependencies>
                <module name="org.apache.httpcomponents"/>
            </dependencies>
        </deployment>
    </jboss-deployment-structure>


If we drop a .war containing this into Wildfly 9 (distribution/server-dist - ATM distribution/demo-dist, and distribution/adapters/wildfly-adapter-zip look buggy as they still use slot=4.3), things are fine.

However, if we dropped this into Wildfly 8 with keycloak adapter modules using org.apache.httpcomponents slot=4.3, we get a java.lang.LinkageError as soon as some Keycloak logic is triggered by user app.

The question: how come jboss modules isolation doesn’t kick in and allow keycloak adapter modules to use slot=4.3 while at the same time user app (our examples) uses slot=main?

The answer is that org.keycloak.adapters.HttpClientBuilder which seems to be our helper class for org.apache.httpcomponents inevitably leaks the version of HttpClient its module refers to - can’t be any other way (unless we change the code to use client app’s classloader - opening a can of worms). Any user app using HttpClientBuilder.build() method receives an instance of HttpClient loaded through org.keycloak.keycloak-adapter-core module, and transitively through org.apache.httpcomponents referred to therein.

Any attempt of an application (.war) to package its own httpcomponents jars, or to refer to a different jboss module than the exact one referred to by org.keycloak.keycloak-adapter-core will result in ‘catastrophic failure’. Example:


    HttpClient client = new HttpClientBuilder().disableTrustManager().build();


HttpClient on the left is loaded by app’s classloader. The one returned by build() on the right is loaded by org.keycloak.keycloak-adapter-core module’s version of httpcomponents. If it’s not the same classloader (jboss module) on both sides loading HttpClient you get a LinkageError.


In light of this I wonder if it wasn’t the best solution to reexport org.apache.httpcomponents to .wars by default, thereby removing the necessity to package jboss-deployment-structure.xml at all, and ensuring that user application always uses the proper module.

Currently jboss-deployment-structure.xml is required for wildfly / as7, and is a nuisance, especially as it has to be different (refer to slot=4.3) for Wildfly 8.

If using HttpClientBuilder is supposed to be completely optional, we could maybe add configuration to keycloak subsystem to control exposing it to all or specific secure deployments.

We could simply add another common attribute that can be used in <realm> and <secure-deployment>. We could expose it by default and have something like:

<expose-httpcomponents>false</expose-httpcomponents>

to inhibit exposing it if a situation calls for it.


WDYT?