[keycloak-dev] User apps and HttpClient

[Stian Thorgersen]

For now let's just make sure examples don't use HttpClientBuilder. That should be relatively quick to fix and solves you're problem. We can worry about the rest later when we start defining public/private stuff.

----- Original Message -----
> From: "Marko Strukelj" <mstrukel at redhat.com>
> To: "Stan Silvert" <ssilvert at redhat.com>
> Cc: keycloak-dev at lists.jboss.org
> Sent: Friday, 22 May, 2015 9:50:27 AM
> Subject: Re: [keycloak-dev] User apps and HttpClient
> 
> I like Stian's solution much better ... it's much simpler :)
> 
> @Stian: Is there some docs where I can get a better understanding of what's
> an API that is exposed to client, and what is implementation details never
> to be used by client apps ...
> 
> Ideally that would be easy to establish based on package names - e.g.
> anything not in org.keycloak.something.impl might be an API, or nothing but
> what's in org.keycloak.something.api might be an API ...
> Or maybe we have one single module that's client API?
> 
> 
> 
> 
> 
> 
> On 5/21/2015 4:56 PM, Marko Strukelj wrote:
> 
> 
> 
> 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?
> What do I think? I think that classloading questions always make my head
> hurt!
> 
> The best solution would be to find a way to detect the problem and fix it at
> deploy time. Using a DependencyProcessor, it should be possible to detect
> that the deployment contains the same module from two different slots. Then
> pick the best slot and spit out a warning message that you are removing the
> undesirable module.
> 
> It should be possible, but I don't know if it actually IS possible. A version
> mismatch between modules is like a cancer. I think you should speak to an
> oncologist or David Lloyd. Since Red Hat doesn't employ any oncologists, go
> with David. :-)
> 
> 
> 
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