[wildfly-dev] Widlfly 9.0.1.Final - subsystem expression evaluation not entirely water proof

[Dennis Brouwer]

Thanks Brain for answering this however I am still a bit puzzled,

Let me explain:

On Tue, Aug 25, 2015 at 5:04 PM, Brian Stansberry <
brian.stansberry at redhat.com> wrote:

> This attribute does not support use of expressions, so any data you
> provide is evaluated simply as a string.
>
>
"This attribute" most likely refers to the name attribute in <channel
name="ee"> if I interpret your sentence correctly. If so, why not create an
extra attribute CLUSTER_NAME next to the existing STACK and MODULE
attributes and use the CLUSTER_NAME to create the JChannel. Using the
current configuration model all containers start up with default cluster
name "ee" unless the standalone*.xml file is edited beforehand. This is
practically undoable because the cluster name defaults to the name of the
channel used and I didn't find a way to overrule this (I might have
overlooked something of course).

The only way to make distinct clusters is to add a bunch of pre-defined
channel definitions and change the channels default. example:

*<subsystem xmlns="urn:jboss:domain:jgroups:3.0">
**      <channels default="${custom_clustername:ee}">
**          <channel name="ee"/>*

*          <channel name="whee"/>*
*          <channel name="foo"/>      **</channels>
**      ...
**</subsytem>*

And then select one of the names using the -Dcustom_clustername=[|whee|foo]
startup property. However the desired behavior is to be flexible and
provide a random name at startup time.


It doesn't support expressions because it is what we call a "model
> reference" attribute. It's value refers to another element in the
> configuration model. We do not allow expressions in those attributes
> because it is not possible to have all the necessary data to resolve the
> expression at the points in time when the correctness of the model must
> be validated.
>
> On 8/25/15 9:31 AM, Dennis Brouwer wrote:
> > Dear reader,
> >
> > We recently moved to Wildfly 9.0.1.Final (from 8.2.0) for testing and
> > stumbled upon a bug regarding expression evaluation in the
> standalone*.xml.
> >
> > Let me give an example for the following subsystem:
> >
> > <subsystem xmlns="urn:jboss:domain:jgroups:3.0">
> >      <channels default="ee">
> >          <channel name="ee"/>
> >      </channels>
> >      ...
> > </subsytem>
> >
> > Since we have several deployment stages on one physical server we need
> > to separate the clusters by using a distinct name for each one of the
> > stages deployed. Hence we introduced a startup property to be
> > substituted in the standalone*.xml configuration like following snippet
> > clarifies:
> >
> > <subsystem xmlns="urn:jboss:domain:jgroups:3.0">
> >      <channels default="${custom_clustername:ee}">
> >          <channel name="${custom_clustername:ee}"/>
> >      </channels>
> >      ...
> > </subsytem>
> >
> > Using this approach however fails to start the container because the
> > channels default attribute is properly evaluated to "ee" (accoding to
> > specs). However the channel name attribute is not evaluated at all and
> > is registered as "${custom_clustername:ee}" (without the quotes).
> >
> > I took the liberty to dig in the class:
> > org.jboss.as.clustering.jgroups.subsystem.JGroupsSubsystemXMLReader and
> > manually do the expression evaluation for the channel name. At first
> > glance this seems to work however the container rewrites the
> > standalone*.xml file at a certain moment resulting in this snippet:
> >
> > <subsystem xmlns="urn:jboss:domain:jgroups:3.0">
> >      <channels default="${custom_clustername:ee}">
> >          <channel name="ee"/>
> >      </channels>
> >      ...
> > </subsytem>
> >
> > Which on subsequent container starts and when using the
> > -Dcustom_clustername=whee startup property causes a problem because the
> > channels default is evaluated to "whee" and the channel name remains
> "ee".
> >
> >
> > So my questions are:
> >
> > 1] How to solve this issue in a correct way?
> > 2] Can somebody provide another mechanism to configure a non default
> > channel name on startup?
> >
> >
> > --
> > Best regards,
> >
> > *Dennis Brouwer*
> > Extraordinary Goalkeeper
> >
> >
> >
> >
> > ZEEF - Kizitos B.V.
> > Amstelboulevard 184
> > 1096 HM Amsterdam
> > www.ZEEF.com <http://www.zeef.com/>
> > US: +1 (415) 992-9409
> > NL: +31 (085) 888-3186
> >
> >
> > _______________________________________________
> > wildfly-dev mailing list
> > wildfly-dev at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/wildfly-dev
> >
>
>
> --
> Brian Stansberry
> Senior Principal Software Engineer
> JBoss by Red Hat
> _______________________________________________
> wildfly-dev mailing list
> wildfly-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/wildfly-dev
>



-- 
Best regards,

*Dennis Brouwer*
Extraordinary Goalkeeper




ZEEF - Kizitos B.V.
Amstelboulevard 184
1096 HM Amsterdam
www.ZEEF.com <http://www.zeef.com/>
US: +1 (415) 992-9409
NL: +31 (085) 888-3186
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