[wildfly-dev] Widlfly 9.0.1.Final - subsystem expression evaluation not entirely water proof
Brian Stansberry
brian.stansberry at redhat.com
Tue Aug 25 12:34:11 EDT 2015
Apologies; I didn't read your original post clearly enough, as your
primary concern was with the "name" attribute on the "channel" element,
not the "default" attribute on the "channels" element. Plus I was
mistaken about "default" not allowing expressions.
I'll defer to the clustering guys to make any recommendations about how,
if possible, to achieve your desired result. They better understand the
use of these attributes.
The "name" attribute on the "channel" element definitely can't allow
expressions. It forms part of the address of a management resource, and
addresses must be fixed.
On 8/25/15 10:54 AM, Dennis Brouwer wrote:
> 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 <mailto: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> <http://www.zeef.com/>
> > US:+1 (415) 992-9409 <tel:%2B1%20%28415%29%20992-9409>
> > NL:+31 (085) 888-3186 <tel:%2B31%20%28085%29%20888-3186>
> >
> >
> > _______________________________________________
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> >
>
>
> --
> Brian Stansberry
> Senior Principal Software Engineer
> JBoss by Red Hat
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>
>
>
>
> --
> 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
--
Brian Stansberry
Senior Principal Software Engineer
JBoss by Red Hat
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