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

Tue Aug 25 15:34:43 EDT 2015

Hi Dennis,

Ultimately, I think your suggestion (i.e. decoupling the name of the JGroups cluster from the name of the channel) is a good one.
I've opened a jira for this:
https://issues.jboss.org/browse/WFLY-5202

I can implement this later today.

Paul

----- Original Message -----
> From: "Dennis Brouwer" <dennis.brouwer at kizitos.com>
> To: "Emmanuel Hugonnet" <ehugonne at redhat.com>
> Cc: wildfly-dev at lists.jboss.org
> Sent: Tuesday, August 25, 2015 2:52:43 PM
> Subject: Re: [wildfly-dev] Widlfly 9.0.1.Final - subsystem expression evaluation not entirely water proof
> 
> Hi Emmanuel,
> 
> Thanks for the suggestion however this is unfortunately not possible, we have
> a bunch developers with Eclipse and JBoss Tools installed and they switch to
> a different stage with only one startup property. I think that indeed adding
> a cluster attribute to the channel element that allows the JChannel name to
> be configured is the cleanest solution. If the cluster attribute is omitted
> then JChannel name should default to the channel name.
> 
> 
> On Tue, Aug 25, 2015 at 7:47 PM, Emmanuel Hugonnet < ehugonne at redhat.com >
> wrote:
> 
> 
> Hi,
> Maybe you could use the admin-only mode to create your channel with your
> random name and then restart the server in normal mode.
> Emmanuel
> 
> Le 25/08/2015 17:54, Dennis Brouwer a écrit :
> > 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
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> > > 
> > > 
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> > > 
> > 
> > 
> > --
> > Brian Stansberry
> > Senior Principal Software Engineer
> > JBoss by Red Hat
> > _______________________________________________
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> > 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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> > 
> 
> 
> 
> 
> --
> Best regards,
> 
> Dennis Brouwer
> Extraordinary Goalkeeper
> 
> 
> 
> 
> ZEEF - Kizitos B.V.
> Amstelboulevard 184
> 1096 HM Amsterdam
> www.ZEEF.com
> US: +1 (415) 992-9409
> NL: +31 (085) 888-3186
> 
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