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https://issues.jboss.org/browse/AS7-4209?page=com.atlassian.jira.plugin.s...
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Brian Stansberry commented on AS7-4209:
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Matej Lazar had previously expressed interest in doing a DOMAIN_PING. That led to this
exchange between myself and Bela Ban:
On 1/4/12 7:00 PM, Brian Stansberry wrote:
There is no standard hook to allow arbitrary operation handlers on a
server to communicate back to their own Host Controller or back to the
master Host Controller. (The communication is possible; the
infrastructure is just not exposed at the required level.) That's
something we'll look at adding in 7.2 or later.
That could be hacked around; i.e. the configuration for a DOMAIN_PING
protocol could include the address/port of the master Host Controller.
But that would be a horrible hack.
If we do this, then it should be an opaque blob stored by the master host controller under
a given key; only the application would know how to interpret its contents.
The only purpose of the master Host Controller in this would be to
forward requests to the DOMAIN_PING service running on relevant servers
to get the required data from them. The master Host Controller won't
keep this information itself. It knows nothing about PingData or JGroups.
I don't think that's what Matej wanted to do: the master host controller (is this
name final ?) has information about all JBoss instances running, so it would be a perfect
starting point to query this information. In this sense, it could act as a replacement of
GossipRouter. Of course, this makes sense only in environments where IP multicasting is
not allowed, e.g. in clouds.
All this said, I don't see this kind of PING implementation
becoming a
standard in the AS. For two reasons:
1) It introduces a dependency by the application server on the master
Host Controller. Without that running master Host Controller, the
JGroups channel will not behave properly.
Correct; discovery would not work, but normal operation (ie. message sending) would work,
since it's not dependent on the master host controller being up.
Currently we have no such
dependency. If the master HC is not running, the admin can't do some
(but not all) administrative tasks. But it doesn't affect the ability of
the applications servers to handle end user requests.
OK
2) We've been specifically warned by large users with experience
running
Websphere deployments about the danger of using the domain management
communication pipelines for exchanging runtime information between
services running on the application servers. Experience showed them that
doing this quickly results in a flood of information between the servers
that ends up degrading the ability to manage the servers.
OK
I don't mean to sound overly negative here; this kind of thing
is
reasonable. It's just something that will take some thought and likely
won't become the default behavior in the AS.
Automatic configuration of 'Initial_hosts' for a cluster
using JGroups TCP-stack in domain mode
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Key: AS7-4209
URL:
https://issues.jboss.org/browse/AS7-4209
Project: Application Server 7
Issue Type: Feature Request
Components: Domain Management
Affects Versions: 7.1.1.Final
Environment: Server running in Domain mode
Reporter: Wolf-Dieter Fink
Assignee: Brian Stansberry
Labels: clustering, domain, jgroups
It is complicated to keep the subsystem JGroups in sync if the tcp-stack is used in
domain mode.
All new servers that join/leave a clustered server group (configuration) must be added or
removed by hand for the jgroup configuration.
The domain server will receive the informations if a host-controller enrol and register
server to a clustered server-group.
So the configuration of the initial_hosts can be done automaticaly to avoid old entries
which cause unnecessary checks and ensure that all active servers are known.
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