[jboss-as7-dev] Problem met on as7 clustering with mod_cluster

[Brian Stansberry]

On 1/20/12 5:13 AM, Weinan Li wrote:
>
> On Jan 20, 2012, at 7:07 PM, Radoslav Husar wrote:
>
>> On 01/20/2012 11:59 AM, Weinan Li wrote:
>>>
>>> On Jan 20, 2012, at 3:58 AM, Radoslav Husar wrote:
>>>
>>>> On 01/19/2012 07:31 PM, Weinan Li wrote:
>>>>> Now there's another question: How can I configure mod_cluster to use
>>>>> round-robin to distribute requests?
>>>>
>>>> Weinan,
>>>>
>>>> mod_cluster has been built around the idea of load-balancing
>>>> intelligently by communicating load from the server to the
>>>> load-balancer. Round-robin is far from intelligent :-) and there is no
>>>> such option.
>>>>
>>>> Look at what options you have for configuring load metrics in AS7
>>>> http://docs.jboss.org/mod_cluster/1.1.0/html_single/#LoadMetric (so
>>>> "requests" might be the best one to actually see it load-balance).
>>>>
>>>> You might also want to try killing the server to see it fail-over to
>>>> the other instance.
>>> I've tried to kill domain controller and the requests are forwarded to
>>> slave host, and sessions are not lost. Cool!
>>>
>>> Another question: can domain controller be also support failover?
>>
>> Now that's a question for Brian :-)
>>
>> But if I remember correctly, this was not coming in 7.1, I cant seem to find the Jira for it.

No, we don't support failover of the domain controller. We haven't made 
it a priority because:

1) Servers don't need a running domain controller in order to handle 
requests.

2) Administrators can still interact with slave host controllers to 
administer them and their servers. They just need to connect to them 
directly. This includes being able start new servers and read metrics 
from the servers. Reading metrics would be a common reason why admins 
would want immediate access to the servers.

3) It's fairly easy to start a new domain controller; all you need is a 
in AS7 installation and a copy of the latest domain.xml. Any host 
controller can be configured to maintain a copy of domain.xml by passing 
the --backup-dc arg to domain.sh.

What you lose without a running domain controller is

1) The ability to make any changes that involve changing something 
stored in domain.xml.

2) The convenience of being able to use the domain controller as a 
single contact point for administering other hosts/servers. You can 
still use the CLI or any custom client you have to contact them directly.

3) The admin console.

> Get it, thank you for help Rado :-) Anyway, I've finished writing this article in Chinese about AS7 Clustering with all your help (I believe this is the first *complete* step-by-step article about how to setting up a working domain+clustering AS7 on internet):
>
> http://bluedash.net/t/cd1e78c90099c8b8aadf7a1884b56669
>

Excellent!

Although now I'm depressed to realize how many characters I've forgotten. ;)

>
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>>
>> Rado
>
> Cheers,
> - Weinan Li
> JBoss, Redhat
>
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-- 
Brian Stansberry
Principal Software Engineer
JBoss by Red Hat