[mod_cluster-dev] Configuring checking a crashed worker

[jean-frederic clere]

On 08/13/2009 06:18 PM, Bela Ban wrote:
>
>
> jean-frederic clere wrote:
>> On 08/13/2009 04:56 PM, Bela Ban wrote:
>>> But this works in mod_jk doesn't it ?
>>
>> mod_jk has a static configuration it is not going to remove something
>> from the configuration.
>>
>>>
>>> Besides, when we have *non-clustered* workers, there is no HA singleton
>>> telling httpd to remove the crashed worker, so httpd has to do it
>>> itself.
>>>
>>> I mean, why can't httpd simply remove a worker W is the socket
>>> connection to W is closed (by W crashing) ?
>>
>> First an entry corresponding shouldn't disturb mod_cluster, see
>> MODCLUSTER-92 about telling it is broken. Of course it would possible
>> to remove broken workers after a while, but I think it must be a
>> switch-able option and the while should be a parameter... Please
>> create a JIRA.
>
> I think what should happen is
> - httpd periodically tests the connection to worker W

Via cping/cpong but only if the worker is not active (no requests for a 
while).

> - httpd detects connection loss to W
> - httpd removes W from its worker tables, so requests are not dispatched
> to W

As soon as the worker W is marked in error the request are not forwarded 
to it. (That is already the since the very first beta of mod_cluster).
So removing would be removing a node, virtualhosts and contexts.

> - httpd also starts a timer, going off in configurable intervals, which
> tests W again. If W comes up again, httpd adds it again

NO:
- We can't unremove stuff.
- May be the customer has changed his configuration and doesn't want 
that httpd to proxy this node.
- the JAVA part will create it anyway (your comment below).

>
> Actually, I think the last point is not necessary, because when W is
> started again, mod-cluster/jboss will tell httpd ! We should actually
> *not* implement the last point because W might never get started again !

Yep ;-)

Cheers

Jean-Frederic

>
> WDYT ?
>
>