[mod_cluster-dev] Powering down a worker
Bela Ban
bban at redhat.com
Wed Jun 9 08:43:06 EDT 2010
I have the scenario where I run httpd/mod-cluster on an EC2 instance and
a few workers on different EC2 instances.
When I "terminate" a worker instance (using the EC2 GUI), apparently the
virtual instance is terminated *ungracefully*, ie. similar to just
pulling the power plug. This means that the shutdown scripts (in
/etc/rc0.d) are not run, and the open sockets (e.g. to mod-cluster) are
not closed, so mod-cluster won't remove the worker.
When I look at mod_cluster_manager, it continues listing the killed
worker in OK state.
My questions:
* I recall that, unlike mod-jk, mod-cluster doesn't have
cping/cpong, or any other heartbeating mechanism. Is this correct
? So would mod-cluster detect a worker's unreachability, e.g. when
I pull the plug on the switch connecting the worker to mod-cluster ?
* I though that the workers detect when a member has crashed and the
cluster master then notifies the proxy. So when we have workers
{A,B,C}, and C crashes ungracefully, wouldn't A notify the proxy
of C's death, so the proxy can remove C ?
--
Bela Ban
Lead JGroups / Clustering Team
JBoss
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