Re: [lvs-users] ipvsadm stop-daemon command

To: Ryan O'Hara <rohara@xxxxxxxxxx>
Subject: Re: [lvs-users] ipvsadm stop-daemon command
Cc: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
From: Simon Horman <horms@xxxxxxxxxxxx>
Date: Thu, 13 Oct 2011 07:40:19 +0900
Hi Ryan,

On Wed, Oct 12, 2011 at 04:12:12PM -0500, Ryan O'Hara wrote:
> What is the purpose of passing a state parameter (backup or master) to
> the ipvsadm stop-daemon command? I fully understand why a state
> parameter is desirable for the start-daemon command, but I can't think
> of why stop-daemon would need this information. Is there more going on
> that simply stopping the sync daemon?

It is possible to have both the master and backup daemon running at the
same time and the purpose of the state parameter to the stop-daemon command
is to allow them to be stopped individually.

> There is no description of the stop-daemon command in the ipvsadm(8)
> man page. Furthermore, it appears there is some inconsistencies in the
> man page with respect to the required state parameter.

It seems that the documentation predates the ability to have more than
one daemon running on a load balancer. Does the following text make
things clearer?

--start-daemon state

        Start the connection synchronization daemon. The state may be
        master or backup. The connection synchronization daemon is
        implemented inside the Linux kernel. Daemons in one or both
        states may be started on a load balancer.

        A daemon running in the master state sends updates of connections
        handled by the load balancer periodically using multicast.  A
        daemon in the backup state receives multicast message and creates
        corresponding connection entries in kernel.

        In a case where a primary load balancer running a synchronisation
        daemon in the master state fails. If a backup load balancer that
        has been running the synchronisation daemon in the backup state
        takes over it will have state of almost all established connections
        and these connections can continue to access the service.

        Daemons may be stopped using --stop-daemon

--stop-daemon state

        Stop the connection synchronization daemon. The state may be master
        or backup and should match the state set when starting the daemon
        that is to be stopped.

        Daemons may be started using --start-daemon

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