David, Exactly.
Robert On Nov 29, 2012, at 1 :57 PM, David Coulson <[email protected]> wrote: > You can do that, but haproxy doesn't have anything to do with the failover > process, other than you run an instance of haproxy on one server, and another > instance on your backup system. As I said, neither of the haproxy instances > communicate anything, so all you need to do is move the IP clients are using > from one server to the other in order to handle a failure. Moving the IP > around is something keepalived, pacemaker, etc handles - Look at their > documentation for specifics and challenges in a two-node config. > > HAProxy doesn't have a concent of primary and backup in terms of it's own > instances. Each of them is stand alone. It's up to you, based on your > network/IP config which one has traffic routed to it. > > David > > > On 11/29/12 1:53 PM, Hermes Flying wrote: >> But if I install 2 HAProxy as load balancers, doesn't one act as the primary >> loadbalancer directing the load to the known servers while the secondary >> takes over load distribution as soon as the heartbeat fails? I remember >> reading this. Is this wrong? >> >> From: David Coulson <[email protected]> >> To: Hermes Flying <[email protected]> >> Cc: Baptiste <[email protected]>; "[email protected]" >> <[email protected]> >> Sent: Thursday, November 29, 2012 8:39 PM >> Subject: Re: HAproxy and detect split-brain (network failures) >> >> You are mixing two totally different things together. >> >> 1) HAProxy will do periodic health checks of backend systems you are routing >> to. Depending if you configure something as 'backup' or 'not backup' will >> determine if/how traffic is routed to it. The backend systems do not 'take >> over'. Haproxy just routes traffic to systems based on your configuration. >> The backend systems don't know/care about the other backend nodes, unless >> your application requires it which is a different story and nothing to do >> with haproxy. HAproxy only cares about a single instance of itself - If you >> have more than one haproxy instance, they do NOT communicate anything >> between each other. >> >> 2) In terms of keepalived, pacemaker, etc, it makes no difference which you >> use with haproxy - all they do is manage the IP address(es) which haproxy is >> listening on, and perhaps restart haproxy if it dies. Their configuration >> and how you maintain quorum in a two-node configuration is a question for >> one of their mailing lists, or just read their documentation. I personally >> use pacemaker. >> >> On 11/29/12 1:35 PM, Hermes Flying wrote: >>> Well I don't follow: >>> "You can have a pool of primary that it routes across, then backup systems >>> that are only used when all primary systems are unavailable." >>> When you are saying that "the backup systems that are used when primary >>> systems are unavailable", how do they decide to take over? How do they know >>> that the other systems are unavailable? >>> Are you saying that they depend on third party components like the ones you >>> mentioned (Keepalived etc)? In this case, what is the most suitable tool to >>> be used along with HAProxy? Is there a reference manual for this somewhere? >>> >>> From: David Coulson mailto:[email protected] >>> To: Hermes Flying mailto:[email protected] >>> Cc: Baptiste mailto:[email protected]; mailto:[email protected] >>> mailto:[email protected] >>> Sent: Thursday, November 29, 2012 8:21 PM >>> Subject: Re: HAproxy and detect split-brain (network failures) >>> >>> HAProxy only does primary and backup in terms of active backend systems - >>> You can have a pool of primary that it routes across, then backup systems >>> that are only used when all primary systems are unavailable. >>> >>> There is no concept of a cluster in terms of haproxy instances, although >>> you can run more than one and manage them via something like pacemaker, >>> keepalived or rgmanager. >>> >>> On 11/29/12 1:19 PM, Hermes Flying wrote: >>>> Hi, >>>> From a quick look into HAProxy, I see that it is a Primary/backup >>>> architecture. So isn't ensuring that both "nodes" don't become primary >>>> part of HAProxy's primary/backup "protocol" ? >>>> >>>> From: Baptiste mailto:[email protected] >>>> To: Hermes Flying mailto:[email protected] >>>> Cc: mailto:[email protected] mailto:[email protected] >>>> Sent: Thursday, November 29, 2012 3:02 PM >>>> Subject: Re: HAproxy and detect split-brain (network failures) >>>> >>>> Hi, >>>> >>>> This is not HAProxy's role, this is the tool you use to ensure high >>>> availability to do that. >>>> >>>> I could see a way where HAProxy can report one interface failing, >>>> maybe this could help you to detect if you're in a split brain >>>> situation. >>>> >>>> cheers >>>> >>>> >>>> >>>> On Thu, Nov 29, 2012 at 11:51 AM, Hermes Flying <[email protected]> >>>> wrote: >>>> > Hi, >>>> > I am looking into using HAProxy as our load balancer. >>>> > I see that you are using a primary/backup approach. I was wondering how >>>> > does >>>> > HAProxy (if it does) address split-brain situation? Do you have a >>>> > mechanism >>>> > to detect and avoid it? Do you have some standard recommendation to all >>>> > those using your solution? >>>> > >>>> > Thanks >>>> >>>> >>> >>> >>> >> >> >> > ____________________________________________ Robert Snyder Outreach Technology Services The Pennsylvania State University The 329 Building, Suite 306E University Park PA 16802 Phone: 814-865-0912 E-mail: [email protected]
