Linux LVS Server (Mansoor Ali)

Tue Jan 30 21:10:42 GMT 2007

Currently I am using the ldirectord. but so far in terms of detecting the 
failed Server, its performance is not that good. Thanks for the suggestion, 
now i will try the keepalived.

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>Subject: lvs-users Digest, Vol 48, Issue 30
>Date: Tue, 30 Jan 2007 17:52:06 +0100 (CET)
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>Today's Topics:
>
>    1. Linux LVS Server (Mansoor Ali)
>    2. Re: Linux LVS Server (Vin?cius Kopelke)
>    3. Re: Linux LVS Server (Graeme Fowler)
>    4. RE: Linux LVS Server (Errol Neal)
>    5. Re: Realservers as client (Joseph Mack NA3T)
>    6. Major issue with LVS-DR when a server gets overloaded
>       (Matthias Saou)
>    7. Re: Major issue with LVS-DR when a server gets overloaded
>       (Joseph Mack NA3T)
>    8. real servers adding with virtual server / directors (vlrk)
>    9. ipt_connlimit through LVS? (Don Sizemore)
>   10. Problem with IP-takeover (Ahmad Ndoung)

>From: "Mansoor Ali" <mhafeez72 at hotmail.com>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: lvs-users at LinuxVirtualServer.org
>Subject: Linux LVS Server
>Date: Tue, 30 Jan 2007 12:25:39 +0000
>Hello guys
>
>I want to ask one thing about the Linux LVS Solution. I have setup the 
>LVS-NAT solution, it worked fine but i m having one small issue onto it. If 
>one of my real server is down,switched-off the Director does not detect it 
>immediatley as well the connections are not forwarded immediately to the 
>second Real Server. At times even it is very difficult to make connection 
>with the Second Real Server.
>
>Is this normal with LVS or there can be some specific configuration 
>required in this regard?
>
>Mani Ali
>
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>From: Vinícius Kopelke <vini at floripa.com.br>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>Subject: Re: Linux LVS Server
>Date: Tue, 30 Jan 2007 10:36:50 -0200
>>>Is this normal with LVS or there can be some specific configuration 
>>>required
>in this regard?
>
>Yes it´s normal. For real servers health checking I use keepalived 
>www.keepalived.org.
>When one of the server of the LVS server pool is down, keepalived informs 
>the linux kernel via a setsockopt call to remove this server entrie from 
>the LVS topology.
>When the server comes up, keepalived add it again.
>
>Its very usefull and easy for implement.
>
>good luck!
>
>----- Original Message ----- From: "Mansoor Ali" <mhafeez72 at hotmail.com>
>To: <lvs-users at LinuxVirtualServer.org>
>Sent: Tuesday, January 30, 2007 10:25 AM
>Subject: Linux LVS Server
>
>
>>Hello guys
>>
>>I want to ask one thing about the Linux LVS Solution. I have setup the 
>>LVS-NAT solution, it worked fine but i m having one small issue onto it. 
>>If one of my real server is down,switched-off the Director does not detect 
>>it immediatley as well the connections are not forwarded immediately to 
>>the second Real Server. At times even it is very difficult to make 
>>connection with the Second Real Server.
>>
>>Is this normal with LVS or there can be some specific configuration 
>>required in this regard?
>>
>>Mani Ali
>>
>>_________________________________________________________________
>>MSN Hotmail is evolving - check out the new Windows Live Mail 
>>http://ideas.live.com
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>>_______________________________________________
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>>Send requests to lvs-users-request at LinuxVirtualServer.org
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>>
>

>From: Graeme Fowler <graeme at graemef.net>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>Subject: Re: Linux LVS Server
>Date: Tue, 30 Jan 2007 12:37:32 +0000
>On 30/01/2007 12:25, Mansoor Ali wrote:
>>I want to ask one thing about the Linux LVS Solution. I have setup the 
>>LVS-NAT solution, it worked fine but i m having one small issue onto it. 
>>If one of my real server is down,switched-off the Director does not detect 
>>it immediatley as well the connections are not forwarded immediately to 
>>the second Real Server. At times even it is very difficult to make 
>>connection with the Second Real Server.
>
>Depending on your setup this is to be expected.
>
>>Is this normal with LVS or there can be some specific configuration 
>>required in this regard?
>
>LVS itself provides no healthcheck facility - it's just a flashy router. 
>You need to add something to it for the high-availability aspects, some of 
>which are described here:
>
>http://www.linuxvirtualserver.org/HighAvailability.html
>
>The two (apparently, although this is not a scientific analysis!) most 
>popular are:
>
>ldirectord http://www.vergenet.net/linux/ldirectord/
>keepalived http://www.keepalived.org/
>
>Graeme

>From: "Errol Neal" <eneal at dfi-intl.com>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>Subject: RE: Linux LVS Server
>Date: Tue, 30 Jan 2007 07:53:58 -0500
> >> Hello guys
>
> >> If one of my real server is down,switched-off the Director does not
>detect it immediatley >> as well the connections are not forwarded ....
>
>You should check out http://www.keepalived.org. It's a VRRP
>implementation that supports high availability, health checking and
>more. It should suffice.
>
>** please note, that the keepalived.conf file is where you'll also
>implement your LVS config
>
>
>
>Errol

>From: Joseph Mack NA3T <jmack at wm7d.net>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: leon at trusc.net,<lvs-users at LinuxVirtualServer.org>
>Subject: Re: Realservers as client
>Date: Tue, 30 Jan 2007 04:59:04 -0800 (PST)
>On Tue, 30 Jan 2007, Leon Botes wrote:
>
>>Well the services on the real servers that need to connect to the database 
>>are themselves balanced. The situation where maybe the database on the 
>>real server dies but the application continues to run would create a 
>>scenario where the application would not be able to write to the database 
>>yet the application would still respond to client requests.
>
>yes you have to handle failover but don't confuse loadbalancing with 
>failover
>
>Joe

>From: Matthias 
>Saou<thias at spam.spam.spam.spam.spam.spam.spam.egg.and.spam.freshrpms.net>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>Subject: Major issue with LVS-DR when a server gets overloaded
>Date: Tue, 30 Jan 2007 14:22:58 +0100
>Hi,
>
>I've been using a Foundry Networks ServerIron XL until now, with DSR
>("Direct Server Response" aka "Direct Response", "DR") to load-balance
>one virtual server to six real web servers.
>
>All 6 real servers are identical and have the same weight. When one of
>the real web servers gets overloaded, the URL checked on it starts
>sending a 500 status code instead of the normal 200. In this case, I
>would expect the real server to be taken out of the load-balancing and
>all traffic to be sent to the other 5 remaining real servers. But no.
>
>In the above scenario, what I saw in the ServerIron logs was that the
>real server was properly detected as "down", but all web traffic got
>sent to this server instead of having it taken offline(!!), nothing
>sent to the others, thus timeouts and some 500 errors for all clients,
>and a real server in bad shape, needing to be rebooted in many cases.
>
>I thought this was a bug with the ServerIron. So I looked at LVS.
>
>I implemented a parallel identical setup using LVS and keepalived. The
>setup is similar, with LVS-DR and all 6 real web servers. Only the
>virtual server IP address changes, obviously, to keep both setups
>in parallel.
>
>My limited testing worked fine, but when I started sending real
>traffic, the exact same issue as with the ServerIron happened!
>Symptoms :
>- The virtual IP address no longer responds on port 80, it times out
>- The real server having problems gets REALLY overloaded
>- All other 5 real servers no longer receive any traffic
>- ipvsadm show no new active or inactive connections (counters stay the
>same), only the persistent connections counters decrease slowly (as
>expected since there are no new connections...)
>
>Even after restarting the problematic real server, keepalived re-adds
>it properly, but nothing works anymore. I need to restart keepalived
>(which flushes the ipvsadm configuration by default) for things to
>start working again.
>
>I am really confused. I've tried stopping the web daemon on one of the
>real servers under production load, and it gets taken out as expected,
>and all keeps working fine. It seems that only when the web server still
>responds with 500 status and gets detected as down, then up, then down
>again etc. does the problem appear. Note that the setup can work fine
>for hours and hours, the issue only appears when a real server has a
>problem.
>
>I would like to have tried some kind of "keep the real server disabled
>for n seconds when it's detected as down" in order to keep the check
>from flip-flopping like this, but there is no such setting in
>keepalived AFAICS.
>
>Has anyone already seen a similar problem? I've read many posts in the
>archive regarding LVS-DR issues, but haven't seen anyone complaining
>from the same, and it seems like the LVS-DR setup works fine for many!
>
>Details :
>- RHEL4 i386 fully updated (2.6.9-42.0.3.ELsmp) on all servers
>- lighttpd and PHP web servers
>- ipvsadm 1.24-6 (from RHN)
>- keepalived 1.1.13
>- virtual server IP address configured as lo:0 on all real servers
>- sysctl changes made on real servers :
>net.ipv4.conf.eth0.arp_ignore = 2 (public lan)
>net.ipv4.conf.eth1.arp_ignore = 2 (private lan)
>- each real server is outputting approx. 3Mbps
>
>I've tried with sh, lc and rr schedulers, but same thing with all.
>
>...help!? :-)
>
>Matthias

>From: Joseph Mack NA3T <jmack at wm7d.net>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>Subject: Re: Major issue with LVS-DR when a server gets overloaded
>Date: Tue, 30 Jan 2007 06:13:57 -0800 (PST)
>On Tue, 30 Jan 2007, Matthias Saou wrote:
>
>>traffic, the exact same issue as with the ServerIron happened!
>>Symptoms :
>>- The virtual IP address no longer responds on port 80, it times out
>>- The real server having problems gets REALLY overloaded
>
>perhaps you should ask about this on the keepalived mailing list. There 
>should be a hysteresis that stops the realserver flapping.
>
>>- All other 5 real servers no longer receive any traffic
>>- ipvsadm show no new active or inactive connections (counters stay the
>>same), only the persistent connections counters decrease slowly (as
>>expected since there are no new connections...)
>
>never seen this before. The other realservers should be receiving packets 
>just fine unless something else is jammed (eg the upstream router is 
>overloaded with icmp unreachable)
>
>>I would like to have tried some kind of "keep the real server disabled
>>for n seconds when it's detected as down" in order to keep the check
>>from flip-flopping like this, but there is no such setting in
>>keepalived AFAICS.
>
>I'm surprised it's not in there. Ask ALexandre about it.
>
>Joe

>From: vlrk <tech_voip at yahoo.co.in>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: lvs-users at LinuxVirtualServer.org
>Subject: real servers adding with virtual server / directors
>Date: Tue, 30 Jan 2007 14:44:08 +0000 (GMT)
>Hello list,
>
>Iam running ipvs and i could not able to add real
>servers to director/ virtual server .
>
>My scenarios is as below.
>
>A-> 192.168.68.49 ( director)
>B-> 192.168.68.73 (real server)
>C-> 192.168.68.49 (real server)
>
>I have kernel version 2.6.10 running redhat EL in
>three machines .
>
>My aim is to acheive the following architectures
>
>in B and C iam running the telnet service so any body
>connectes to telent 192.168.68.49 it has to check with
>real servers and connect to them based on availability
>.
>
>I want use tunneling .
>
>the following commands i used .
>
>ipvsadm -A -t 192.168.68.49:23
>ipvsadm -a -t 192.168.68.49:23 -r 192.168.68.73:23 -i
>ipvsadm -a -t 192.168.68.49:23 -r 192.168.68.74:23 -i
>
>and in sysctl.conf of all ips ipv4 forward is enabled.
>No firewall or iptables running.
>
>if i try to connect from other machine like .254 it s
>trying to connect and in A machine if see ipvsdm it
>shows that 74 machine connection state as inactive, it
>never tries to 73.
>
>as a matter of fact i never seen B and C as connected
>state in director when i see with ipvsadm.
>
>
>so how to solve this .
>
>Am i missing any thing here .
>
>regards
>vlrk
>
>
>
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>From: Don Sizemore <dls at metalab.unc.edu>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: lvs-users at LinuxVirtualServer.org
>Subject: ipt_connlimit through LVS?
>Date: Tue, 30 Jan 2007 10:39:07 -0500 (EST)
>
>   hi all,
>
>   probably a dumb question on my part, but my googling and ipvsadm 
>man-paging hasn't turned up what i'm looking for.  is there any way to 
>limit connections per IP through IPVS, to mimic the netfilter connection 
>limit module ipt_connlimit?
>
>   i see ipvsadm's threshold option, but it does totals per server.
>
>   thank you,					919.962.5646 w
>   donald sizemore, ii				919.260.4915 c
>   ibiblio.org n stoof				919.962.8071 f

>From: "Ahmad Ndoung" <hasman16 at gmail.com>
>Reply-To: "LinuxVirtualServer.org users mailing 
>list."<lvs-users at LinuxVirtualServer.org>
>To: lvs-users at LinuxVirtualServer.org
>Subject: Problem with IP-takeover
>Date: Tue, 30 Jan 2007 10:51:52 -0600
>Hi to all
>I have a problem with my system and need help.
>I am using RHEL 4 in 4 machines, 2 for load balancing and 2 real servers.
>The master load balancer works fine but the problem is when it goes down 
>and
>after the backup system kicks in, it does not inherit the VIP, is there any
>way this can be done automatically?
>What should I look for in my systems to make sure that I have the proper
>configuration.
>
>Thanks

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