Re: Does perl have Failover with Open Source Web Platforms?
> If a 30 second delay is acceptable, even round robin dns forms a type of > failover. If the first ip fails, the browser tries the second, etc. This is incorrect. IE does support some aliveness checking (http://www.geocities.com/tufansevim/dnsroundrobin.html) and will cycle through A records till it gets a response, but this is not specification and most dns resolvers and will not work for all clients. (http://www.acmebw.com/askmrdns/archive.php?category=81&question=359). Round Robin DNS should only be used in load sharing (it does not load balance) scenario until most DNS resolvers handle DNS SRV records, which will be the correct way for a DNS to provide failover. (http://www.isc.org/ml-archives/bind-users/2000/09/msg00350.html) LVS, as you mentioned, is an excellent solution. If you want to stay with a DNS solution then one of the Dynamic DNS servers may fit the bill, but your end up with other problems. - the name server propagation time you'll have - the problem of driving a lot of traffic to your DNS server because of the low TTL's. - DNS servers that don't honor TTL times that are too low - then giving out that bad info to it's users Christian Brink
Re: Does perl have Failover with Open Source Web Platforms?
Richard Heintze wrote: He needs declarative role based authorization and authentication for his web site -- and maybe fault tolerance too depending on the price of the hardware for a linux server. These are two separate things. Authen/Authz can be implemented any way you like on mod_perl. It does not impose an application structure. If you want an already built implementation, you could look at some of the many auth modules on CPAN or at OpenInteract which includes a user/group security model. For the CPAN list, start here: http://www.cpan.org/modules/00modlist.long.html#ID15_WorldWideW and look at the PerlAuthenHandler and PerlAuthzHandler modules. For failover, the question is what are you failing over? Any old load-balancer will give you failover between machines. Failing over your data is a matter of how you implement your application. I believe JBoss fails over session data. You get the same result with mod_perl if you store your session data in a database, using something like Apache::Session. Also, what are your favorite hardware vendors for linux clusters? Red Hat sells a software failover system that you can use, but most people just use a load-balancing switch like big/ip for this. No special hardware or software is required for that. - Perrin
Re: Does perl have Failover with Open Source Web Platforms?
On March 13, 2003 11:48 am, Richard Heintze wrote: > My client is partial to perl so I installed mod_perl > on Apache HTTPD on his windows servers. > > Now, however, he wants to price a linux cluster with > raid to replace his windows servers. > > He needs declarative role based authorization and > authentication for his web site -- and maybe fault > tolerance too depending on the price of the hardware > for a linux server. > > JBoss is cheap and open source with these features. And its java and may not perform as well as well formed mod_perl, but I'm probably opining from my impressions based on BEA on slowlaris compared to mod_perl on linux. > My client, however, is partial to perl. How can we get > perl with failover on a linux cluster? Lots of different ways. Depends on where you want the failover; If a 30 second delay is acceptable, even round robin dns forms a type of failover. If the first ip fails, the browser tries the second, etc. Then you separate application server from db, and put the db on some kind of redundancy/failover; like a app level retry list, a OS level failover, with proxy ARP and whatever to minimize downtime etc. An overview of OS level failover on linux: http://www.linuxvirtualserver.org/Documents.html So in summary, failover is a big fat word with lots of meaning. The faster you want it, the more money you spend. A 30 second failover was good enough for me, so I used round robin dns. Your mileage my vary. > Also, what are your favorite hardware vendors for > linux clusters? Whitebox hardware with name brand components, but I'm cheap. This is another question that is too broad. What level of service do you require? My local clone shop knows dick about linux but is happy to sell me machines with no OS loaded. You may want Scyld.com or one of the other cluster specialists if you are talking getting vendor expertise. They tend to focus on compute clusters, not web. -- Jay "yohimbe" Thorne [EMAIL PROTECTED] Mgr Sys & Tech, Userfriendly.org
