On Wed, 2007-10-03 at 11:14 +0800, Orlando Andico wrote: > Even HTTP tries (badly) to maintain session state by > using cookies. If you are failed over to another web > server, how does your session state (cookies and > associated data) follow you?
some people solve that by putting cookies and sessions (php sessions, for instance), in the database. others solve it by putting them on NFS. No solution is perfect. NFS is probably the more general solution since it will correctly handle handoffs of uploaded files (db can handle sessions, but I don't know how, in PHP for instance, to have uploaded files go straight to the DB, so for at least uploaded files, you have to have a filesystem somewhere). I'm not clear on how well apache+php handles cookie filename generation. there are probably race conditions there. But I don't see a lot of whining about it, so it's probably not a big deal (i.e., statistically acceptable, probability of race condition exceeds the highest prime Bruce Schneier can factor using just his fingers and toes, etc). > This is a huge problem domain that load-balancing alone > doesn't even begin to touch. I haven't seen commercial solutions for this, NFS is good enough for what I've worked with. But I'm sure banks and such would pay a lot more for assurances, uptime, and ease of use. > Some of the other offerings in the market offer true > zero-hands failover and true application-transparent > failover. And yes, some of them use a custom network > stack and custom election algorithms. As I'm just a > lowly consultant, I don't have access to the details > of the implementations. One of the downsides of > closed-source. > > You'd be amazed at how far and how much closed-source > can do. There's nothing that I know of like it in > the Free Software world. I've always been a pragmatist. And even without a lot of experience with enterprise software, I keep up enough to have an idea what some enterprise systems can do (and also, how terrible other enterprise systems can be). The trick though, is to work overseas, in some first world country where companies are willing to pay the equivalent of millions of pesos for software. In the philippines, most developers/sysads won't work with companies that are willing to pay that much. > Sure for playing around, YMMV. I don't work in the > playing around space. Or for low-budget niches. It's not all just about playing around. Many companies just can't afford the prices in the enterprise space (or if they can, it's a multi-year running battle to get multi-million peso purchases approved). Not everyone is in your space, Orly :-). tiger _________________________________________________ Philippine Linux Users' Group (PLUG) Mailing List [email protected] (#PLUG @ irc.free.net.ph) Read the Guidelines: http://linux.org.ph/lists Searchable Archives: http://archives.free.net.ph
