Terry L. Inzauro wrote: > Quanah Gibson-Mount wrote: >> >> --On Thursday, October 12, 2006 9:04 PM +0200 Michael Ströder >> <[EMAIL PROTECTED]> wrote: >> >>> HI! >>> >>> I support Giovanni's statement that fail-over should preferrably be >>> implemented in LDAP clients. Because the client really knows what to do >>> if all fails. In practice this means to really teach the developers hard! >> Sadly, Stanford has plenty of proprietary software that accesses our >> LDAP servers. >> >>> Regarding TCP-level load-balancers: Typically the servers are located in >>> one data center. IMHO this works quite well for most read-only >>> applications. If you need fail-over for write requests you either need >>> multi-master replication (with lack of data integrity) or some sort of >>> hot-standby server which completely takes over the service. >>> >>> Also with using proxy servers for balancing the requests you should >>> carefully think about your network topology to avoid WAN traffic to >>> other data centers. >>> >>> If you'd like to implement fail-over between different locations >>> probably DNS gets involved. But not simply DNS round robin! >> >> Stanford uses a software load balancer to a pool of replica systems (in >> our case, we have a single source system for all writes, so we don't >> worry about applications writing to the directories). The main issue >> I've found with using the software load balancer is that Java caches the >> returned IP, so you need to do some junk to get it to do retries if the >> connection to the system it is talking to fails. >> >> The software we use lets you run external commands on each individual >> system that help determine the weights, so it is more than simple DNS >> round robin. For example, in Stanford's case, we have it run a local >> ldapsearch to verify slapd is running. If it is successful, then it >> uses the system load to determine the weight. If it is unsuccessful, it >> makes the weight extremely high, essentially dropping it from the pool. >> >> --Quanah >> >> -- >> Quanah Gibson-Mount >> Principal Software Developer >> ITS/Shared Application Services >> Stanford University >> GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html >> >> --- >> You are currently subscribed to [email protected] as: >> [EMAIL PROTECTED] >> To unsubscribe send email to [EMAIL PROTECTED] with the word >> UNSUBSCRIBE as the SUBJECT of the message. > > > can i ask what you use for your software based load balancer linux lvs or is > it a "stanford" in-house application. > > > _Terry > > > >
oops. please disregard my previous post. it helps to read further down the thread ;) happy friday the 13! _Terry --- You are currently subscribed to [email protected] as: [EMAIL PROTECTED] To unsubscribe send email to [EMAIL PROTECTED] with the word UNSUBSCRIBE as the SUBJECT of the message.
