Ultra Monkey: High Availability and Load Balancing Solution for Linux [Monkey]
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Ultra Monkey 3 : Download | Installation | Configuration || Linux Virtual Server | Linux-HA | Ldirectord


Ldirectord [offsite] runs on linux-directors to monitor the health of the real-servers by periodically making a request and checking for an expected response. For HTTP servers this means requesting a known URL and checking that the response contains an expected string. This is called a "negotiate" check. Ldirectord has support for performing a negotiate check for HTTP, HTTPS, FTP, IMAP, POP, SMTP, LDAP, NNTP and MySQL servers. Adding negotiate check support for other protocols is usually quite simple. Ldirectord is also able to perform a simple check "connect" check for other servcies. The connect check simply verifies that the port on the real-servers is able to accept a connection.

If a real-servers fails then the server is made quiescent and will be reinserted once it comes back on line. If all the real-servers are down then a fall-back server is inserted into the pool, which will be made quiescent one of the real web servers comes back on line. Typically, the fall-back server is localhost. If an HTTP virtual service is being provided then it is useful to run an Apache HTTP server that returns a page indicating that the service is temporarily inaccessible.

Details on how to configure ldirectord are included in the discussion of sample topologies. Some additional techincal notes on running ldirectord are also provided. Ultra Monkey 3 makes use of ldirectord, which is also known as ldriectordy 1.99. The reason the same version has two different version numbers is because it lives in two different branches of the linux-HA CVS tree, this is not relevant to Ultra Monkey's operation.

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Last Updated: Sat Mar 4 16:33:57 2006 +0900

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