What is Drain in Loadbalancer

A feature in Load balancer called server draining enables you to take a server offline without any loss of service to users. When a server is drained it stops taking new connections and calls. These new connections and calls are routed through other servers in the pool. A server being drained allows its sessions on existing connections to continue until they naturally end. When all existing sessions have ended, the server is ready to be taken offline.
Most external load-balancing devices do not have this concept of a drain time; they simply persist the existing connections on a server and redirect new connections to other servers

Load balancer node conditions
ENABLED Node is permitted to accept new connections.
DISABLED Node is not permitted to accept any new connections regardless of session persistence configuration. Existing connections are forcibly terminated.
DRAINING Node is allowed to service existing established connections and connections that are being directed to it as a result of the session persistence configuration.

AWS ELB how to configure
http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/config-conn-drain.html
F5 how to
https://support.f5.com/kb/en-us/products/big-ip_gtm/manuals/product/bigipgtm9_2_2/BIG-IP_9_2_2GTM_Guide-09-1.html

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Posted on October 15, 2014, in Networking. Bookmark the permalink. Leave a comment.

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