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My question is pretty simple, and I have been unable to determine this from the amazon documentation.

When I attach a new node to an ELB (whether by having an auto scaling policy execute, or manually) does the ELB wait for the health check to pass before enabling the node, or do new nodes get a "innocent until proven guilty" approach when being added?

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up vote 2 down vote accepted

ELB will check the instance and wait for the configured number of healthy checks to succeed.

During this time, ELB's status for that instance will show as "Instance registration in progress".

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Thanks. That seems a bit counter intuitive. For example, I have an auto-scale policy that will add nodes, but the time to detect a spike and then add a node, is extended by the ELB health check. I don't want to spam my nodes with health check requests every 15 seconds if I can prevent it... but it seems I will have to. – BoomShaka Apr 16 '13 at 16:38
Surely you don't want a node that failed somehow in provisioning to start receiving requests. Your health check endpoint should be something that uses minimal resources, mine runs every 6 seconds with no appreciable load on the servers. – ceejayoz Apr 16 '13 at 16:56
Yeah, I guess you have a point. Thanks for the help. – BoomShaka Apr 17 '13 at 21:11

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