ip_hash detailed behaviour

Maxim Dounin mdounin at mdounin.ru
Fri Nov 15 17:34:42 UTC 2013


On Fri, Nov 15, 2013 at 03:13:44PM -0200, Martin Loy wrote:

> Hello
> I would like to know more about the behaviour of ip_hash when NGINX is
> reloaded and in the scenario of removing an upstream node.
> Is ip_hash somehow clever/sticky and would reasign the IPs to the same node
> after a reload or restart?

The ip_hash just uses a hash function to distribute clients among 
configured upstream servers.  If a number of upstream servers 
changes, the distribution changes as well.

> and what would happen if an upstream node is
> marked/flagged as down.

In this case clients which are normally passed to the server 
marked down will be distributed between other servers.

See http://nginx.org/r/ip_hash for more details.

Maxim Dounin

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