Hello! On Sat, Feb 01, 2020 at 11:48:00AM -0800, Ian Morris Nieves wrote:
> Here is the setup: > - I am running nginx in a single docker container and it has an > upstream to a docker service which is composed of 3 docker > containers (which happens to be php-fpm) > - the service is configured to _not_ expose a single virtual ip > address (vip), instead the service exposes the ip addresses of > all 3 containers through docker’s built-in DNS. When this DNS > is asked for the IP address of the service it will respond with > a list of 3 IP address but the list will rotate in round-robin > fashion each time a lookup is performed. Thus the first IP in > the list will not be the same for any 2 consecutive lookups. > > My first question is: > Is it the correct behavior that consistent hashing depends on > the order of IP addresses in the DNS query response? I can > imagine arguments either way, and it is possible that this > critical detail is outside the scope of consistent hashing. I > will also forward this question to the author of Ketama. Consistent hashing uses the _name_ as written in the configuration, not the IP addresses the name resolves to. If a name resolves to multiple IP addresses, these addresses are considered equal and requests are distributed between them using round-robin balancing. That is, to balance multiple servers (containers) using consistent hashing, you have to configure an upstream block with multiple "server" directives in it. -- Maxim Dounin http://mdounin.ru/ _______________________________________________ nginx mailing list nginx@nginx.org http://mailman.nginx.org/mailman/listinfo/nginx
