Re: [PATCH] ipvs: Fix reuse connection if RS weight is 0

hello

On Thu, Oct 28, 2021 at 5:09 AM Julian Anastasov [off-list ref] wrote:

        Hello,

On Wed, 27 Oct 2021, yangxingwu wrote:

quoted

what we want is if RS weight is 0, then no new connections should be
served even if conn_reuse_mode is 0, just as commit dc7b3eb900aa
("ipvs: Fix reuse connection if real server is
dead") trying to do

Pls let me know if there are any other issues of concern

        My concern is with the behaviour people expect
from each sysctl var: conn_reuse_mode decides if port reuse
is considered for rescheduling and expire_nodest_conn
should have priority only for unavailable servers (nodest means
No Destination), not in this case.

        We don't know how people use the conn_reuse_mode=0
mode, one may bind to a local port and try to send multiple
connections in a row with the hope they will go to same real
server, i.e. as part from same "session", even while weight=0.
If they do not want such behaviour (99% of the cases), they
will use the default conn_reuse_mode=1. OTOH, you have different
expectations for mode 0, not sure why but you do not want to use
the default mode=1 which is safer to use. May be the setups
forget to stay with conn_reuse_mode=1 on kernels 5.9+ and
set the var to 0 ?

The problem is we can NOT decide what the customers do, many of them
run kubernetes with old versions of kube-proxy. And most importantly,
upgrade to new version is a very long and painful process, that's why
we want to fix this at the kernel level

        The problem with mentioned commit dc7b3eb900aa is that
it breaks FTP and persistent connections while the goal of
weight=0 is graceful inhibition of the server. We made
the mistake to add priority for expire_nodest_conn when weight=0.
This can be fixed with a !cp->control check. We do not want
expire_nodest_conn to kill every connection during the
graceful period.

ok, got it, I will try to fix this problem

Regards

--
Julian Anastasov [off-list ref]