This reverts commit 266b1a8 ("MEDIUM: server: Inherit CLI weight changes and
agent-check weight responses") from Michal Idzikowski, which is still broken.
It stops propagating weights at the first error encountered, leaving servers
in a random state depending on what LB algorithms are used on other servers
tracking the one experiencing the weight change. It's unsure what the best
way to address this is, but we cannot leave the servers in an inconsistent
state between farms. For example :
backend site1
mode http
balance uri
hash-type consistent
server s1 127.0.0.1:8001 weight 10 track servers/s1
backend site2
mode http
balance uri
server s1 127.0.0.1:8001 weight 10 track servers/s1
backend site3
mode http
balance uri
hash-type consistent
server s1 127.0.0.1:8001 weight 10 track servers/s1
backend servers
server s1 127.0.0.1:8001 weight 10 check inter 1s
The weight change is applied on "servers/s1". It tries to propagate
to the servers tracking it, which are site1/s1, site2/s1 and site3/s1.
Let's say that "weight 50%" is requested. The servers are linked in
reverse-order, so the change is applied to "servers/s1", then to
"site3/s1", then to "site2/s1" and this one fails and rejects the
change. The change is aborted and never propagated to "site1/s1",
which keeps the server in a different state from "site3/s1". At the
very least, in case of error, the changes should probably be unrolled.
Also the error reported on the CLI (when changing from the CLI) simply says :
Backend is using a static LB algorithm and only accepts weights '0%' and '100%'.
Without more indications what the faulty backend is.
Let's revert this change for now, as initially feared it will definitely
cause more harm than good and at least needs to be revisited. It was never
backported to any stable branch so no backport is needed.
04bf98149b