[Bug 1308314] [NEW] incorrect balancing in weight value 256

[Tom Zhou]

Public bug reported:

Haproxy can work correctly with wight 256,  the node with weight 256
either takes all the traffic or takes none traffic:

1-1 weight: web1:256, web2:1, web3:1 (incorrect case.)
(1024 accesses * 3 times to vip)
result 1
web1: 1024
web2: 0
web3: 0
result 2
web1: 1024
web2: 0
web3: 0
result 3
web1 counted: 1024
web2 counted: 0
web3 counted: 0

1-2 weight: web1:255, web2:1, web3:1 (correct case.)
(1024 accesses * 3 times to vip)
result 1
web1 counted: 1017
web2 counted: 4
web3 counted: 3
result 2
web1 counted: 1016
web2 counted: 4
web3 counted: 4
result 3
web1 counted: 1016
web2 counted: 4
web3 counted: 4

2-1 web1:256, web2:128, web3:128 (incorrect case.)
(256 accesses * 3 times to vip)
result 1
web1 counted: 1
web2 counted: 128
web3 counted: 127
result 2
web1 counted: 0
web2 counted: 128
web3 counted: 128
result 3
web1 counted: 0
web2 counted: 128
web3 counted: 128

2-2 web1:255, web2:128, web3:128(correct case.)
(256 accesses * 3 times to vip)
result 1
web1 counted: 128
web2 counted: 64
web3 counted: 64
result 2
web1 counted: 128
web2 counted: 64
web3 counted: 64
result 3
web1 counted: 128
web2 counted: 64
web3 counted: 64

>From the haproxy aspect, they have fixed a bug of "Roundrobin can not
work well when a server's weight is 256" , make sure that below patch
has been used on above environment.

  Mail of "Roundrobin can not work well when a server's weight is 256"
  https://www.mail-archive.com/haproxy@formilux.org/msg10613.html
  Patch:
  https://dev.openwrt.org/browser/packages/net/haproxy/patches/0005-BUG-MEDIUM-server-set-the-macro-for-server-s-max-wei.patch

** Affects: haproxy (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1308314

Title:
  incorrect balancing in weight value 256

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