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simplify sticky balancer and fix a bug #4169

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Jun 7, 2019
Merged

simplify sticky balancer and fix a bug #4169

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b9b1ffb
simplify sticky balancer
ElvinEfendi Jun 6, 2019
e2c6202
bugfix: check all previously failing upstreams, not just the last one
ElvinEfendi Jun 6, 2019
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109 changes: 52 additions & 57 deletions rootfs/etc/nginx/lua/balancer/sticky.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -75,80 +75,75 @@ function _M.get_last_failure()
return ngx_balancer.get_last_failure()
end

function _M.balance(self)
local cookie, err = ck:new()
if not cookie then
ngx.log(ngx.ERR, "error while initializing cookie: " .. tostring(err))
return
local function get_failed_upstreams()
local indexed_upstream_addrs = {}
local upstream_addrs = split.split_upstream_var(ngx.var.upstream_addr) or {}

for _, addr in ipairs(upstream_addrs) do
indexed_upstream_addrs[addr] = true
end

-- upstream_from_cookie: upstream which is pointed by sticky cookie
local upstream_from_cookie = nil
return indexed_upstream_addrs
end

local key = cookie:get(self:cookie_name())
if key then
upstream_from_cookie = self.instance:find(key)
end
local function pick_new_upstream(self)
local failed_upstreams = get_failed_upstreams()

-- get state of the previous attempt
local state_name = self.get_last_failure()
for i = 1, MAX_UPSTREAM_CHECKS_COUNT do
local key = string.format("%s.%s.%s", ngx.now() + i, ngx.worker.pid(), math.random(999999))

if upstream_from_cookie ~= nil then
-- use previous upstream if this is the first attempt or previous attempt succeeded
-- or ingress is configured to ignore previous request result
if state_name == nil or not self.cookie_session_affinity.change_on_failure then
return upstream_from_cookie
local new_upstream = self.instance:find(key)

if not failed_upstreams[new_upstream] then
return new_upstream, key
end
end

-- failed_upstream: upstream which failed during previous attempt
local failed_upstream = nil

-- If previous attempt failed recent upstream can be obtained from ngx.var.upstream_addr.
-- Do nothing if ingress is configured to ignore previous request result.
if state_name ~= nil and self.cookie_session_affinity.change_on_failure then
local upstream_addr = ngx.var.upstream_addr
failed_upstream = split.get_last_value(upstream_addr)
return nil, nil
end

if failed_upstream == nil then
ngx.log(ngx.ERR, string.format("failed to get failed_upstream from upstream_addr (%s)", upstream_addr))
local function should_set_cookie(self)
if self.cookie_session_affinity.locations then
local locs = self.cookie_session_affinity.locations[ngx.var.host]
if locs ~= nil then
for _, path in pairs(locs) do
if ngx.var.location_path == path then
return true
end
end
end
end

-- new_upstream: upstream which is pointed by new key
local new_upstream = nil

-- generate new upstream key if sticky cookie not set or previous attempt failed
for _ = 1, MAX_UPSTREAM_CHECKS_COUNT do
key = string.format("%s.%s.%s", ngx.now(), ngx.worker.pid(), math.random(999999))

new_upstream = self.instance:find(key)

if failed_upstream ~= new_upstream then
-- set cookie only when we get NOT THE SAME upstream
if upstream_from_cookie ~= new_upstream then
if self.cookie_session_affinity.locations then
local locs = self.cookie_session_affinity.locations[ngx.var.host]
if locs ~= nil then
for _, path in pairs(locs) do
if ngx.var.location_path == path then
set_cookie(self, key)
break
end
end
end
end
return false
end

end
function _M.balance(self)
local cookie, err = ck:new()
if not cookie then
ngx.log(ngx.ERR, "error while initializing cookie: " .. tostring(err))
return
end

-- new upstream was obtained; return it to the balancer
do return new_upstream end
end
local upstream_from_cookie

local key = cookie:get(self:cookie_name())
if key then
upstream_from_cookie = self.instance:find(key)
end

-- generated key points to the failed upstream; try another key
local last_failure = self.get_last_failure()
local should_pick_new_upstream = last_failure ~= nil and self.cookie_session_affinity.change_on_failure or upstream_from_cookie == nil

if not should_pick_new_upstream then
return upstream_from_cookie
end

ngx.log(ngx.WARN, string.format("failed to get new upstream; using upstream %s", new_upstream))
local new_upstream, key = pick_new_upstream(self)
if not new_upstream then
ngx.log(ngx.WARN, string.format("failed to get new upstream; using upstream %s", new_upstream))
elseif should_set_cookie(self) then
set_cookie(self, key)
end

return new_upstream
end
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6 changes: 0 additions & 6 deletions rootfs/etc/nginx/lua/util/split.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -16,12 +16,6 @@ function _M.get_first_value(var)
return t[1]
end

function _M.get_last_value(var)
local t = _M.split_upstream_var(var) or {}
if #t == 0 then return nil end
return t[#t]
end

-- http://nginx.org/en/docs/http/ngx_http_upstream_module.html#example
-- CAVEAT: nginx is giving out : instead of , so the docs are wrong
-- 127.0.0.1:26157 : 127.0.0.1:26157 , ngx.var.upstream_addr
Expand Down