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Refactor EWMA to not use shared dictionaries

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Henry Tran 2018-07-30 15:55:47 -04:00 • committed by Elvin Efendi
parent bc6f2e7016
commit 3cbfd63992
3 changed files with 8 additions and 69 deletions
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59
rootfs/etc/nginx/lua/balancer/ewma.lua
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@ -5,38 +5,17 @@
-- /finagle-core/src/main/scala/com/twitter/finagle/loadbalancer/PeakEwma.scala
local resty_lock = require("resty.lock")
local util = require("util")
local split = require("util.split")
local DECAY_TIME = 10 -- this value is in seconds
local LOCK_KEY = ":ewma_key"
local PICK_SET_SIZE = 2
local ewma_lock = resty_lock:new("locks", {timeout = 0, exptime = 0.1})
local balancer_ewma = {}
local balancer_ewma_last_touched_at = {}
local _M = { name = "ewma" }
local function lock(upstream)
local _, err = ewma_lock:lock(upstream .. LOCK_KEY)
if err then
if err ~= "timeout" then
ngx.log(ngx.ERR, string.format("EWMA Balancer failed to lock: %s", tostring(err)))
end
end
return err
end
local function unlock()
local ok, err = ewma_lock:unlock()
if not ok then
ngx.log(ngx.ERR, string.format("EWMA Balancer failed to unlock: %s", tostring(err)))
end
return err
end
local function decay_ewma(ewma, last_touched_at, rtt, now)
local td = now - last_touched_at
td = (td > 0) and td or 0
@ -47,40 +26,18 @@ local function decay_ewma(ewma, last_touched_at, rtt, now)
end
local function get_or_update_ewma(upstream, rtt, update)
local lock_err = nil
if update then
lock_err = lock(upstream)
end
local ewma = ngx.shared.balancer_ewma:get(upstream) or 0
if lock_err ~= nil then
return ewma, lock_err
end
local ewma = balancer_ewma[upstream] or 0
local now = ngx.now()
local last_touched_at = ngx.shared.balancer_ewma_last_touched_at:get(upstream) or 0
local last_touched_at = balancer_ewma_last_touched_at[upstream] or 0
ewma = decay_ewma(ewma, last_touched_at, rtt, now)
if not update then
return ewma, nil
end
local success, err, forcible = ngx.shared.balancer_ewma_last_touched_at:set(upstream, now)
if not success then
ngx.log(ngx.WARN, "balancer_ewma_last_touched_at:set failed " .. err)
end
if forcible then
ngx.log(ngx.WARN, "balancer_ewma_last_touched_at:set valid items forcibly overwritten")
end
success, err, forcible = ngx.shared.balancer_ewma:set(upstream, ewma)
if not success then
ngx.log(ngx.WARN, "balancer_ewma:set failed " .. err)
end
if forcible then
ngx.log(ngx.WARN, "balancer_ewma:set valid items forcibly overwritten")
end
unlock()
balancer_ewma_last_touched_at[upstream] = now
balancer_ewma[upstream] = ewma
return ewma, nil
end
@ -153,8 +110,8 @@ function _M.sync(self, backend)
self.peers = backend.endpoints
-- TODO: Reset state of EWMA per backend
ngx.shared.balancer_ewma:flush_all()
ngx.shared.balancer_ewma_last_touched_at:flush_all()
balancer_ewma = {}
balancer_ewma_last_touched_at = {}
end
function _M.new(self, backend)