Merge pull request #3341 from Shopify/canary_upstream

Add canary annotation and alternative backends for traffic shaping

rootfs/etc/nginx/lua/balancer.lua

@@ -127,9 +127,57 @@ local function sync_backends()
   end
 end
 
+local function route_to_alternative_balancer(balancer)
+  if not balancer.alternative_backends then
+    return false
+  end
+
+  -- TODO: support traffic shaping for n > 1 alternative backends
+  local alternative_balancer = balancers[balancer.alternative_backends[1]]
+
+  local clean_target_header = util.replace_special_char(alternative_balancer.traffic_shaping_policy.header, "-", "_")
+
+  local header = ngx.var["http_" .. clean_target_header]
+  if header then
+    if header == "always" then
+      return true
+    elseif header == "never" then
+      return false
+    end
+  end
+
+  local clean_target_cookie = util.replace_special_char(alternative_balancer.traffic_shaping_policy.cookie, "-", "_")
+
+  local cookie = ngx.var["cookie_" .. clean_target_cookie]
+  if cookie then
+    if cookie == "always" then
+      return true
+    elseif cookie == "never" then
+      return false
+    end
+  end
+
+  if math.random(100) <= alternative_balancer.traffic_shaping_policy.weight then
+    return true
+  end
+
+  return false
+end
+
 local function get_balancer()
   local backend_name = ngx.var.proxy_upstream_name
-  return balancers[backend_name]
+
+  local balancer = balancers[backend_name]
+  if not balancer then
+    return
+  end
+
+  if route_to_alternative_balancer(balancer) then
+    local alternative_balancer = balancers[balancer.alternative_backends[1]]
+    return alternative_balancer
+  end
+
+  return balancer
 end
 
 function _M.init_worker()

rootfs/etc/nginx/lua/balancer/chash.lua

@@ -6,7 +6,10 @@ local _M = balancer_resty:new({ factory = resty_chash, name = "chash" })
 
 function _M.new(self, backend)
   local nodes = util.get_nodes(backend.endpoints)
-  local o = { instance = self.factory:new(nodes), hash_by = backend["upstream-hash-by"] }
+  local o = {
+    instance = self.factory:new(nodes),
+    hash_by = backend["upstream-hash-by"],
+  }
   setmetatable(o, self)
   self.__index = self
   return o

rootfs/etc/nginx/lua/balancer/ewma.lua

@@ -102,6 +102,9 @@ function _M.after_balance(_)
 end
 
 function _M.sync(self, backend)
+  self.traffic_shaping_policy = backend.trafficShapingPolicy
+  self.alternative_backends = backend.alternativeBackends
+
   local changed = not util.deep_compare(self.peers, backend.endpoints)
   if not changed then
     return
@@ -115,7 +118,9 @@ function _M.sync(self, backend)
 end
 
 function _M.new(self, backend)
-  local o = { peers = backend.endpoints }
+  local o = {
+    peers = backend.endpoints,
+  }
   setmetatable(o, self)
   self.__index = self
   return o

rootfs/etc/nginx/lua/balancer/resty.lua

@@ -10,6 +10,9 @@ function _M.new(self, o)
 end
 
 function _M.sync(self, backend)
+  self.traffic_shaping_policy = backend.trafficShapingPolicy
+  self.alternative_backends = backend.alternativeBackends
+
   local nodes = util.get_nodes(backend.endpoints)
   local changed = not util.deep_compare(self.instance.nodes, nodes)
   if not changed then

rootfs/etc/nginx/lua/balancer/round_robin.lua

@@ -6,7 +6,9 @@ local _M = balancer_resty:new({ factory = resty_roundrobin, name = "round_robin"
 
 function _M.new(self, backend)
   local nodes = util.get_nodes(backend.endpoints)
-  local o = { instance = self.factory:new(nodes) }
+  local o = {
+    instance = self.factory:new(nodes),
+  }
   setmetatable(o, self)
   self.__index = self
   return o

rootfs/etc/nginx/lua/util.lua

@@ -108,4 +108,10 @@ local function tablelength(T)
 end
 _M.tablelength = tablelength
 
+-- replaces special character value a with value b for all occurences in a string
+local function replace_special_char(str, a, b)
+  return string.gsub(str, "%" .. a, b)
+end
+_M.replace_special_char = replace_special_char
+
 return _M