Dynamic LB sync non-external backends only when necessary

rootfs/etc/nginx/lua/balancer.lua

@@ -23,6 +23,7 @@ local ngx = ngx
 -- it will take <the delay until controller POSTed the backend object to the
 -- Nginx endpoint> + BACKENDS_SYNC_INTERVAL
 local BACKENDS_SYNC_INTERVAL = 1
+local BACKENDS_FORCE_SYNC_INTERVAL = 30
 
 local DEFAULT_LB_ALG = "round_robin"
 local IMPLEMENTATIONS = {
@@ -36,6 +37,8 @@ local IMPLEMENTATIONS = {
 
 local _M = {}
 local balancers = {}
+local backends_with_external_name = {}
+local backends_last_synced_at = 0
 
 local function get_implementation(backend)
   local name = backend["load-balance"] or DEFAULT_LB_ALG
@@ -92,6 +95,12 @@ local function format_ipv6_endpoints(endpoints)
   return formatted_endpoints
 end
 
+local function is_backend_with_external_name(backend)
+  local serv_type = backend.service and backend.service.spec
+                      and backend.service.spec["type"]
+  return serv_type == "ExternalName"
+end
+
 local function sync_backend(backend)
   if not backend.endpoints or #backend.endpoints == 0 then
     balancers[backend.name] = nil
@@ -117,9 +126,7 @@ local function sync_backend(backend)
     return
   end
 
-  local service_type = backend.service and backend.service.spec
-                       and backend.service.spec["type"]
-  if service_type == "ExternalName" then
+  if is_backend_with_external_name(backend) then
     backend = resolve_external_names(backend)
   end
 
@@ -129,6 +136,17 @@ local function sync_backend(backend)
 end
 
 local function sync_backends()
+  local raw_backends_last_synced_at = configuration.get_raw_backends_last_synced_at()
+  ngx.update_time()
+  local current_timestamp = ngx.time()
+  if current_timestamp - backends_last_synced_at < BACKENDS_FORCE_SYNC_INTERVAL
+      and raw_backends_last_synced_at <= backends_last_synced_at then
+    for _, backend_with_external_name in pairs(backends_with_external_name) do
+      sync_backend(backend_with_external_name)
+    end
+    return
+  end
+
   local backends_data = configuration.get_backends_data()
   if not backends_data then
     balancers = {}
@@ -145,13 +163,19 @@ local function sync_backends()
   for _, new_backend in ipairs(new_backends) do
     sync_backend(new_backend)
     balancers_to_keep[new_backend.name] = balancers[new_backend.name]
+    if is_backend_with_external_name(new_backend) then
+      local backend_with_external_name = util.deepcopy(new_backend)
+      backends_with_external_name[backend_with_external_name.name] = backend_with_external_name
+    end
   end
 
   for backend_name, _ in pairs(balancers) do
     if not balancers_to_keep[backend_name] then
       balancers[backend_name] = nil
+      backends_with_external_name[backend_name] = nil
     end
   end
+  backends_last_synced_at = raw_backends_last_synced_at
 end
 
 local function route_to_alternative_balancer(balancer)

rootfs/etc/nginx/lua/configuration.lua

@@ -24,6 +24,14 @@ function _M.get_general_data()
   return configuration_data:get("general")
 end
 
+function _M.get_raw_backends_last_synced_at()
+  local raw_backends_last_synced_at = configuration_data:get("raw_backends_last_synced_at")
+  if raw_backends_last_synced_at == nil then
+    raw_backends_last_synced_at = 1
+  end
+  return raw_backends_last_synced_at
+end
+
 local function fetch_request_body()
   ngx.req.read_body()
   local body = ngx.req.get_body_data()
@@ -187,6 +195,16 @@ local function handle_backends()
     return
   end
 
+  ngx.update_time()
+  local raw_backends_last_synced_at = ngx.time()
+  success, err = configuration_data:set("raw_backends_last_synced_at", raw_backends_last_synced_at)
+  if not success then
+    ngx.log(ngx.ERR, "dynamic-configuration: error updating when backends sync, " ..
+                     "new upstream peers waiting for force syncing: " .. tostring(err))
+    ngx.status = ngx.HTTP_BAD_REQUEST
+    return
+  end
+
   ngx.status = ngx.HTTP_CREATED
 end
 

rootfs/etc/nginx/lua/tcp_udp_balancer.lua

@@ -18,6 +18,7 @@ local getmetatable = getmetatable
 -- it will take <the delay until controller POSTed the backend object
 -- to the Nginx endpoint> + BACKENDS_SYNC_INTERVAL
 local BACKENDS_SYNC_INTERVAL = 1
+local BACKENDS_FORCE_SYNC_INTERVAL = 30
 
 local DEFAULT_LB_ALG = "round_robin"
 local IMPLEMENTATIONS = {
@@ -26,6 +27,8 @@ local IMPLEMENTATIONS = {
 
 local _M = {}
 local balancers = {}
+local backends_with_external_name = {}
+local backends_last_synced_at = 0
 
 local function get_implementation(backend)
   local name = backend["load-balance"] or DEFAULT_LB_ALG
@@ -65,6 +68,12 @@ local function format_ipv6_endpoints(endpoints)
   return formatted_endpoints
 end
 
+local function is_backend_with_external_name(backend)
+  local serv_type = backend.service and backend.service.spec
+                      and backend.service.spec["type"]
+  return serv_type == "ExternalName"
+end
+
 local function sync_backend(backend)
   if not backend.endpoints or #backend.endpoints == 0 then
     return
@@ -89,9 +98,7 @@ local function sync_backend(backend)
     return
   end
 
-  local service_type = backend.service and backend.service.spec and
-    backend.service.spec["type"]
-  if service_type == "ExternalName" then
+  if is_backend_with_external_name(backend) then
     backend = resolve_external_names(backend)
   end
 
@@ -101,6 +108,17 @@ local function sync_backend(backend)
 end
 
 local function sync_backends()
+  local raw_backends_last_synced_at = configuration.get_raw_backends_last_synced_at()
+  ngx.update_time()
+  local current_timestamp = ngx.time()
+  if current_timestamp - backends_last_synced_at < BACKENDS_FORCE_SYNC_INTERVAL
+      and raw_backends_last_synced_at <= backends_last_synced_at then
+    for _, backend_with_external_name in pairs(backends_with_external_name) do
+      sync_backend(backend_with_external_name)
+    end
+    return
+  end
+
   local backends_data = configuration.get_backends_data()
   if not backends_data then
     balancers = {}
@@ -117,13 +135,19 @@ local function sync_backends()
   for _, new_backend in ipairs(new_backends) do
     sync_backend(new_backend)
     balancers_to_keep[new_backend.name] = balancers[new_backend.name]
+    if is_backend_with_external_name(new_backend) then
+      local backend_with_external_name = util.deepcopy(new_backend)
+      backends_with_external_name[backend_with_external_name.name] = backend_with_external_name
+    end
   end
 
   for backend_name, _ in pairs(balancers) do
     if not balancers_to_keep[backend_name] then
       balancers[backend_name] = nil
+      backends_with_external_name[backend_name] = nil
     end
   end
+  backends_last_synced_at = raw_backends_last_synced_at
 end
 
 local function get_balancer()

rootfs/etc/nginx/lua/tcp_udp_configuration.lua

@@ -9,6 +9,14 @@ function _M.get_backends_data()
   return tcp_udp_configuration_data:get("backends")
 end
 
+function _M.get_raw_backends_last_synced_at()
+  local raw_backends_last_synced_at = tcp_udp_configuration_data:get("raw_backends_last_synced_at")
+  if raw_backends_last_synced_at == nil then
+    raw_backends_last_synced_at = 1
+  end
+  return raw_backends_last_synced_at
+end
+
 function _M.call()
   local sock, err = ngx.req.socket(true)
   if not sock then
@@ -35,6 +43,17 @@ function _M.call()
     ngx.say("error: ", err_conf)
     return
   end
+
+  ngx.update_time()
+  local raw_backends_last_synced_at = ngx.time()
+  success, err = tcp_udp_configuration_data:set("raw_backends_last_synced_at",
+                      raw_backends_last_synced_at)
+  if not success then
+    ngx.log(ngx.ERR, "dynamic-configuration: error updating when backends sync, " ..
+                     "new upstream peers waiting for force syncing: " .. tostring(err))
+    ngx.status = ngx.HTTP_BAD_REQUEST
+    return
+  end
 end
 
 return _M